Rahayu & Ng: New genera and species of Hexapodidae
Taxonomy & Systematics
RAFFLES BULLETIN OF ZOOLOGY 62: 396–483

Date of publication: 4 July 2014
http://zoobank.org/ urn:lsid:zoobank.org:pub:4CF42744-861A-4635-9703-E6639CEBFAA9

New genera and new species of Hexapodidae (Crustacea, Brachyura)from the Indo-West Pacific and east Atlantic
Dwi Listyo Rahayu1 & Peter K. L. Ng1, 2
Abstract. The hexapodid genera Hexapus De Haan, 1833, Hexapinus Manning & Holthuis, 1981, Latohexapus
Huang, Hsueh & Ng, 2002, and Hexaplax Doflein, 1904, are revised and redescribed on the basis of their respective
type species. Hexapus s. str. is redefined and a new species is described from Indonesia. Hexapinus is restricted forH. latipes (De Haan, 1835), H. edwardsi (Serène & Soh, 1976) and three new species from Indonesia, Philippines,
China and Japan. A new genus, Mariaplax, is established for Lambdophallus anfractus Rathbun, 1909, Hexapus
granuliferus Campbell & Stephenson, 1970, and 11 new species from the China, Japan, Vietnam, Philippines,
Indonesia, Singapore, New Guinea and Australia. A new genus, Rayapinus, is recognised for an unusual new species
from Japan. Two new species of Hexaplax from Papua New Guinea, Philippines, Taiwan, and Japan are described.
A new genus, Theoxapus, is also established for the east Atlantic Hexapus buchanani Monod, 1956, which had
previously been placed in Hexapinus. A revised key to the genera of Hexapodidae is presented.
Key words. Crustacea, Brachyura, Hexapodidae, taxonomy, Indo-West Pacific, East Atlantic, new genera, new species

INTRODUCTION

The present study treats seven genera (three new) and25 species (18 new) from the Indo-West Pacific and east
Atlantic: Hexapus sexpes (Fabricius, 1798), Hexapus timika,
new species, Hexapinus latipes (De Haan, 1835), Hexapinus
ceres, new species, Hexapinus latus, new species, Hexapinus
simplex, new species, Mariaplax, new genus, Mariaplax
anfracta (Rathbun, 1909), new combination, Mariaplax
chenae, new species, Mariaplax cyrtophallus, new species,
Mariaplax daviei, new species, Mariaplax galaxeae, newspecies, Mariaplax granulifera (Campbell & Stephenson,1970), new combination, Mariaplax mica, new species,
Mariaplax narusei, new species, Mariaplax ourabay, newspecies, Mariaplax propinqua, new species, Mariaplax
secus, new species, Mariaplax sinensis, new species,
Mariaplax streptophallus, new species, Rayapinus, newgenus, Rayapinus maenosonoi, new species, Latohexapus
granosus Huang, Hsueh & Ng, 2002, Hexaplax megalops
Doflein, 1904, Hexaplax aurantium, new species, Hexaplaxsaudade, new species, Theoxapus, new genus, and Theoxapus
buchanani (Monod, 1956), new combination.

Unique among the extant Brachyura in the complete absenceof the last pair of ambulatory legs, members of the family
Hexapodidae Miers, 1886, occur throughout temperate andtropical seas. In their revision of west African crabs, Manning& Holthuis (1981) followed Guinot (1978) in treating theHexapodidae as a distinct family, recognising 11 genera and18 species. Since then, two new genera have been describedand 19 extant species are known at present (Huang et al.,
2002; Guinot, 2006; Ng et al., 2008). Of these, 11 generaand 10 species occur in the Indo-West Pacific.
The present study started some 20 years ago when thelate Chen Hui-Lian (Qingdao, China) gave a collection ofhexapodid crabs to the second author for a proposed study ofEast Asian species. However, this study was never finished
due to her untimely death in the interim. In 2008, the firstauthor obtained specimens of a new species from Lombok,
as well as several specimens from other parts of Indonesia,
and initiated a study of this material with the second author.
This study gradually expanded to include material from
Australia, New Guinea, China, Taiwan, Vietnam, Japan,
Indonesia, Philippines, Malaysia and Singapore.

Specimens examined are deposited in the Institute of
Oceanology, Chinese Academy of Science, Qingdao, China(IOCAS); National Museum of Nature and Science, Tsukuba,
Japan (NSMT); Kanagawa Prefectural Museum of Natural
History, Iriuda, Japan (KPM); Ryukyu University Museum,Fujukan, Okinawa, Japan (RUMF); Natural History Museum
and Institute, Chiba, Japan (CMB); Crustacean Collection of
the National Museum of the Philippines, Manila (NMCR),
Zoological Reference Collection of the Raffles Museum of
Biodiversity Research, National University of Singapore,
Singapore (ZRC); Museum Zoologi Bogor, Indonesian
Institute of Sciences (MZB); Western Australian Museum,
Perth, Australia (WAM); Queensland Museum, Brisbane,

Tropical Marine Science Institute, National University of Singapore; and Marine
Bio-industry Implementation Unit-Research Center for Oceanography - Indonesian
Institute of Sciences (LIPI), Teluk Kodek, Pemenang, Lombok Utara, NTB, Indonesia;
Email: dwilistyo@yahoo.com
1

Lee Kong Chian Natural History Museum and Department of Biological Sciences,
National University of Singapore, Lower Kent Ridge Road, Singapore 119260; Email:dbsngkl@nus.edu.sg

2© National University of Singapore
ISSN 2345-7600 (electronic) | ISSN 0217-2445 (print)

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Australia (QM); The Natural History Museum, London,
United Kingdom (NHM); The Naturalis (ex Rijksmuseum
van Natuurlijke Historie), Leiden, The Netherlands (RMNH);
Muséum national d’Histoire naturelle, Paris, France (MNHN);
Zoological Museum of Berlin (ZMB); and the U.S. National
Museum of Natural History, Smithsonian Institution,
Washington D.C., U.S.A. (USNM). The abbreviations P2, P3,
and P4 are used for the second, third, and fourth pereopods (=first, second, and third ambulatory legs), respectively; G1 forfirst male gonopod; and coll. is for collected. Measurements
provided, in millimetres, are of the carapace width and length,
respectively. Detailed descriptions are only provided for thetype species of each genus, with other species only diagnosed.
As the generic concepts have changed substantially in recent
years, the synonymy for genera is restricted primarily to theoriginal citation.

known from only few specimens, we are fortunate in thisstudy to be able to study abundant material of four species(Hexapinus simplex, new species, Mariaplax chenae, newspecies, Hexaplax megalops, and Hexaplax aurantium, newspecies). They demonstrate that the characters of the carapace,third maxillipeds, and pereopods do not vary substantially.
The good series of specimens of both sexes and various sizes
also allows us to ascertain variation in key characters aswell as changes in the G1 structure associated with growth.
Comparative material. Tritoplax stebbingi (Barnard, 1950):
lectotype male (14.1 × 9.5 mm), 1 female (12.2 × 8.2 mm)(NHM), Agulhas Bay (St. Sebastian Bay to Algoa Bay),South Africa, coll. 19 November 1946 (Fig. 7).
Key to genera of Hexapodidae(modified from Manning & Holthuis, 1981)

TAXONOMY

1. Eye hammer-shaped, cornea very large, much broader thanpeduncle; carpus, propodus, and dactylus of third maxillipedvery slender; P2–P4 very long, slender, merus of longest pairlonger than carapace [Indo-West Pacific]..................................
............................................................ Hexaplax Doflein, 1904
– Eye relatively small or reduced, cornea scarcely or not broader
than peduncle; third maxilliped and P2–P4 various...............2
2. Eyes fixed; P2–P4 long, slender, merus of longest pair much
longer than carapace; male thoracic sternal groove long, narrow,transverse, extending laterally from sternoabdominal cavity tobeyond base of third maxilliped; carpus, propodus and dactylusof third maxilliped slender [Indian Ocean]...............................
.................................................... Lambdophallus Alcock, 1900
– Eyes movable; P2–P4 relatively short, merus of longest pairshorter or subequal in length to carapace; male thoracic
sternal groove with or without transverse extension fromsternoabdominal cavity to base of third maxilliped; third
maxilliped various....................................................................3
3. Propodus of third maxilliped strongly dilated distally............4– Propodus of third maxilliped not strongly dilated distally,
slender; carpus and dactylus relatively slender.......................6
4. G1 stout, strongly twisted into a tight spiral [South Africa]....
.......................................Spiroplax Manning & Holthuis, 1981
– G1 variously shaped, not twisted into tight spiral..................5
5. Male abdominal somite 6 relatively long; male telson withlateral margins concave; G1 slender, sinuous directed anteriorly[West Africa]................................ Thaumastoplax Miers, 1881
– Male abdominal somite 6 relatively shorter; male telson withlateral margins convex; G1 recurved posteriorly [Indo-West
Pacific]........................................... Hexalaughlia Guinot, 2006
6. Some of female abdominal somites fused...............................7– All female abdominal somites free..........................................8
7. Female abdominal somite 1 free, somites 2–6 fused, but sutures
visible [Guatemala].............Stevea Manning & Holthus, 1981
– Female abdominal somites 1–6 fused, suture visible only onsomites 5 and 6 [Japan]........................ Rayapinus, new genus
8. Exopod of third maxilliped with flagellum; dactylus of P2–P4
neither enlarged nor distinctly flattened dorsoventrally; maleabdominal somite 6 constricted proximally.............................9– Exopod of third maxilliped without flagellum; dactylus of
P2–P4 enlarged, triangular, strongly flattened dorsoventrally;
male abdominal somite 6 not constricted proximally [WestAfrica].........................................Pseudohexapus Monod, 1956
9. Male abdominal somite 6 much longer than combined lengthof somites 3–5 [Galapagos]...............Paeduma Rathbun, 1897
– Male abdominal somite 6 shorter than combined length ofsomites 3–5.............................................................................10

Family Hexapodidae Miers, 1886
Remarks. Following suggestions by Monod (1956), Manning& Holthuis (1981) distinguished the various hexapodid genera
using a combination of characters such as the structure of
the eyes, shape of the third maxilliped (especially the shapeof the propodus), presence or absence of a flagellum on
the exopod of the third maxilliped, relative length of thesecond, third, and fourth pereopods, structure of the malethoracic sternal groove, shape and configuration of the maleabdomen, and structure of the G1. To separate Hexapus De
Haan, 1833, and Hexapinus Manning & Holthuis, 1981,
Manning & Holthuis (1981: 169) argued that Hexapus has
broad and deep male thoracic sternal grooves that extend
anterolaterally from the sternoabdominal cavity to the basesof the third maxillipeds; while those in Hexapinus are notas long or broad, being only a triangular projection and notreaching the bases of the third maxillipeds. The present study
shows that the shape and extent of the male thoracic sternalgroove cannot always be used to separate the two genera. This
character varies with the size of the individual and there areintermediate conditions between species in other hexapodid
genera (see Mariaplax chenae, new species). These genericgroupings are better defined by other characters. As such,
both genera need to be rediagnosed.
In this paper, separation of the genera in the family
Hexapodidae essentially follows the system suggested by
Manning & Holthuis (1981) except for relying less on the
shape and extent of the male thoracic sternal groove. One
new character added is the shape and proportions of theischium and merus of the third maxillipeds. At the species
level, the structure of the adult G1 is important and it cansometimes be the only reliable means of separating species
that are otherwise very close (e.g., see Mariaplax granuliferus
and M. daviei, new species). If only juveniles or females are
known, species identifications may be difficult.
That been said, the proportions of the carapace and pereopods
as well as structure of the male abdomens are usually usefulin discriminating species. While most hexapodid taxa are397

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Fig. 1. Colours in life. A, Hexapinus simplex, new species, paratype male (8.7 × 5.0 mm) (MZB), Lombok, Indonesia; B, Hexapinus
simplex, new species, male (9.3 × 5.8 mm) (ZRC), Lembeh Straits, Sulawesi Indonesia; C, Hexapinus simplex, new species, male (12.6
× 8.4 mm) (RUMF-ZC-2110), Tekebu, Amami-Ohshima Island, Japan; D, Hexapinus simplex, new species, male (12.6 × 8.4 mm) (ZRC
2013.1688), Funaura, Iriomote Island, Japan; E, Hexapinus simplex, new species, female (8.3 × 6.0 mm) (ZRC 2013.1687), Raffles
Reserve near Raffles Lighthouse, Singapore; F, Hexapinus simplex, new species, male (11.2 × 7.0 mm) (ZRC), Pulau Senang, Singapore;
G, Mariaplax galaxeae, new species, holotype female (4.2 × 3.2 mm) (ZRC 2013.1690), Singapore Strait; H, Mariaplax chenae, newspecies, East China Sea (courtsey W.-L. Liu, specimen not examined); I, Mariaplax secus, new species, holotype male (4.7 × 3.0 mm)(MNHN IU-2013-916), Madang, Papua New Guinea; J, Mariaplax mica, new species, holotype female (6.7 × 4.5 mm) (NMCR 39069),
Bohol Sea, Philippines.

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10. Male telson distinctly trilobed or trifoil in shape with distinct
lateral angular projection, male abdominal somite 6 divided
longitudinally [South Africa].....................................................
........................................Tritoplax Manning & Holthuis, 1981
– Male telson various, male abdominal somite 6 entire..........11
11. Carapace regions distinct; thoracic sternites 1 and 2 strongly
bent inwards towards buccal cavity [West Pacific]...................
..................................Latohexapus Huang, Hsueh & Ng, 2002–

Carapace regions indistinct; thoracic sternites 1 and 2 gently
curved or flat, not bent inwards towards buccal cavity........12
12. Third maxilliped slender, ischium width about 2/3 to 3/4 merus
length......................................................................................13– Third maxilliped broad, ischium width usually subequal to or
longer than merus length.......................................................14

Fig. 2. Colours in life. A, Mariaplax ourabay, new species, holotype male (7.6 × 5.4 mm) (RUMF-ZC-2114), Oura Bay, Okinawa Island,
Japan; B, Mariaplax ourabay, new species, paratype female (9.2 × 7.0 mm) (ZRC 2012.1032), Oura Bay, Okinawa Island, Japan; C,
Mariaplax narusei, new species, holotype male (9.6 × 5.8 mm) (RUMF-ZC-2112), Funaura Bay, Iriomote Island, Japan; D, Rayapinus
maenosonoi, new species, holotype male (6.6 × 4.9 mm) (RUMF-ZC-2115) Sesoko, Okinawa, Japan; E, Hexaplax megalops Doflein,
1904, male, (13.5 × 9.0 mm) (MNHN-IU-2011-1026), west of New Hanover; F, Hexaplax aurantium, new species, paratype male (12.1 ×
8.4 mm) (MNHN-IU-2011-1527), south of Lae, Gulf of Huon; G, Hexaplax saudade, new species, paratype male (16.9 × 9.8 mm) (ZRC
2013.1692), AURORA, 2007, station CP2658, Philippines; H, Hexaplax saudade, new species, male (15.9 × 11.1 mm) (ZRC 2008.1456),
Su-Ao fish port, Ilan province, Taiwan.

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The form of the ischium and merus of the third maxilliped
easily distinguishes Hexapus from Hexapinus. The two
Hexapus species recognised here have distinctively moreelongate third maxillipeds, with the merus subovate andthe ischium longer than broad (e.g., Fig. 5E). In Hexapinus
species, the third maxilliped is distinctively shorter, withthe merus squarish and the ischium broader than long (e.g.,
Fig. 13E). The P2–P4 (notably the meri) of Hexapus arealso proportionately more slender and elongated (Fig. 3A)
compared to those of Hexapinus that are distinctly shorterand stouter (Fig. 18A, C). The male abdomen of Hexapus
is relatively short and broad (Fig. 5F) while in Hexapinus,
it is elongated and slender (Fig. 21E–G). These charactersseparate the two genera, with the P2–P4 and third maxilliped
also effectively distinguishing females as well. The maleabdomen of Hexapus is similar to that of Mariaplax, newgenus, but their third maxillipeds are very different, withthat of Mariaplax appearing intermediate in condition (e.g.,
Fig. 38B) between Hexapus and Hexapinus. Mariaplax canalso usually be distinguished from Hexapus and Hexapinus
by its differently structured G1, its relatively longer P2–P4(except M. narusei, new species), with the merus usuallypossessing a deep longitudinal median groove on the outersurface, sometimes it is not so obvious because of the dense
tubercles (P2–P4 relatively shorter and the median groove
absent or if present, very shallow).

13. Male abdominal somite 6 and telson very slender, narrower thansomites 3–5; G1 slender, sinuous, tapering abruptly to almost
filiform apex, with strong recurved spines near midlength [WestAfrica]............................................... Parahexapus Balss, 1922
– Male abdominal somite 6 and telson relatively stout, almost as
broad as somites 3–5; G1 relatively stout, bent 60° medially,
directed anterolaterally, with distal part gradually tapered [IndoWest Pacific].......................................Hexapus De Haan, 1833
14. Ischium of third maxilliped strongly expanded mesially, exopod
broad; P2–P4 without longitudinal groove on outer surface ofmerus; G1 gently curved [West Pacific]....................................
..................................... Hexapinus Manning & Holthuis, 1981
– Ischium of third maxilliped not strongly expanded mesially,
exopod relatively narrow; P2–P4 may have longitudinal grooveon outer surface of merus at least on P3; G1 various..........15
15.Carapace subtrapezoidal; one or all of P2–P4 with distinct
longitudinal groove on outer surface of merus (except in M.
cyrtophallus); G1 twisted, curved, S-shaped or sinuous, apex
tapering into more or less pointed tip [Indo-West Pacific].......
............................................................... Mariaplax, new genus– Carapace ovate; P2–P4 without groove on outer surface ofmerus; G1 straight, tip covered by dense setae, almost samewide as proximal part [East Atlantic]........................................
...............................................................Theoxapus, new genus

Hexapus De Haan, 1833
Hexapus De Haan, 1833: 5.

Diagnosis. Carapace broader than long, surface pitted,
granules lining margin; regions indistinct, with shallow
median H-shaped depression. Anterolateral margin arcuate;
pterygostomial region with rows of long, oblique striae andscattered tubercles. Eyes very small, slightly movable, corneas
subglobular. Third maxillipeds narrow, not covering buccal
cavity, with gap when closed; ischium narrow, longer thanmerus, mesial margin rounded subproximally, straight distally,
carpus, propodus and dactylus cylindrical, dactylus longer
than propodus; exopod relatively broad compared to ischium.
Chelipeds unequal or subequal. P2–P4 relatively short; merus
relatively short, without median longitudinal groove on outersurface; dactylus as long as or slightly longer than propodus,
upcurved or straight. Thoracic sternites 1 and 2 fused; sternite
3 partly or fully separated from sternite 4 by tuberculateridge; sternite 8 exposed, rectangular, slightly longer thanabdominal somite 1. Sternoabdominal cavity reaches baseof thoracic sternite 3. Male thoracic sternal groove oblique,short. Male abdomen relatively narrow, somites 1, 2 and 6
free, somites 3–5 fused; telson subtriangular. G1 slender,
slightly curved subdistally, distal part gradually tapering,
apice not concealed under abdomen, exposed on sternalgroove. Female abdomen with 6 free somites and telson.

With regards to the male thoracic sternal groove, Hexapus
sexpes has a distinct male sternal groove that extends fromthe end of the sternoabdominal cavity to the middle part ofsternite 4, before the base of the third maxillipeds (Figs. 4A,
D, 5B, C), but in Hexapus timika, new species, the grooveis very short and is just a very short extension from thesternaobdominal cavity (Figs. 8B, 9C). Hexapinus simplex,
new species, on the other hand, has a male sternal groove that
resembles that of Hexapus sexpes (Figs. 5B, 20B). Although
the condition of the male thoracic sternal groove does notvary substantially in Hexapus and Hexapinus species (evenfor Hexapinus simplex for which there is a very good series),
its value as a taxonomic character in the Hexapodidae isquestionable. In the genus Mariaplax (notably for M. chenae,
new species, for which there is a good series), the conditionof the male thoracic sternal groove varies with size and isintermediate in condition (see remarks for this species).
Hexapus sexpes (Fabricius, 1798)(Figs. 3–6)
Cancer sexpes Fabricius, 1798: 334.
Hexapus (Hexapus) estuarinus Sankarankutty, 1975: 1, figs. 1, 2.
Hexapus estuarinus – Ng et al., 2008: 86.
Hexapus sexpes – Manning & Holthuis, 1981: 172; Manning,
1982: 158, figs. 1, 2; Ng et al., 2008: 86; Low & Ng, 2012: 60.

Species included. Cancer sexpes Fabricius, 1798 (typespecies by original designation) and H. timika, new species.

Material examined. 1 male (8.5 × 5.4 mm), 1 female (7.1 × 4.5mm) (ZRC 2012.1014), 1 male (7.5 × 5.1 mm), 1 female (6.3 ×
4.1 mm) (CMB-ZC 11354), sand flat, Ko Sirae, Phuket, Thailand,coll. T. Komai, 22 December 2009; 1 female (5.8 × 3.9 mm) (ZRC
1965.11.24.5), Penang Strait, Malaysia.

Remarks. Manning & Holthuis (1981) separated Hexapus
De Haan, 1833, s. str. from Hexapinus Manning & Holthuis,
1981, primarily by the extent of the male thoracic sternalgroove, being proportionately longer in Hexapus. However,due consideration of the third maxilliped, male abdomen
and ambulatory leg structures suggest that the male thoracic
sternal groove is not a good character by itself.
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Diagnosis. Carapace subquadrate, about 1.5 times as broadas long; regions indistinct; scattered granules on anterolateralsurfaces, dorsal surface pitted. Front deflexed, divided into
2 lobes. Eye small, slightly movable, cornea narrower thanpeduncle. Pterygostomial region with 4 long oblique striae
and scattered tubercles. Third maxillipeds narrow; ischium
longer and narrower than merus, mesial margin rounded
subproximally, straight distally. Male chelipeds stout,
unequal; major chela with gap when fingers closed, with large
tooth at cutting edge of dactylus; minor chela with relatively
wider gap when fingers closed; cutting edges of dactylus
and fixed finger with row of small teeth. Female chelipeds
equal. P2–P4 relatively short, stout, P3 longest. Male
thoracic sternum broad; short thoracic sternal groove extend
obliquely from sternoabdominal cavity to middle of sternite

4; sternoabdominal cavity reaches base of sternite 3. Male
abdomen relatively narrow; somites 1 and 2 free, somites
3–5 fused; somite 6 slightly shorter than length of somites
3–5, expanded laterally near base; telson subtriangular withrounded tip. G1 bent 60° medially, directed anterolaterally,
with subdistal protuberance, distal part gradually tapered,
not concealed under abdomen, exposed on thoracic sternalgroove, obscured by setae of telson, lower margin with row oftiny spines. Female abdomen with 6 somites and telson free.
Description. Carapace subquadrate, about 1.5 times as
broad as long; regions indistinct, with median H-shaped
shallow depression; scattered granules on anterolateralsurfaces, dorsal surface pitted (Figs. 3, 5A). Anterolateral
margin arcuate; posterolateral corner with feeble angle overFig. 3. Hexapus sexpes (Fabricius, 1798), male (8.5 × 5.4 mm) (ZRC 2012.1014). A, overall view of carapace, chelipeds and P2–P4; B,
carapace.

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Rahayu & Ng: New genera and species of Hexapodidae
base of posterior pereopods; lateral margin of carapace
wall strongly produced posteriorly. Front deflexed, divided
into 2 lobes, not projecting beyond outer edge of orbits(Fig. 4B). Orbit distinct, transverse; eye small, slightly
movable, cornea black, narrower than peduncle (Figs. 4B,
5D). Pterygostomial region with row of long oblique striae
and scattered tubercles, oblique row of setae under row of
striae adjacent to Milne Edwards’ opening (Figs. 4A, 5D).
Third maxillipeds narrow, not covering buccal cavity, with
gap when closed (Figs. 4D, 5E); ischium longer than merus,
mesial margin rounded subproximally, straight distally; merus
slightly wider than ischium, some granules dorsomesially;
carpus, propodus and dactylus cylindrical; dactylus longer
than propodus; combined length of dactylus, propodus andcarpus shorter than that of merus and ischium; exopod
relatively broad, width of exopod about 0.6 times width ofischium, flagellum well developed.

4–7 well developed, separated from each other by distinct
suture; sternite 8 exposed, rectangular, slightly longer thanabdominal somite 1; sternoabdominal cavity reaches baseof sternite 3. Male abdomen relatively narrow (Figs. 4A, D,
5F); somites 1 and 2 free, somites 3–5 fused, lateral margin
sinuous; somite 6 slightly shorter than length of somites 3–5,
expanded laterally near base; telson subtriangular, distal
margin rounded, setose.
G1 (Fig. 6D, E) bent 60° medially, directed anterolaterally,
with subdistal protuberance, distal part gradually tapered,lower margin with row of tiny spines; distal part not concealed
under abdomen, exposed on thoracic sternal groove, obscured
by setae of telson.
Female abdomen with 6 free somites and telson (Fig. 5G).
Colour. In life, the species is dirty white overall.

Male chelipeds stout, unequal (Fig. 4C). Major chela (Figs.
4C, 6A) with gap when fingers closed, with large tooth at
cutting edge of dactylus; dactylus with row of setae on
proximal third of upper margin; outer and inner surfacesof dactylus glabrous; palm slightly wider than long, outersurface with tubercles on lower half; upper margin withfew tubercles proximally; inner surface with tubercles nearupper margin and midlength; carpus with row of tubercles
on upper margin, setose on upper inner margin, inner angle
blunt, unarmed; merus short, unarmed, fringe of setae
dorsomesially. Minor chela (Figs. 4C, 6B) with relatively
wider gap when fingers closed; dactylus with short row
of tubercles on upper margin proximally, cutting edges ofdactylus and fixed finger with row of small teeth; shallow
longitudinal groove on outer surface of dactylus and fixed
finger; outer surface of palm covered by large tubercles onlower half, carpus and merus unarmed, fringe of setae oneach upper inner margin. Female cheliped equal, narrowgap when fingers closed.

Remarks. Manning & Holthuis (1981) were uncertain about
the identity of H. estuarinus Sankarankutty, 1975, from India.
Later, Manning (1982) considered it to be a junior synonymof H. sexpes, but Ng et al. (2008) provisionally treated it
as valid species in view of the differences observed by
Sankarankutty (1975). The study of fresh material leads us
to concur with Manning (1982) (see also Low & Ng, 2012).
The present material from Phuket agrees very well with theredescription of the dried type of H. sexpes by Manning(1982); the only difference being in the shape of the minor
chela. According to Manning (1982), the fingers of the minor
chela are not gaping, while in the present material, those of
the minor cheliped form a large hiatus, meeting only at thetips. The prominently crossed fingers of the minor chela in thetype (Manning, 1982: fig. 1d) may be an artifact due to poor
preservation (the specimen was dried). In fresh specimens(Fig. 4D), the tips are only partially crossed.
Being the best known member of the family, “Hexapus
sexpes” has been reported by many workers over the last
200 years. However, it is often difficult to ascertain what
species they actually referred to, especially in the context
of the substantial changes in hexapodid taxonomy that haveoccurred in the last 50 years. The records by Tesch (1918),
Sakai (1939, 1976), Serène & Soh (1976) and Guinot(1979) are probably referrable to Hexapinus as good figures
are provided (see discussion for the genus). Stebbing’s(1910: 315, pl. 15) “Hexapus sexpes” is now Tritoplax
stebbingi (Barnards, 1950) (see Manning & Holthuis, 1981).
Stephensen’s (1946: 182, fig. 53) “Hexapus sexpes” fromthe Persian Gulf, was described as a new species (Hexapus
stephenseni) by Serène & Soh (1976). Manning & Holthuis(1981: 180) believed Stephensen’s specimen may be in
Tritoplax Manning & Holthuis, 1981, and Huang et al. (2002)
and Ng et al. (2008) followed their suggestion by referring
Hexapus stephenseni there. We have re-examined the typesof T. stebbingi, the type species of Tritoplax (Fig. 7) andare now certain Hexapus stebbingi and Hexapus stephenseni
cannot be classified in the same genus. The present study
refers Hexapus stephenseni to Mariaplax, new genus, instead.
Records of “Hexapus sexpes” by various authors from theP2–P4 relatively short, stout, P3 longest (Fig. 3A). P2 most
slender, dactylus slightly upcurved, fringe of setae on upperand lower margins, slightly longer than propodus, lattercovered by short setae on outer surface, longer, denser setae
on upper and lower margins; carpus slightly longer thanpropodus, unarmed, tufts of setae distally; merus almost
twice length of carpus, upper margin with tufts of shortsetae, outer surface with sparse short setae on lower half,lower margin with rows of tubercles obscured by long, dense
setae. P3 stouter, longer than P2. P4 (Fig. 6C) stouter thanP3. Setation of dactylus, propodus and carpus of P3 andP4 similar to that of P2; merus of P3 and P4 with rows oftubercles on upper and lower margin obscured by dense
setae; outer face of P3 covered by short setae, outer face of
P4 glabrous, about 2.5 times as long as broad.
Male thoracic sternum broad (Figs. 4A, D, 5B, C), sternites
1 and 2 fused, separated from sternite 3 by distinct ridge;
sternite 3 and 4 separated by distinct ridge laterally, mediallyappear fused, short thoracic sternal groove (Figs. 4A, D, 5B,C) extends obliquely from sternoabdominal cavity to middleof sternite 4 and below base of third maxilliped, sternites
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Fig. 4. Hexapus sexpes (Fabricius, 1798), male (8.5 × 5.4 mm) (ZRC 2012.1014). A, ventral view of cephalothorax; B, front, showing
orbit and eye; C, chelae; D, third maxilliped and abdomen.

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Rahayu & Ng: New genera and species of Hexapodidae
Indo-West Pacific: Zehntner (1894: 159, Ambon, Indonesia);
Nobili (1906: 146, Persian Gulf); Balss (1938: 74, MarshallIslands); and Griffin (1972: 85, off Yamba, New South Wales,
Australia) (see also Davie, 2002: 232) for the moment mustbe treated as incerta cedis as the description and/or figures
were too brief or absent. Although A. Milne-Edwards (1873:

253, pl. 12, fig. 1, New Caledonia), Guinot (1979: Pl. 24 fig.
6, Persian Gulf) and Guinot & Bouchard (1998: Fig. 17E,
Persian Gulf) gave short descriptions and/or figures of theirmaterial, they are insufficient to allow us to determine theprecise identities of the genus or species.

Fig. 5. Hexapus sexpes (Fabricius, 1798). A–F, male (8.5 × 5.4 mm) (ZRC 2012.1014); G, female (5.8 × 3.9 mm) (ZRC 1965.11.24.5).
A, carapace; B, thoracic sternites 3 and 4, showing thoracic sternal groove and telson; C, thoracic sternites 1–4, showing thoracic sternalgroove; D, anterior view of cephalothorax; E, left third maxilliped; F, male abdomen and telson; G, female abdomen and telson. Scalebars = 1.0 mm.

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Type locality. Southern India.

Diagnosis. Carapace rounded, about 1.5 times as broadas long; regions indistinct, with median H-shaped shallow
depression; dorsal surface with flattened granules (Fig.
8A). Anterolateral margin arcuate; posterolateral cornerwith feeble angle over base of posterior pereopods (Fig.
9A). Orbit distinct, eye slightly movable, cornea globular.
Pterygostomial region (Fig. 9B) with long oblique striae andscattered tubercles. Third maxillipeds narrow, not covering
buccal cavity, with gap when closed (Figs. 8B, 9D); ischium
longer than merus, mesial margin rounded subproximally,straight distally; merus slightly wider than ischium; combined
length of dactylus, propodus and carpus shorter than thatof merus and ischium; exopod relatively broad, about 0.5

Distribution. Cochin, south west India; Phuket, Thailand;and Penang Strait, Malaysia. Intertidal to subtidal.
Hexapus timika, new species(Figs. 8, 9)Material examined. Holotype: male (4.6 × 3.0 mm) (MZB Cru
3789), station OT 14A, Otakwa, Timika, Papua, Indonesia, coll. A.
Haris, 8 December 2003. Paratype: Indonesia: 1 male (6.2 × 4.5mm) (ZRC 2013.0946), station EM 771, Muara Mawati, Timika,
Papua, coll. A. Haris, 11 August 2001.

Fig. 6. Hexapus sexpes (Fabricius, 1798), male (8.5 × 5.4 mm) (ZRC 2012.1014). A. major chela; B, minor chela; C, right P4; D, E,
right G1. Scale bars = 1.0 mm.

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Rahayu & Ng: New genera and species of Hexapodidae
width of ischium, flagellum well developed. Chelipeds
stout, unequal (Fig. 8B); major chela with gap when fingers
closed, with large tooth at cutting edge of dactylus; palmslightly longer than wide; minor chela with narrow gap
when fingers closed; shallow longitudinal groove on outersurface of dactylus and fixed finger; outer surface of palm
covered by large tubercles on lower half. P2–P4 (Fig. 8A)
relatively short, slender; dactylus of P2 slightly upcurved,
dactylus of P3 and P4 straight; merus of P4 about 3 times aslong as broad. Male thoracic sternum broad (Figs. 8B, 9C),
sternites 1 and 2 fused, separated from sternite 3 by distinct
ridge; sternite 3 and 4 separated by distinct ridge, very shortthoracic sternal groove extends slightly from sternoabdominal
cavity (Fig. 9C); sternite 8 exposed, triangular, slightly shorter
than abdominal somite 1; sternoabdominal cavity reaches
base of sternite 3. Male abdomen relatively wide (Figs. 8B,
9E); somites 1 and 2 free, somites 3–5 fused, lateral margin
weakly produced subproximally, slightly constricted distally;
somite 6 half length of somites 3–5, expanded laterally nearbase; telson triangular with rounded tip, margin setose. G1(Fig. 9F, G) bent 60° on distal third, directed anterolaterally,
distal part tapered, unarmed, not concealed under abdomen,
exposed on thoracic sternal groove, obscured by setae of
telson. Female unknown.

Fig. 7. Tritoplax stebbingi (Barnard, 1950). A, B, lectotype, male (14.1 × 9.5 mm); C, lectotype, female (12.2 × 8.2 mm). A, overall viewof carapace, chelipeds and P2–P4; B, C, ventral view of carapace.

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Fig. 8. Hexapus timika, new species, holotype male (4.6 × 3.0 mm) (MZB Cru 3789). A, overall view of carapace, chelipeds and P2–P4;
B, ventral surface of cephalothorax.

Type locality. Otakwa, Papua, Indonesia.

Colour. In life, dirty white overall, covered with black mudand stains.

Distribution. Timika, Papua, Indonesia. Subtidal, 7–14 m.

Etymology. Named after the type locality Timika. The nameis used as a noun in apposition.

Genus Hexapinus Manning & Holthuis, 1981
Hexapinus Manning & Holthuis, 1981: 169.

Remarks. The differences in the shape of the carapace,male abdomen and G1 between H. sexpes and H. timika,
new species, are distinct. The carapace of H. sexpes issubquadrate with dorsal surface pitted, the granulation is
only on the dorsolateral surface (Figs. 3A, 5A) while in H.
timika, the carapace is more or less rounded, and the dorsal
surface covered by flattened granules (Figs. 8A, 9A). The
abdomen of H. sexpes is also relatively narrower and longer
than the stouter and wider abdomen of H. timika (Fig. 5F
versus Fig. 9E). The G1 of H. sexpes and H. timika are bothbent at around 60° but in H. sexpes, a protuberance is present
subdistally and the lower margin has a row of small spines(Fig. 6D, E), whereas in H. timika, it is unarmed (Fig. 9F, G).

Diagnosis. Carapace broader than long; regions notdemarcated except for poorly defined cardiac region;
anterolateral margin arcuate, posterolateral margin sinuous.
Eye movable, small, stout, transverse; with small cornea.
Third maxillipeds broad, completely covering buccal cavity;
merus and ischium subequal, ischium subauriculiform,
expanded distally, mesial margin strongly convex; carpus,
propodus and dactylus slender, subcylindrical; dactylus
same length as, or longer than propodus; exopod broad, or
narrow compared to ischium width, flagellum well developed.
Pterygostomial region with row of oblique striae. Chelipeds

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Rahayu & Ng: New genera and species of Hexapodidae
equal or subequal. P2–P4 very short; merus short without
median longitudinal groove on outer surface; dactylus almost
as long as or slightly longer than propodus. Male thoracic
sternum broad; sternites 1 and 2 fused, separated fromsternite 3 by distinct ridge; sternite 3 delimited from sternite
4 laterally; thoracic sternal groove short, extends obliquelyfrom sternoabdominal cavity, sometimes to middle ofsternite 4; sternites 4–7 well developed, separated by distinct
sutures; sternite 8 exposed, triangular or quadrangular, half orsame length as male abdominal somite 1. Sternoabdominal
cavity elongated, reaching base of thoracic sternite 3. Male
abdomen relatively long, slender, extending beyond bases ofFig. 9. Hexapus timika, new species, holotype male (4.6 × 3.0 mm) (MZB Cru 3789). A, dorso-lateral margin of carapace; B, ventral
view of cephalothorax; C, thoracic sternites 1–4, showing thoracic sternal groove and sternoabdominal cavity; D, left third maxilliped; E,
male abdomen and telson; F, G, G1. Scale bars: A–E = 1.0 mm; F, G = 0.5 mm.

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RAFFLES BULLETIN OF ZOOLOGY 2014
third maxilliped, moderately narrow; somites 1 and 2 free,somites 3–5 fused, narrow; somite 6 slightly shorter than
fused somites 3–5; telson subpentagonal, with rounded distal
margin. G1 simple, slightly curved, lying in oblique grooveon anterior part of sternum, distal one-fifth not concealed
under abdomen. Female abdomen with 6 free somites androunded or subtriangular telson.

ischium (Tesch, 1918: pl. 17 fig. 1a) is indicative. It isdifferent from H. simplex, new species, here described fromnearby Lombok Island as it has a relatively short and wide
male abdominal somite 6. In the form of the abdomen, it
resembles what is known for H. latipes (Figs. 10B, 13G).
The same is true for Guinot (1979: 115, 145, Figs. 32, 33A,
B, C–E, 37F) who used Tesch’s specimen for her study.
Sakai’s (1939: 577, text fig. 68, pl. CII, fig. 4) female
specimen from Kii Peninsula in Japan seems closest to H.
simplex with regard to its relatively smoother carapace.
Sakai (1976: 554) had access to more Japanese material,and he appears to have material of both species; one from
Sagami Bay closely resembling H. latipes in its heavily
pitted carapace (Sakai, 1976: pl. 196, fig. 1) with the othersmoother animal from Yoron Island likely to be H. simplex(Sakai, 1976: pl. 196, fig. 2). Odawara’s (1965: 47, fig. a–d)
Japanese records could be either as well but as his figures
clearly depict heavily pitted specimens, this suggests they
are probably H. latipes. Serène & Soh’s (1976: 24, fig. 24,
pl. 7, fig. A) “Hexapus ?sexpes” from the Andaman Sea
is almost certainly a species of Hexapinus but we cannot
identify it for the moment with any known taxon. De Man’s(1888: 322, pl. 13, fig. 3) female specimen from Ambon is
also likely to be a species of Hexapinus although he does
not show the maxillipeds; it resembles H. simplex describedfrom nearby Lombok. All these specimens will need to be
re-examined to ascertain their precise identities.

Species included. Hexapus latipes De Haan, 1835 (typespecies by original designation), Hexapus edwardsi Serène& Soh, 1976, Hexapinus ceres, new species, Hexapinus
latus, new species, and Hexapinus simplex, new species.
Remarks. The type species of Hexapinus, Hexapus latipes
De Haan, 1835, is poorly known. The series of specimens
available, including the dried type, does not include any adultmales and so male diagnostic characters are not available.
The type specimen is dried and almost certainly a young
female, with the telson missing. The genus characters of themale abdomen, G1 and female abdomen are therefore based
mainly on H. simplex, new species.
As redefined here, the most characteristic feature of
Hexapinus s. str. is the third maxilliped possessing a shortand distally expanded ischium with a strongly convex mesial
margin (Figs. 13C–E, 15B, 17B, 20G). No other hexapodid
genus has such a third maxilliped. Some species of Mariaplax,
new genus, have third maxillipeds that approach the condition
in Hexapinus (e.g., M. mica, new species, and M. narusei,
new species, Figs. 38B, 40D), but none are as short andlaterally expanded. The male abdomen of Hexapinus isalso distinctively more slender and elongated (Fig. 21E–G)
compared to Hexapus (Figs. 5F, 9E) or Mariaplax (Fig. 25F).
Compared to Hexapus, the P2–P4 of Hexapinus are relatively
shorter and stouter (cf. Figs. 1A, 18A, C). Mariaplax species
are distinctive because their P2–P4 are usually prominently
longer and more slender, with almost always with a distinct
longitudinal groove on the outer surface (Fig. 24A).

Miyake’s (1983: 151, pl. 51–1) “Hexapus anfractus” fromJapan is probably a species of Hexapinus with regard toits broad carapace and short pereopods. However, a reexamination of his specimen(s) will be required to determine
its precise identity.
Serène & Soh’s (1976: 25, fig. 27, pl. 7, fig. D) species,
Hexapus edwardsi, described from a subadult male fromthe Andaman Sea, is also probably a species of Hexapinus
as redefined here, especially considering the shapes of thethird maxilliped and male abdomen (Serène & Soh, 1976: 25,
fig. 27, plate 7, fig. D). It is here transferred to Hexapinus.

Manning & Holthuis (1981) included Hexapus buchanani
Monod, 1956, and H. granuliferus Campbell & Stephenson,
1970, in Hexapinus. However, the shapes of the third
maxillipeds of H. buchanani (Fig. 67B, 68G), and H.
granuliferus (Fig. 36E; see Campbell & Stephenson, 1970:
286, fig. 49) are quite different from Hexapinus as defined atpresent. The shapes of the third maxilliped of H. granuliferus
conform to what is here described as Mariaplax, new genus,
and this species is transferred there. Hexapus buchanani
Monod, 1956, was collected from West Africa and it differsfrom other hexapodids in a suite of characters: the carapace
is ovate (Figs. 67A, 68E), the meri of P2–P4 do not have alongitudinal groove on the outer surface (Figs. 67A, 68E),
the abdomen is proportionately more elongate (Fig. 68F),
and it has a relatively much straighter G1 (Fig. 68H, I). As
such we establish Theoxapus, new genus, for this species(see later).

Hexapinus latipes (De Haan, 1835)(Figs. 10–13)
Hexapus latipes De Haan, 1835: pl. D.
Hexapus sexpes – De Haan, 1835: 35, 63, pl. 11, fig. 5; Odawara,
1965: 47, fig. a–d; Takeda, 1979: 153. (not Cancer sexpes
Fabricius, 1798)
Hexapus (Hexapus) sexpes – Sakai, 1976: 554 (part), pl. 196, fig.
1. (not Cancer sexpes Fabricius, 1798)
Hexapinus latipes – Manning & Holthuis, 1981: 170; Yamaguchi& Baba, 1993: 434, fig. 154; Ng et al., 2008: 86.
Material examined. Lectotype: female (10.0 × 6.7 mm) (RMNH
31783d), Japan. Others: Japan: 1 female (10.2 × 7.6 mm) (NSMT-Cr5694), Kushimoto, Kii Peninsula, Wakayama Prefecture, 33°27.2'N
135°45.4'E–33°27.2'N 135°45.6'E, 19–27 m, dredge, coll. M.
Takeda, 17 July 1978; 1 female (30.4 × 17.9 mm) (KPM NH
7123), Enoshima Island, T. Sakai Collection; 1 female (28.7 × 16.7mm) (KPM NH 7460) Minabe, Wakayama, T. Sakai Collection; 1
female (30.4 × 17.5 mm) (KPM NH 6331), Mikawa-Ishiki, Aichi
Prefecture, T. Sakai Collection.

Tesch’s (1918: 240, pl. 17, fig. 1) specimens from theIndonesian Kei islands probably belong to a species ofHexapinus. The third maxilliped figured, with the expanded409

Rahayu & Ng: New genera and species of Hexapodidae
Diagnosis. Carapace subquadrate, about 1.2–1.3 times
as broad as long, dorsal surface pitted, region indistinct.
Anterolateral margin arcuate, posterolateral margin sinuouswith 1 protuberance; posterolateral corner with angled
prominence over base of posterior pereopods; lateral marginof carapace wall produced medially. Orbit distinct, transverse;
eye small, slightly movable. Pterygostomial region with rowof oblique striae. Third maxillipeds broad; ischium of third
maxillipeds longer than merus, strongly expanded distally,
with rounded mesial margin, merus broader than long;exopod relatively broad, flagellum well developed. Chelipeds
stout, unequal; major chela with very slightly gaping fingers
when closed, large tooth at cutting edge of dactylus; minor
chela with same ornamentation as major chela, fingers not
gaping when closed. P2–P4 short, stout; P3 longest. Female
thoracic sternum relatively broad; thoracic sternal groove

very short, extends obliquely from sternoabdominal cavity;
sternoabdominal cavity reaches distal part of sternite 4.
Description. Carapace subquadrate, about 1.3 times as broadas long, dorsal surface pitted, region indistinct, medianH-shaped depression shallow; some granules present on
dorsolateral margins, only scattered granules on posterior
margin (Figs. 10A, 11A, 12A, 13A). Anterolateral margin
arcuate, posterolateral margin sinuous with 1 protuberance;
posterolateral corner with angled prominence over base ofposterior pereopods; lateral margin of carapace wall produced
medially. Front deflexed, obscurely divided into 2 lobes, notprojecting beyond lower edge of orbits (Fig. 10C). Orbit
distinct, transverse; eye small, slightly movable, cornea
small, as wide as peduncle (Figs. 10C, 12C). Pterygostomial
region with row of oblique, broken or entire, striae, obliqueFig. 10. Hexapinus latipes (De Haan, 1835), lectotype female (10.0 × 6.7 mm) (RMNH 31783d). A, overall view of carapace, chelipeds
and P2–P4; B, ventral surface of cephalothorax; C, frontal view of cephalothorax; D, card with mouthparts.

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RAFFLES BULLETIN OF ZOOLOGY 2014
row of setae under row of striae adjacent of Milne Edwards’
opening. Third maxillipeds (Fig. 13C–E) broad; ischium ofthird maxillipeds 1.2 times as broad as long, longer thanmerus, strongly expanded distally, with rounded mesial
margin, merus broader than long, carpus, propodus anddactylus cylindrical; dactylus longer than propodus, combined
length of dactylus, propodus and carpus shorter than that ofmerus and ischium; exopod relatively broad, about 0.5 times
width of ischium, flagellum well developed.

lower margins, slightly longer than propodus, outer surface
of propodus with tubercles obscured by tufts of short setae,
lower margin with long setae, strong spines distally, carpus
longer than propodus, outer surface with tubercles on upper
half covered by short setae, short setae on lower margin,
merus almost twice length of carpus, outer surface withtubercles and short setae, upper and lower margins withtufts of dense short setae. P3 stouter, longer than P2; P4
stouter than P3. Ornamentation of P3 and P4 similar to P2
but with longer, denser setation; merus of P4 about 2 times
as long as broad.

Chelipeds stout, unequal (Fig. 11C). Major chela withvery slightly gaping fingers when closed, large tooth at
cutting edge of dactylus; dactylus with scattered tubercles
on upper outer surface proximally, tufts of setae on upper
margin proximally; inner surface near upper margin withlongitudinal ridge; palm slightly wider than long, surface
covered with tubercles; lower margin with long and dense
setae medially, fixed finger smooth; carpus without setae
on upper outer surface, setose on upper inner surface, innerangle blunt, unarmed, outer face covered by tubercles; merus
short, upper outer surface covered with tubercles, fringe ofsetae dorsomesially. Minor chela with same ornamentationas major chela, fingers not gaping when closed.

Female thoracic sternum relatively broad (Figs. 10B, 11B,
12B), sternites 1 and 2 fused, separated from sternite 3
by distinct ridge; sternite 3 separated from sternite 4 byridge laterally, thoracic sternal groove very short, extends
obliquely from sternoabdominal cavity (Fig. 13B); sternites
4–7 well developed, separated by distinct sutures; sternite 8
exposed, triangular, half length of female abdominal somite
1, sternoabdominal cavity reaches distal part of sternite 4.
Juvenile female abdomen relatively narrow (Figs. 10B, 13G);
somites 1 and 2 free; somites 3–5 separated by shallow
grooves, lateral margin sinuous; somite 6 slightly shorter
than somites 3–5, lateral margin sinuous; adult female
abdomen relatively broad (Figs. 12B, 13F) with 6 somites
free and rounded telson.

P2–P4 (Figs. 10A, 11A) short, stout; P3 longest. P2 most
slender, dactylus upcurved, fringe of setae on upper andFig. 11. Hexapinus latipes (De Haan, 1835), female (10.2 × 7.6 mm) (NSMT-Cr 5694). A, overall view of carapace, chelipeds and P2–P4;
B, ventral surface of cephalothorax; C, chelae.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 12. Hexapinus latipes (De Haan, 1835), 1 female (30.4 × 17.5 mm) (KPM NH 6331). A, overall view of carapace, chelipeds andP2–P4; B, ventral surface of cephalothorax; C, frontal view of cephalothorax.

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Fig. 13. Hexapinus latipes (De Haan, 1835). A, B, E, G, female (10.2 × 7.6 mm) (NSMT-Cr 5694); C, holotype female (10.6 × 6.4mm) (RMNH 31783d; D, F, female (30.4 × 17.5 mm) (KPM NH 6331). A, overall view of carapace; B, thoracic sternites 1–5, showing
thoracic sternal groove and sternoabdominal cavity; C–E, left third maxilliped; F, G, female abdomen and telson. Scale bars: A, B, D–G= 1.0 mm; C not to scale.

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Rahayu & Ng: New genera and species of Hexapodidae
of “Hexapus latipes” in Japan; two other species, Hexapinus
simplex, new species, and Mariaplax chenae, new species,
both of which have been confused with “Hexapus latipes”
at one time or another (see discussion for these species),
occur in the islands.

G1 not known.
Colour. Not known.
Remarks. The lectotype of H. latipes is a small dried
specimen (10.0 × 6.7 mm, RMNH 31783d) and not in very
good condition (Fig. 10). It has been listed as a male byManning & Holthuis (1981: 170), and in every respect, it
does look like a male. The abdomen is relatively narrow
and triangular (De Haan, 1835: pl. 11, fig. 5; Figs. 10B),
and somites 3–5 even appear to be fused. However, a close
examination of the abdomen shows that the sutures between
somites 3–5 are still discernible albeit rather shallow. The
short and stout abdomen, while superficially resembling
the male abdomens of Hexapus and Mariaplax, new genus,
differ in that in these genera, male abdominal somites 3–5
are completely fused without any trace of sutures (e.g.,
Figs. 5F, 25F). Another specimen from Japan examinedwhich is about the same size (10.2 × 7.6 mm, NSMT-Cr5694) (Fig. 11A) also resembles the holotype and has thesame abdominal structure (Fig. 13G). However, when theabdomen is detached, it is clear that it is actually a juvenile
female, with the pleopods already evident. Like the holotype
specimen, the abdominal somites 3–5 also have shallow
but distinct sutures (Fig. 13G). We are therefore certainthat the holotype specimen of Hexapinus latipes, which issmaller than the NSMT juvenile female, is also a female.
We have observed the same situation in Hexapinus simplex,
new species, in which both male and female specimens are
known. Juvenile females of this species possess abdomens
that resemble those of males except they are relatively shorterand stouter, and the sutures between abdominal somites 3–5
are still visible (Fig. 21D). True males of Hexapinus simplex,
even when juvenile (5.4 × 3.4 mm, ZRC 2013.1689), haveelongate abdomens, with somites 3–5 completely fused (Fig.
21E, F). We believe when males of Hexapinus latipes arefound, the male abdomens will also be more elongate andslender. Odawara (1965) briefly describes and illustrates amale (28.0 × 17.0 mm) and a female (33.0 × 19.5 mm) ofwhat he identifies as “Hexapus sexpes” (Odawara, 1965: 48,
text fig. a–d) from Japan. His figures leave little doubt in
our mind that his species is what we now call Hexapinus
latipes. Odawara’s (1965: 48 fig. d) of the male ventral surface
shows a male abdomen that appears to be relatively elongate,especially somite 6, and agrees in general with what is here
defined for the genus. Unfortunately, we have not been able
to locate these specimens; they are not in NSMT or KPM.

The figure of the third maxilliped of the type of Hexapinus
latipes in the original publication (De Haan, 1835: pl. D)(present Fig. 13C) is problematic. The figure of the entire
buccal cavity with the intact third maxillipeds shows athird maxilliped that closely resembles that of our present
specimens (Fig. 13E). However, De Haan’s figure of theright third maxilliped (De Haan, 1835: pl. D) does not look
like that of the other Hexapinus species, with the merus andischium too quadrate in shape, and the exopod too slender. In
fact, it closely resembles the third maxilliped of Mariaplax
species. In the RMNH is a box containing several mouthparts
glued onto a card labelled as “Hexapus latipes” which were
almost certainly extracted from the type specimen (Fig.
10D; see also Yamaguchi & Baba, 1993: 434). Yamaguchi& Baba (1993: fig. 154b) depicted the card but it is too
small to see details; it is figured here again (Fig. 13C). The
third maxilliped on the card is the left one (Fig. 10D) andis almost identical to those observed in our present material,with the merus less quadrate and the ischium clearly wider
than long with the mesial margin prominently convex (Fig.
13C). Where the right third maxilliped has gone is notknown. The specimen itself no longer has any mouthparts,
with both third maxillipeds removed (Fig. 10B). It would
therefore appear that De Haan’s original figure of the third
maxilliped is simply inaccurate. It is also possible that De
Haan had more than one specimen of what he called “Hexapus
latipes”, and the right third maxilliped he figured wasactually from a similar-sized Mariaplax specimen (perhaps
M. chenae, which is known from Japan), but the specimen
is just no longer around. Whatever be the case, there is only
one extant specimen left in RMNH and it is the lectotype ofthe species, and we are now certain this is what Manning &Holthuis (1981) as well as ourselves are now recognising as
Hexapinus latipes (De Haan, 1835) s. str.
The form of the third maxilliped is relatively constant. One
slight variation observed is that the exopod of a young female(10.2 × 7.6 mm, NSMT-Cr 5694) is relatively narrower, being
only slightly more than 0.4 times the width of the ischium.
In other specimens, the exopod is wider, at 0.5 times thewidth of the ischium (Fig. 13C, D).
Type locality. Japan.

The above observations are also supported by the fact that H.
latipes is a large species, at least for the Hexapodidae. We
have adult females measuring 30.4 mm in carapace width(KPM NH 7123), and possess all the non-sexual charactersof smaller specimens. We are confident they are conspecific.
Manning & Holthuis (1981: 170) suggested that because of
the substantial size differences observed between the reported
specimens of “Hexapus latipes” from Japan, it seemed there
are possibly two species present there. We now know thatthe small ones are merely juvenile females. However, theseauthors are not incorrect that there is more than one species

Distribution. Kii Peninsula, Enoshima Island, Aichi
Prefecture, Japan. Subtidal, 27 m.
Hexapinus ceres, new species(Figs. 14, 15)Material examined. Holotype: female (5.2 × 3.2 mm) (NMCR
39070), dive site at Basura, Anilao, Batangas, Philippines, 5 m,coll. H. Takakura, 22 August 2011.

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Diagnosis. Carapace subquadrate, about 1.6 times as
broad as long, dorsal surface granulated; regions indistinct,
median depression shallow (Fig. 14A). Lateral margin withprotuberance medially (Figs. 14A, 15A). Eye small, slightly
movable, cornea globular, wider than tuberculate peduncle(Fig. 14C). Pterygostomial region with row of oblique striae.
Third maxillipeds with outer surface tuberculate (Figs. 14D,
15B); ischium almost as long as merus, with rounded mesial
margin; dactylus missing; exopod short, broad, more than 0.5
times width of ischium, flagellum well developed. Chelipeds
slender (Fig. 14C, D) with slight gap when fingers closed.
P2–P4 (Fig. 14A, B) short, stout, covered by tubercles;
merus of P4 2 times as long as broad; dactylus of P2–P4
slightly longer than propodus, upper margin tuberculate.
Female thoracic sternum relatively broad (Fig. 14B, D),sternites 1 and 2 fused, separated from sternite 3 by distinct
ridge; sternite 3 separated laterally from sternite 4, appears
medially fused, sternites 4–7 well developed, separated by
distinct sutures. Female abdomen relatively broad (Figs.
14B, D, 15C) with 6 free somites and telson. Male unknown.
Colour. Not known.
Etymology. From the Latin “ceres” for grain; alluding to
the granular dorsal carapace surface. The name is used asa noun in apposition.
Remarks. Although this species is known from only one
female specimen, it can be placed in Hexapinus mainly on
the basis of the form of the ischium and merus of the third

Fig. 14. Hexapinus ceres, new species, holotype female (5.5 × 3.3 mm) (NMCR 39070). A, overall view of carapace, left cheliped andP2–P4; B, ventral view of cephalothorax; C, frontal view of cephalothorax; D, abdomen and telson.

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Fig. 15. Hexapinus ceres, new species, holotype female (5.5 × 3.3 mm) (NMCR 39070). A, anterior view of carapace; B, left third
maxilliped (dactylus missing); C, abdomen and telson. Scale bars = 1.0 mm.

eye small, slightly movable, cornea pigmented (Fig. 16C).
Pterygostomial region with row of oblique striae. Third
maxillipeds relatively broad (Figs. 16B, 17B); ischium 1.1
times as broad as long, longer than merus, strongly expanded
distomesially, with rounded mesial margin; combined lengthof dactylus, propodus and carpus shorter than that of merus
and ischium; exopod narrow, about 0.3 times width ofischium, flagellum well developed. Chelipeds stout, unequal(Fig. 16C); major chela gaping when fingers closed; palmslightly wider than long, outer surface smooth, tubercles on
upper margin; minor chela with narrower gap between closed
fingers (Fig. 16C). P2–P4 (Fig. 16A) short, stout, P3 longest;merus of P4 about 2 times as long as broad; dactylus longer
than propodus; dactylus of P4 slightly upcurved. Female
thoracic sternum broad (Figs. 16B), sternites 1 and 2 fused,
separated from sternite 3 by distinct ridge; sternite 3 separated
from sternite 4 by distinct ridge. Female abdomen broad(Figs. 16B, 17C) with 6 free somites and subtriangular telson.

maxilliped (Fig. 15B), although the mesial margin of theischium is relatively less convex compared to its congeners.
Its exopod is also broad like its congeners although it isrelatively shorter (Fig. 15B). It shares the pereopod condition
with other Hexapinus species: the P2–P4 are short and stout
with the dactylus slightly longer than propodus, and the merusof P4 is about twice as long as broad, without a longitudinalgroove (Fig. 14A). A male specimen will nevertheless need
to be collected to confirm the generic position of this species.
Hexapinus ceres, new species, differs markedly from H.
latipes, H. latus, new species, and H. simplex, new species,in having numerous closely spaced tubercles on the carapace,chelipeds and P2–P4.
Type locality. Batangas, Philippines.
Distribution. Batangas, Philippines. Subtidal, 5 m.
Hexapinus latus, new species(Figs. 16, 17)

Colour. In life, the carapace and appendages are creamishwhite overall.

Material examined. Holotype: female (8.1 × 5.0 mm) (MZB Cru
3918), Kecinan, Lombok, Indonesia, coll. 15 May 2007. Paratype:Indonesia: 1 female (6.5 × 4.0 mm) (ZRC 2013.1691), Sira,
northern Lombok, Indonesia, coll. 21 July 2009.

Etymology. From the Latin latus for broad/wide, alluding
to the broad carapace.
Remarks. Although only female specimens were available,
this species clearly belongs to Hexapinus as it has a broad
and mesially convex ischium of the third maxilliped, and
the P2–P4 are short. The broad carapace of H. latus, newspecies, is similar to H. simplex, new species. However,comparisons of similar-sized females show that H. latus has
a proportionately broader abdomen with the telson as longas somite 6 (Fig. 17C) while in H. simplex the abdomen isnarrow and the telson is shorter than the sixth abdominal
somite (Fig. 21D). In addition, the merus of the third
maxilliped of H. latus is shorter than the ischium (Fig. 17B),

Diagnosis. Carapace subquadrate, about 1.6 times as broadas long, dorsal surface very smooth, region indistinct,
median H-shaped depression shallow; some small granules
present on dorsolateral margins, only scattered tiny granules
on posterior margin (Fig. 16A). Anterolateral margin
arcuate, posterolateral margin sinuous with 1 protuberance;
posterolateral corner with angled prominence over baseof posterior pereopods; lateral margin of carapace wall
produced medially. Front deflexed (Fig. 16C). Orbit distinct,
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Fig. 16. Hexapinus latus, new species, holotype female (8.1 × 5.0 mm) (MZB Cru 3918). A, overall view of carapace, chelipeds andP2–P4; B, ventral view of cephalothorax; C, frontal view of cephalothorax.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 17. Hexapinus latus, new species, holotype female (8.1 × 5.0 mm) (MZB). A, dorsal view of carapace; B, left third maxilliped; C,abdomen and telson. Scale bars: A, C = 1.0 mm; B = 0.5 mm.

Hexapinus simplex, new species(Figs. 1A–F, 18–21)

while in H. simplex, the merus is longer than the ischium(Fig. 20G). The posterolateral margin of the carapace ofH. latus has only one protuberance (Fig. 16A) while in H.
simplex it always has two protuberances (Fig. 18B). The
dorsal carapace surface of H. latus is very smooth (Fig.
16A); specimens of H. simplex the size of H. latus on theother hand, are always distinctively pitted (Fig. 18).

Hexapus (Hexapus) sexpes – Sakai, 1976: 554 (part), pl. 196, fig.
2. (not Cancer sexpes Fabricius, 1798)
Material examined. Holotype: male (7.8 × 5.0 mm) (MZBCru
3790), Ekas, Lombok, 8°52'9"S 116°27' 26.1"E, Indonesia, coll.
15 October 2007. Paratypes: Indonesia: 4 males (8.0 × 5.6 mm,
6.4 × 4.4 mm, 5.6 × 3.8 mm, 5.1 × 3.5 mm), 2 females (6.9 × 4.5
mm, 5.3 × 3.5 mm), 1 ovigerous female (10.9 × 6.7 mm) (MZB
Cru 3791); 3 males (6.4 × 4.4 mm, 5.1 × 3.5 mm, 4.5 × 3.1 mm),
2 females (10.0 × 6.0 mm, 6.7 × 4.5 mm)(ZRC 2012.1015), 1
ovigerous female (10.9 × 7.1 mm) (ZRC 2009.750), Ekas, eastern
Lombok, 8°52'9"S 116°27' 39"E, 15 October 2007; 1 male (5.4 × 3.4mm), 2 females (4.5 × 2.8 mm, 6.9 × 4.5 mm) (ZRC 2013.1689),
Ekas, eastern Lombok, 8°52'9"S 116°27' 39"E, coll. 22 July 2009;
5 males (7.3 × 5.0 mm – 8.5 × 5.8 mm), 5 females (4.1 × 2.9mm – 8.9 × 5.9 mm) (USNM), Ekas, eastern Lombok, 8°52'9"S116°27' 39"E, coll. 22 July 2009. Others: Indonesia: 28 males(3.3 × 2.0 mm – 8.7 × 5.0 mm), 22 females (3.8 × 2.3 mm – 9.2
× 5.3 mm), 7 ovigerous females (9.5 × 5.3 mm) (MZB Cru 3919);
30 males (4.6 × 3.0 mm – 8.5 × 5.1 mm), 20 females (5.3 × 3.5
mm – 9.1 × 5.7 mm), 6 ovigerous females (8.0 × 4.8 mm – 8.7 ×
5.8 mm) (ZRC 2010.0297), Ekas, eastern Lombok, coll. 22 July
2009; 1 male (9.3 × 5.8 mm) (ZRC), Lembeh Straits, Sulawesi,
subtidal, diving, coll. H. H. Tan, 17 July 2003. Singapore: 1
female (11.9 × 7.3 mm) (ZRC 2013.1686), St. John Island, northlagoon, 1°13.116'N 103°51.079'E, coll. P. K. L. Ng & A. Anker,
yabby pump, 31 May 2013; 1 ovigerous female (8.3 × 6.0 mm)(ZRC 2013.1687), DR2, Raffles Reserve near Raffles Lighthouse,
1°10'273N 103°45'613E, coll. RV Galaxea, 20 May 2013; 1 male
(11.2 × 7.0 mm) (ZRC), station Sen-AA04, Pulau Senang, northernside near jetty, intertidal sand-mud flat with abundant rubble androcks, 01°10.504'N 103°44.1790.5'E, 0.5 m, from burrow together
with chaetopterid worm, coll. A. Anker, yabby pump, 30 March
2014; 1 male (6.0 × 3.6 mm) (ZRC), station grid 0523 DR3 AA19,
sandy with broken shell substrate, between Pulau Tekong East andPengerang, 01°23.914'N 104°05.353'E – 01°24.141'N 104°05.400'E,
10.6-10.7 m, trawl, coll. S. C. Lim et al., 25 March 2014. China: 3
females (10.0 × 6.2 mm, 13.7 × 7.7 mm, 11.5 × 6.7 mm) (MNHN),
station 57K29, coastal waters of Guangdong Province, off Longwo,

Although H. latus was collected in the same island as H.
simplex, the differences discussed above argue against them
being conspecific. The habitats of also appear to be somewhat
different. The specimens of H. latus were collected fromcoarse white sand in shallow depressions in the reef flat.
The area had previously been mined for building material
by local villagers. The area is always filled with some water,even during low tide. Hexapinus simplex on the other handseems to prefer finer substrates (see next species).
Hexapinus latus also differs from H. latipes in having broad
female abdomen. In a female specimen of H. latipes (10.2
× 7.6 mm, NSMT-Cr 5694), which is slightly larger than
the female type specimens of H. latus, the abdomen is still
narrow and resembles that of a male (Fig. 17C versus Fig.
13G). The female abdomens of both H. latus and H. ceres,
even though they are relatively small, are already broad.
Hexapinus latus and H. ceres are easily distinguished; thecarapace surface, chelipeds and P2–P4 of H. latus are smooth(Fig. 17A) but in H. ceres, these are covered with closely
spaced granules (Fig. 14A).
Type locality. Kecinan, Lombok, Indonesia
Distribution. North coast of Lombok Island, Indonesia.
Intertidal.

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Fig. 18. Hexapinus simplex, new species. A, B, holotype male (7.8 × 5.0 mm) (MZB Cru 3790); C, paratype female (6.9 × 4.5 mm) (MZB3791). A, C, overall view of carapace, chelipeds and P2–P4; B, carapace.

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Fig. 19. Hexapinus simplex, new species, holotype male (7.8 × 5.0 mm) (MZB Cru 3790). A, frontal view of cephalothorax; B, ventral
view of cephalothorax; C, abdomen and telson; D, chelae.

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China Sea. Japan: 1 female (9.2 × 7.4 mm) (RUMF-ZC-2107),river mouth of Nakara River, Iriomote Island, coll. J. Nawa, 22
July 2005; 1 ovigerous female (16.1 × 11.1 mm) (RUMF-ZC-2108),
Oura Bay, Okinawa Island, in front of Camp Schwab, coll. 21 Jul.
2010; 1 female (13.6 × 8.1 mm), 1 male (12.6 × 8.4 mm) (RUMF-

South China Sea, coll. 22 April 1957; 1 male (12.7 × 7.5 mm), 1
female (12.5 × 8.2 mm) (ZRC 2012.1016), station 75C-2368, pearl
shell culture ground, Dongshan, Fujian Province, Taiwan Strait,
coll. 1 June 1975; 1 female (12.5 × 7.5 mm) (ZRC 2012.1017),
station 6160, southeast Hainan Island, 18°30'N 110°30'E, South

Fig. 20. Hexapinus simplex, new species, holotype male (7.8 × 5.0 mm) (MZB Cru 3791). A, carapace; B, thoracic sternites 1–5, showing
thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternal groove and telson; D, anterior view of cephalothorax; E, majorchela; F, minor chela; G, left third maxilliped. Scale bars = 1.0 mm.

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mesial margin; combined length of dactylus, propodus andcarpus shorter than that of merus and ischium; exopod broad,about 0.5 times width of ischium, flagellum well developed.
Chelipeds stout, unequal (Fig. 19A, D), dactylus with tufts
of setae on upper margin proximally; major chela (Fig. 20E)
slightly gaping when fingers closed; palm slightly wider thanlong, surface covered with tubercles on upper half; minor
chela (Fig. 20F) with wider gap between closed fingers.
P2–P4 (Fig. 18A, C) short, stout, P3 longest; merus of P4
1.9 times as long as broad; dactylus of P2–P4 straight. Male
thoracic sternum broad (Figs. 19B, C, 20B, C), sternites
1 and 2 fused, separated from sternite 3 by distinct ridge;
sternite 3 separated from sternite 4 laterally, medially appear
fused, short thoracic sternal groove, extends obliquely fromsternoabdominal cavity to middle of sternite 3 to below
base of third maxilliped (Fig. 20B, C); sternite 8 exposed,
triangular, half length of abdominal somite 1; sternoabdominal
cavity reaches base of sternite 2 (Fig. 20C). Male abdomen
relatively narrow (Figs. 19B, C, 21E–G), somites 1 and 2
free; somites 3–5 fused, lateral margin sinuous; somite 6
sligthly shorter than length of somites 3–5, lateral margin
sinuous; telson subpentagonal with setose margin. G1 (Fig.
21A, B) bent submedially, directed anterolaterally, distal
part tapered, glabrous or with sparse short setae, apices
not concealed under abdomen, exposed on thoracic sternal

ZC-2110), Tekebu, Amami Island, coll. T. Maenosono, 25 April
2012; 2 males (10.7 × 7.1 mm, 10.9 × 7.2 mm), 1 female (12.4 ×
7.4 mm) (RUMF-ZC-2109), Funaura Bay, Iriomote Island, coll.
T. Naruse, 12 and 17 Jun. 2007; 1 male (12.6 × 8.4 mm) (ZRC
2013.1688), Funaura Bay, Iriomote Island, coll. T. Naruse, 1 July
2011; 2 females (13.0 × 8.2 mm, 12.5 × 8.1 mm), 1ovigerous female(12.9 × 7.9 mm) (ZRC 2012.1018), Tekebu, Amami Island, coll.
T. Maenosono, 27 Apr. 2012;1 male (13.1 × 8.0 mm), 10 females(12.2 × 7.3 mm – 15.3 × 8.7 mm), 3 ovigerous females (13.3 × 7.8mm – 13.8 × 8.0 mm) (RUMF-ZC-2111) Tekebu, Amami Island,coll. T. Maenosono, 27 April 2012.

Diagnosis. Carapace subquadrate, about 1.5–1.6 times as
broad as long, dorsal surface finely pitted to smooth, regions
indistinct, median H-shaped depression shallow; somegranules present on dorsolateral margins, only scattered
granules on posterior margin (Figs. 18, 20A). Anterolateral
margin arcuate, posterolateral margin sinuous with 2
protuberances; posterolateral corner with angled prominenceover base of posterior pereopods. Front deflexed, fringed
medially with setae (Fig. 19A). Eye small, slightly movable,
cornea pigmented (Figs. 19A, 20A). Pterygostomial region
with row of oblique, broken and entire, striae (Fig. 20D).
Third maxillipeds relatively broad, densely setose (Figs. 19B,
20G); ischium 1.1 times as broad as long, slightly shorter
than merus, strongly expanded distomesially, with rounded

Fig. 21. Hexapinus simplex, new species. A, B, F, holotype male (7.8 × 5.0 mm) (MZB); C, paratype female (6.9 × 4.5 mm) (ZRC
2013.1689); D, paratype female (4.5 × 2.8 mm) (ZRC 2013.1689); E, paratype male (5.4 × 3.4 mm) (ZRC 2013.1689); G, male (12.7 ×
7.5 mm)(ZRC 2012.1016). A, B, G1; C, D, female abdomen and telson; E–G, male abdomen and telson. Scale bars = 1.0 mm.

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With regards to the male thoracic sternal groove, the condition
does not vary in Hexapinus simplex, even when the specimens
are small. All the male specimens, however, have distinct G1
structures suggestinng none of them are immature.

groove, obscured by setae of telson. Female abdomen (Fig.
21C, D) with 6 free somites and rounded telson.
Colour. Fresh specimens from Lombok, Indonesia, arebrownish grey in colour (Fig. 1A). One specimen collectedby diving from Sulawesi is a striking bright orange (Fig.
1B). Those from Amami Island, Ryukyus, Japan, are brown,with the chelipeds, and P2–P4 light brown (Fig. 1C). The
specimen from Iriomote Island, Ryukyus, has a reddish
brown carapace and light brown chelipeds and P2–P4 (Fig.
1D). Specimens from Singapore are light to greyish-brownon the dorsal surfaces (Fig. 1E, F).

Biological notes. In Lombok, specimens were collected bysieving substrates consisting of mud, fine and coarse sandin intertidal areas, among frames established for seaweed
culture. In Singapore, the specimens were collected byyabby pumping and dredging on sandy mud substrates. The
specimens from the Ryukyus were collected from burrows
in intertidal seagrass beds by using yabbie pumps. The
specimens from Amami-Ohshima were collected from tubesof chaetopterid worms. Zehntner (1984) and Sakai (1976)
observed the association of their specimens of “Hexapus
sexpes” with annelid tubes.

Etymology. The species name is derived from the relatively
simple appearance of the carapace and G1.
Remarks. Hexapinus simplex, new species, is easily
distinguished from other species in the genus by having thelateral margin of the carapace arcuate anterolaterally and theposterolateral margin sinuous with two distinct protuberances(Figs. 18B, 20A). In H. latipes and H. latus, there is only
one protuberance on posterolateral margin (Figs. 10A, 11A,
12A, 13A, 16A, 17A), while in H. ceres the protuberance ison the median part of lateral margin of the carapace (Figs.
14A, 15A).

Type locality. Ekas, Lombok, Indonesia.
Distribution. South coast of Lombok Island, Indonesia;
Singapore; Ryukyu Islands, Japan; South China Sea; andTaiwan Strait. Intertidal and subtidal.
Mariaplax, new genus
Diagnosis. Carapace broader than long, surface granular,
region indistinct, H-shaped medial depression shallow.
Anterolateral margin arcuate; pterygostomial region withrows of long and short, broken or entire, oblique striae andscattered tubercles. Eyes small, slightly movable, corneas
subglobular. Third maxilliped broad, completely covering
buccal cavity; ischium longer than merus, mesial margin
straight, oblique, or very slightly rounded; carpus, propodus
and dactylus cylindrical, dactylus longer than propodus;
exopod narrow compared to width of ischium, flagellum
present. Chelipeds equal or subequal. P2–P4 relatively long;merus slender, usually with distinct median groove on lateralsurface on some of legs; dactylus straight or upcurved, aslong as propodus. Thoracic sternites 1 and 2 fused, sternite 3
partly or completely separated from sternite 4 by tuberculateridge, sternite 8 exposed, triangular or subrectangular, as
long as or half length of first abdominal somite. Male
sternoabdominal cavity reaches distal margin of thoracic
sternite 4; thoracic sternal groove oblique, short or long,straight or curved, wide or narrow, sometimes reaches baseof cheliped. Male abdomen relatively narrow; somites 1, 2
and 6 free, somites 3–5 fused; telson shorter than somite 6,
subtriangular to subpentagonal, distal margin rounded. G1curved or twisted, more or less S-shaped, apice exposedon thoracic sternal groove, not concealed under abdomen.
Female abdomen with 6 free somites and telson.

Hexapinus simplex is also different from H. latipes by the
relatively shorter ischium of the third maxilliped with morestrongly convex mesial margin, with merus as broad as long
(Fig. 20G versus Fig. 13C). Furthermore the carapace of
H. simplex is broader (1.5–1.6 times as broad as long), thesurface smooth with some granules on dorsolateral surface
and posterolateral margin. In H. latipes the carapace is moresquarish (1.2–1.3 times as broad as long) and the carapace
surface is more heavily pitted with only a few granules on
dorsolateral surface.
Hexapinus simplex is the only species in the genus in whichmales were available for study. In all adult specimens, themale abdomen is slender with a long somite 6 that is almost
as long as the entire length of fused somites 3–5 (Fig. 21G).
In adults, the length of somite 6 does not vary with the size
although the shape of male telson varies slightly (Fig. 21E–G).
In one small male (5.4 × 3.4 mm, ZRC 2013.1689), the telson
is only very slightly subpentagonal with the distal marginrounded (Fig. 21E); in the holotype male (7.8 × 5.0 mm,
MZB Cru 3790), it is subpentagonal with a rounded distal
magin (Fig. 21F), while in larger specimens (e.g., male 12.7
× 7.5 mm, ZRC 2012.1016) is more rounded (Fig. 21G). The
abdomen of a small paratype female from Lombok (4.5 ×
2.8 mm, ZRC 2013.1689) is interesting as it is narrow andresembles that of a male except it is relatively shorter andless narrow (Fig. 21D). In this specimen, which is clearly ajuvenile female, the sutures between somites 3–5 are shallow
but are complete although all the somites do not appear to
articulate very freely. This is the same condition observedin juvenile female of Hexapinus latipes (see discussion forthat species). Male specimens of Hexapinus simplex, evenwhen juvenile, on the other hand, always have elongate
and slender abdomens with somites 3–5 completely fused.

Etymology. We dedicate this new genus to Mary J. Rathbun
who described Lambdophallus anfractus, the type species.
The name “Mariaplax” is derived from “Maria”, the Latin ofher first name Mary, and “-plax”, a typical suffix for many
crab genera. Gender of genus feminine.
Species included. Lambdophallus anfractus Rathbun, 1909
(type species by present designation), M. chenae, new species,423

Rahayu & Ng: New genera and species of Hexapodidae1976), which was placed in Tritoplax by Huang et al. (2002)
and Ng et al. (2008), should be transferred to Mariaplax.

M. cyrtophallus, new species, M. daviei, new species, M.
galaxeae, new species, Hexapus granuliferus Campbell &Stephenson, 1970, M. mica, new species, M. narusei, newspecies, M. ourabay, new species, M. propinqua, new species,
M. secus, new species, M. sinensis, new species, Hexapus
stephenseni Serène & Soh, 1976, and M. streptophallus,
new species.

Mariaplax anfracta (Rathbun, 1909), new combination(Figs. 22, 23)
Lambdophallus anfractus Rathbun, 1909: 113; Rathbun, 1910: 348,
fig. 36; Guinot, 1979: fig. 33F.
Hexapus anfractus – Manning & Holthuis, 1981: 172, fig. 33; Nget al., 2008: 86.

Remarks. Rathbun (1909) assigned her new species toLambdophallus without any comments. Manning & Holthuis(1981) transferred Lambdophallus anfractus to Hexapus on
the basis of the G1 shape, and the shape and extension of
the male thoracic sternal groove. However, as discussed
for Mariaplax chenae, new species (see later), the form of
the male thoracic sternal groove sometimes varies with thesize of the specimen.

Material examined. Paratypes: Thailand: 1 male (5.0 × 3.2 mm),
1 female (6.1 × 4.0 mm), 1 ovigerous female (6.6 × 4.3 mm)(USNM 39752), west coast of Koh Chang, Gulf of Thailand, 6fms, 26 January 1900. Others: Thailand: 1 female (5.2 × 3.4 mm)(ZRC 2012.1019), sand flat, Ko Sirae, Phuket, coll. T. Komai, 22
December 2009. Malaysia: 1 ovigerous female (4.1 × 2.8 mm)(ZRC 1965.11.24.6), Penang Strait.

Lambdophallus anfractus shares a unique suite of third
maxilliped, ambulatory leg, male abdominal and G1 characterswith Hexapus granuliferus Campbell & Stephenson, 1970,
and H. stephenseni Serène & Soh, 1976, as well as 11 new
species from the Indo-West Pacific. These characters argue
for establishing a new genus Mariaplax, for these species.

Diagnosis. Carapace subquadrate about 1.5 times as broadas long, dorsal surface finely granulated, punctate with shortpubescence; regions indistinct. Anterolateral margin arcuate,
gently granular; posterolateral margin with protuberance,
posterolateral corner with angled prominence over base ofposterior pereopods. Orbit distinct, transverse; eye almost
immovable. Pterygostomial region covered by granules andwith row of 4 striae. Third maxillipeds broad, completely
covering buccal cavity; ischium almost as long as broad,slightly longer than merus, with scattered granules, mesial
margin straight; exopod narrow. Chelipeds asymmetrical,
major chela slightly gaping when fingers closed; large teeth
on cutting edge of dactylus and fixed finger; minor chela withrelatively wider gap when fingers closed. P2–P4 tomentose,
surfaces granulated, P3 stoutest, longest; merus of P4 2.5times as long as broad, with distinct median groove on lateralsurface. Male thoracic sternum relatively broad, surface finely
granular; deep, wide transverse groove extends obliquelyfrom edge of sternoabdominal cavity, subparallel to frontal
margin, not reaching base of chelipeds. Sternoabdominal
cavity reaching distal margin of thoracic sternite 4. Male
abdomen relatively narrow, surface granular, somites 1 and
2 free; somites 3–5 fused, lateral margin slightly arched;somite 6 as long as wide, lateral margin expanded into blunt
triangular projection subproximally; telson subtriangular,
distal margin rounded, sparsely setose. G1 S-shaped, distal
part tapered, sparse short setae present medially; distal part
exposed on thoracic sternal groove, not concealed underabdomen. Female abdomen relatively broad, with 6 somites
free and telson.

Mariaplax, new genus, differs markedly from Lambdophallus
in that it has slightly movable eyes, with globular
corneas (versus immovable eyes with small corneas in
Lambdophallus); the male telson is shorter than the sixth
abdominal somite (Fig. 23C) (versus the telson is longer than
the sixth abdominal somite in Lambdophallus, Alcock, 1902:
pl. 62, fig. 1); and the G1 is usually twisted and S-shapedin Mariaplax (see Fig. 23F, G) (with the exception of M.
cyrtophallus, new species and M. secus, new species) (versus
sharply bent at a 90° angle and L-shaped in Lambdophallus,
Alcock, 1902: pl. 62, fig. 1).
Mariaplax differs from Hexapus s. str. as follows: the third
maxilliped of Mariaplax is broad, completely covering the
buccal cavity, and the ischium is as broad as the merus (Fig.
23D) (the third maxilliped is longitudinally narrow, showing
most of the underlying mouthparts, with the ischium muchnarrower than the merus in Hexapus, Fig. 4E); P2–P4 isrelatively longer, with the merus usually possessing a shallow
or deep longitudinal groove on the outer surface in Mariaplax(the groove on outer surface of P2–P4 is absent in Hexapus).
Hexapinus s. str. differs from Mariaplax in possessing asubauriculiform ischium of the third maxillipeds (Fig. 13C)
(subtruncate or subquadrate ischium in Mariaplax, Fig. 23D),a male thoracic sternite 4 which is transversely narrower
but longitudinally broader (Fig. 10B) (transversely broader
but longitudinally narrower in Mariaplax, Fig. 23B, C), andthe short P2–P4 with almost evenly convex lateral surface(Figs. 11A, 12A) (long P2–P4 with longitudinal groove on
the outer surface of the merus in Mariaplax, Fig. 22A, C).

Description. Carapace subquadrate about 1.5 times as broadas long, dorsal surface finely granulated, punctate with shortpubescence; regions indistinct, with shallow median H-shaped
depression (Fig. 22A, C). Anterolateral margin arcuate,
gently granular; posterolateral margin with protuberance,
posterolateral corner with angled prominence over base ofposterior pereopods (Figs. 22A, C, 23A). Front deflexed,
divided into 2 lobes, not projecting beyond edge of orbits(Fig. 22B). Orbit distinct, transverse; eye almost immovable,
small, cornea pigmented, wider than peduncle. Pterygostomial

As discussed earlier, Hexapus granuliferus Campbell &Stephenson, 1970, originally placed in Hexapinus by Manning& Holthuis (1981), and Hexapus stephenseni (Serène &Soh,

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region covered by granules and with row of oblique striae.
Third maxillipeds broad (Fig. 23D), completely covering
buccal cavity; ischium almost as long as broad, slightly
longer than merus, with scattered granules, mesial margin
straight, narrow proximal part very short, about one-tenthlength of ischium, dactylus, propodus and carpus cylindrical,
dactylus longer than propodus, combined length of dactylus,
propodus and carpus slightly longer than that of merus andischium; exopod narrow, about 0.4 times width of ischiumslightly granular, flagellum well developed.

Chelipeds asymmetrical (Fig. 22B). Major chela (Fig. 23E)
slightly gaping when fingers closed; large teeth present on
cutting edge of dactylus and fixed finger; outer surface ofdactylus with shallow, narrow groove medially, small granules
and sparse setae present proximally; inner surface near upper
margin with longitudinal ridge; palm almost as long as wideor slightly longer than wide, surface finely tuberculate; carpus
glabrous dorsally, inner angle blunt, unarmed; merus short,unarmed, fringe of setae dorsomesially. Minor chela withrelatively wider gap when fingers closed; cutting edge of

Fig. 22. Mariaplax anfracta (Rathbun, 1909). A, B, paratype female (6.1 × 4.0 mm) (USNM 39752); C, paratype male (5.0 × 3.2 mm)(USNM 39752). A, C, overall views of carapace, chelipeds and P2–P4; B, frontal view of cephalothorax.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 23. Mariaplax anfracta (Rathbun, 1909). A–G, paratype male (5.0 × 3.2 mm) (USNM 39752); H, female (4.1 × 2.8 mm) (ZRC
1965.11.24.6). A, dorso-lateral margin of carapace; B, thoracic sternites 1–4, showing sternoabdominal cavity and thoracic sternal groove;C, thoracic sternites3 and 4, showing thoracic sternal groove and telson; D, right third maxilliped; E, major chela; F, G, G1; H, female
abdomen and telson. Scale bars = 1.0 mm.

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Records of “Hexapus anfractus” from China by Huang(1994: 592) and Yang et al. (2008: 772) cannot be reliably
identified and are probably mixed. Specimens from China
we have examined that have been identified as this species
belong to two new species, Mariaplax chenae and M. sinensis.

dactylus and fixed finger with row of moderately large teeth;
dactylus with tubercles on upper half of outer surface; innersurface with longitudinal ridge near upper margin; outersurface of fixed finger with longitudinal ridge; dorsal surfaceof palm covered by granules, carpus and merus unarmed,
fringe of sparse setae on each dorsomesial margin.

Type locality. West coast of Koh Chang, Gulf of Thailand.

P2–P4 tomentose, surfaces granular (Fig. 22A, C). P2 most
slender; dactylus gently upcurved, fringe of long setae on
upper and lower margins, slightly shorter than propodus;
propodus with row of tiny tubercles on upper and lower
margins with long setae; carpus longer than propodus,
unarmed, tufts of setae distally; merus twice length of
carpus, upper and lower outer surface with rows of granules
accompanied by tufts of long setae, shallow longitudinalgroove on outer surface medially. P3 stouter and longer
than P2; dactylus straight, longer than propodus; propodus
and carpus with long setae on upper and lower margins, andmost of upper outer surface; merus slightly more than twice
length of carpus, upper and lower outer surfaces with rowsof granules accompanied by tufts of long setae, shallow
longitudinal groove on outer surface medially. P4 stouter andshorter than P3, dactylus gently upcurved; upper and lower
outer surface of propodus and carpus with rows of granules
obscured by tufts of long and short setae; merus slightly
twice length of carpus, 2.5 times as long as broad, upperand lower outer surfaces with rows of granules obscured bytufts of long and short setae, shallow longitudinal grooveon outer surface medially.

Distribution. Gulf of Thailand, Phuket; and Penang Strait,
Malaysia. Intertidal to 12 m.
Mariaplax chenae, new species(Figs. 1H, 24–27)
Hexapus (Hexapus) granuliferus – Dai et al., 1986: 388, pl. 56(5),text fig. 205(1-2); Dai & Yang, 1991: 418, pl. 56(5), text fig.
205(1–2). (not Hexapus granuliferus Campbell & Stephenson,
1970)
Hexapus granuliferus – Liu & He, 2007: 149, unnumbered figure.
(not Hexapus granuliferus Campbell & Stephenson, 1970)
Hexapinus granuliferus – Yang et al., 2008: 771.
Hexapus (Lambdophallus) anfractus – Sakai, 1976: 554, pl. 196,
fig. 3. (not Lambdophallus anfractus Rathbun, 1909)
Material examined. Holotype: male (9.2 × 6.1 mm) (IOCAS),
station 1066 (R578B-23), coastal waters of Zhejiang Province,
East China Sea, China, 39 m, soft mud, coll. AT & J. Xu, 27
August 1960. Paratypes: China: 1 male (4.0 × 2.7 mm) (ZRC
2012.1020), station 9 (K 56A-7), Jiaozhou Bay, southern coast of
Shandong Peninsula, Yellow Sea, very likely 36°06'N 120°17'E,
11 m, soft mud, 5 September 1979; 1 female (5.3 × 3.5 mm)(ZRC 2012.1021), station 23 (WC38B-10), coastal water outside
Dongtou Island, Zhejiang Province, East China Sea, 4 m, soft mud,coll. AT, Y. Cui & Y. Wu, 8 October 1979; 1 male (5.3 × 3.6 mm)(ZRC 2012.1022), station 29 (WC26B-56), coastal waters outside
Dongtou Island, Zhejiang Province, East China Sea, 12 m, soft
mud, coll. AT, Y. Cui & Y. Wu, 3 October 1979; 2 males (9.9 × 6.7
mm, 7.1 × 4.8 mm), 1 female (8.2 × 5.4 mm) (ZRC 2012.1023),
off Xiamen, Fujian Province, soft mud, 13 Aug. 1981. Others:
China: 1 female (4.4 × 2.3 mm) (ZRC 2012.1024), station 817,
Wutong, Xiamen, Fujian Province, mud, 5 m, coll. 18 May 1981;
1 female juvenile (3.3 × 2.1 mm) (ZRC 2012.1025), station 4071,
East China Sea, soft mud, 8 mm, coll. Y. Cui, 10 December 1979; 1
female (6.0 × 4.0 mm) (ZRC 2012.1026), East China Sea, soft mud,
20 m, coll. Y. Cui, 14 December 1979; 1 female (6.4 × 4.3 mm)(ZRC 2012.1027), station 40, Jiaozhou Bay, Qingdao, Shandong,
soft mud, 12 m, coll. Y. Cui, 7 September 1979; 1 female (5.0 ×
3.4 mm) (ZRC 2012.1028), station 819, Wutong, Xiamen, Fujian
Province, mud, 6 m, 15 July 1981; 2 females (7.7 × 5.2 mm, 8.6
× 5.8 mm) (ZRC 2012.1029), Xiamen Harbour, Fujian Province,
February 1988; 2 females (4.4 × 2.5 mm, 4.5 × 2.9 mm) (ZRC
2012.1030), Xiamen Harbour, Fujian Province, coll. April 1988.
Japan: 1 female (10.8 × 7.5 mm) (NSMT-Cr. 8229), Suo-nadaSea, Seto Inland Sea, coll. T. Habe; 1 male (9.5 × 6.5 mm) (ZRC
1970.1.20.26), Anake Bay, Nagasaki, coll. T. Sakai, 1967; 1 female(NSMT-Cr 6894), Amakusa, Ike-jima Island, Matsu-shima, coll.
Y. Fukuda, 10 June 1979.

Male thoracic sternum relatively broad (Fig. 23B, C),surface finely granular; sternites 1 and 2 fused, separated
from sternite 3 by distinct ridge; sternite 3 separated fromsternite 4 by distinct ridge; deep, wide transverse groove
extends obliquely from edge of sternoabdominal cavity(Fig. 23B), thoracic sternal groove subparallel to frontal
margin, not reaching base of chelipeds; sternite 8 exposed,
rectangular, equal to length of male abdominal somite 1;
sternoabdominal cavity reaching distal margin of thoracic
sternite 4 (Fig. 23B). Male abdomen relatively narrow (Fig.
23C), surface granular, somites 1 and 2 free; somites 3–5
fused, lateral margin slightly arched; somite 6 as long as
wide, lateral margin expanded into blunt triangular projection
subproximally; telson subtriangular, distal margin rounded,sparsely setose (Fig. 23C).
G1 (Fig. 23F, G) S-shaped, distal part tapered, sparse shortsetae present medially; distal part exposed on thoracic sternalgroove, not concealed under abdomen.
Female abdomen relatively broad, with 6 free somites andsubtriangular telson (Fig. 23H).
Colour. Not known.

Diagnosis. Carapace subquadrate, about 1.5 times as
broad as long, dorsal surface granulated; regions indistinct,
median H-shaped depression shallow (Figs. 24A, 25A). Eye
small, slightly movable, cornea not pigmented (Fig. 24B).
Pterygostomial region with long and short, oblique striae andRemarks. Mariaplax anfracta, new combination, is a small
sized species. One paratype female and a non-type female
from Penang, both ovigerous, measured less than 7 mm incarapace width.

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Fig. 24. Mariaplax chenae, new species, holotype male (9.2 × 6.1 mm) (IOCAS). A, overall view of carapace, chelipeds and P2–P4; B,
frontal view of cephalothorax; C, abdomen and telson; D, chelae.

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scattered tubercles (Fig. 25B). Third maxillipeds relatively
broad, almost completely covering buccal cavity (Figs. 25E,
26D, 27F); ischium longer than merus, distalmost mesial
margin slightly rounded, median part of mesial margin
straight; combined length of dactylus, propodus and carpus

shorter than that of merus and ischium; exopod relatively
narrow, about 0.4 width of ischium, flagellum well developed.
Chelipeds stout, unequal (Fig. 24D); major chela (Fig. 25G)
with gap when fingers closed; dactylus and fixed finger withshallow longitudinal groove on outer surface; palm almost as

Fig. 25. Mariaplax chenae, new species, A–J, holotype male (9.2 × 6.1 mm) (IOCAS); K, paratype female (8.2 × 5.4 mm) (ZRC 2012.1023).
A, dorso-lateral margin of carapace; B, anterior view of cephalothorax; C, thoracic sternites 3 and 4, showing thoracic sternal groove andtelson; D, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; E, left third maxilliped; F, male abdomen
and telson, G, major chela; H, minor chela; I, J, G1; K, female abdomen and telson. Scale bars = 1.0 mm.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 26. Mariaplax chenae, new species, paratype male (5.3 × 3.6 mm) (ZRC 2012.1022). A, thoracic sternites 1–5, showing sternoabdominal
cavity and thoracic sternal groove; B, thoracic sternites1–5, showing thoracic sternal groove and telson; C, male abdomen and telson; D,left third maxilliped; E, F, G1. Scale bars = 1.0 mm.

Fig. 27. Mariaplax chenae, new species, paratype male (4.0 × 2.7 mm) (ZRC 2012.1020). A, thoracic sternites 1–5, showing sternoabdominal
cavity and thoracic sternal groove; B, thoracic sternites 1–5, showing thoracic sternal groove and telson; C, D, G1; E, male abdomen andtelson; F, left third maxilliped. Scale bars = 1.0 mm.

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anfracta, the ischium is only slightly longer than merus, andalthough the lateral and mesial margins of the ischium areparallel, the narrow proximal part is very short, only about
one-tenth the length of the ischium (Fig. 23D). Although theG1 of M. chenae varied with individual size, the difference isnoticeable in the same size male individual of both species.
The G1 of M. chenae (male, 5.3 × 3.6 mm, ZRC 2012.1022)
is stout, tapering to twisted tip (Fig. 26E, F) while in M.
anfracta (male, 5.0 × 3.2 mm, USNM 39752), the G1 ismore slender, sinuous, the bent tip is longer, but not clearly
twisted (Fig. 23F, G).

long as broad covered by tubercles; minor chela (Fig. 25H)with relatively smaller gap when fingers closed. P2–P4 (Fig.
24A) short, relatively slender; merus of P4 3 times as long as
broad, tubercles on upper and lower halves of outer surface,
separated by longitudinal groove; dactylus of P4 slightly
upcurved. Male thoracic sternum relatively broad (Figs. 24C,
25C, D); sternites 1 and 2 fused, separated from sternite 3 bydistinct ridge; sternite 3 separated from sternite 4 by distinct
ridge laterally, medially appearing fused, thoracic sternalgroove extends obliquely from sternoabdominal cavity, notreaching base of third maxillipeds (Figs. 24C, 25D); sternite
8 exposed, subrectangular, as long as abdominal somite 1;
sternoabdominal cavity reaches middle to sternite 4. Male
abdomen relatively narrow (Figs. 24C, 25F); somites 1 and
2 free, somites 3–5 fused, lateral margin slightly sinuous;
somite 6 shorter than length of somites 3–5, lateral margin
expanded subproximally, forming triangular projection; telson
subtriangular, distal margin rounded, sparsely setose. G1(Fig. 25I, J) S-shaped distally, directed anterolaterally, distal
part tapering, slightly twisted, apice not concealed underabdomen, row of spinules on midlength laterally, long setae
on mesial and lateral margins. Female abdomen relatively
narrow, 6 free somites and telson (Fig. 25K).

Significantly, M. anfracta s. str. is also a much smaller
species, with males measuring 5.0 × 3.2 mm (USNM 39752)
already mature, and females measuring 4.1 × 2.8 mm (ZRC
1965.11.24.6) already ovigerous. Female specimens of M.
chenae of similar sizes are still immature.
The Chinese records of “Hexapus granuliferus” by Dai etal. (1986), Dai & Yang (1991) and Liu & He (2007), as
well as the Japanese records of “Hexapus (Lambdophallus)
anfractus” by Sakai (1976) are almost certainly M. chenae.
The figures provided in these references agree very well withwhat is here diagnosed for this species.

Variation. In larger individuals of M. chenae, new species(e.g., 9.2 × 6.1 mm, holotype, IOCAS), the male thoracic
sternal groove is relatively wider and longer, oblique, andreaching the middle of sternite 4 (Fig. 25C, D), and theG1 is curved medially with the tip twisted (Fig. 25I, J).
In a small individual (5.3 × 3.6 mm, ZRC 2012.1022), thethoracic sternal groove is slightly wider, shorter and oblique,but not reaching the middle of sternite 4 (Fig. 26A, B), theG1 curved at midlength, without row of spinules and thetip is only slightly twisted (Fig. 26E, F). In an even smaller
individual (4.0 × 2.7 mm, ZRC 2012.1020), the thoracic
sternal groove is very short, oblique, and barely extends
from the sternoabdominal cavity into sternite 4 (Fig. 27A,
B), with the G1 only slightly curved, tip not twisted (Fig.
27C, D). The shape of male abdomen, however, does notvary substantially with size (Figs. 25F, 26C, 27E).

Type locality. Coastal waters of Zhejiang Province, East
China Sea, China.
Distribution. East China Sea and Japan. Subtidal, 4–39 m.
Mariaplax cyrtophallus, new species(Figs. 28, 29)
Material examined. Holotype: male (6.5 × 4.2 mm) (MZB), off
Otakwa, Timika, Papua, Indonesia, near 05º01'32"S 137º10'56.7"E,
coll. A. Haris, 7 November 2000.

Diagnosis. Carapace subquadrate, about 1.5 times as broadas long, dorsal surface strongly granulated; regions indistinct,
with H-shaped shallow depression medially (Figs. 28A, 29A).
Eye small, slightly movable, cornea black, wider than granularpeduncle. Pterygostomial region (Figs. 28B, 29D) covered by
granules, with row of 5 oblique striae. Third maxillipeds broad(Figs. 28B, 29E), completely covering buccal cavity; ischiumslightly longer than merus, slightly expanded subproximally,
with oblique mesial margin, combined length of dactylus,
propodus and carpus almost as long as that of merus andischium; exopod relatively narrow, about 0.4 width ofischium, flagellum well developed. Chelipeds asymmetrical,
covered by closely spaced tubercles (Fig. 29G, H); majorchela (Fig. 29G) with slightly gaping finger when closed;
dactylus and fixed finger with longitudinal ridge at midline
distally; palm slightly shorter than broad; minor chela (Fig.
29H) with narrow gap when fingers closed; dactylus andfixed finger with median longitudinal ridge distally. P2–P4(Fig. 29I) relatively long, slender, covered by dense granules;
P3 longest (Fig. 29I); merus of P4 relatively long, about
3.4 times as long as broad; dactylus of P4 gently upcurved(Fig. 29J); merus without discernible distinct median grooveon lateral surface (Fig. 29J). Male thoracic sternum broad

Colour. Carapace, cheliped and pereopods uniformly
yellowish-brown (Fig. 1H).
Etymology. The species is named after the late Chen HuiLian, a doyen of Chinese crab taxonomy and a good friend.
She had in fact passed the present material to the second
author many years ago as part of an anticipated broader studyof Asian hexapodids. However, this was never realised with
her untimely death.
Remarks. Mariaplax chenae, new species, resembles M.
anfracta in having closely spaced tubercles on the carapace
and cheliped, and the rounded distal margin of the telson.
However, there are differences in the shapes of the third
maxillipeds and G1s. In M. chenae, the ischium of the third
maxilipped is obviously longer than the merus, the lateraland mesial margins along the distal half of the ischium areparallel, with distalmost mesial margin slightly rounded, theproximal half being narrow (Figs. 25E, 26D, 27F). In M.
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Rahayu & Ng: New genera and species of Hexapodidae(Fig. 29B, C), surface prominently granular; sternites 1
and 2 fused, separated from sternite 3 by distinct furrow;sternite 3 separated from sternite 4 laterally, medially appear
fused, thoracic sternal groove deep, transverse, extending
laterally from edge of sternoabdominal cavity, parallel tofrontal margin, not reaching base of chelipeds (Figs. 28B,
29C); sternite 8 exposed, quadrangular, as long as maleabdominal somite 1; sternoabdominal cavity not reaching
middle to sternite 4 (Fig. 29C). Male abdomen relatively
narrow (Fig. 29F), surface granular; somites 1 and 2 free,somites 3–5 fused, lateral margin slightly arched; somite 6
shorter than length of somites 3–5, median part of lateral
margin expanded into blunt triangular projection; telson
subpentagonal (Figs. 28B, 29F), slightly shorter than somite
6, distal margin rounded, sparsely setose. G1 (Fig. 29J, K)
bent 90° at midlength, directed anterolaterally, distal parttapered, not concealed under abdomen, exposed on thoracic
sternal groove. Female unknown.
Colour. Dirty white when freshly preserved.

Fig. 28. Mariaplax cyrtophallus, new species, holotype male (6.5 × 3.8 mm) (MZB). A, dorsal view carapace; B, ventral view of cephalothorax.

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Fig. 29. Mariaplax cyrtophallus, new species, holotype male (6.5 × 3.8 mm) (MZB). A, dorso-lateral margin of carapace; B, thoracic
sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternal groove andtelson; D, anterior view of cephalothorax; E, left third maxilliped; F, male abdomen and telson, G, major chela; H, minor chela; I, left
P4; J, K, left G1. Tubercles on thoracic sternum omitted. Scale bars = 1.0 mm.

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Rahayu & Ng: New genera and species of Hexapodidae
Etymology. From the Latin cyrto, bend, and phallus, forpenis; alluding to the bent structure of the G1. The nameis used as a noun in apposition.

broad as long, dorsal surface pubescent, finely granulated(Fig. 30A). Anterolateral margin arcuate; posterolateral cornerwith angled prominence over base of posterior pereopods(Figs. 30A, 31A). Eye small, slightly movable, cornea wider
than peduncle. Pterygostomial region with oblique row ofbroken striae. Third maxillipeds broad, completely covering
buccal cavity (Figs. 30C, 31D); mesial margin of ischiumof third maxillipeds slightly rounded; combined length ofdactylus, propodus and carpus subequal to that of merus andischium; exopod narrow, 0.4 width of ischium, flagellum
well developed. Chelipeds stout, unequal (Figs. 30D, E,
31F, G); major chela (Figs. 30D, 31F) with narrow gap
when fingers closed, dactylus and fixed finger with shallow
longitudinal groove on outer surface; palm pubescent, finely
tuberculate, slightly wider than long; minor chela (Figs.
30E, 31G) with relatively wider gap when fingers closed;
dorsal surface of palm covered by large tubercles and shortpubescent. P2–P4 relatively long (Fig. 30A, B); merus of
P4 3.7 times as long as broad; outer face with longitudinalgroove and sparse short setae. Male thoracic sternum broad(Figs. 30B, C, 31B, C), sternites 1 and 2 fused, separated fromsternite 3 by distinct ridge; sternite 3 not clearly delimited
from sternite 4, thoracic sternal groove very short, slightly
extend outward from sternoabdominal cavity; sternite 8
exposed, quadrangular, as long as male abdominal somite
1; sternoabdominal cavity not reaching base of sternite 3.
Male abdomen relatively narrow (Figs. 30B, 31E); somites
1 and 2 free; somites 3–5 fused, lateral margin slightly
arched; somite 6 slightly shorter than half length of somites
3–5, lateral margin expanded medially into blunt triangularprojection; distal margin of telson rounded, setose. G1 (Fig.
31H, I) slightly curved medially, directed anterolaterally,
distal part tapered, ended in blunt tip, not concealed underabdomen, exposed on thoracic sternal groove, obscured bysetae of telson. Abdomen of female with 6 free somites andtelson (Fig. 31J).

Remarks. Several features of the present new species suggest
its affinity to Lambdophallus, notably the transverse sternalgroove extends a good distance laterally and is parallel tofrontal margin, the G1 bent at a 90° angle, and the shape ofthe third maxilliped that is slightly expanded subproximallyand has straight mesial margin. However, Lambdophallus
has immovable and very short eyes peduncle, the third
maxillipeds was rather narrow and leave wide gap between
them, the male thoracic sternal groove starts above thearticulation of the sixth abdominal somite and the telson
was longer than the sixth somite (Alcock, 1902: pl. 62, fig.
1). These characters indicate that we cannot place this new
species in Lambdophallus. Although the longitudinal grooveon the outer surface of the merus of P2–P4 is indiscernible,
obscured by tubercles, other characters such as the movableeyes peduncle, the male thoracic sternal groove that starts
almost at subdistalmargin of the telson, the telson that was
shorter than the sixth abdominal somite, and the obliquemesial margin of ischium of the third maxilliped clearlyplace this species in Mariaplax. The structure of the malethoracic sternal groove (Fig. 29B, C) and shape of the G1 of
M. cyrtophallus, new species (Fig. 29I, J), however, easily
distinguishes it from all congeners.
Unusual among members of the genus is that M. cyrtophallus
does not have a discernible median groove on the lateralsurface of the ambulatory merus. This is distinct in allother congeners, although it may be shallow at times. In M.
cyrtophallus, the surface of the merus is covered with dense
granules and no groove can be seen. In all other aspects,
however, M. cyrtophallus is a typical Mariaplax species.
It is apparently closest to M. secus, new species, from theother side of the island of New Guinea, which also has asimilar strongly bent G1; but in M. secus, the lateral surfaceof the ambulatory merus has a distinct longitudinal groove(see discussion for that species).

Colour. Not known.
Etymology. Named after our friend, Peter Davie, whoprovided important advice on the type material of Hexapus
granuliferus.

Distribution. Timika, Papua, Indonesia. Intertidal, 15–30 m.
Mariaplax daviei, new species(Figs. 30, 31)

Remarks. The holotype and male paratype of H. granuliferus
described by Campbell & Stephenson (1970) are notconspecific, and should be referred to two separate species.
The shape of the third maxilliped, structure of the G1, andthe relative length of P2–P4 of both species, however, agreewith Mariaplax as presently defined (see remarks for M.
granulifera). The G1 of M. daviei, new species, resembles
those of H. simplex, both are simple, arched, and without
spinules. Nevertheless these two species cannot be placed in
the same genus as the generic characters such as the strongly
convex mesial margin of the ischium of the third maxilliped
and the longitudinally broad sternite 4 in Hexapinus, areonly slightly rounded mesial margin of ischium of the third
maxilliped and transversally broad sternite 4 in Mariaplax.

Hexapus sexpes – Haswell, 1882: 71. (not Cancer sexpes Fabricius,
1798)
Hexapus granuliferus – Campbell & Stephenson, 1970: 286 (inpart), fig. 49G, H. (not Hexapus granuliferus Campbell &Stephenson, 1970)
Material examined. Holotype: male (6.0 × 4.5 mm) (WAM
C23270), Tasmania, Spring Bay, 42°33.00'S 147°55.50'E, 15 m,
black mud and some fine shell, coll. R. S. Wilson, 23 April 1985.
Paratypes: Australia: 3 females (5.1 × 3.9 mm, 6.2 × 4.9 mm, 6.8
× 5.0 mm) (WAM C23270), same locality as holotype; 2 females(4.6 × 3.3 mm, 3.8 × 2.6 mm), 1 ovigerous female (4.8 × 3.3mm) (WAM), Jervis Bay, New South Wales, coll. P. Hutching,
5 June 1989.

Type locality. Spring Bay, Tasmania, Australia.

Diagnosis. Carapace subquadrate, about 1.3–1.4 times as
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Fig. 30. Mariaplax daviei, new species, holotype male (6.0 × 4.5 mm) (WAM C23270). A, overall view of carapace, chelipeds and P2–P4;
B, ventral view of cephalothorax; C, ventral view of cephalothorax showing third maxillipeds and telson, D, major chela; E, minor chela.

Distribution. Port Jackson, New Southwell and Tasmania,
Australia; 15 m.

(Figs. 32A). Anterolateral margin arcuate; posterolateralcorner with slight protuberance angle over base of posterior
pereopods. Eye small, slightly movable, cornea globular(Fig. 32C). Pterygostomial region with row of long and shortstriae with scattered tubercles. Third maxillipeds relatively
broad, almost completely covering buccal cavity (Figs. 32C,
33B); ischium of third maxillipeds longer than merus, withstraight margin; combined length of dactylus, propodus
and carpus slightly shorter than that of merus and ischium;
exopod narrow, 0.3 times width of ischium, flagellum welldeveloped. Chelipeds stout, unequal, covered by tubercles(Fig. 32B, C); major chela with gap when fingers closed,

Mariaplax galaxeae, new species(Figs. 1G, 32, 33)
Material examined. Holotype: female (4.2 × 3.2 mm) (ZRC
2013.1690), station TB99, Singapore Strait, 1°18'861N 104°05'128,
33.7–36.7 m, Singapore, coll. RV Galaxea, 28 May 2013.

Diagnosis. Carapace subquadrate, about 1.4 times as broad as
long; dorsal surface covered by tubercles; regions indistinct
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longer than telson; telson with rounded tip, margin withsparse setae. Male unknown.

large teeth on cutting edges; dactylus with shallow grooveon outer surface, palm slightly wider than long; minor chela
with narrow gap between closed fingers, smaller teeth on
cutting edges; dactylus with shallow longitudinal groove
medially. P2–P4 relatively long (Fig. 32A), long setae on
anterior and posterior margin of dactylus, propodus, shortsetae on carpus and merus; merus of P4 about 2.6 times aslong as broad, longitudinal groove on outer face; dactylus of
P2 and P4 slightly upcurved, dactylus of P3 straight. Female
thoracic sternum broad (Fig. 32B), covered by tubercles;
sternites 1 and 2 fused, separated from sternite 3 by distinct
ridge; sternite 3 and 4 fused, abdominal cavity reached distal
margin of sternite 3. Female abdomen relatively broad (Figs.
32B, 33C); all somites and telson free; somite 6 slightly

Colour. Carapace cream, mottled light and dark brown;chelipeds and P2−P4 light brown (Fig. 1G).
Etymology. Named after the Tropical Marine Science
Institute research vessel “Galaxea”, which was used during
Singapore Strait Expedition of the Comprehensive Marine
Biodiversity Survey for collecting material.
Remarks. Mariaplax galaxeae, new species, resembles
M. cyrtophallus, new species, and M. mica, new species,in having the carapace, chelipeds and P2–P4 strongly

Fig. 31. Mariaplax daviei, new species. A–I, holotype male (6.0 × 4.5 mm) (WAM C23270); J, paratype female (6.2 × 4.9 mm) (WAM
C23270). A, dorso-lateral margin of carapace; B, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C,thoracic sternites 1–5, showing thoracic sternal groove and telson; D, right third maxilliped; E, male abdomen and telson, F, major chela;G, minor chela; H, I, G1; J, female abdomen and telson. Scale bars = 1.0 mm.

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Fig. 32. Mariaplax galaxeae, new species, holotype female (4.2 × 3.2 mm) (ZRC 2013.1690). A, overall view of carapace, chelipeds andP2–P4; B, ventral view of cephalothorax; C, frontal view of cephalothorax.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 33. Mariaplax galaxeae, new species, holotype female (4.2 × 3.2 mm) (ZRC 2013.1690). A, dorsal view of carapace; B, left third
maxilliped; C, abdomen and telson. Scale bars: A, C = 1.0 mm; B = 0.5 mm.

tuberculated. Differences can be seen in the shape of thethird maxillipeds and the propotion of width to length ofthe carapace. In M. galaxeae, the mesial and lateral margins
along the distal three quarterof the ischium of the third
maxilliped are parallel, straight, the narrow proximal part
relatively short (Fig. 33B), while in M. cyrtophallus and M.
mica, the mesial margin is oblique with slightly expanded
subproximally, the narrow proximal part short (Fig. 29E
and Fig. 38B, respectively). The carapace of M. galaxeae
is visibly more quadrangular with 1.4 times as broad aslong compared to 1.5 as broad as long in M. cyrtophallus
and M. mica. Furthermore, the pereopods are shorter in M.
galaxeae, which has the merus of P4 2.6 as long as broadwhereas in M. cyrtophallus and M. mica it is 3.4 and 3.6
times s long as broad respectively.

Hexapus ?granuliferus – Serène & Soh, 1976: 25, fig. 26, pl. 7, fig. C
Hexapinus granuliferus – Manning & Holthuis, 1981: 169 (not fig.
32c, d); Davie, 2002: 232.
Material examined. Holotype: female (6.5 × 3.8 mm) (QMW3108), Red Buoy, Moreton Bay, Queensland, Australia, coll. 24
April 1968 (photographs examined). Others: Australia: 1 male (6.2
× 4.5 mm), 2 females (6.1 × 4.4 mm, 5.9 × 4.4 mm) (QM-W8299),
Middle Bank North Moreton Bay, sandy mud, 105 feet, coll. S.
Cook, 29 September 1972.

Diagnosis. Carapace subquadrate, about 1.4 times as broad as
long; dorsal surface covered by tubercles; regions indistinct(Figs. 34A, 35A). Anterolateral margin arcuate; posterolateralcorner with angled prominence over base of posterior
pereopods (Figs. 34A, 35A, 36A). Eye small, slightly
movable, cornea globular (Fig. 34B). Pterygostomial region
with row of long and short, oblique striae and with scatteredtubercles (Figs. 34B, 35C). Third maxillipeds relatively broad,almost completely covering buccal cavity (Figs. 34B, 35B,
C, 36E); ischium of third maxillipeds noticeably longer thanmerus, mesial margin straight; combined length of dactylus,
propodus and carpus shorter than that of merus and ischium;
exopod relatively narrow, 0.4 width of ischium, flagellum
well developed. Chelipeds stout, unequal; major chela (Fig.
36F) with gap when fingers closed; dactylus with shallow
groove on outer surface, groove present on outer surface of
fixed finger distally; palm slightly wider than long, surface
with sparse tubercles; minor chela (Fig. 36G) with wider
gap between closed fingers, dactylus and fixed finger withshallow longitudinal groove medially. P2–P4 relatively
long (Fig. 34A) merus of P4 2.9 times as long as broad;dactylus of P2 upcurved (Fig. 36H). Male thoracic sternum

The shape of the third maxilliped is comparable to that ofM. anfracta, but the narrow proximal part of the ischium iseven shorter in M. anfracta (Fig. 33B versus Fig. 23D). The
abdomen of the same size female is also relatively broader in
M. anfracta (Fig. 23H) compare to M. galaxeae (Fig. 33C).
Type locality. Singapore Strait, Singapore.
Distribution. Singapore Strait, Singapore. Subtidal, 33–36 m.
Mariaplax granulifera (Campbell & Stephenson, 1970)(Figs. 34–36)
Hexapus granuliferus Campbell & Stephenson, 1970: 286 (part),
fig. 49 (not fig. 49G, H = Mariaplax daviei, new species); Ng
et al., 2008: 86.

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Fig. 34. Mariaplax granulifera (Campbell & Stephenson, 1970), holotype female (6.5 × 3.8 mm) (QM-W3108). A, overall view of carapace
and P2–P4; B, frontal view of cephalothorax; C, abdomen and telson.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 35. Mariaplax granulifera (Campbell & Stephenson, 1970), male (6.2 × 4.5 mm) (QM-W8299). A, dorsal view of carapace; B,
ventral view of cephalothorax, showing abdomen and telson; C, anteroventral view of cephalothorax showing third maxillipeds andsternoabdominal cavity.

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RAFFLES BULLETIN OF ZOOLOGY 2014

Fig. 36. Mariaplax granulifera (Campbell &Stephenson, 1970), male (6.2 × 4.5 mm) (QM-W8299). A, dorsolateral margin of carapace;B, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternalgroove and telson; D, male abdomen and telson; E, left third maxilliped; F, major chela; G, minor chela; H, left P4; I, J, G1. Scale bars
= 1.0 mm441

Rahayu & Ng: New genera and species of Hexapodidae
broad (Figs. 35B, 36B, C), covered by tubercles; sternites
1 and 2 fused, separated from sternite 3 by distinct ridge;
sternite 3 separated from sternite 4 by distinct tuberculateridge laterally, thoracic sternal groove wide, short, directed
anteriorly, extends from sternoabdominal cavity to base ofsternite 3 (Figs. 35C, 36C); sternite 8 exposed, rectangular,slightly longer than abdominal somite 1; sternoabdominal
cavity not reaching base of sternite 3 (Fig. 36B). Male
abdomen relatively wide (Figs. 35B, 36D); somites 1 and 2
free, somites 3–5 fused, wider than somite 6, lateral marginrounded; somite 6 sligthly shorter than length of somites
3–5, lateral margin slightly expanded medially forming blunt
triangular projection; telson with distal margin rounded,sparsely setose. G1 (Fig. 36I, J) stout, slightly S-shaped, distal
part tapered, basal part swollen, row of spines on midlength
mesially, sparse short setae laterally and mesially, distal partnot concealed under abdomen, exposed on thoracic sternalgroove, obscured by setae of telson. Female abdomen with
6 free somites and telson (Fig. 34C).

daviei (Fig. 31H, I). In the form of their third maxillipeds
and pereopods, however, both species are clearly referable
to Mariaplax.

Colour. Not known.

Diagnosis. Carapace subquadrate, about 1.5 times as broad as
long; dorsal surface covered by tubercles; regions indistinct(Fig. 37A). Anterolateral margin arcuate; posterolateral cornerwith angled prominence over base of posterior pereopods(Figs. 37A, 38A). Eye small, slightly movable, cornea
globular (Fig. 37C). Pterygostomial region with row of
oblique striae (Fig. 37B). Third maxillipeds relatively broad,almost completely covering buccal cavity (Figs. 37B, 38B);
ischium of third maxillipeds slightly expanded subproximaly,
mesial margin oblique; combined length of dactylus, propodus
and carpus shorter than that of merus and ischium; exopod
narrow, 0.3 width of ischium, flagellum well developed.
Chelipeds stout, unequal (Fig. 37D) pubescent, tuberculated;major chela with gap when fingers closed; minor chela withnarrower gap between closed fingers. P2–P4 long, slender(Fig. 37A) covered by tubercles; merus of P4 3.6 times aslong as broad; dactylus of P2 and P4 upcurved (Fig. 37A);
outer surface of merus with longitudinal groove (Fig. 37A).
Female thoracic sternum relatively broad (Fig. 37B), coveredby tubercles; sternites 1 and 2 fused, separated from sternite
3 by distinct ridge; sternite 3 separated from sternite 4 bydistinct tuberculate ridge laterally; sternoabdominal cavity notreaches base of sternite 3. Female abdomen wide (Figs. 37B,
38C); somites 1 to 6 free, telson with rounded distal margin.

The “Hexapus ?granuliferus” of Serène & Soh (1976) from
Queensland, Australia, is assigned to this species because of
the shape of the third maxilliped and female abdomen (cf.
Serene & Soh, 1976, fig. 26; Fig. 26C).
Type locality. Red Buoy, Moreton Bay, Australia.
Distribution. Moreton Bay, Australia. Subtidal, 35 m.
Mariaplax mica, new species(Figs. 1J, 37, 38)
Material examined. Holotype: female (6.7 × 4.5 mm) (NMCR
39069), PANGLAO 2005, station CP 2407, 9°41.3'N, 123°48.5'E,
Bohol Sea, Philippines, coll. M/V BFAR, 204 –256m, 1 June 2005.

Remarks. The holotype of Hexapus granuliferus is a female
from Moreton Bay, Queensland, while the paratypes are one
male and one female from Port Jackson, New South Wales.
Campbell & Stephenson (1970) described and figured theholotype female (6.5 × 3.8 mm, in the QM) and a paratypemale (15.5 × 9.1 mm, in the Australian Museum). Manning& Holthuis (1981) assigned this species to Hexapinus on
the basis of the short, oblique male thoracic sternal groove.
Interestingly, when we examined specimens from eastern
Australia that had been assigned to H. granuliferus, wefound there were in fact two kinds of G1 structures. A malefrom Moreton Bay (QM-W8299) had a relatively stouter G1
with the inner margin gently serrated medially (Fig. 36I,
J) while the male from Tasmania (WAM C23270) (whichis also in southeastern Australia like Port Jackson) had amore slender G1 with a smooth inner margin (Fig. 31H,
I). They clearly belong to two separate species. Campbell& Stephenson (1970) stated that the tip of the G1 of theparatype male (their fig. 49G, H) is probably broken, but
this is incorrect; the G1 of the present Tasmanian male (Fig.
31H, I) is almost identical to that in their figure. Mariaplax
granulifera is here restricted for the Moreton Bay material;
while the specimens from southeastern Australia (including
the paratype of Hexapus granuliferus) are referred to anotherspecies, M. daviei, new species.

Colour. In life, pinkish brown overall, with the tubercles
on the pereopods dark brown (Fig. 1J).
Etymology. From Latin mica, tuberculate, alluding to theheavily granular carapace and pereopods. Name is used asa noun in apposition.

Mariaplax granulifera and M. daviei are very close ingeneral appearance of the carapace, but some differences
are noticeable: the male sixth abdominal somite of M.
granulifera is slightly shorter than the length of somites
3–5, and distinctly longer than telson (Fig. 36D) while in
M. daviei the somite 6 is distinctly shorter than somite 3–5
and nearly as long as telson (Fig. 31E); and the ischium of
the third maxilliped of M. granulifera is slightly longer thanthat of M. daviei (Fig. 36E versus Fig. 31D). Furthermore
the form of G1 is certainly different, being slightly S shapedin M. granulifera (Fig. 36I, J) versus slightly curved in M.

Remarks. Mariaplax mica, new species, resembles M.
cyrtophallus, new species, in the heavily granulated carapace
and pereopods, a similar shape of the third maxilliped
and the relatively long P2–P4. However, the carapace isdistinctively more squarish in M. mica (Figs. 37A) while in
M. cyrtophallus the anterolateral margin of the carapace isnarrower, sloping to wider posterolateral margin (Fig. 28A).
The P2–P4 are also proportionately longer and the granules
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on the carapace and pereopods are relatively larger in M.
mica (Figs. 37A, 38A versus Figs. 28A, 29I).

Mariaplax narusei, new species(Figs. 2C, 39, 40)

They also appear to have different depth preferences: M. mica
was collected from more than 200 m while M. cyrtophallus
was collected from shallow waters 15–30 m.

Material examined. Holotype: male (9.6 × 5.8 mm) (RUMFZC-2112), Funaura Bay, Iriomote Island, Ryukyu Islands, Japan,
coll. T. Naruse, 1 July 2011. Paratypes: Japan: 1 female (12.0 ×
7.1 mm) (ZRC 2012.1031), 1 ovigerous female (11.5 × 6.7 mm)(RUMF-ZC-2113), same locality as holotype.

Type locality. Bohol Sea, Philippines.

Diagnosis. Carapace much broader than long, about 1.7
times as broad as long, dorsal surface smooth, granulated
near margin; regions indistinct, H-shaped depression

Distribution. Bohol Sea, Philippines. Deep water, 204–256m.

Fig. 37. Mariaplax mica, new species, holotype female (6.7 × 4.5 mm) (NMCR 39069). A, overall view of carapace, chelipeds and P2–P4;
B, ventral view of cephalothorax; C, frontal view of cephalothorax; D, chelae.

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Fig. 38. Mariaplax mica, new species, holotype female (6.7 × 4.5 mm) (NMCR 39069). A, dorsolateral margin of carapace; B, left third
maxilliped; C, abdomen and telson. Scale bars = 1.0 mm.

abdomen broad, with 6 somites free and subtriangular telson(Fig. 40H).

shallow medially (Fig. 39A). Anterolateral margin arcuate;
posterolateral margin with angled prominence over base ofposterior pereopods (Figs. 39A, 40A,). Eye small, slightly
movable, cornea globular, peduncle granular (Fig. 39C).
Pterygostomial region with row of 3 relatively long, widely
separated oblique striae and some tubercles. Third maxillipeds
broad, completely covering buccal cavity (Figs. 39D, 40D);
ischium of third maxillipeds slightly longer and wider thanmerus, with straight mesial margin; combined length ofdactylus, propodus and carpus slightly shorter than that ofmerus and ischium; exopod narrow, 0.4 width of ischium,
flagellum well developed. Chelipeds stout, unequal (Fig.
39E); major chela with gap when fingers closed; palm slightly
wider than long, outer surface covered by tubercles; minor
chela with relatively wider gap when fingers closed. P2–P4
relatively long (Fig. 39A); dactylus of P2 slightly upcurved;
P3 with shallow longitudinal groove on outer surface; P4
entirely covered by tubercles, merus 2.8 times as long as
broad. Male thoracic sternum relatively broad (Figs. 39B,
40B, C); sternites 1 and 2 fused, slightly curved posteriorly,
separated from sternite 3 by distinct ridge; sternite 3 separated
from sternite 4 by distinct tuberculate ridge laterally,
thoracic sternal groove narrow, short, oblique, extends fromsternoabdominal cavity to middle of sternite 4 (Figs. 39B,
40B); sternite 8 exposed, rectangular, slightly longer thanabdominal somite 1; abdominal cavity not reaching base ofsternite 3 (Figs. 39B, 40C). Male abdomen relatively narrow(Figs. 39B, 40E); somites 1 and 2 free, somites 3–5 fused,slightly wider than somite 6; lateral margin sinuous, somite
6 sligthly shorter than length of somites 3–5, lateral margin
slightly expanded medially; telson subpentagonal with distal
margin rounded, margin sparsely setose. G1 (Fig. 40F, G)
stout, bent 60° along two-thirds of length, slightly twisted,distal part tapered, apices not concealed under abdomen,
exposed on thoracic sternal groove, obscured by setae of
telson, with sparse short setae laterally and mesially. Female

Colour. In life, generally uniformly yellowish brown withthe carapace slightly darker (Fig. 2C).
Etymology. This species is named after Tohru Naruse who
kindly passed the specimens to us for this study; and helped
us carefully read this long manuscript.
Remarks. Mariaplax narusei, new species, can be
distinguished from congeners by the following characters:
the carapace is much broader than long, the ischium of thethird maxilliped is wider than the merus, and P4 is entirely
covered by tubercles.
The much broader carapace and the shape of the G1
superficially resemble the condition in Latohexapus granosus.
However, the carapace of L. granosus is covered by numerous
tubercles and the regions are distinct, thoracic sternites 1
and 2 are bent inwards towards the buccal cavity, and theG1 is not twisted (Huang et al., 2002: Figs. 1B, 3A, B, D,
E; 54A, C). In M. narusei, the carapace surface is smoothwith the regions indistinct, thoracic sternites 1 and 2 areonly very slightly curved (not bent inwards) and the G1 istwisted medially (Figs. 39A, 40F, G).
Two characters of M. narusei resemble species of Hexapinus:
the ischium of the third maxilliped is relatively broader thanthe merus, and the P2 to P4 are relatively shorter. However,
the ischium of the third maxillipeds is still more angular in
M. narusei, with the mesial margin not distinctly convex(Fig. 40D) (versus the mesial margin is strongly convex andsubauriculiform in Hexapinus species). Unlike Hexapinus
species, the outer surface of the ambulatory merus in M.
narusei has a longitudinal groove albeit shallow (Fig. 39A)
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Fig. 39. Mariaplax narusei, new species, holotype male (9.6 × 5.8 mm) (RUMF-ZC-2112). A, overall view of carapace, chelipeds andP2–P4; B, ventral view of cephalothorax; C, frontal view of cephalothorax; D, third maxillipeds; E, chelae.

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Distribution. Iriomote Island, Ryukyu Islands, Japan.
Intertidal.

(versus smooth and entire). The G1 structures are also
different, with that of M. narusei S-shaped (Fig. 40F, G)(typical for Mariaplax species) while Hexapinus species
have gently curved G1s.

Mariaplax ourabay, new species(Figs. 2A, B, 41, 42)

Type locality. Funaura Bay, Iriomote Island, Ryukyu Islands,
Japan.

Material examined. Holotype: male (7.6 × 5.4 mm) (RUMFZC-2114), Futami, Oura Bay, Okinawa Island, Ryukyu Islands,

Fig. 40. Mariaplax narusei, new species. A–G, holotype male (9.6 × 5.8 mm) (RUMF-ZC-2112); H, paratype female (12.0 × 7.1 mm)(ZRC 2012.1031). A, dorsolateral margin of carapace; B, thoracic sternites 1–5, showing thoracic sternal groove and telson; C, thoracic
sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; D, left third maxilliped; E, male abdomen and telson; F, G,
G1; H, female abdomen and telson. Scale bars = 1.0 mm.

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Japan, coll. Oura Bay Survey Team, 20 June 2009. Paratype: Japan:
1 ovigerous female (9.2 × 7.0 mm) (ZRC 2012.1032), same locality
as holotype, 22 June 2009

depression shallow medially (Fig. 41A). Eye small, slightly
movable, cornea small, globular, narrower than peduncle,
peduncle with scattered granules. Pterygostomial region withrow of oblique striae and scattered tubercles. Third maxilliped(Figs. 41B, 42D) broad, ischium longer than merus, mesial

Diagnosis. Carapace subquadrate, about 1.4 times as broad as
long, dorsal surface granulated; regions indistinct, H-shaped

Fig. 41. Mariaplax ourabay, new species, holotype male (7.6 × 5.4 mm) (RUMF-ZC-2114). A, overall view of carapace, chelipeds andP2–P4; B, ventral view of cephalothorax; C, abdomen and telson; D, chelae.

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Rahayu & Ng: New genera and species of Hexapodidae
margin straight; combined length of dactylus, propodus andcarpus shorter than that of merus and ischium; exopod narrow,
0.4 width of ischium, flagellum well developed. Chelipeds(Fig. 41D) stout, unequal; major chela with slight gap whenfingers closed, palm slightly wider than long, surface covered
with tubercles; minor chela with narrow gap when fingers
closed, dorsal surface of palm covered by large tubercles.
P2–P4 relatively long (Fig. 41A); merus of P4 2.8 times aslong as broad, shallow longitudinal median groove present; P2
with dactylus upcurved. Male thoracic sternum broad (Figs.
41B, C, 42B, C); sternites 1 and 2 fused, separated fromsternite 3 by distinct ridge; sternites 3 and 4 fused; thoracic
sternal groove short, extends obliquely from sternoabdominal
cavity to middle of sternite 3 (Figs. 41B, 42B); sternite 8
exposed, rectangular, slightly longer than abdominal somite
1; sternoabdominal cavity reaches base of sternite 3. Male
abdomen (Figs. 41C, 42E) relatively narrow; somites 1 and
2 free, somites 3–5 fused, lateral margin sinuous; somite 6slightly shorter than length of somites 3–5, lateral margin
expanded medially into blunt triangular projection; telson
almost as long as somite 6, distal margin rounded, marginsetose. G1 (Fig. 42F, G) slender, slightly S-shaped, sparse

Fig. 42. Mariaplax ourabay, new species, holotype male (7.6 × 5.4 mm) (RUMF-ZC-2114). A, dorsolateral margin of carapace; B, thoracic
sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternal groove andtelson; D, left third maxilliped; E, male abdomen and telson; F, G, G1; H, female abdomen and telson. Scale bars = 1.0 mm.

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short setae on mesial and lateral margins; distal part tapered,
not concealed under abdomen, exposed on thoracic sternalgroove, obscured by setae of telson. Female abdomen
relatively narrow, with 6 free somites and telson (Fig. 42H).

distinct ridge; transverse sternal groove extends obliquelyfrom edge of sternoabdominal cavity, almost reaching base ofchelipeds (Figs. 44A, 45C, D); sternite 8 exposed, triangular,slightly shorter than abdominal somite 1; sternoabdominal
cavity reaching middle to thoracic sternite 4 (Figs. 44A,
45C). Male abdomen relatively narrow (Figs. 44A, 45F),
surface granular, somites 1 and 2 free; somites 3–5 fused,lateral margin slightly arched; somite 6 as long as wide,
lateral margin expanded into blunt triangular projection
subproximally; telson subpentagonal, distal margin rounded,sparsely setose. G1 (Fig. 45I, J) S-shaped, distal part tapered,sparse short setae present medially; row of 3 large teeth onlateral margin medially; distal part exposed on thoracic sternalgroove, not concealed under abdomen. Female unknown.

Colour. In life, carapace mottled pink and cream, with thebranchial region darker pink, pereopods cream (Fig. 2A).
Female lighter coloured than male (Fig. 2B)
Etymology. Named after the type locality Oura Bay, Okinawa
Islands, Japan. The name is used as a noun in apposition.
Remarks. The male telson of Mariaplax ourabay, newspecies, is almost as long as the sixth abdominal somite, acharacters shared only with M. granulifera. However, themale abdomen of these two species differs in the length
proportion of the somite 6 to that of the somites 3–5 (0.6
in M. ourabay versus 0.8 in M. granulifera). Furthermore,
the G1 structures of these two species differ markedly: M.
ourabay has long, slender G1 with a pointed tip (Fig. 42F,
G) while in M. granulifera, the G1 is stout and proximallymuch wider than the tip (Fig. 36I, J).

Colour. Not known.
Etymology. From the Latin propinqua for close; alluding to
the similarity of the new species with M. anfracta.
Remarks. This species closely resembles M. anfracta in the
shape of G1 and the tuberculation of carapace, chelipeds andP2 to P4. However, the G1 of M. propinqua, new species,
is relatively more slender with a row of three strong teethon the lateral margin medially (Fig. 45I, J) (G1 is relatively
stouter, without the presence of teeth in M. anfracta (Fig.
23F, G). In addition, the carapace and anterior thoracic
sternum are also relatively wider in M. propinqua (Figs. 43A,
44A versus Figs. 22A, 23B, C). The telson of M. anfracta
is subtriangular while in M. propinqua is subpentagonal,
furthermore P2–P4 are shorter in M. anfracta, the merus of
P4 is 2.5 as long as wide (Figs. 22A, C) versus 3.5 as longas wide in M. propinqua (Fig. 43A).

Type locality. Futami, Oura Bay, Okinawa Island, Ryukyu
Islands, Japan.
Distribution. Oura Bay, Okinawa Island, Ryukyu Islands,
Japan. Intertidal.
Mariaplax propinqua, new species(Figs. 43–45)
Material examined. Holotype: male (10.3 × 6.5 mm) (IOCAS),
station 6197, 21°00'N 109°00'E, Tonkin Gulf, China. Paratype:
China: 1 male (9.0 × 5.6 mm) (ZRC 2012.1033), station 6214,
20°45'N 108°30'E, coll. cruise boat 228, 15 February 1960.

Type locality. Tonkin Gulf, Vietnam.
Distribution. Tonkin Gulf, Vietnam. Subtidal.

Diagnosis. Carapace subquadrate, about 1.5 times as
broad as long, dorsal surface granulated; regions indistinct,
with shallow median H-shaped depression (Fig. 43A).
Anterolateral margin arcuate; posterolateral margin with
angled prominence over base of posterior pereopods(Figs. 43A, 45A). Front deflexed, divided into 2 lobes, notprojecting beyond edge of orbits (Fig. 43B). Eye slightly
movable, small, cornea pigmented, wider than peduncle.
Pterygostomial region with row of oblique striae (Figs.
43B, C, 45B). Third maxillipeds broad (Figs. 43C, 44A,
45E), completely covering buccal cavity; ischium slightly
longer than merus, combined length of dactylus, propodus
and carpus slightly shorter than that of merus and ischium;
exopod narrow, 0.3 width of ischium, slightly granular,
flagellum well developed. Chelipeds asymmetrical (Fig.
44B, C). Fingers gaping when closed, palm of both chela
finely tuberculate (Figs. 44B, C, 45G, H). P2–P4 tomentose,
surfaces granulated (Fig. 43A); merus of P4 3.5 times aslong as broad, shallow longitudinal groove on outer surface
medially; dactylus of P4 gently upcurved. Male thoracic
sternum relatively broad (Figs. 44A, 45C, D), surface finely
granular; sternites 1 and 2 fused, separated from sternite
3 by distinct ridge; sternite 3 separated from sternite 4 by

Mariaplax secus, new species(Figs. 1I, 46, 47)
Material examined. Holotype: male (4.7 × 3.0 mm) (MNHN
IU-2013-916), station DW3953, 05°14'S 145°49'E, Bismarck Sea,
Madang, south of Cape Kussoron, 130–140 m, Papua New Guinea,
coll. Expedition PAPUA NUIGINI, 2012, 7 November 2012.

Diagnosis. Carapace subquadrate, about 1.6 times as broadas long, dorsal surface strongly granulated; regions indistinct,
with inconspicuous H-shaped shallow depression medially(Figs. 46A, 47A). Eye small, very slightly movable, cornea
black, wider than granular peduncle. Pterygostomial region
covered with granules, with short row of oblique striae. Third
maxillipeds (Figs. 46B, 47C) broad, covering buccal cavity;ischium longer than merus, slightly expanded subproximally,
with oblique mesial margin, combined length of dactylus,
propodus and carpus almost as long as that of merus andischium, dactylus as long as propodus; exopod relatively
narrow, about 0.4 width of ischium, flagellum well developed.
Chelipeds asymmetrical, covered by closely spaced tubercles
and very short setae (Fig. 46D); major chela with broad
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Rahayu & Ng: New genera and species of Hexapodidae
margin with few granules proximally; merus of P4 long, about
4.3 times as long as broad. Male thoracic sternum broad (Figs.
46B, 47B), surface prominently granular; sternites 1 and 2
fused, separated from sternite 3 by distinct furrow; sternite
3 and 4 fused, thoracic sternal groove deep, relatively short,extending obliquely from edge of sternoabdominal cavity(Figs. 46B, 47B); sternite 8 exposed, quadrangular, slightly

gaping finger when closed; dactylus and fixed finger withlongitudinal ridge at midline distally; palm slightly shorter
than broad; minor chela with broad gap when fingers closed;
dactylus and fixed finger with median longitudinal ridge
distally. P2–P4 (Fig. 46A) relatively long, slender, covered
by dense granules; P3 longest, lateral surface of merus withshallow longitudinal groove; dactylus of P4 upcurved, ventral

Fig. 43. Mariaplax propinqua, new species, holotype male (10.3 × 6.5 mm) (IOCAS). A, overall view of carapace, chelipeds and P2–P4;
B, frontal view of cephalothorax; C, ventral view of cephalothorax.

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RAFFLES BULLETIN OF ZOOLOGY 2014
longer than male abdominal somite 1; sternoabdominal cavity
reaching to middle of sternite 4 (Fig. 47B), distal margin
sinuous. Male abdomen broad, short (Figs. 46B, 47D), notcovering sternoabdominal cavity, reaching only to fifth
sternite; surface granular; somites 1 and 2 free, somites 3–6
fused, lateral margin slightly arched; telson subtriangular(Figs. 47D), distal margin rounded. G1 (Fig. 47E, F) bent
ca. 90° at midlength, directed anterolaterally, tuft of longsetae on mesial surface near midlength, distal part tapered,
not concealed under abdomen, exposed just before thoracic
sternal groove. Female unknown.

species being M. cyrtophallus, new species. The differences
between these two species are as follow: the carapace is more
rectangular, being 1.6 times as broad as long in M. secus(Fig. 46A) (1.5 times as broad as long in M. cyrtophallus,
Fig. 28A); the ischium of the third maxilliped is as long as
broad with the dactylus the same length as the propodusin M. secus (Fig. 47C) (slightly longer than broad with thedactylus much longer than the propodus in M. cyrtophallus,
Fig. 29E); the thoracic sternum is proportionately less broadin M. secus compared to that of M. cyrtophallus (Fig. 47B
versus Fig. 29B); the distal part of sternoabdominal cavity
is relatively long and narrow, with distal margin sinuous in
M. secus (Figs. 46B, 47B) (short, broad with rounded distal
margin in M. cyrtophallus, Fig. 29B); the lateral surfaceof the P3 merus has a distinct shallow longitudinal groovein M. secus (Fig. 46A) (an indistinct groove, obscured bytubercles, in M. cyrtophallus, Fig. 29I); the P4 merus isrelatively much longer, being 4.3 times as long as broad in
M. secus (Fig. 46A) (versus 3.4 times as long as broad in M.
cyrtophallus, Fig. 29I); and the G1 has a tuft of long medial

Colour. Dirty white in life (Fig. 1I).
Etymology. From the Latin secus, for different; alluding to
the unusual shape of the male abdomen. The name is used
as a noun in apposition.
Remarks. This is the second species in Mariaplax to have theG1 bent at a 90° angle, forming a L-shaped structure; the otherFig. 44. Mariaplax propinqua, new species, holotype male (10.3 × 6.5 mm) (IOCAS). A, abdomen and telson; B, major chela; C, minor chela.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 45. Mariaplax propinqua, new species, holotype male (10.3 × 6.5 mm) (IOCAS). A, dorsolateral margin of carapace; B, anterior viewof cephalothorax; C, thoracic sternites 3–5, showing thoracic sternal groove and telson; D, thoracic sternites 1–5, showing sternoabdominal
cavity and thoracic sternal groove; E, left third maxilliped; F, male abdomen and telson, G, major chela; H, minor chela; I, J, G1. Scalebars = 1.0 mm.

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RAFFLES BULLETIN OF ZOOLOGY 2014setae in M. secus (Fig. 47E, F) (few setae along dorsal andventral margin in M. cyrtophallus, Fig. 29J, K).

case, the differences in the carapace, third maxillipeds,
thoracic sternum and P2–P4 argue for them to be recognised
as separate species.

The male abdomen in M. secus is unusual, being broad andvery short, with somite 6 apparently fused to somites 3–5. It
is completely different from all know hexapodids. However,this is likely to be associated with some parasitic infection(e.g., a rhizocephalan as it appears unusually swollen), or the
result of past damage and anomalous regrowth. As such, twoof the other observed differences between M. secus and M.
cyrtophallus: the differently structured male sternoabdominal
cavities and G1s, should be used with caution. It is possible
they have also been affected by the above factors. In any

Interestingly, both M. cyrtophallus and M. secus are foundin the island of Indonesian Papua – Papua New Guinea, thelatter from the east, the former from the west.
Type locality. Madang, south of Cape Kussoron, BismarckSea, Papua New Guinea.
Distribution. Madang, Papua New Guinea. Subtidal,
130–140 m.

Fig. 46. Mariaplax secus, new species, holotype male (4.7 × 3.0 mm) (MNHN IU-2013-916). A, overall view of carapace, chelipeds andP2–P4; B, ventral view of cephalothorax; C, front view of cephalothorax; D, major chela and minor chela.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 47. Mariaplax secus, new species, holotype male (4.7 × 3.0 mm) (MNHN IU-2013-916). A, dorsolateral margin of carapace; B,
thoracic sternites 1–6, showing sternoabdominal cavity, thoracic sternal groove and telson; C, left third maxilliped; D, male abdomen andtelson; E, F, G1. Scale bars: A, B, D = 1.0 mm; C, E, F = 0.5 mm.

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wider than peduncle. Pterygostomial region with row of
oblique striae. Third maxillipeds broad (Figs. 48B, 49D),
without distinct gap between them; ischium longer thanbroad, much longer than merus, mesial margin straight,
combined length of dactylus, propodus and carpus shorter
than that of merus and ischium; exopod narrow, 0.4 widthof ischium, slightly granular, flagellum well developed.
Chelipeds asymmetrical; both chelae (Fig. 48C) with gap
when fingers closed; palm slightly longer than wide, surface
finely tuberculate. P2–P4 tomentose, surfaces granulated (Fig.
48A); merus of P4 three times as long as broad, shallow
longitudinal groove on outer surface medially; dactylus ofP4 gently upcurved. Male thoracic sternum broad (Figs. 48B,

Mariaplax sinensis, new species(Figs. 48, 49)
Material examined. Holotype: male (7.5 × 5.2 mm) (IOCAS),
station 21, Bohai Gulf, very close to 38°40'N 117°50'E, to 7 m
depth, soft mud, coll. D. Sun & G. Lin, 27 August 1979.

Diagnosis. Carapace subquadrate, about 1.5 times as
broad as long, dorsal surface granulated; regions indistinct,
with shallow median H-shaped depression (Fig. 48A).
Anterolateral margin arcuate; posterolateral margin with
angled prominence over base of posterior pereopods (Figs.
48A, 49A). Eye slightly movable, small, cornea pigmented,

Fig. 48. Mariaplax sinensis, new species, holotype male (7.5 × 5.2 mm) (IOCAS). A, overall view of carapace, chelipeds and P2–P4; B,
ventral view of cephalothorax; C, major and minor chelae.

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Rahayu & Ng: New genera and species of Hexapodidae
49B, C), surface finely granular; sternites 1 and 2 fused,
separated from sternite 3 by distinct ridge; sternite 3 separated
from sternite 4 by distinct ridge; wide transverse groove
extends obliquely from edge of sternoabdominal cavity,
not reaching base of chelipeds (Figs. 48B, 49B); sternite
8 exposed, subrectangular, slightly longer than abdominal
somite 1; sternoabdominal cavity reaching midlength ofthoracic sternite 4 (Fig. 49C). Male abdomen relatively
narrow (Fig. 49E), surface granular, somites 1 and 2 free;somites 3–5 fused, lateral margin slightly arched; somite 6slightly shorter than somites 3–5, lateral margin expanded
into blunt triangular projection subproximally; telson
subtriangular, distal margin rounded (Figs. 48B, 49E). G1
slender (Fig. 49F, G), S-shaped, distal part tapered, sparse
short setae present laterally and mesially; row of minutespines on mesial margin medially; distal part exposed on
thoracic sternal groove, not concealed under abdomen.
Colour. Not known.

Fig. 49. Mariaplax sinensis, new species, holotype male (7.5 × 5.2 mm) (IOCAS). A, dorsolateral margin of carapace; B, thoracic sternites
1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternal groove and telson;
D, left third maxilliped; E, male abdomen and telson; F, G, G1. Scale bars = 1.0 mm.

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Etymology. Named after the type locality, China.

the shape of the G1 is different, being relatively stouter anddistally twisted (Fig. 25I, J) (versus more slender, tapering,and only slightly twisted distally in M. sinensis, Fig. 49F, G).

Remarks. Mariaplax anfracta, M. propinqua, new species,
and M. sinensis, new species, share the same general shape of
G1: S-shaped with a long and bent distal part. The differences
between these three species are as follow: the male anterior
thoracic sternum in M. sinensis is proportionately much wider(Fig. 49B, C) (versus Figs. 23B, C, 44A, 45C, D), and thepresence of row of small spines on the G1 medial lateral
margin in M. sinensis (Fig. 49F, G) (no spines present in M.
anfracta, Fig. 23F, G; and three large spines in M. propinqua,Fig. 45I, J). Although M. chenae also possesses a row ofminute spines at the middle of the lateral margin of the G1,

Type locality. Bohai Gulf, East China Sea.
Distribution. East China Sea. Subtidal, 7 m.
Mariaplax streptophallus, new species(Figs. 50, 51)
Material examined. Holotype: male (7.5 × 5.4 mm) (WAM
C.15310), Cape Bowling Green, Queensland, Australia, coll. W.
Goode, 23 November 1962.

Fig. 50. Mariaplax streptophallus, new species, holotype male (7.5 × 5.4 mm) (WAM C.15310). A, overall view of carapace, chelipeds
and P2–P4; B, ventral view of cephalothorax; C, third maxilliped; D, major chela, E, minor chela.

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 51. Mariaplax streptophallus, new species, holotype male (7.5 × 5.4 mm) (WAM C.15310). A, dorsolateral margin of carapace; B,
thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternalgroove and telson; D, left third maxilliped; E, male abdomen and telson, F, major chela; G, minor chela; H, I, G1. Scale bars = 1.0 mm.

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Diagnosis. Carapace subquadrate, about 1.4 times as broadas long, dorsal surface pitted, granulated near margin;
region indistinct, H-shaped depression on surface near
middle shallow (Fig. 50A). Anterolateral margin arcuate;
posterolateral margin with angled prominence over base ofposterior pereopods (Figs. 50A, 51A). Eye small, slightly
movable, cornea globular. Pterygostomial region with rowof oblique striae (Fig. 50C). Third maxillipeds relatively
broad, almost completely covering buccal cavity (Figs. 50C,
51D); ischium of third maxilliped longer than merus, mesial
margin very slightly oblique; combined length of dactylus,
propodus and carpus shorter than that of merus and ischium;
exopod relatively narrow, 0.3 width of ischium, flagellum
well developed. Chelipeds stout, unequal; major (Figs. 50D,
51F) and minor (Figs. 50E, 51G) chelae with gap whenfingers closed; palm almost as long as wide, surface pitted.
P2–P4 relatively short; merus of P4 2.8 times as long as
broad, longitudinal groove medially; dactylus of P2 and P4
slightly upcurved. Male thoracic sternum broad (Figs. 50B,
51B, C), sternites 1 and 2 fused, separated from sternite 3
by distinct ridge; sternite 3 separated from sternite 4 bydistinct ridge, thoracic sternal groove directed anteriorly,
curved inwards, extends from sternoabdominal cavity tobase of sternite 3 (Figs. 50B, 51C); sternite 8 exposed,
triangular, as long as abdominal somite 1; sternoabdominal
cavity not reaching base of sternite 3 (Fig. 51B). Male
abdomen relatively narrow (Figs. 50B, 51E); somites 1 and
2 free; somites 3–5 fused, lateral margin slightly sinuous;
somite 6 slightly shorter than length of somites3–5, lateral
margin expanded medially into blunt triangular projection;
distal margin of telson rounded, with sparse setae. G1 (Fig.
51H, I) bent submedially, twisted, directed anteriorly, distal
part tapered, with row of spines mesially, sparse short setae
laterally and mesially, distal quarter not concealed underabdomen, exposed on thoracic sternal groove, obscured bysetae of telson. Female unknown.

Mariaplax streptophallus resembles M. anfracta in the lessgranulated surface of the carapace but differs in having a
proportionately wider carapace (Fig. 50A versus Fig. 22A,
C), slightly oblique mesial margin of the ischium of thethird maxilliped (Fig. 51D versus Fig. 23D), a relatively
longer and more slender male abdomen (Fig. 51E versus
Fig. 23C), and the male thoracic sternal groove is directed
anteriorly (Fig. 51B, C versus Fig. 23B, C).
Type locality. Cape Bowling Green, Queensland, Australia
Distribution. Bowling Green, Queensland, Australia.
Subtidal.
Rayapinus, new genus
Diagnosis. Carapace broader than long; surface almost smoothwith sparse tubercles on margin or distinctly granulated;regions indistinct, with shallow U-shaped depression
medially. Anterolateral margin arcuate; pterygostomial region
with row of long and short, broken or entire, oblique striae
and scattered tubercles. Eye short, stout, slightly movable,
cornea subglobular. Third maxilliped broad, without gap whenclosed; ischium narrow slightly longer than merus, mesial
margin rounded; carpus, propodus and dactylus cylindrical;
dactylus longer than propodus; exopod moderately wide.
Chelipeds unequal, P2–P4 short, stout; propodus anddactylus very short; propodus rounded, dactylus shorter thanpropodus; dactylus of P2 and P4 slightly curved. Thoracic
sternites 1 and 2 fused; sternite 3 separated from sternite 4
by tuberculate ridge laterally, median area appearing fused;sternites 4–7 well developed, separated from each other by
distinct suture; sternite 8 exposed, triangular, as long as
male abdominal somite 1. Sternoabdominal cavity reaches
middle of thoracic sternite 4. Male thoracic sternal groove
short. Male abdomen narrow, somites 1, 2 and 6 free, somites
3–5 fused; telson rounded. G1 stout, bent subdistally, apicenot concealed under abdomen. Female abdomen relatively
narrow, somites 1–6 fused, telson almost as long as somite 6.

Colour. Not known.
Etymology. From the Latin “strepto” for twisted, and“phallus” for penis, alluding to the twisted structure of theG1. The name is used as a noun in apposition.

Etymology. Named in honor of Ray Manning. The name
Rayapinus is derived from his first name, Ray, with “-pinus”,
the suffix of the allied genus Hexapinus. Gender masculine.

Remarks. Mariaplax streptophallus, new species, differsfrom congeners in having a row of spinules near the tip of
the G1. Mariaplax chenae, new species, M. propinqua, newspecies, and M. sinensis, new species, also have spines on
their G1, but these are positioned along the midlength of
the G1. The male thoracic sternal groove, which is directed
anteriorly (Fig. 51B, C), resembles that of M. granulifera(Fig. 36B, C), but in M. streptophallus, the groove is curved
inwards while in M. granulifera it is directed anteriorly.
While it has a twisted G1 like M. chenae, the condition ismore extreme in M. streptophallus, with the entire structure
bent and twisted submedially, directed anteriorly and tapering
distally (Fig. 51H, I). In M. chenae, only the G1 tip istwisted (Fig. 25I, J).

Remarks. This genus is remarkable for its short and stout
P2–P4 with the propodus and dactylus especially short,and the characteristic G1 shape that has wide apices withrow of spines. The extension of the male thoracic sternalgroove is similar to that of Hexapinus but the shapes of
their third maxillipeds and male abdomens are different. In
Hexapinus, the ischium of the third maxilliped is strongly
dilated mesially (Fig. 13C) and the male abdominal somite 6
is slightly shorter than somites 3–5 (Fig. 21C). In Rayapinus,
the ischium of the third maxilliped is not dilated mesially(Fig. 53E) and the male abdominal somite 6 is much shorter
than somites 3–5 (Fig. 53F).
Species included. Rayapinus maenosonoi, new species (typespecies by present designation).

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Rahayu & Ng: New genera and species of Hexapodidae
Rayapinus maenosonoi, new species(Figs. 2D, 52, 53)

eye small; pterygostomial region with row of striae. Third
maxillipeds relatively broad, tuberculate; ischium longer
than merus, with rounded mesial margin; merus broader thanlong; exopod relatively narrow, flagellum well developed.
Chelipeds stout, unequal; major chela with slight gap whenfingers closed; minor chela with relatively wider gap between
fingers. P2–P4 short, stout, P3 longest; merus of P4 2 times aslong as broad. Male thoracic sternum broad; sternoabdominal
cavity not reaching base of sternite 3; thoracic sternal groove
short, extends obliquely from sternoabdominal cavity. Male
abdomen relatively narrow; somites 1 and 2 free; somites 3–5
fused, lateral margin sinuous; somite 6 distinctly shorter thanMaterial examined. Holotype: male (6.6 × 4.6 mm) (RUMFZC-2115), Sesoko Island near Okinawa Island, Ryukyu Islands,
Japan, coll. T. Maenosono, 11 May 2010. Paratype: Japan: 1 female(4.3 × 3.1 mm) (ZRC 2012.1034), same locality as holotype, coll.
T. Maenosono, 8 June 2009.

Diagnosis. Carapace subquadrate, about 1.4 times as broad as
long, dorsal surface smooth; regions indistinct; anterolateral
margin arcuate; posterolateral corner with angled prominenceover base of posterior pereopods; orbit distinct, transverse;

Fig. 52. Rayapinus maenosonoi, new species, holotype male (6.6 × 4.9 mm) (RUMF-ZC-2115). A, overall view of carapace, chelipeds
and P2–P4; B, ventral view of cephalothorax; C, frontal view of cephalothorax; D, chelae.

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Fig. 53. Rayapinus maenosonoi, new species. A–K, holotype male (6.6 × 4.9 mm) (RUMF-ZC-2115); L, paratype female (4.3 × 3.1 mm)(ZRC 2012.1034). A, carapace; B, anterior view of carapace; C, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic
sternal groove; D, thoracic sternites 1–5, showing thoracic sternal groove and telson; E, left third maxilliped; F, male abdomen and telson,
G, major chela; H, minor chela; I, left P4; J, K, G1; L, female abdomen and telson. Setae on chelae not drawn. Scale bars = 1.0 mm.

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length of somites 3–5, lateral margin with blunt triangularexpansion medially; telson short with distal margin rounded,
setose. G1 stout, bent subdistally, apices wide, not concealed
under abdomen. Female abdomen narrow, somites 1–6 fused,suture visible between somites 5 and 6 but functionally
fused; lateral margin of somite 6 expanded subproximally,telson almost as long as somite 6, distal margin rounded.

abdominal somite 1; sternoabdominal cavity not reaching
middle of sternite 4. Male abdomen relatively narrow (Figs.
52B, 53F); somites 1 and 2 free; somites 3–5 fused, lateral
margin sinuous; somite 6 distinctly shorter than lengthof somites 3–5, lateral margin forming blunt triangularexpansion medially; telson short, with rounded, setose margin.
G1 (Fig. 53J, K) bent subdistally, directed anterolaterally,
distal part slightly tapered, tip rounded with several spines,
mesial and lateral margin with sparse long setae, apices
not concealed under abdomen, exposed on thoracic sternalgroove, obscured by setae of telson. Female abdomen narrow(Fig. 53L), with somites 1–6 fused, somites 1–5 with very
shallow, indiscernible sutures, suture visible between somite
5 and 6 but functionally fused; somite 6 distinctly shorter
than somites 3–5, lateral margin expanded subproximally,telson almost as long as somite 6, distal margin rounded.

Description. Carapace subquadrate, about 1.4 times as
broad as long, dorsal surface smooth; regions indistinct,
median U-shaped depression shallow; some granules
present on dorsolateral margins, only scattered granules onposterior margin (Fig. 52A). Anterolateral margin arcuate;
posterolateral corner with angled prominence over baseof posterior pereopods (Figs. 52A, 53A). Orbit distinct,
transverse; eye small, slightly movable, cornea black, wider
than tuberculate peduncle (Fig. 53B). Pterygostomial region
with row of oblique striae, oblique row of setae under row
of striae, adjacent to Milne Edwards’ opening (Fig. 53B).
Third maxillipeds relatively broad, tuberculate, without gap
between them (Figs. 52B, 53E); ischium longer than merus,
with rounded mesial margin; merus broader than long; carpus,
propodus and dactylus cylindrical; dactylus longer thanpropodus, combined length of dactylus, propodus and carpus
shorter than that of merus and ischium; exopod narrow, 0.4
width of ischium, flagellum well developed.

Colour. In life, carapace yellow or light yellow, merus andcarpus of chelipeds and P2–P4 yellow, propodus and dactylus
white yellowish (Fig. 2D).
Etymology. Named after Tadafumi Maenosono who collected
the type specimens.
Remarks. As mentioned earlier, Rayapinus, new genus,
is similar to Hexapinus in the extent of the male thoracic
sternal groove. However, Rayapinus maenosonoi can be easily
separated from Hexapinus latipes and H. simplex by having
proportionately much shorter and stouter P2–P4 with a very
short dactylus, and a G1 in which the distal part is expanded.

Chelipeds stout, unequal (Fig. 52D). Major chela (Fig. 53G)
with slight gap when fingers closed; large teeth present at
cutting edge of dactylus; dactylus with longitudinal grooveon outer surface, tufts of setae on cutting edge proximally;
inner surface near upper margin with longitudinal ridge; palmslightly wider than long, surface with sparse tubercles onouter surface, shallow longitudinal groove on outer surface of
fixed finger; carpus without setae dorsally, row of tubercles
and setae dorsomesially; merus short, few tubercles andfringe of setae dorsomesially. Minor chela (Fig. 53H) withrelatively wider gap between closed fingers; dactylus withlongitudinal groove on outer surface; inner surface withlongitudinal ridge near upper margin; outer surface of palm
covered by large tubercles, carpus and merus unarmed, fringeof setae on each dorsomesial margin. P2–P4 short, stout (Fig.
52A); P3 longest; P2 most slender, dactylus upcurved, few
tubercles on upper margin, fringe of short setae on upperand lower margins, slightly shorter than propodus, latterwith row of tubercles on upper and lower margins distally
accompanied by setae, carpus longer than propodus, tubercles
on outer upper half, tufts of setae distally, merus about 1.7
times length of carpus, upper and lower margins with row
of tubercles and tufts of short setae. P3 stouter, longer thanP2; P4 (Fig. 53I) stouter than P3; ornamentation and setation
as on P2; merus of P4 2 times as long as broad.

Type locality. Sesoko Island near Okinawa Island, Ryukyu
Islands, Japan,
Distribution. Okinawa Island, Ryukyu Islands, Japan.
Subtidal, 1.5–2 m.
Latohexapus Huang, Hsueh & Ng, 2002
Latohexapus Huang, Hsueh & Ng, 2002: 652.

Emended diagnosis. Carapace much broader than long;regions distinct, separated by deep groove, strongly
granulated. Eye movable; anterolateral margin arcuate.
Pterygostomial region with row of striae, granular;
ischium of third maxillipeds expanded distally, longer thanmerus; exopod with well developed flagellum. Chelipeds
asymmetrical, with prominent teeth at base of fingers.
Surfaces of P2–P4 granular, dactylus upcurved. Male
thoracic sternum very broad; surface prominently granular;sternites 1 and 2 fused, strongly bent backward, separated
from sternite 3 by distinct transverse ridge; deep transverse
groove separating thoracic sternites 3 and 4; sternoabdominal
cavity extending from edge of abdominal cavity to base ofchelipeds; sternite 8 exposed. Male abdomen with somites
3–5 fused; somite 6 appearing hexagonal, with median partprominently expanded into triangular projection; telson
subpentagonal. G1 very slender, directed anterolaterally,
distal quarter not concealed under abdomen.

Male thoracic sternum broad (Figs. 52B, 53C, D), sternites
1 and 2 fused, separated from sternite 3 by distinct ridge;
sternite 3 separated laterally from sternite 4, medially appear
fused, sternites 4–7 well developed, separated by distinct
sutures; thoracic sternal groove short, extends obliquelyfrom sternoabdominal cavity, reaching middle of sternite 4(Figs. 52B, 53D); sternite 8 exposed, triangular, as long as
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Fig. 54. Latohexapus granosus Huang, Hsueh & Ng, 2002, holotype male (16.3 × 8.2 mm) (ZRC 2002.001). A, overall view of carapace,chelipeds and P2–P4; B, frontal view of cephalothorax; C, ventral view of cephalothorax.

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Rahayu & Ng: New genera and species of Hexapodidae
Species included. Latohexapus granosus Huang, Hsueh &Ng, 2002 (type species by original designation).

2. Latohexapus is the only genus known to have thoracic
sternites 1 and 2 sharply bent inwards and downwards into
the buccal cavity (Fig. 54B, C).

Remarks. So far this is the only genus in the family thathas the carapace much broader than long and with theregions distinctly demarcated. As discussed by Huang et al.
(2002), the extension of the male thoracic sternal groove iscomparable to the condition in Lambdophallus but several
differences such as movable eyes (versus immovable eyesin Lambdophallus), the shapes of the third maxillipeds with
the ischium expanded distally in Latohexapus (Huang et al.,
2002: fig. 4D) (versus slightly convex in Lambdophallus,
Manning & Holthuis, 1981: fig. 34b), and the male abdominal
somite 6 appearing hexagonal (Huang et al., 2002: fig. 4G)(versus almost squarish in Lambdophallus, Manning &Holthuis, 1981: fig. 34C) easily distinguishes the two genera.

Type locality. Bertzuliau, Yulin County, Taiwan.
Distribution. Yulin County, Taiwan. Subtidal.
Hexaplax Doflein, 1904
Hexaplax Doflein, 1904: 122; Manning & Holthuis, 1981: 171.

Diagnosis. Carapace broader than long, surface very finely
granular; regions indistinct, with shallow median H-shaped
depression. Anterolateral margin arcuate; pterygostomial
region with row of short striae forming long oblique
stridulatory ridge. Eye large, movable; cornea dilated.
Third maxilliped wide, leaving gap when closed; ischium
longer than merus, dilated distally, mesial margin rounded;
carpus, propodus and dactylus cylindrical; dactylus longer
than propodus; exopod narrow, flagellum present. Chelipeds
stout, subequal or unequal, P2–P4 long, slender. Thoracic
sternites 1 and 2 fused; sternites 3 and 4 fused; sternite 8
exposed, triangular, reaching proximal half of male abdominal
somite 2. Sternal abdominal cavity reaching distal margin ofthoracic sternite 4. Male thoracic sternal groove absent. Male
abdomen relatively narrow; somite 1 hidden under carapace;male abdominal somites 2 and 6 free; somites 3–5 fused (butsutures may be visible); distal margin of telson rounded. G1straight to sinuous, apice concealed under abdomen. Female
abdomen with 6 free somites and telson.

Latohexapus granosus Huang, Hsueh & Ng, 2002
(Fig. 54)
Latohexapus granosus Huang et al., 2002: 656, figs. 1B, 3, 4; Ng
et al., 2008: 86.
Material examined. Holotype: male (16.3 × 8.2 mm) (ZRC
2002.001), port at Bertzuliau, Yulin County, Taiwan, coll. P.-Y.
Hsu, 23 March 2000.

Diagnosis. Carapace about 1.9 times as broad as long,
dorsal surface distinctly granulated; regions separated bydeep grooves; anterolateral margin arcuate; posterolateralcorner with small angle over base of posterior pereopods(Fig. 54A). Orbit distinct, transverse; eye movable (Fig.
54A, B). Pterygostomial region with row of oblique striae(Fig. 54B). Third maxillipeds broad, completely covering
buccal cavity; exopod with well developed flagellum (Fig.
54B, C). Chelipeds asymmetrical; major chela with wide gap
when fingers closed, granulated (Fig. 54C); minor chela withnarrower gap when fingers closed; ornamentation similar
to that of major chela. P2–P4 relatively short; P3 longest,
surfaces granulated; deep longitudinal groove on lateral faceof merus of P4 (Fig. 54A). Male thoracic sternum very broad(Fig. 54C); sternites 1, 2 fused, strongly bent inwards towards
buccal cavity; thoracic sternal groove extending obliquelyfrom edge of abdominal cavity, bending to become subparallelto frontal margin to base of chelipeds; sternoabdominal cavity
reaching base of sternite 3; sternite 8 exposed, triangular,
as long as abdominal somite 1. Male abdomen relatively
narrow (Fig. 54C), surface granular; somites 3–5 fused,lateral margin sinuous; somite 6 with median part of lateral
margin prominently expanded into triangular projection,
appearing evenly hexagonal; telson rounded. G1 slender,
bent submedially, directed anterolaterally, distal part tapered,
not concealed under abdomen.

Species included. Hexaplax megalops Doflein, 1904 (typespecies by original designation), Hexaplax aurantium, newspecies, and Hexaplax saudade, new species.
Remarks. Hexaplax is characterised by the large hammershaped cornea, and long, slender P2–P4, and has long
believed to be monotypic. Examination of recent collections
from Taiwan, the Philippines and Papua New Guinea showthat specimens from the Pacific belong to two new species.
It is a deep-water genus, with all three species collectedfrom 400 to 500 m.
The record of “Hexaplax sp.” by Rathbun (1910: 349, textfig. 37) from the Gulf of Thailand is problematic. Her figureof the carapace (Rathbun, 1910: text-fig. 37a) superficiallyresembles Hexaplax megalops (or one of the other two
species) and Rathbun commented that it had reniform
eyes. However, it was a very small male only 1.8 mm incarapace width and in poor condition. Most surprisingly, it
was obtained in only six fathoms (ca. 11 m) of water thatis much shallower than what is known for members of thisgenus which are almost always from the deep sea, in excess
of 200 m. The third maxilliped she figured (Rathbun, 1910:
349, text-fig. 37b), however, suggests that her specimen is
not a Hexaplax species, being elongated with a rectangularischium and the dactylus is shorter than the propodus. In
Hexaplax, the ischium is much shorter and broader, andthe dactylus is much longer than the propodus (Figs. 62A,

Colour. In life, the carapace and appendages are dirty white
overall, but stained black in many parts by the mud.
Remarks. Huang et al. (2002) gave a relatively complete
description and figures of the genus and species, and there
is no need to repeat it. One useful character not used by
Huang et al. (2002) is the form of thoracic sternites 1 and
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64A, 66A). This specimen will need to be re-examined toascertain what genus it belongs to.

fingers closed; with large teeth at cutting edge of dactylus
and fixed finger; dactylus, palm and carpus finely granulated
on outer surface; minor chela with slight gap when fingers
closed; ornamentation similar to that of major chela. P2–P4
long, slender; outer surface finely granulated on upper half,lower half almost smooth; merus of P4 8 times as long as
broad, upper margin of merus and carpus finely serrated,outer surface of merus flattened; shallow longitudinal grooveon outer surface of propodus. Male thoracic sternum broad,surface finely granular; sternites 1 and 2 fused, separated
from sternite 3 by distinct ridge; sternite 3 not separated
from sternite 4, sternites 4–7 well developed, separated by
distinct sutures. Male abdomen relatively narrow; somite
1 hidden under carapace; somite 2 free, somites 3–5 fusedwith shallow but distinct suture still visible, lateral margin
sinuous; somite 6 wider than long, lateral margin slightly
expanded subproximally; telson rounded, as long as somite 6.
G1 long, stout, tapering to pointed tip; row of 4 tiny spines
subdistally. Female thoracic sternum broad, female abdomen
relatively broad; somite 1 hidden under carapace; somites
2–6 free; telson rounded, slightly shorter than somite 6.

Hexaplax megalops Doflein, 1904
(Figs. 2E, 55, 56A, B, 57A, 58A, B, 59A–C, 60A,
61C, 62)
Hexaplax megalops Doflein, 1904: 122, pl. 31 figs, 3, 4, pl. 50 fig.
7; Ng et al., 2008: 86 (part).
Material examined. Holotype: male (15.0 × 10.0 mm) (ZMB)(photographs), station 199, 00°15.5'N98°04'E, 470 m, Nias,
Indonesia, coll. German Deep Sea Expedition, RV Valdivia,
1898–1899. Others: 13 males (10.8 × 6.6 mm – 18.7 × 10.7mm), 10 females (13.9 × 9.4 mm – 17.7 × 12.2 mm), 1 ovigerous
female (16.9 × 11.2 mm) (MNHN-IU 2011-2251), station CP 3740
09°12'S 152°16'E, 556–645 m, coll. BIOPAPUA Expedition, 10
October 2010; 1 female (17.9 × 12.9 mm) (MNHN-IU-2011-2820),
station CP 3739, 09°09'S 152°15'E, Woodlark Island, 503–546 m,
coll. BIOPAPUA Expedition, 10 October 2010; 3 males (11.7 ×
8.0 mm – 18.0 × 11.7 mm), 5 females (15.7 × 10.5 mm – 17.6
× 11.7 mm) (MNHN-IU-2011-2425), 2 males (14.6 × 9.4 mm,
15.0 × 10.0 mm), 2 females (17.9 × 11.9 mm, 18.1 × 12.3 mm)(ZRC 2013.1695 ex MNHN-IU-2011-2425), station CP 3743,
09°11'S 152°16'E, Woodlark Island, 540–585 m, coll. BIOPAPUA
Expedition, 10 October 2010; 1 male (12.7 × 8.5 mm), 2 females(15.7 × 10.8 mm, 13.6 × 9.3 mm) (MNHN-IU 2011-2149), station
CP 3741, 09°14'S 152°18'E, Woodlark Island, 694–766 m, coll.
BIOPAPUA Expedition, 10 October 2010; 1 female (14.3 × 9.6mm) (MNHN-IU-2011-3275), station CP 3671, 04°04'S 151°56'E,
north of Rabaul, 585–601 m, coll. BIOPAPUA Expedition, 29
September 2010; 2 males (13.9 × 9.4 mm, 10.8 × 7.2 mm), 1
female (13.9 × 9.3 mm) (MNHN-IU-2011-1168), 1 male (13.4 × 8.9mm) (MNHN-IU-2011-3343), station CP 3739, 09°09'S 152°15'E,
Woodlark Islands, 503–546 m, coll. BIOPAPUA Expedition, 10
October 2010; 1 female (12.5 × 8.3 mm) (MNHN-IU-2011-987),
station CP 3655, 02°15'S 150°16'E, west of New Hanover, 402–440m, coll. BIOPAPUA Expedition, 28 August 2010; 6 males (13.6
× 9.0 mm – 15.9 × 10.1 mm), 7 females (7.8 × 5.4 mm – 14.5 ×
9.8 mm) (MNHN-IU-2011-980), 1 male (13.5 × 9.0 mm) (MNHNIU-2011-1026), station CP 3654, 02°14'S 150°16'E, west of New
Hanover, 490–505 m, coll. BIOPAPUA Expedition, 28 August 2010;
2 males (12.3 × 8.2 mm, 13.0 × 8.4 mm), 3 females (13.7 × 9.3
mm – 18.1 × 12.1 mm) (MNHN-IU-2011-999), station CP 3670,
04°06'S 151°56'E, north of Rabaul, 497–500 m, coll. BIOPAPUA
Expedition, 24 September 2010.

Description. Carapace subquadrate, about 1.5 times as
broad as long, dorsal surface smooth, few fine granules onanterolateral surface; regions indistinct, median H-shaped
depression shallow (Fig. 55). Anterolateral margin arcuate;
posterolateral corner with small angle over base of posterior
pereopods. Front not deflexed (Fig. 56A, B), divided into
2 lobes, not projecting beyond distal edge of orbits. Orbit
distinct, transverse; eye movable, large, corneas dilated,pigmented, much wider than peduncle (Figs. 55, 56A, B).
Pterygostomial region with oblique stridulatory ridge consistof long row of 28 short striae with ca. 17 relatively shorter,
less produced, reaching distal edge of mouthpart (Fig. 60A);
shallow oblique groove above ridge. Third maxillipeds (Figs.
58A, B, 62A) relatively broad, not completely covering
buccal cavity, with gap when closed; ischium longer thanbroad, longer than merus, dilated distally, mesial margin
with row of small teeth, rounded; merus squarish, as long as
broad; exopod relatively narrow, about 0.3 width of ischium,
flagellum well developed.
Chelipeds subequal (Fig. 57A, B); major chela with gap
when fingers closed; with large teeth at cutting edge of
dactylus and fixed finger; dactylus, palm and carpus finely
granulated on outer surface; outer surface of dactylus with
2 longitudinal ridges, inner surface with longitudinal ridge
consist of oblique striae; fixed finger with 2 longitudinalridges; lower margin with row tiny teeth continuing to lower
margin of palm, inner surface of palm with 2 low longitudinalridges; minor chela with slight gap when fingers closed;
ornamentation similar to that of major chela.

Diagnosis. Carapace subquadrate, about 1.5 times as broad as
long, dorsal surface smooth, few fine granules on anterolateralsurface; regions indistinct, median H-shaped depression
shallow. Anterolateral margin arcuate; posterolateral cornerwith small angle over base of posterior pereopods. Front not
deflexed, divided into 2 lobes, not projecting beyond distaledge of orbits in dorsal view. Orbit distinct, transverse; eyemovable, large, corneas dilated, pigmented, much wider thanpeduncle. Pterygostomial region with long row of about
45 short striae forming oblique stridulatory ridge whichreaches posterior margin of epistome; shallow oblique groove
above ridge. Third maxillipeds not completely covering
buccal cavity, with gap when closed; ischium longer thanmerus, dilated distally, mesial margin with row of small
teeth, rounded; merus squarish, as long as broad; exopod
relatively narrow, about 0.3 width of ischium, flagellum welldeveloped. Chelipeds subequal; major chela with gap whenP2–P4 long, slender (Fig. 55); P2 most slender; dactylus
straight, slightly shorter or as long as propodus, longitudinalridge medially on outer surface, propodus and carpus smoothon outer surface; carpus shorter than propodus; merus 2.9
times length of carpus, upper margin with small granules.
P3 longer than P2; dactylus straight, shorter than propodus,
longitudinal ridge medially on outer surface, propodus465

Rahayu & Ng: New genera and species of Hexapodidaesmooth with shallow longitudinal groove on outer surface;
carpus shorter than propodus, outer surface finely granulated
on upper half, upper margin with row of small denticles;
merus 3.2 times length of carpus, upper and lower margin
with row of small denticles distally, proximally smooth,outer surface with tiny granules on distal upper half. P4
shorter than P3; merus 3.4 times length of carpus, 8.8 times
as long as broad, outer surface of merus slightly flattened,ornamentation same as P3 (Fig. 59A, B, C).

Male thoracic sternum broad (Fig. 58A, B), surface finely
granular; sternites 1 and 2 fused, separated from sternite 3 bydistinct ridge; sternite 3 not separated from sternite 4, sternites
4–7 well developed, separated by distinct sutures; sternite 8
not visible; sternoabdominal cavity reaching middle of sternite
4, no thoracic sternal groove. Male abdomen relatively narrow(Figs. 58B, 62B); somite 1 hidden under carapace; somite 2
free, somites 3–5 fused with shallow suture visible, lateral
margin sinuous; somite 6 wider than long, lateral margin

Fig. 55. Hexaplax megalops Doflein, 1904. Overall view of carapace, chelipeds and P2–P4. A. holotype male (15.0 × 10.0 mm) (ZMB);
B, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); C, female (17.7 × 12.2 mm) (MNHN-IU-2011-2251).

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Fig. 56. Frontal view of cephalothorax. A. Hexaplax megalops Doflein, 1904, holotype male (15.0 × 10.0 mm) (ZMB); B, Hexaplax
megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); C. Hexaplax aurantium, new species, holotype male (15.3 ×
10.8 mm) (MNHN-IU-2011-2158); D. Hexaplax saudade, new species, holotype male (16.4 × 12.1 mm) (NMCR).

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Fig. 57. Chelae. A. Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); B, Hexaplax aurantium, newspecies, holotype male (15.3 × 10.8 mm) (MNHN-IU-2011-2158); C, Hexaplax aurantium, new species, paratype female (13.2 × 9.5 mm)(ZRC 2013.1696); D, Hexaplax saudade, new species, holotype male (16.4 × 12.1 mm) (NMCR).

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long in H. aurantium, new species, and H. saudade, newspecies, Figs. 63, 65); the dorsal surface of the carapace
is unevenly convex in frontal view, with the branchialregions more inflated than the gastric regions (Fig. 56A,
B) (the surface is evenly convex in H. aurantium and H.
saudade, Fig. 56C, D); the merus of the third maxillipedof H. megalops is longer than broad (Fig. 62A) while in H.
aurantium and H. saudade, it is about as long as broad (Figs.
64A, 66A); the P2–P4 of H. megalops is proportionately
the longest among the three species with the merus of P4 is
8.8 times as long as broad (Fig. 59A–C) (in H. aurantiumand H. saudade, the merus is 7.6 times and 7 times as longas broad, respectively (Fig. 59D–H). In addition, the outersurface of the carapace, chelipeds and P2–P4 of H. megalops
are almost smooth (Figs. 55, 57A, B, 59A–C), while in H.
aurantium, these structures are densely granulated (Figs. 57
C, 59D–F, 63), and in H. saudade, they are finely granulated(Fig. 57D, 59G, H, 65). Comparisons of female specimensof H. aurantium and H. saudade of similar sizes also showthat the abdomen is relatively broader in H. aurantium,with the thoracic sternum also proportionately broader in
H. saudade (Fig. 64E versus Fig. 66E). The stridulatory
striae on the pterygostomial region of the three species arealso different. Hexaplax megalops has the most, with ca. 45
closely-spaced striae, including the relatively smaller and lessslightly expanded subproximally; telson rounded, as long as
somite 6. G1 long, stout, tapering to pointed tip (Figs. 58A,
62C, D); row of 4 tiny spines subdistally. Female thoracic
sternum broad, female abdomen relatively broad (Fig. 62E);
somite 1 hidden under carapace; somite 2–6 free; telsonrounded, slightly shorter than somite 6.
Colour. In life, the carapace is orangish-yellow, with themargin orange, the eye is cream, the orbit is lined withorange, and there is an orange spot under the cornea. The
cheliped is white with an orange spot at the articulation of
the dactylus and palm, with the distal margins of the carpus,
merus, dactylus and propodus of P2−P4 white, the carpus
is white with a tinge of orange, and the merus is orange
distally and orangish-white proximally (Fig. 2E).
Remarks. The three species of Hexaplax share the samegeneral shape of the carapace, third maxilliped and P2–P4.
It is therefore not surprising that material from the Pacifichave been referred to H. megalops without query, especiallysince few specimens have been collected. The good series of
specimens of all three species on hand allows more detailed
comparisons to be made. The carapace of H. megalops s. str.
is proportionately broader, about 1.5 times as broad as long
(Fig. 55) (carapace slightly narrower, being 1.4 as broad as

Fig. 58. Ventral view of carapace showing abdomen and telson and third maxillipeds. A, Hexaplax megalops Doflein, 1904, holotype male
(15.0 × 10.0 mm) (ZMB); B, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); C, Hexaplax aurantium,
new species, holotype male (15.3 × 10.8 mm) (MNHN-IU-2011-2158); D, Hexaplax saudade, new species, paratype male (17.9 × 12.7mm) (ZRC 2013.1694)

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 59. Right P4, outer surface. A, Hexaplax megalops Doflein, 1904, holotype male (15.0 × 10.0 mm); B, Hexaplax megalops Doflein,
1904, female (17.7 × 12.2 mm) (MNHN-IU-2011-2251); C, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHNIU-2011-2251); D, Hexaplax aurantium, new species, holotype male (15.3 × 10.8 mm)(MNHN-IU-2011-2158); E, Hexaplax aurantium,
new species, paratype female (17.6 × 12.4 mm) (MNHN-IU-2011-2158); F, Hexaplax aurantium, new species, paratype female (13.2 ×
9.5 mm) (MNHN); G, Hexaplax saudade, new species, holotype male (16.4 × 12.1 mm); H, Hexaplax saudade, new species, paratype
female (13.1 × 9.7 mm).

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Fig. 60. Pterygostomial region showing row of stridulatory striae. A, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHNIU-2011-2251); B, Hexaplax aurantium, new species, holotype male (15.3 × 10.8 mm)(MNHN-IU-2011-2158); C, Hexaplax saudade,
new species, holotype male (16.4 × 12.1 mm) (NMCR).

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Rahayu & Ng: New genera and species of Hexapodidae

Fig. 61. A, Hexaplax aurantium, new species, paratype female (13.2 × 9.5 mm); B, Hexaplax saudade, new species, paratype male (17.9 ×
12.7 mm) (ZRC 2013.1694); C, Hexaplax megalops Doflein, 1904, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251). A, front showing eyesin orbit; B, anteroventral view of cephalothorax showing abdomen and telson, third maxillipeds and stridulatory ridge on pterygostomial
regions; C, inner surface of palm.

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Distribution. Nias, Indonesia; and northeast Papua New
Guinea. Deep water, 402–766 m.

produced ones adjacent to the epistome (Fig. 60A), while H.
aurantium and H. saudade have 38 or 39 striae which arespaced relatively further apart (Fig. 60B, C). Doflein’s (1904)
figure of the abdomen of the type specimen (Doflein, 1904:
pl. 31 fig. 4) depicted an abdomen with 6 free somites andtelson. In the specimens of H. megalops studied here, maleabdominal somites 3–5 are fused, but the suture separatingthem is distinct but shallow (Fig. 58B). It is similar in H.
aurantium (Fig. 58C), but in H. saudade, the sutures are
not discernible and somites 3–5 appear as one large plate(Fig. 58D). The G1s of the three species are different. In
H. megalops, the G1 is relatively longer and stouter, with arow of four small denticles on the mesial margin (Fig. 62C,
D); in H. aurantium, the G1 is more slender, without any
teeth or denticles (Fig. 64C, D); while in H. saudade, theG1 is more slender, with small denticles on the median partof the mesial margin (Fig. 66C, D; see also Serène, 1964:
270, text fig. 21B).

Hexaplax aurantium, new species(Figs. 2F, 56C, 57C, 58C, 59D–F, 60B, 61A, 63, 64)
Hexaplax megalops – Tesch, 1918: 242. (not Hexaplax megalops
Doflein, 1904)
Material examined. Holotype: male (15.3 × 10.8 mm) (MNHNIU-2158), CP 3707, 04°59'S 145°50'E, Madang, 460–466 m,
Papua New Guinea, coll. BIOPAPUA Expedition, 2 October 2010.
Paratypes: Papua New Guinea: 6 females (12.4 × 8.7 mm – 18.7
× 13.3 mm) (MNHN-IU-2011-2794), station CP 3692, 02°10'S
147°19'E, southeast Manus Island, 408–448 m, coll. BIOPAPUA
Expedition, 29 September 2010; 2 males (12.0 × 8.6 mm, 12.1 ×
8.4 mm), 3 females (11.8 × 8.8 mm – 16.3 × 11.5 mm) (MNHNIU-2011-1527), 2 males (14.0 × 9.5 mm, 14.2 × 9.8 mm), 5 females(11.9 × 8.3 mm – 15.2 × 10.7 mm) (MNHN-IU-2011-1066), station
CP 3635, 07°29'S 147°33'E, south of Lae, Gulf of Huon, 280–302
m, coll. BIOPAPUA Expedition, 23 August 2010; 3 males (13.1

Type locality. Nias, Indonesia.

Fig. 62. Hexaplax megalops Doflein, 1904. A–D, male (18.7 × 12.1 mm) (MNHN-IU-2011-2251); E, female (17.7 × 12.2 mm) (MNHNIU-2011-2251). A, left third maxilliped; B, male abdomen and telson; C, D, G1; E, female abdomen and telson. Scale bars = 1.0 mm.

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Rahayu & Ng: New genera and species of Hexapodidae
fused, separated from sternite 3 by distinct ridge; sternite 3
not separated from sternite 4, sternites 4–7 well developed,
separated by distinct sutures; sternoabdominal cavity reaching
middle of sternite 4, no thoracic sternal groove; sternite 8 notvisible. Male abdomen relatively narrow (Figs. 58C, 64B);
somite 1 hidden under carapace; somite 2 free, somites 3–5
fused with shallow suture visible, lateral margin sinuous;
somite 6 wider than long, lateral margin slightly expanded
subproximally; telson rounded, about same length as somite
6. G1 long, slender, tapering to pointed tip (Fig. 64C, D),
unarmed. Female thoracic sternum broad; sternoabdominal
cavity reaching middle of sternite 4; female abdomen
relatively broad (Fig. 64E); somite 1 hidden under carapace;somite 2–6 free; telson rounded, as long as somite 6.

× 9.0 mm – 18.1 × 12.4 mm), 4 females (17.3 × 12.4 mm – 20.7
× 15.0 mm) (MNHN-IU-2011-3519), station CP 3708, 04°58'S
145°50'E, Madang, 502–529 m, coll. BIOPAPUA Expedition, 2October 2010; 2 males (14.6 × 10.0 mm, 16.9 × 11.6 mm), 3
females (13.3 × 9.6 mm – 16.6 × 12.1 mm) (ZRC 2013.1696 ex
MNHN-IU-2158), station CP 3707, 04°59'S 145°50'E, Madang,
460–466 m, coll. BIOPAPUA Expedition, 2 October 2010; 1 male
(13.8 × 9.6 mm), 2 females (14.6 × 10.4 mm, 14.9 × 10.6 mm)(MNHN-IU-1461), 1 male (13.0 × 8.7 mm) (MNHN-IU-1392),
station CP 3669, 04°08'S 151°56'E, north of Rabaul, 382–389 m,coll. BIOPAPUA Expedition, 24 September 2010; 2 females (13.9
× 9.4 mm, 16.5 × 11.3 mm) (MNHN-IU-2640), station CP 3691,
02°11'S 147°18'E, southeast of Manus Island, 499–517 m, coll.
BIOPAPUA Expedition, 29September 2010; 1 female (12.2 × 8.6mm) (MNHN-IU-2011-1723), station CP 3729, 07°52'S 148°03'E,
Mambare Bay, 575–655 m, coll. BIOPAPUA Expedition, 8 October
2010; 1 female (9.5 × 6.6 mm) (MNHN-IU-2011-993), station CP
3734, 08°16'S 150°30'E, Lancasey Island, 389 m, coll. BIOPAPUA
Expedition, 9 October 2010; 1 male (13.6 × 9.6 mm) (MNHNIU-2011-987), station CP 3655, 02°15'S 150°16'E, west of New
Hanover, 402–440 m, coll. BIOPAPUA Expedition, 28 August 2010;
1 male (12.3 × 8.6 mm), 3 females (9.6 × 6.9 mm – 14.1 ×9.9 mm)(MNHN-IU-2011-3386), station CP 3646, 06°45'S 147°49'E, Tami
Island, 460–485m, coll. BIOPAPUA Expedition, 24 August 2010;
3 males (12.1 × 8.5 mm – 14.6 × 10.1 mm), 4 females (10.1 × 7.2
mm – 18.5 × 12.9 mm (MNHN-IU-2011-1704), station CP 3728,
07°52'S 148°01'E, Mambare Bay, 498–501 m, coll. BIOPAPUA
Expedition, 8 October 2010; 1 female (13.2 × 9.5 mm) (ZRC 2013.
1697), CP 3957, 05°05'S 145°51'E, Bismarck Sea, Madang, westof Sek Island, 452–504 m, coll. Expedition PAPUA NUIGINI, 28
November 2012.

Colour. In life, the carapace is cream-mottled with orange
margin, the eye is cream with orange longitudinal stripeson the lateral and mesial margins, and an orange spot under
the cornea. T cheliped is white with an orange stripe on thearticulation of the dactylus and palm, and distal margins of
the carpus and merus of P2−P4 are orangish-white (Fig. 2F).
Etymology. From the Latin noun aurantium for citrus;
alluding to the orange colour of the species in life.
Remarks. See remarks for H. megalops s. str. for differenceswith congeners.
Tesch (1918) recorded several specimens of “Hexaplax
megalops” from Saleyer Island (southern Sulawesi) and northof Bali. On the basis of the adult measurements provided
by Tesch (1918: 243), the carapace width to length ratios ofthese specimens ranged from 1.34 to 1.43, indicating they
probably belong to H. aurantium, new species. Hexaplax
megalops, which also occurs in New Guinea waters andmay be present in Sulawesi and Bali, has a proportionately
broader carapace, with a width to length ratio of 1.5.

Diagnosis. Carapace subquadrate, about 1.4 times as broadas long, dorsal surface finely granulated; regions indistinct,
median H-shaped depression shallow (Fig. 63). Anterolateral
margin arcuate; posterolateral corner with small angle overbase of posterior pereopods. Front not deflexed (Fig. 56C),
divided into 2 lobes, not projecting beyond distal edge oforbits. Orbit distinct, transverse; eye movable, large, corneas
dilated, pigmented, much wider than peduncle (Figs. 56C,
61A). Pterygostomial region with oblique stridulatory ridge
consist of long row of 25 short striae, including about 14
shorter, less produced striae adjacent to epistome (Fig. 60B);
shallow oblique groove above ridge. Third maxillipeds (Figs.
64A) relatively broad, not completely covering buccal cavity,with gap when closed; ischium longer than broad, longer
than merus, dilated distally, mesial margin rounded; merus
squarish, as long as broad; exopod relatively narrow, about
0.3 width of ischium, flagellum well developed. Chelipeds
subequal (Fig. 57C); major chela with slight gap whenfingers closed; with large teeth at cutting edge of dactylus
and fixed finger; dactylus, palm and carpus granulated onouter surface; outer surface of dactylus with 2 longitudinalridges; inner surface with longitudinal ridge consist of
oblique striae; fixed finger with 2 longitudinal ridges; lower
margin with row small teeth continuing to lower marginof palm; minor chela with gap proximally when fingers
closed; ornamentation similar to that of major chela. P2–P4
long, slender (Fig. 63); outer surface granulated; merus of
P4 7.6 times as longas broad, upper margin of merus andcarpus granulated, shallow longitudinal groove on outersurface of propodus (Fig. 59D–F). Male thoracic sternum
broad (Fig. 58C), surface finely granular; sternites 1 and 2

Type locality. Madang, Papua New Guinea.
Distribution. Papua New Guinea. Deep water, 280−655 m.
Hexaplax saudade, new species(Figs. 2G, H, 56D, 57D, 58D, 59G, H, 60C, 61B, 65, 66)
Hexaplax megalops – Serène, 1964: 270, text fig. 21, pl. 24A;
Sakai, 1965: 40, 45, pl. 6 fig. 8; Sakai, 1976: 556, pl. 196 fig.
4; Ng et al., 2008: 86 (part), fig. 78. (not Hexaplax megalops
Doflein, 1904)
Material examined. Holotype: male (16.4 × 12.1 mm) (NMCR),
station CP 2660, 15°52.2'N 121°48.8'E, 542 m, Philippines, coll.
AURORA 2007 Expedition, 20 May 2007. Paratypes: Philippines:
3 males (11.6 × 8.2 mm, 14.8 × 10.5 mm, 18.2 × 13.2 mm), 3
females (14.3 × 10.8 mm, 14.6 × 10.6 mm, 16.9 × 9.8 mm, 18.6 ×
13.6 mm) (ZRC 2013.1692), 3 males (13.6 × 9.7 mm, 15.3 × 11.2mm, 17.2 × 12.0 mm), 2 females (15.2 × 11.1 mm, 15.8 × 11.7mm) (MNHN), station CP 2658, 15°58.03'N 121°49.11'E, 422 m,
coll. AURORA 2007 Expedition, 20 May 2007; 1 male (16.4 × 12.1mm), 1 female (11.4 × 8.0 mm) (ZRC 2013.1693), station CP 2660,
15°52.2'N 121°48.8'E, 542 m, coll. AURORA 2007 Expedition, 20
May 2007; 1 male (17.9 × 12.7 mm), 2 females (16.6 × 12.3 mm,

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RAFFLES BULLETIN OF ZOOLOGY 201413.1 × 9.7 mm) (ZRC 2013.1694), station CP 2735, 15°59.52'N
121°50.93'E, 431 m, coll. AURORA 2007 Expedition, 1 June 2007.
Others: Taiwan: 1 male (15.9 × 11.1 mm) (ZRC 2008.1456), SuAo fish port, Ilan province, trawled, deep-sea, coll. C.-W. Lin, 29
July 2004. Japan: 1 male (15.1 × 11.6 mm) (NSMT-Cr 13586),
Tosa Bay, 400 m, coll. Kotaka Maru, M. Takeda, 9 May 2000.

Anterolateral margin arcuate; posterolateral corner with small
angle over base of posterior pereopods. Front not deflexed(Fig. and 56D), divided into 2 lobes, not projecting beyond
distal edge of orbits. Orbit distinct, transverse; eye movable,
large, corneas dilated, pigmented, much wider than peduncle(Fig. 56D). Pterygostomial region with oblique stridulatory
ridge consist of long row of 24 short, widely-spaced striae,
including ca. 14 shorter, less produced striae adjacent toepistome (Fig. 60C); shallow oblique groove above ridge.

Diagnosis. Carapace subquadrate (Fig. 65A), about 1.4
times as broad as long, dorsal surface very finely granulated;regions indistinct, median H-shaped depression shallow.

Fig. 63. Hexaplax aurantium, new species. Overall view of carapace, chelipeds and P2–P4. A, holotype male (15.3 × 10.8 mm) (MNHNIU-2011-2158); B, paratype female (17.6 × 12.4 mm) (ZRC 2013.1696, ex MNHN-IU-2011-2158); C, paratype female (13.2 × 9.5 mm)(ZRC 2013.1697).

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Rahayu & Ng: New genera and species of Hexapodidae
Third maxillipeds broad (Fig. 66A), not covering buccal
cavity, with gap when closed; ischium longer than broad,
longer than merus, with scattered granules, dilated distally,
mesial margin rounded; merus squarish, as long as broad;dactylus longer than propodus; exopod relatively narrow,less than 0.3 width of ischium; flagellum well developed.
Chelipeds subequal (Fig. 57D); major chela with slight
gap when fingers closed; with large teeth at cutting edgeof dactylus and fixed finger; outer surface of dactylus with
2 longitudinal ridges; inner surface near upper margin withlongitudinal ridge; palm longer than wide, outer surface finely
granulated; fixed finger with 2 longitudinal ridges; lower
margin with row small teeth continuing to lower margin of

palm; carpus finely granulated on outer surface, inner angle
blunt, upper margin with row of small tubercles obscured byshort setae, long setae on outer angle; merus short, row of
denticles on outer and inner lower margins, fringe of setae
dorsomesially. Minor chela without gap when fingers closed;
ornamentation similar to that of major chela. P2–P4 long,
slender (Fig. 65); outer surface finely granulated; merus of P4
about 7 times as long as broad (Fig. 59G, H). Male thoracic
sternum broad (Fig. 58D), surface finely granular; sternites
1 and 2 fused, separated from sternite 3 by distinct ridge;
sternite 3 not separated from sternite 4, sternites 4–7 welldeveloped, separated by distinct sutures; sternoabdominal
cavity reaching middle of sternite 4, no thoracic sternal

Fig. 64. Hexaplax aurantium, new species. A–D, holotype male (15.3 × 10.8 mm) (MNHN-IU-2011-2158); E, paratype female (13.2 ×
9.5 mm). A, left third maxilliped; B, male abdomen and telson; C, D, G1; E, female abdomen and telson. Scale bars = 1.0 mm.

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RAFFLES BULLETIN OF ZOOLOGY 2014

Fig. 65. Hexaplax saudade, new species, overall view of carapace, chelipeds and P2–P4. A, holotype male (16.4 × 12.1 mm) (NMCR);
B, paratype male (17.9 × 12.7 mm); C, paratype male (18.2 × 13.2 mm); D, paratype female (13.1 × 9.7 mm).

477

Rahayu & Ng: New genera and species of Hexapodidae
Remarks. See remarks for H. megalops s. str. for differenceswith congeners.

groove; sternite 8 exposed, triangular, reaching half lengthof male abdominal somite 2. Male abdomen relatively
narrow (Figs. 58D, 66B); somite 1 hidden under carapace;somite 2 free, somites 3–5 fused, lateral margin sinuous;
somite 6 wider than long, lateral margin slightly expanded
subproximally; telson rounded, as long as somite 6. Female
abdomen not much wider than male (Fig. 66E), 6 free somites
and telson, first somite hidden under carapace. G1 (Fig. 66C,
D) concealed under abdomen, straight, distal part tapered,sparse short setae present in proximal half, small spinules
on mesial margin medially.

The records of “Hexaplax megalops” from Philippines(Serène, 1964; Ng et al., 2008) and Tosa Bay in Japan(Sakai, 1965; Sakai, 1976) are clearly Hexaplax saudade, newspecies. The figure of a fresh specimen in Sakai (1965, 1976)
agrees well with those of the new species from Philippines(Fig. 2E) and Taiwan (Fig. 2F). We have also examined amale specimen from Tosa Bay specimen (NSMT-Cr 13586)
which agrees with our definition of H. saudade.

Colour. In life, the carapace is light brown with a tinge oforange or orangish-brown medially. The cheliped transparent
white with an orange line at the articulation of the dactylus
and palm; P2–P4 transparent are whitish on the dactylus,
propodus and carpus; with the merus light brown tinged oforange distally (Fig. 2G, H).

Type locality. Philippine Sea, Philippines.

Etymology. The species name is derived from the Portuguese
word “saudade” which means a melancholic longing forsomething that cannot exist or be realised; alluding to thelong-held belief that Hexaplax was a monotypic genus. The
name is used as a Latin noun in apposition.

Diagnosis. Carapace broader than long, slightly convex,
surface granular, region indistinct, with H-shaped medial
depression. Anterolateral margin rounded; lateral margins
straight, parallel. Eyes short, movable, corneas subglobular,
visible. Third maxilliped broad, completely covering buccal

Distribution. Philippines, Taiwan and Japan. Deep water,
422–542 m.
Theoxapus, new genus

Fig. 66. Hexaplax saudade, new species. A–D, holotype male (16.4 × 12.1 mm) (NMCR); E, paratype female (13.1 × 9.7 mm). A, left
third maxilliped; B, male abdomen and telson; C, D, G1; E, female abdomen and telson. Scale bars = 1.0 mm.

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RAFFLES BULLETIN OF ZOOLOGY 2014
cavity; ischium notably broader and longer than merus, mesial
margin slightly convex, crenulated; merus relatively ovoid,
crenulated on mesial and lateral margin; carpus, propodus
and dactylus cylindrical, dactylus longer than propodus;
exopod narrow compared to width of ischium, slightly
sinuous, margins crenulated, flagellum present. Chelipeds
unequal, granulated; P2–P4 relatively long, granulated andsetose; merus slender, dactylus straight or upcurved, as longas propodus. Thoracic sternum broad, granulated. Male
sternoabdominal cavity reaches distal margin of thoracic

sternite 4; without sternal groove. Male abdomen relatively
narrow; somites 1, 2 and 6 free, somites 3–5 fused; telson
slightly shorter than somite 6, ovate, distal margin rounded.
G1 slightly sinuous, stout, dense stiff setae on subdistal,
obscuring pointed tip. Female unknown.
Etymology. The genus is named after famed French
explorer, naturalist and carcinologist Théodore André Monod(1902–2000), whose 1956 book on West African crabs
remains a mainstay of researchers. The name is an arbritaryFig. 67. Theoxapus buchanani (Monod, 1956), holotype male (7.0 × 4.9 mm) (NHM 1957.12.4.29). A, overall view of carapace, chelipeds
and P2–P4; B, ventral view of cephalothorax; C, frontal view of cephalothorax; D, chelae.

479

Rahayu & Ng: New genera and species of Hexapodidae
1956, is closest to species in Mariaplax, new genus, in thatit has a similarly shaped third maxilliped (Fig. 68G). Like
many Mariaplax species, Hexapus buchanani also has aprominently granulated carapace and pereopods (Figs. 67A,
68E). However, Hexapus buchanani cannot be referred toMariaplax as it has distinctively more ovate carapace withthe lateral margins subparallel (Figs. 67A, 68E) (rather
than more trapezoidal with the lateral margins diverging),
the ambulatory meri do not have a longitudinal groove on
the outer surface, not even on P3 (Figs. 67A, 68E); there
is no trace of a male thoracic sternal groove or depression
adjacent to the sternoabdominal cavity (Fig. 67B); it has a
proportionately more elongate male abdomen (Fig. 68F);
the telson is elongated and much longer than broad (Fig.
68F); and it has a relatively much straighter G1 which
has the distal part surrounded by long setae (Fig. 68H, I).
Externally, especially with regards to the general carapace
shape, Hexapus buchanani resembles other West Africantaxa, notably Parahexapus africanus (Balss, 1922). However,Hexapus buchanani differs markedly from Parahexapus

combination of his first name, with the suffix of the genus
Hexapus. Gender of genus masculine.
Species included. Hexapus buchanani Monod, 1956 (bymonotypy).
Remarks. When Monod (1956: 372) described Hexapus
buchanani and placed it in the subgenus Hexapus, he included
H. sexpes sensu Balss (1922). As Balss (1922) indicatedthat the shape of the third maxilliped is similar to Hexapus
sexpes sensu Stebbing (1910: 315), he therefore placed his
species in Hexapus s. str. Hexapus sexpes sensu Stebbing(1910) is now known as Tritoplax stebbingi (Barnard, 1947)(see Manning & Holthuis, 1981: 180). Manning & Holthuis(1981: 171), who did not have specimens, transferred
Hexapus (Hexapus) buchanani to Hexapinus Manning &Holthuis, 1981, without any comments, although it was
the only member of the genus occuring in the Atlantic.
Considering the present revision of Hexapus s. str. andHexapinus s. str., Hexapus (Hexapus) buchanani Monod,

Fig. 68. A–D, Parahexapus africanus (Balss, 1922); E–I, Theoxapus buchanani (Monod, 1956). A, E, overall views of carapaces, chelipeds
and P2–P4; C, G, left third maxillipeds; B, F, male abdomen and telsons; D, H, G1s; I, distal part of G1. A, C, after Monod, 1956: figs.
494, 496; B, D, after Crosnier, 1967: figs. 30, 33; E–I, after Monod, 1956: figs. 497–500.

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RAFFLES BULLETIN OF ZOOLOGY 2014
africanus in that the ischium of the third maxilliped isquadrate (Fig. 68G) (elongated and ovate in P. africanus, Fig.
68C); the exopod of the third maxilliped is proportionately
longer, reaching to half the length of the merus (Fig. 68G)
(relatively shorter, reaching to just beyond the length of theischium in P. africanus, Fig. 68C); fused male abdominal
somites 3–5 are proportionately longer, and longer thansomite 6 (Fig. 68F) (fused male abdominal somites 3–5 areproportionately shorter, and subequal in length to somite
6 in P. africanus, Fig. 68B); and the G1 is stouter withthe tip tapered and the distal part covered with long setae(Fig. 68H, I) (G1 very slender, with the distal third sharpy
tapering and the median surfaces lined with short spines inP. africanus, Fig. 68D).

Male abdomen relatively narrow (Fig. 68F); somites 1 and
2 free, somites 3–5 fused, lateral margin sinuous; somite 6
long, lateral margin slightly expanded subproximally; telsonrounded, slightly shorter than somite 6. G1 (Fig. 68H, I)
concealed under abdomen, slightly sinuous, dense stiff setae
subdistally, covering tapered, pointed tip.

These differences are significant are indicate that Hexapus
buchanani cannot be transferred to Mariaplax or Parahexapus,
or any of the other recognised genera. A new genus,
Theoxapus, is therefore established here to accommodate
the species.

ACKNOWLEDGEMENTS

Colour. Not known.
Remarks. See discussion for genus.
Type locality. Gold Coast, West Africa.
Distribution. West Africa.

Many friends have been very generous with their time forthis study, which has taken far longer than it should have.
We thank Peter Davie (QM) for his many helpful comments
and discussion about the taxonomy of hexapodids; Charles
Fransen (RMNH) for checking the types of Hexapinus
latipes; Diana Jones and Andrew Hosie (WAM) for loanof important material; Hironori Komatsu (NSMT) and
Tohru Naruse (RUMF) for sending us their collections ofhexapodids; Takehiro Sato (KPM) for helping with Sakai’smaterial in Kanagawa; Paul Clark (NHM) for permission to
examine his specimens; Oliver Coleman (ZMB) for helping
to check and photograph the type of Hexaplax megalops;
Laure Cobari, Paula Martin-Lefèvre and Anouchka Sato
(MNHN) for loan of Hexaplax material; Chan Tim-Yan(National Taiwan Ocean University) for Taiwanese material
and photographs; and Li Xin Zheng (IOCAS) for kindly
tracking down the old station data for material left to us
by the late Chen Hui-Lian. Thanks are also due to Rafael
Lemaitre and Karen Reed (USNM) for hosting the second
author in the museum’s Support Centre. The expeditions
we have been involved also obtained many important
specimens. We thank the crew and scientists on board theresearch vessels DA-BFAR and Alis who collected many ofthe deep-water samples. The various Philippine expeditions
were jointly organised by MNHN (through Philippe Bouchet);
Bureau of Fisheries and Aquatic Resources (BFAR), Manila(through Ludivina Labe); National Museum of the Philippines(NMCR) (through Marivene Manuel-Santos); University of
San Carlos (USC, Cebu) (through Danilo Largo); National
Ocean University, Keelung, Taiwan (through Chan TinYam); RMBR; ASEAN Research Centre for Biodiversity
and Conservation (Manila); and the National University ofSingapore, with key funding from the Total Foundation andFrench Ministry of Foreign Affairs. The BIOPAPUA cruise
was led by Sarah Samadi and Philippe Bouchet (MNHN).
The Expedition PAPUA NUIGINI (under Philippe Bouchet,Sarah Samadi and Claude Payri) was organised by MNHN,
Pro Natura International, Institut de Recherche pour leDéveloppement, and University of Papua New Guinea with
Divine Word University; funded by the Total Foundation,
Prince Albert II of Monaco Foundation, Fondation EDF,
Stavros Niarchos Foundation and Entrepose Contracting;and operated under a permit by the Papua New Guinea
Department of Environment and Conservation.

Theoxapus buchanani, new combination(Figs. 67, 68E–I)
Hexapus buchanani Monod, 1956: 372, figs. 497–501.
Hexapinus buchanani – Manning & Holthuis, 1982: 169, Fig. 31;
Ng et al., 2008: 86; Hendrickx, 2013: fig. 3A.
Material examined. Holotype: male (7.0 × 4.9 mm) (NHM
1957.12.4.20), station 57-29-1-53, Gold Coast, West Africa, 7 m,coll. J. B. Buchanan.

Diagnosis. Carapace subquadrate (Figs. 67A, 68E), about 1.4
times as broad as long, dorsal surface granulated, convex;
regions indistinct, distinct median H-shaped depression.
Anterolateral margin rounded; crenulated, lateral margin
parallel, straight, posterior margin straight. Front slightly
deflexed (Fig. 67C), slightly divided into 2 lobes, projecting
beyond edge of orbits. Orbit distinct, transverse; eye movable,
corneas subglobular, pigmented (Fig. 67C). Third maxillipeds
broad (Figs. 67B, 68G), covering buccal cavity, without gap
when closed; ischium notably broader, longer than merus,
mesial margin slightly convex, crenulated; merus relatively
ovoid, crenulated on mesial and lateral margins; carpus,
propodus and dactylus cylindrical, dactylus longer thanpropodus; exopod narrow, 0.3 width of ischium, slightly
sinuous, margins crenulated, flagellum well developed.
Chelipeds subequal (Fig. 67D); major chela with slight
gap when fingers closed; with large teeth at cutting edge of
dactylus and fixed finger; outer surface of dactylus and palm
granulated; palm longer than wide; minor chela with wider
gap when fingers closed; ornamentation similar to that ofmajor chela. P2–P4 relatively long, granulated and setose(Figs. 67A, 68E); P3 longest; P2 most slender; dactylus sligtly
upcurved; P3 longer than P2; dactylus straight; P4 shorter
than P3, merus about 3 times as long as broad. Male thoracic
sternum broad (Fig. 67B), surface granulated; sternites 1 and2 fused, separated from sternite 3 by distinct ridge; sternite 3
not separated from sternite 4, sternites 4–7 well developed,
separated by distinct sutures; sternoabdominal cavity
reaching middle of sternite 4, no thoracic sternal groove.
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Rahayu & Ng: New genera and species of Hexapodidae
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