Ng: Geosesarma from northern Peninsular Malaysia
Taxonomy & Systematics
RAFFLES BULLETIN OF ZOOLOGY 65: 226–242

Date of publication: 29 June 2017
http://zoobank.org/urn:lsid:zoobank.org:pub:94DDC8A4-4575-4331-9DBF-4A2494D79A6F

On the identities of the highland vampire crabs, Geosesarma foxi
(Kemp, 1918) and G. serenei Ng, 1986, with description of a new
phytotelmic species from Penang, Peninsular Malaysia (Crustacea:
Decapoda: Brachyura: Sesarmidae)
Peter K. L. Ng
Abstract. The identities of two poorly known semiterrestrial sesarmid crabs Geosesarma foxi (Kemp, 1918) andG. serenei Ng, 1986, from northern Peninsular Malaysia are clarified with the study of additional material. A
new species associated with phytotelms in Penang, G. faustum n. sp., is described and distinguished from thetwo known species by various carapace, male pleon and gonopod characters. The taxonomy of the three species
is discussed. All three are highland species, occurring only at altitudes higher than 700 m; and are characterisedby their quadrate carapace, long and slender ambulatory legs, absence of a flagellum on the exopod of their third
maxilliped, and relatively slender male first gonopod.
Key words. Phytotelmata, Southeast Asia, Sesarmidae, montane crabs, Geosesarma, taxonomy, new taxa

INTRODUCTION

In May 2014, Ji Tan and Chan Zi Yang, two students ofYong Hoi Sen in the University of Malaysia, collected several
yellow crabs from among South American bromeliads whichwere being grown around a hotel at the top of Penang Hill
in Penang Island in Peninsular Malaysia. Examination ofthese specimens indicated they were superficially close to
G. foxi and G. serenei, but their precise identification would
require fresh specimens of G. foxi being collected for detailed
comparisons. By a remarkable coincidence, specimens of
G. foxi were eventually collected from Langkawi on three
separate occasions a few years later, just a few months
apart. In July 2016, a Malaysian hiker found an intact deadmale specimen on a hiking trail on the way to the summitof Gunung Raya. In December 2016, a Taiwanese biologist
managed to collect several specimens while climbing thesame trail down the mountain, and several weeks later inJanuary 2017, a Singaporean visitor obtained more while
he was staying at a resort at the summit of Gunung Raya.

In their survey of the freshwater crabs of Pulau Langkawi,
a large island off the west coast of the state of Kedah in
Peninsular Malaysia, Ng & Ng (1987) commented that they
were unable to find the semiterrestrial sesarmid Geosesarma
foxi (Kemp, 1918) which had been described from specimens
found near the top of Gunung Raya, the highest peak there(see also Ng & Ng, 1989: 76). The types of Geosesarma
foxi are deposited in the Zoological Survey of India (ZSI)
in Calcutta, and the curator of the ZSI at that time, Maya
Deb, kindly provided sketches of the male first gonopod andthe exopod of the third maxilliped of the lectotype, whichwere published in Ng (1988: fig. 54C, D). Ng (1986a) had
earlier referred specimens collected from Bukit Larut [=Maxwell Hills] in mainland Perak, identified as “Sesarma
foxi” by Tweedie (1936) to a new species, G. serenei.
During the Langkawi Scientific and Heritage Expeditionof 2003 organised by the Malayan Nature Society, oneof the participating scientists, Amirrudin Ahmad (now at
the Universiti Malaysia Terengganu), sent the author aphotograph of a red crab found badly crushed on a road goingup Gunung Raya, which, judging by its carapace shape andcolour was probably G. foxi. The condition of that specimen,
however, was too poor for it to be useful for study.

In this paper, the identity of Geosesarma foxi (Kemp, 1918)
is finally clarified on the basis of the good series of fresh
specimens, and the species is diagnosed and figured. Detailed
comparisons are now also made with the morphologicallysimilar G. serenei Ng, 1986. The material from Penang Island
is here shown to be a new species, and while resembling G.
foxi and G. serenei, differs in a number of carapace, malepleon and first gonopod characters. This new species, G.
faustum, is diagnosed in the present paper and comparedwith morphologically similar congeners.
The terminology used essentially follows that in Ng (1988)
with recent amendments recommended by Davie et al.
(2015). Measurements, in millimetres, are of the maximum
carapace width and length, respectively. The abbreviations

Lee Kong Chian Natural History Museum, Faculty of Science, National University ofSingapore, 2 Conservatory Drive, Singapore 117377, Republic of Singapore; Email:peterng@nus.edu.sg© National University of Singapore
ISSN 2345-7600 (electronic) | ISSN 0217-2445 (print)

226

RAFFLES BULLETIN OF ZOOLOGY 2017
G1 and G2 are used for the male first and second gonopods,
respectively. Specimens examined are deposited in the
Zoological Reference Collection (ZRC) of the Lee Kong
Chian Natural History Museum, National University ofSingapore.
TAXONOMYFamily Sesarmidae Dana, 1851
Geosesarma De Man, 1892
Type species. Sesarma (Geosesarma) nodulifera De Man,
1892, subsequent designation by Serène & Soh (1970).
Remarks. Members of Geosesarma De Man, 1892, arepopularly known as “vampire crabs” because of the brightyellow eyes of a number of species (Rademacher &Mengedoht, 2011; Ng et al., 2015). The genus currently
contains 58 species (cf. Ng et al., 2008; Schubart & Ng, 2014;
Ng, 2015; Ng et al., 2015; Manuel-Santos et al., 2016; Ng& Lemaitre, 2017); almost all of which are semiterestrial in
habits, living in and around freshwater habitats in Southeast
Asia. They are regarded as secondary freshwater crabs bysome authors (Yeo et al., 2008) although most species
have large eggs and practice completely abbreviated larval
development (cf. Ng, 1988).

Fig. 1. Geosesarma foxi (Kemp, 1918), lectotype male (9.8 × 9.8mm), Gunung Raya, Langkawi (after Kemp, 1918: figs. 3, 4). A,
overall dorsal view; B, outer view of left chela.

Low, 16 July 2016; 3 males (11.5 × 11.4 mm, 9.6 × 9.7
mm, 7.8 × 7.7 mm), 3 females (11.8 × 11.9 mm, 7.5 × 7.3mm, 6.8 × 6.7 mm) (ZRC 2016.619), near start of Tangga
Helang Seribu Kenangan hiking trail from below summitof Gunung Raya, Langkawi Island, Peninsular Malaysia, ca.
780 m asl, coll. J.-J. Li, 31 December 2016; 4 males (10.9
× 10.9 mm, 9.9 × 10.0 mm, 8.0 × 7.9 mm, 6.6 × 6.7 mm),
1 ovigerous female (11.7 × 11.8 mm), 3 females (10.8 ×
10.9 mm, 8.6 × 8.4 mm, 8.2 × 8.1 mm) (ZRC 2016.618),
near start of Tangga Helang Seribu Kenangan hiking trail
from below summit of Gunung Raya, Langkawi Island,
Peninsular Malaysia, ca. 780 m asl, coll. P.Y.C. Ng, 12–13
January 2017.

Geosesarma foxi (Kemp, 1918) belongs to a group of
Geosesarma species generally characterised by their quadrate
carapaces, slender and relatively long ambulatory legs, withthe exopod of the third maxilliped not possessing a flagellum,
and that usually occur in highlands. Ng (1988) treated thetwo Malaysian species, Geosesarma foxi (Kemp, 1918) from
Langkawi Island (Kedah), and G. serenei Ng, 1986, from
Bukit Larut in Perak; commenting that the taxonomy of
the material referred to “G. foxi” from southern PeninsularThailand needed to be revised in the future. A third species,
which may be allied to G. foxi and G. serenei, is G. krathing
Ng & Naiyanetr, 1992, described from Krathing Waterfall in
Chantaburi Province in eastern Thailand, near the Cambodian
border. While this species shares the quadrate carapace andlong slender ambulatory legs of G. foxi and G. serenei (andtheir male first gonopods are also superficially similar), theexopod of its third maxilliped has a well-developed flagellum(Ng & Naiyanetr, 1992: fig. 1B).

Diagnosis. Carapace quadrate, slightly wider than longor subequal, adult width to length ratio 1.00–1.04, lateral
margins parallel (Figs. 1A, 3A–C, 4); dorsal surface with
regions just visible, anterior regions with small rounded
granules on gastric regions (Figs. 3A–C, 4); front distinctly
deflexed, frontal lobes broad with gently convex margins in
dorsal view; postfrontal, postorbital cristae sharp, distinct(Figs. 3B–D, 4); external orbital tooth triangular, directed
obliquely laterally, outer margin gently convex, tip notextending beyond lateral margin; second lateral tooth distinct,
clearly separated from rest of margin by wide cleft (Figs.
3B, C, 4). Merus of third maxilliped subovate, shorter thanischium; exopod slender with no trace of flagellum (Fig.
7A). Outer surface of palm of adult male covered with smallrounded granules and striae; inner surface granulated but
without transverse ridge; dorsal margin of dactylus with 7
or 8 low, non-chitinous tubercles on proximal half (Figs. 1B,
3A, 4A, B, 5D). Ambulatory legs with long, slender merus,
with sharp subdistal spine on dorsal margin, surfaces gently
rugose (Figs. 1A, 3A, 4A, B). Male pleon broadly triangular;
somite 6 wide, with convex lateral margins; telson almost
semicircular, not recessed into distal margin of somite 6(Fig. 5A–C). G1 slender; outer margin of subdistal part ofGeosesarma foxi (Kemp, 1918)(Figs. 1–5, 7A–H)
Sesarma foxi Kemp, 1918: 238, figs. 3, 4.
Sesarma (Geosesarma) foxi – Serène, 1968: 107.
Geosesarma foxi – Serène & Soh, 1970: 407; Ng & Ng, 1987: 13;
Ng, 1988: 122, fig. 54; Ng, 2004: 333 (list); Ng & Yeo, 2007:
115 (list); Ng et al., 2008: 220 (list).

Material examined. 1 male (11.4 × 11.0 mm) (ZRC
2016.0598), ca. mid-way Tangga Helang Seribu Kenangan
hiking trail from base to just before summit of Gunung
Raya, Langkawi Island, Peninsular Malaysia, coll. R.-M.
227

Ng: Geosesarma from northern Peninsular Malaysia

Fig. 2. Geosesarma foxi (Kemp, 1918), colour in life, Gunung Raya, Langkawi. A, B, male (10.9 × 10.9 mm) (ZRC 2016.618); C, male
(9.9 × 10.0 mm) (ZRC 2016.618); D, female (10.8 × 10.9 mm) (ZRC 2016.618); E, juvenile male (8.0 × 7.9 mm) (ZRC 2016.618); F, male
(11.5 × 11.4 mm) (ZRC 2016.619); G, probably male (9.6 × 9.7 mm) (ZRC 2016.619). Photo credits: A–E, Paul Y.C. Ng; F, G, J.-J. Li.

subterminal segment (in ventral view) with distinct shelf-likeangle (Fig. 7B–E), distal chitinous part elongated, distal partgently curved, tip spatuliform (Fig. 7B–G).

distal margin of somite 6 (Fig. 5E). The vulvae on thoracic
sternite 6 are large, positioned closer to suture with sternite
5, with an operculum and a large truncate vulvar process
which arches over the opening (Fig. 5F). One female (11.7
× 11.8 mm, ZRC 2016.618) had several subovate eggs still
under its pleon, with each measuring ca. 1.5 mm in diameter.

Females. Females resemble males in all non-sexual
characters, with the chelae equal, relatively slenderer andless inflated (Fig. 4B). The pleon is ovate, covering mostof the thoracic sternum, with the telson broadly triangularwith convex lateral margins and distinctly inserted into the

Variation. The carapace proportions vary slightly, withsmaller males and females sometimes appearing slightly
228

RAFFLES BULLETIN OF ZOOLOGY 2017

Fig. 3. Geosesarma foxi (Kemp, 1918), male (11.4 × 11.0 mm) (ZRC 2016.0598), Gunung Raya, Langkawi. A, overall dorsal view; B,
C, dorsal view of carapace (viewed from slightly different angles); D, frontal view of cephalothorax.

229

Ng: Geosesarma from northern Peninsular Malaysia

Fig. 4. Geosesarma foxi (Kemp, 1918). A, C, male (9.9 × 10.0 mm) (ZRC 2016.618); B, D, female (10.8 × 10.9 mm) (ZRC 2016.618).
Both specimens from Gunung Raya, Langkawi. A, B, overall dorsal view; C, D, dorsal view of carapace.

230

RAFFLES BULLETIN OF ZOOLOGY 2017

Fig. 5. Geosesarma foxi (Kemp, 1918). A–D, male (11.4 × 11.0 mm) (ZRC 2016.0598); E, F, female (10.8 × 10.9 mm) (ZRC 2016.618).
Both specimens from Gunung Raya, Langkawi. A, anterior thoracic sternum, telson and pleonal somites 4–6; B, anterior thoracic sternum,
telson and pleonal somites 3–6; C, posterior thoracic sternum, telson and pleonal somites 2–6; D, outer view of right chela; E, female
pleon; F, female sternopleonal cavity showing vulvae.

more trapezoidal in shape, with the lateral margins slightly
diverging (e.g., Fig. 4B). The second lateral tooth (after theexternal orbital tooth) is always distinct, although it mayvary in size (Figs. 3B, C, 4C, D), and demarcated fromthe rest of the margin by a wide cleft. Smaller males (lessthan 7 mm carapace width) also have slender, equal chelae;
and the G1, while resembling those of adults, are relatively
straighter and poorly chitinised.

deep brown with a fine mottling and dark chromatophores are
thickly sprinkled on the abdomen.” The series of specimens on
hand essentially confirm his observations. In live specimens,
the anterior half of the carapace (from the H-shaped gastrocardiac groove) as well as the chelipeds are deep orange toalmost red (Fig. 2). The intensity of the colour varies only
slightly. The posterior half of the carapace and ambulatory
legs vary from light brown to purplish black, and covered
with numerous small white or light blue spots (Fig. 2). The
frontal surfaces of the cephalothorax and thoracic sternum
are deep orange (Fig. 2B), while the abdomen is orange withnumerous small dark brown spots and mottling.

Colour. Kemp (1918: 240) described his fresh specimens of
G. foxi as follows: “the carapace of the specimens is of a very
dull reddish brown; the chelipedes are pale yellow suffusedwith pale red on the carpus and palm; the walking legs are231

Ng: Geosesarma from northern Peninsular Malaysia
Taxonomic remarks. Kemp (1918: 240) described thespecies from two males measuring 9.8 × 9.8 mm and 9.7
× 9.8 mm, without specifying a holotype. Ng (1988: 122)
designated the slightly larger male in the Zoological Surveyof India in Calcutta as the lectotype of Sesarma foxi Kemp,
1918. For comparisons with G. serenei and G. faustum nsp., see remarks for the latter species.

transverse ridge; dorsal margin of dactylus with 6 or 7
low, non-chitinous tubercles on proximal half (Fig. 6A,
D). Ambulatory legs with long, slender merus, with sharp
subdistal spine on dorsal margin, surfaces gently rugose(Fig. 6A, E). Male pleon broadly triangular; somite 6 wide,with convex lateral margins; telson almost semicircular, notrecessed into distal margin of somite 6 (Fig. 6C). G1 slender;outer margin of subdistal part of subterminal segment (inventral view) with gently sloping shelf-like area (Fig. 7I, J),
distal chitinous part elongated, distal part almost straight,
tip spatuliform (Fig. 7I–L).

Sympatric taxa. Three other species of freshwater crabs
occur on Gunung Raya. The semiterrestrial potamid Stoliczia
bella Ng & Ng, 1987, is found in or near permanent water
bodies from near the base to about 700 m asl on Gunung
Raya. At the base of Gunung Raya, the fully aquatic
gecarcinucid Siamthelphusa improvisa (Lanchester, 1902) iscommon in shallow streams with vegetation. The gecarcinucid
Phricotelphusa gracilipes Ng & Ng, 1987, is found in mostof the streams and springs around the mountain, and evenoccurs in the forest floor and summit, sometimes far frompermanent water sources. The author has also found it inpiles of moist decaying leaves along the same trail where
G. foxi was collected.

Females. The adult female resembles the adult male in nonsexual characters, with the chelae equal, relatively slenderer
and less inflated. The pleon is ovate, covering most of thethoracic sternum, with the telson broadly triangular withconvex lateral margins and distinctly inserted into the distal
margin of somite 6 (Fig. 6G). The vulvae on thoracic sternite
6 are relatively large, positioned closer to suture with sternite
5, with an operculum and a large truncate vulvar process
which arches over the opening (Fig. 6H).

Geosesarma serenei Ng, 1986
(Figs. 6, 7I–P)

Variation. The few specimens on hand do not lend muchfor a discussion on their variation. Smaller specimens (7mm carapace width, ZRC 2003.64) closely resemble theadult holotype male except that the second lateral tooth isrelatively larger, the chelae are equal and slenderer (Fig.
6E, F). The G1 of this small male is weakly chitinised andclearly juvenile in form, and while it superficially resembles
that of the adult, the distal part is almost straight and notchitinous (Fig. 7N–P).

Sesarma ? maculata – Lanchester, 1902: 550 (not Sesarma maculata
De Man, 1892)
Sesarma (Sesarma) foxi – Tweedie, 1936: 52 (not Sesarma foxi
Kemp, 1918).
Sesarma foxi – Tweedie, 1940: 108, fig. 11 (not Sesarma foxi
Kemp, 1918).
Geosesarma serenei Ng, 1986a: 6, fig. 2; Ng, 1988: 124, figs. 53A,
55; Ng, 2004: 333 (list); Ng & Yeo, 2007: 115 (list); Ng etal., 2008: 220 (list).

Colour. The live colour of this species is not known, but
probably similar to those of G. foxi and G. faustum n. sp.
The small specimens of G. serenei (ZRC 2003.64) havethe distinctive spots characteristic of the other two species.

Material examined. Holotype: male (8.3 × 8.2 mm) (ZRC
1964.9.8.1), Bukit Larut, Maxwell Hill, 4°47′N 100°45′E,
Perak, Peninsular Malaysia, ca. 1150 m, coll. H.M.
Pendlebury, February 1932. Paratype: ovigerous female(10.4 × 9.7 mm) (ZRC 1964.9.8.2), same data as holotype.
Others: 1 young male (7.0 × 6.9 mm), 1 female (7.4 × 7.1mm) (ZRC 2003.64), Bukit Larut, Maxwell Hill, beyond
Gunung Hijau Resthouse, 4°47′N 100°45′E, Perak, Peninsular
Malaysia, ca. 1150 m, at night, coll. T.M. Leong & G. Lim,
27 March 2003.

Taxonomic remarks. In discussing differences with G.
serenei, Ng (1988: 122) noted that the “subterminal segmentof the G1 of G. foxi however, appears to be stouter andslightly shorter, and the terminal segment is also relatively
shorter and the tip rounder. The two taxa may eventually
prove conspecific when more specimens of both species
become available, and the variations presently noted shown
to be merely due to variation.” This comparison was basedon the sketch of the G1 provided to him by the Zoological
Survey of India (Ng, 1988: fig. 54D). The present series of
specimens of G. foxi show that this difference is not valid
as it is now clear from examining the material that the G1
in Ng (1988) had been drawn with the structure tilted ata slight angle, making it appear stouter than it actually is.
There are, however, other characters that can separate thetwo species. For detailed differences with G. foxi and G.
faustum n sp., see remarks for the latter species.

Diagnosis. Carapace quadrate, slightly wider than longor subequal, adult width to length ratio 1.01–1.04, lateral
margins parallel (Fig. 6A, B, F); dorsal surface with regions
just visible, anterior regions with small rounded granules ongastric regions (Fig. 6A, B, E, F); front distinctly deflexed,
frontal lobes broad with truncate margins in dorsal view;
postfrontal, postorbital cristae sharp, distinct (Fig. 6B, F);
external orbital tooth triangular, directed obliquely laterally,outer margin gently convex, tip not extending beyond lateral
margin; second lateral tooth distinct, clearly separated fromrest of margin by wide clef (Fig. 6B, F). Merus of third
maxilliped subovate, shorter than ischium; exopod slenderwith no trace of flagellum (cf. Ng, 1988: fig. 55C). Outersurface of palm of adult male covered with small rounded
granules and striae; inner surface granulated but without

In recording G. serenei (as S. foxi), Tweedie (1940: 108)
commented that he had “two adult males, two females
and two juveniles from Lacom, Peninsular Siam [present
day Thailand], collected by the ‘Skeat’ Expedition of
1899–1900 and erroneously determined as S. maculata de
232

RAFFLES BULLETIN OF ZOOLOGY 2017

Fig. 6. Geosesarma serenei Ng, 1986. A–D, holotype male (8.3 × 8.2 mm) (ZRC 1964.9.8.1); E, F, young male (7.0 × 6.9 mm) (ZRC
2003.64); G, H, paratype ovigerous female (10.4 × 9.7 mm) (ZRC 1964.9.8.2). All specimens from Bukit Larut, Perak. A, E, overall
dorsal view; B, F, dorsal view of carapace; C, male pleon; D, outer view of left chela; G, female pleon; H, female sternopleonal cavity
showing vulvae.

233Ng: Geosesarma from northern Peninsular Malaysia

Fig. 7. A–H, Geosesarma foxi (Kemp, 1918), male (11.4 × 11.0 mm) (2016.0598), Gunung Raya, Langkawi; I–M, G. serenei Ng, 1986,
holotype male (8.3 × 8.2 mm) (ZRC 1964.9.8.1), Bukit Larut, Perak; N–P, G. serenei Ng, 1986, young male (7.0 × 6.9 mm) (ZRC
2003.64), Bukit Larut. A, left third maxilliped (mostly denuded); B, I, N, left G1 (ventral view); C, J, left G1 (dorsal view); D, distal partof left G1 (ventral view); E, distal part of left G1 (dorsal view); F, K, O, distal part of left G1 (outer lateral view); G, L, P, distal part ofleft G1 (mesial view); H, M, left G2. Scales = 0.5 mm.

234

RAFFLES BULLETIN OF ZOOLOGY 2017
in dorsal view; postfrontal, postorbital cristae sharp, distinct(Figs. 9A–C, 10); external orbital tooth acutely triangular,
directed obliquely laterally, outer margin gently convex, tip
not extending beyond lateral margin; second lateral tooth
low, barely discernible from rest of margin, often fused withrest of margin (Figs. 9B, C, 10). Merus of third maxilliped
subovate, shorter than ischium; exopod slender with notrace of flagellum (Fig. 12A). Outer surface of palm ofadult male covered with small rounded granules and striae;
inner surface granulated but without transverse ridge; dorsal
margin of dactylus with 7–9 low, non-chitinous tubercles
on proximal half (Figs. 9A, 10, 11D). Ambulatory legs withlong, slender merus, with sharp subdistal spine on dorsal
margin, surfaces gently rugose (Figs. 9A, 10). Male pleon
broadly triangular; somite 6 very wide, with convex lateral
margins; telson relatively triangular, not recessed into distal
margin of somite 6 (Figs. 11A–C, E). G1 slender; outermargin of subdistal part of subterminal segment (in ventralview) with sloping, subangular shelf-like area (Fig. 12B–E),
distal chitinous part conspicuously elongated, distal partgently curved, tip spatuliform (Figs. 11F, 12B–G).

Man by Lanchester (l.c.). The two largest specimens of
this series measure 11.7 (♂) and 11.0 (♀) mm. in anterior
carapace breadth, and are the largest specimens of S. foxi
so far recorded.” In describing G. serenei, Ng (1986a: 36)
placed Lanchester’s (1902) and Tweedie’s (1936) material
from Peninsular Thailand under the synonymy of the new
species with doubt. Tweedie (1940: 108–109) notes thatthe locality “Lacom” given by Lanchester is difficult tointerpret precisely. It probably refers to Lakon, which is analternative name for Nakon Si Thammarat. Other records
indicate that the species is montane in habit and the ‘Skeat’specimens probably came from the hills a short distanceinland from Nakon Si Thammarat, which range up to a heightof over 1500 metres. The present author agrees with thisinterpretation. Material from Nakon Si Thammarat will need
to be examined to ascertain if the species there is actually
G. serenei or another taxon.
Sympatric taxa. Another species of Geosesarma, G.
cataracta Ng, 1986, also occurs on Bukit Larut, but lives
at relatively lower altitudes among the mosses adjacent towaterfalls, possessing proportionately shorter and stouterambulatory legs and a different G1 structure (see Ng, 1986a,
1988). Two species of potamids are present on Bukit Larut,
Stoliczia tweediei (Roux, 1934) and S. larutensis Ng &Schubart, 2014. Stoliczia tweediei is a fully aquatic species
and is present in the waterfalls at altitudes up to 900 m asl;
while S. larutensis is semiterrestrial and lives in the damp
forests of the summit, probably with G. serenei (see Ng,
1993; Ng & Schubart, 2014). One species of gecarcinucid,
Phricotelphusa hockingi Ng, 1986, occurs in the streams
and waterfalls but apparently does not reach the summit(Ng, 1986b, 1988).

Females. Females resemble males in all non-sexual
characters, with the chelae equal, relatively slenderer and lessinflated (Figs. 8H, 10B). The pleon is ovate, covering mostof the thoracic sternum, with the telson broadly triangularwith convex lateral margins and distinctly inserted into the
distal margin of somite 6 (Fig. 11G). The vulvae on thoracic
sternite 6 are large, positioned closer to suture with sternite
5, with an operculum and a large truncate vulvar process
which arches over the opening (Fig. 11H). The ovigerous
females (10.6 × 10.4 mm, 9.5 × 9.4 mm, ZRC 2014.340)
had large subovate eggs, each measuring about 1.5 mm indiameter (Fig. 8D).

Geosesarma faustum n. sp.
(Figs. 8–12)

Variation. The margins of the frontal lobes in G. faustum
is usually subtruncate, but in several specimens, it appears
more convex (Fig. 10A). As in G. foxi, the carapace shapevaries slightly from just longer than broad to broader thanlong. The carapaces of many of the adult females and young
males appear to be slightly more trapezoidal with the lateral
margins gently diverging (Figs. 8H, 9C).

Material examined. Holotype: male (10.6 × 10.5 mm)(ZRC 2016.617), Penang Hill, near Bellevue Hotel, Penang,
800 m, Peninsular Malaysia, inside introduced bromeliad
Neoregalia compacta (Bromeliaceae), coll. J. Tan & Z.Y.
Chan, June 2014. Paratypes: 2 males (10.6 × 10.5 mm, 8.9
× 8.7 mm), 4 females (12.0 × 11.5 mm, 11.1 × 10.7 mm,
11.0 × 10.7 mm, 10.6 × 10.6 mm), 2 ovigerous females (10.6
× 10.4 mm, 9.5 × 9.4 mm) (ZRC 2014.340), same data as
holotype; 5 males (10.2 × 10.1 mm, 10.0 × 10.3 mm, 8.6
× 8.4 mm, 8.3 × 8.2 mm, 6.2 × 6.0 mm), 2 females (10.8
× 10.9 mm, 8.6 × 8.6 mm), 1 ovigerous female (9.2 × 9.3mm), 1 young female (6.8 × 6.5 mm) (ZRC 2016.0599),
in various bromeliads and Pandanus growing in shaded
gardens at summit of Penang Hill, mostly near Bellevue
Hotel, Penang, ca. 850 m, Peninsular Malaysia, coll. P.K.L.
Ng & P.Y.C. Ng, 20 December 2016.

Colour. The colour and pattern of G. faustum n. sp. isvery similar to G. foxi. The anterior half of the carapace,chelipeds, suborbital, subhepatic and pterygostomial regions
are usually pale yellow to light orange (Fig. 8), never red.
The posterior half of the carapace and ambulatory legs varyfrom brown to purplish black, with numerous small whiteor light blue spots (Fig. 8).
Etymology. The species name is derived from the Latin forfortunate and lucky; alluding to the circumstances leading
to the discovery of the new species.

Diagnosis. Carapace quadrate, slightly wider than longor subequal, adult width to length ratio 0.97–1.04, lateral
margins parallel (Figs. 9A–C, 10); dorsal surface with
regions just visible, anterior regions with small rounded
granules on gastric regions (Fig. 9B–D); front distinctly
deflexed, frontal lobes broad, usually with truncate margins

Taxonomic remarks. Kemp (1918: 240) reported on a
“Sesarma sp.” from an altitude of about 370 m on Penang
Hill. Tweedie (1940) obtained more specimens from Penang
Hill (no altitude provided), named the species Sesarma
penangensis, and referred Kemp’s (1918) record to his new235

Ng: Geosesarma from northern Peninsular Malaysia

Fig. 8. Geosesarma faustum n. sp., colour in life, Penang Hill, Penang. A, B, specimens photographed in bromeliad in situ, part of typespecies; C, holotype male (10.6 × 10.5 mm) (ZRC 2016.617); D, paratype ovigerous female (10.6 × 10.4 mm) (ZRC 2014.340); E–G,
paratype male (10.2 × 10.1 mm) (ZRC 2016.0599); H, paratype female (10.8 × 10.9 mm) (ZRC 2016.0599). Photo credits: A–D, Ji Tan;
E–H, Paul Y. C. Ng.

lower altitudes; it is easily distinguished from G. faustum
by its distinctly broader than long carapace, conspicuously
shorter and stouter ambulatory legs, the exopod of thethird maxilliped possessing a long flagellum and the G1 is
proportionately stouter with short, spade-like chitinous distal
part (cf. Ng, 1988: fig. 58A, C–E).

taxon. From Kemp’s (1918) description of his specimens,
the author has little doubt that Tweedie is correct, and his
specimens are not conspecific with what is here described
as G. faustum. Geosesarma faustum is one of the highland
Geosesarma species (see earlier; Ng, 1988), while G.
penangense is a congener that is generally found at relatively
236

RAFFLES BULLETIN OF ZOOLOGY 2017

Fig. 9. Geosesarma faustum n. sp. A, B, D, holotype male (10.6 × 10.5 mm) (ZRC 2016.617), Penang Hill, Penang; C, paratype female (12.0
× 11.5 mm) (ZRC 2014.340), Penang Hill, Penang. A, overall dorsal view; B, C, dorsal view of carapace; D, frontal view of cephalothorax.

237

Ng: Geosesarma from northern Peninsular Malaysia
Geosesarma foxi and G. faustum n. sp. share a similar colour
pattern, with the anterior half of the carapace and chelipeds
bright yellow or orange, with the dark brown to almost black
posterior half of the carapace and ambulatory legs covered
with numerous small white dots. The same appears to be thecase for G. serenei, with the more recent specimens showing
traces of the small dots on the ambulatory legs.
While G. foxi s. str. is very similar to G. faustum, adults of
G. faustum can easily be distinguished by the second lateral
tooth on the carapace being poorly developed or almost
undiscernible (Figs. 9B, C, 10) (distinct in G. foxi, Figs. 1A,
3B, C, 4); the male pleonal somite 6 is more subtruncate inshape (Fig. 11A–C, E) (margins distinctly more convex in
G. foxi, Fig. 5A–C); the telson is more triangular in shape(Fig. 11A) (more semicircular in G. foxi, Fig. 5A); the outermargin of the subdistal part of the subterminal segment isgently sloping (Fig. 12B–E) (area forms a distinct angularshelf-like structure in G. foxi, Fig. 7B–E); and the chitinous
distal part of the G1 is proportionately longer (Fig. 12B–E)(proportionately shorter in G. foxi, Fig. 7B–E). In addition,
the external orbital tooth is usually relatively more acutely
triangular (Figs. 9A–C, 10) (more broadly triangular in G.
foxi, Figs. 3A–C, 4). The colour in life of the anterior halfof the carapace and chelipeds of adult G. foxi s. str. is deeporange (Fig. 2A–D), sometimes becoming almost red (Fig.
2F, G). In contrast, the live colour of G. faustum tends tobe pale yellow (Fig. 8A–D) to light orange (Fig. 8E–H).
Although colour will probably vary slightly in a species,
the good series of specimens of both species indicate thatthe orange of G. foxi generally tends to be darker.

Fig. 10. Geosesarma faustum n. sp., overall dorsal view. A,
paratype male (10.6 × 10.5 mm) (ZRC 2014.340), Penang Hill,
Penang; B, paratype female (12.0 × 11.5 mm) (ZRC 2014.340),
Penang Hill, Penang.

Sympatric taxa. A second species of Geosesarma, G.
penangense (Tweedie, 1940) is present on Penang Hill,
but has not been found higher than 370 m asl (see above).
Living in the waterfalls and rocky streams is the fully aquatic
potamid Stoliczia stoliczkana (Wood-Mason, 1871), but
this species is not known from the summit (see Ng, 1992).

Compared to G. serenei, the external orbital tooth of adultG. faustum is relatively more acutely triangular (Figs. 9A–C,
10) (more broadly triangular in G. serenei, Fig. 6A, B, E,
F); the second lateral tooth on the carapace of G. faustum n.
sp. is poorly developed or almost undiscernible (Figs. 9B, C,
10) (more distinct in G. serenei, Fig. 6A, B, E, F); the malepleonal somite 6 is more subtruncate in shape (Figs. 11A–C,
E) (relatively less broad in G. serenei, Fig. 6C); the telson
is more triangular in shape (Fig. 11A) (more semicircularin G. serenei, Fig. 6C); and the chitinous distal part of theG1 is proportionately longer (Fig. 12B–E) (proportionately
shorter in G. serenei, Fig. 7I, J). The live colours of G.
serenei are not known.

GENERAL DISCUSSION
Geosesarma foxi, G. serenei and G. faustum are high altitude
species, occurring in montane habitats higher than 700 m
asl. With regards to G. foxi, Kemp (1918: 240) recordedthat the “specimens obtained by Mr. Buxton, the types ofthe species, were found on Gunong Raya in Langkawi I,
at a height of 2000 ft. They were collected in moist places
under stones or rotten wood at some distance from any
stream.” He also noted that “It appears probable that inthese places the Sesarma have been able to adopt a strictly
terrestrial mode of life and to ascend to considerable altitudes
owing to the damp climate that prevails...” (Kemp, 1918:
238). The recent specimens of G. foxi were all found near
the summit of Gunung Raya: “they were collected in thedensely forested area near the top of the Gunung Rayahiking trail, at roughly 700 m plus asl. Geosesarma foxi is
nocturnal, and the majority of specimens were collectedlate at night (after 10 pm) foraging among the plants, often
ferns, along the side of the trail. The area is a considerable
distance from any stream or permanent water source, butalmost always moist due to cool temperatures of the highaltitude and thick mist that blankets the area in the earlymorning and night. During the day, this species probably
takes refuge in the moist leaf litter or in phytotelms such as
between the leaves of Pandanus spp.” (P.Y.C. Ng, personalcommunication).

In its carapace shape, elongated ambulatory legs and color
pattern, G. faustum bears a close resemblance to what has beenreported in the aquarium trade as “Geosesarma krathing” (seeRademacher & Mengedoht, 2011). This material supposedly
came from the type locality, Krathing Waterfalls in Thailand,but considering the general unreliability of aquarium records,
it is quite possible that the specimens were from Penang oreven Langkawi instead. While the colour (yellow) and pattern(the anterior half of the carapace and chelipeds are yellow)
are very similar, these aquarium specimens do not appear
to have the posterior part of the carapace and legs covered
with fine spots like in true G. faustum (Fig. 8).

238

RAFFLES BULLETIN OF ZOOLOGY 2017

Fig. 11. Geosesarma faustum n. sp. A–D, holotype male (10.6 × 10.5 mm) (ZRC 2016.617); E, F, paratype male (10.6 × 10.5 mm) (ZRC
2014.340); G, H, paratype female (12.0 × 11.5 mm) (ZRC 2014.340). All specimens from Penang Hill, Penang. A, anterior thoracic
sternum, telson and pleonal somites 5 and 6; B, anterior thoracic sternum, telson and pleonal somites 3–6; C, posterior thoracic sternum,
telson and pleonal somites 2–6; D, outer view of right chela; E, posterior thoracic sternum, telson and pleonal somites 3–6; F, malesternopleonal cavity showing G1s; G, female pleon; H, female sternopleonal cavity showing vulvae.

239

Ng: Geosesarma from northern Peninsular Malaysia

Fig. 12. A–H, G. faustum n. sp., holotype male (10.6 × 10.5 mm) (ZRC 2016.617), Penang Hill, Penang. A, left third maxilliped (mostly
denuded); B, left G1 (ventral view); C, left G1 (dorsal view); D, distal part of left G1 (ventral view); E, distal part of left G1 (dorsalview); F, distal part of left G1 (outer lateral view); G, distal part of left G1 (mesial view); H, left G2. Scales = 0.5 mm.

Not much is known about the ecology of G. serenei, withthe types collected at the summit of Bukit Larut, over 1000
m asl. As far as is known, they were found in the forest,with the recent material (ZRC 2003.64) collected at night.

Geosesarma faustum was observed to hide between the leavesof the bromeliads and Pandanus, scurrying into the water if
disturbed (Fig. 8A, B). They were common during the day,especially in more shaded areas, and when there was cloud
cover with light rain. Several females with eggs were seen,
and numerous very small crabs were also seen around theplants, suggesting the crabs are breeding in the phytotelm.
The large size of the eggs of all three species indicatesthat they practice direct development but it is not known ifthey carry the young crabs under their pleon, on the backof their carapaces (see Ng & Tan, 1995), or perhaps release
the newly hatched crabs in the waters of the phytotelms.

The discovery of G. faustum in Penang is interesting because
the species has never been reported in earlier publications
despite the fact that Penang had been a major British bastion
since 1786 and Penang Hill, the highest point on the island,has been inhabited for most of that time. This may not be
surprising considering the biology of G. foxi and G. serenei.
They are very cryptic species, hiding in the dense forest or
among vegetation during the day, coming out to forage only
late at night. Phytotelms are probably one of their major
habitats or foraging sites. In natural forests or urban habitats
where water may be scarcer, the crabs are rarely seen. Evenfor G. foxi, they have only been found recently, and notin large numbers. Since 2010, Penang Hill, especially thesummit area, has been developed with the addition of new
tourist facilities, hotels and natural attractions. These include
many ecogardens and newly planted areas. Many areas areheavily planted with non-native bromeliads and Pandanus.
The density of bromeliad plantings in and around the hotelarea as well as the gardens means a new habitat has beencreated for species of Geosesarma, allowing them to flourish
in good numbers so much so that they are now far moreaccessible for scientists to study. In the natural ecosystem,
they are almost certainly more widely dispersed due to themore scattered distribution of suitable plants and the densityof the vegetation on the forest floor.

Several species of Geosesarma are known to use various
phytotelmata. Geosesarma malayanum Ng & Lim, in Ng,
1986, has been found in the cups of pitcher plants at highaltitudes (Ng & Lim, 1987), while G. peraccae (Nobili,1903) and G. nemesis Ng, 1986, from Singapore havebeen known to also frequent or use pitcher plants (notably
Nepenthes ampullaria) (Tan & Ng, 2008; Ng & Court,2010). In Sarawak (and Brunei), G. gracillimum (De Man,
1902) has been found in pitcher plants (unpublished data).
As to their conservation status, Ng & Yeo (2007: 115) listed
G. foxi as “endangered”, while G. serenei was regarded as“critically endangered”; the authors noting that the small
known distribution range and possible threats to the forests
were problems. While the present study has managed
to get more specimens of G. foxi for study, the various
environmental threats facing this species have not been240

RAFFLES BULLETIN OF ZOOLOGY 2017
reduced. In fact, the threats may get worse in the years
ahead as more parts of Gunung Raya (and Bukit Larut forG. serenei) are opened for increasing numbers of tourists.
The same may be true for G. faustum, although the prolificplanting of plants like bromeliads on the summit of Penang
Hill has clearly helped the species, at least for the moment.
Another potential problem is the aquarium trade. Ng et al.
(2015: 12) noted that over-collecting is a serious threat fora species if it becomes popular in the trade as catching
animals from the wild is not a sustainable practice. The easeby which Geosesarma crabs are kept and their often striking
colours in life and habits, have made them much sought after
terrarium subjects (see Rademacher & Mengedoht, 2011; Ng
et al., 2015). The conservation status of primarily or wholly
freshwater sesarmids like Geosesarma, however, have notbeen analysed following IUCN Red List guidelines, as had
been done for primary freshwater crabs (see Cumberlidge
et al., 2009).

Foederatæ Duce, lexit et descripsit. Proceedings of the Academyof Natural Sciences of Philadelphia, 5: 247–254.
Davie PJF, Guinot D & Ng PKL (2015) Anatomy and functional
morphology of Brachyura. In: Castro P, Davie PJF, Guinot D,
Schram FR & Von Vaupel Klein JC (eds.) Treatise on Zoology– Anatomy, Taxonomy, Biology. The Crustacea. Volume 9C–I.
Decapoda: Brachyura (Part 1). Pp. 11–163.
Kemp S (1918) Zoological results of a tour in the Far East. Crustacea
Decapoda and Stomatopoda. Memoirs of the Asiatic Societyof Bengal, 6: 217–297.
Lanchester WF (1902) Brachyura, Stomatopoda and Macrura. On
the Crustacea collected during the “Skeat” Expedition to the
Malay Peninsula, together with a note on the genus Actaeopsis.
Part I. Proceedings of the Zoological Society of London, 71(2):534–574, pls. 33, 34.
Man JG De (1892) Decapoden des Indischen Archipels. Zoologische
Ergebnisse einer Reise in Niederlandisch OstIndien, 2: 265–527.
Manuel-Santos MR, Ng PKL & Freitag H (2016) Two new
species of Geosesarma De Man, 1892 (Crustacea: Brachyura:
Sesarmidae) from Palawan, the Philippines. Raffles Bulletinof Zoology, 64: 335–342.
Ng PKL (1986a) Preliminary descriptions of 17 new freshwater
crabs of the genera Geosesarma, Parathelphusa, Johora andStoliczia (Crustacea Decapoda, Brachyura) from South East
Asia. Journal of the Singapore National Academy of Science,
15: 36–44.
Ng PKL (1986b) Phricotelphusa hockpingi sp. nov., a new
gecarcinucid freshwater crab from Perak, West Malaysia(Decapoda, Brachyura). Crustaceana, 51(3): 270–276.
Ng PKL (1988) The Freshwater Crabs of Peninsular Malaysia
and Singapore. Department of Zoology, National Universityof Singapore, Shinglee Press, pp. i–viii, 1–156, figs. 1–63, 4
colour pls.
Ng PKL (1992) Crabs of the Stoliczia stoliczkana (Wood Mason,
1871) species complex (Crustacea: Decapoda: Brachyura:
Potamidae). Malaysian Journal of Science, 14: 1–25.
Ng PKL (1993) Freshwater crabs allied to Stoliczia tweediei(Roux, 1934) (Crustacea: Decapoda: Brachyura: Potamidae),with descriptions of two new species from Kedah and Perak,
Peninsular Malaysia. Verhanderlingen der Naturforschenden
Gesellschaft Basel, 103: 81–95.
Ng PKL (2004) Crustacea: Decapoda, Brachyura. In: Yule C &Yong HS (eds.) Freshwater Invertebrates of the Malaysian
Region. Malaysian Academy of Sciences, pp. 311–336.
Ng PKL (2015) Semiterrestrial crabs of the genus Geosesarma De
Man, 1892 (Crustacea, Brachyura, Sesarmidae) from western
Borneo, Indonesia, with descriptions of three new species.
Zootaxa, 4048(1): 37–56.
Ng PKL & Court D (2010) Plant Pools: Phytotelms. In: Yeo
DCJ, Wang LK & Lim KKP (eds.) Private Lives. An Exposé
of Singapore’s Freshwaters. Raffles Museum of Biodiversity
Research, National University of Singapore. Pp. 186–187.
Ng PKL, Guinot D & Davie PJF (2008) Systema Brachyurorum:
Part I. An annotated checklist of extant brachyuran crabs of
the world. Raffles Bulletin of Zoology, Supplement 17: 1–286.
Ng PKL & Lemaitre R (2017) On the taxonomy of two poorly known
species of Geosesarma De Man, 1892 (Crustacea: Brachyura:
Sesarmidae) from the Philippines. Zootaxa, 4250(5): 475–483.
Ng PKL & Lim RP (1987) The taxonomy and biology of thenepenthiphilous sesarmine freshwater crab, Geosesarma
malayanum Ng and Lim, 1986 (Crustacea, Decapoda,
Brachyura, Grapsidae) from Peninsular Malaysia. Malayan
Nature Journal, 41: 393–402.
Ng PKL & Naiyanetr P (1992) On a new species of Geosesarma
de Man, 1892 (Crustacea: Decapoda: Brachyura: Grapsidae)
from Chanthaburi Province, eastern Thailand. Zoologische
Mededelingen, 66(34): 449–452.

ACKNOWLEDGEMENTS
The search for fresh specimens of Geosesarma foxi has beena long one. I am grateful to Jalil Md. Som and Amirrudin
Ahmad for sending me their photograph of the species somany years ago and trying in vain to get more for me intheir fish surveys in the island in 2003 (see Ahmad & Lim,
2006). I am very indebted to two young men, Ji Tan and
Chan Zi Yang, whose sharp eyes and inquisitive spirit got
the crabs, provided notes and photographs of the new species
from Penang; and for their mentor, Yong Hoi Sen (Universityof Malaysia), for referring them and the specimens to me.
Thanks are also due to Anton van der Schans, Adrian Loo
and Hugh Tan for help in identifying the cultured bromeliad
from Penang Hill. Mary-Ruth Low kindly retained the deadspecimen she saw on Gunung Raya for me, courtesy of her
brother Martyn Low who told her I had been searching forthe crab for many years. Li Jheng-Jhang (National Taiwan
Ocean University) was kind to send his specimens from
Gunung Raya to me for study, his photographs for use,
as well as sharing his observations of the animal. Many
useful comments from Darren Yeo and Shih Hsi-Te helped
improve the manuscript. Finally, I am also very grateful to
my son, Paul Y. C. Ng, whose intrepid exploits helped his
father finally see G. foxi, a species he had been searchingfor over 30 years!
LITERATURE CITED
Ahmad A & Lim KKP (2006) Inland fishes recorded from theLangkawi Islands, Peninsular Malaysia. Malayan Nature
Journal, 59(1): 103–120.
Cumberlidge N, Ng PKL, Yeo DCJ, Magalhães C, Campos MR,
Alvarez F, Naruse T, Daniels SR, Esser LJ, Attipoe FYK,
Clotilde-Ba F-L, Darwall W, McIvor A, Baillie JEM, Collen
B & Ram M (2009) Freshwater crabs and the biodiversity
crisis: importance, threats, status, and conservation challenges.
Biological Conservation, 142(8): 1665–1673.
Dana JD (1851) Conspectus Crustaceorum quæ in Orbis Terrarum
circumnavigatione, Carolo Wilkes e Classe Reipublicæ

241

Ng: Geosesarma from northern Peninsular Malaysia
Ng PKL & Ng HP (1987) The freshwater crabs of Pulau Langkawi,
Peninsular Malaysia. Malaysian Journal of Science, 9: 1–15.
Ng PKL & Ng HP (1989) Exploring the freshwaters of Pulau
Langkawi. Nature Malaysiana, 14(3): 76–83.
Ng PKL & Schubart CD (2014) A new species of freshwater
crab of the genus Stoliczia Bott, 1966 (Crustacea: Brachyura:
Potamidae) from the summit of Bukit Larut, Perak, Peninsular
Malaysia. Raffles Bulletin of Zoology, 62: 484–489.
Ng PKL, Schubart CD & Lukhaup C (2015) New species of“vampire crabs” (Geosesarma De Man, 1892) from central Java,
Indonesia, and the identity of Sesarma (Geosesarma) nodulifera
De Man, 1892 (Crustacea, Brachyura, Thoracotremata,Sesarmidae). Raffles Bulletin of Zoology, 63: 3–13.
Ng PKL & Tan CGS (1995) Geosesarma notophorum sp. nov.
(Decapoda, Brachyura, Grapsidae, Sesarminae), a terrestrial
crab from Sumatra, with novel brooding behaviour. Crustaceana,
68(3): 390–395.
Ng PKL & Yeo DCJ (2007) Malaysian freshwater crabs: conservation
prospects and challenges. In: Chua L (ed.) Proceedings of the
Seminar on the Status of Biological Diversity in Malaysia &Threat Assessment of Plant Species in Malaysia, 28–30 June
2005, Forest Research Institute Malaysia, Kepong. Pp. 95–120.
Nobili G (1903) Crostacei di Singapore. Bollettino dei Musei diZoologia ed Anatomia comparata della Regia, Università diTorino, 18(455): 1–39.
Rademacher M & Mengedoht O (2011) Krabben-Fibel. Die
schönsten Krabben für das Aquaterrarium. Dähne Verlag,
Ettlingen, Germany, 95 pp.

Roux J (1934) New freshwater decapod crustaceans from the
Malay Peninsula. Bulletin of the Raffles Museum, 9: 28–33,
figs. 1, 2, pl. 4.
Schubart CD & Ng PKL (2014) Two new species of land-dwellingcrabs of the genus Geosesarma De Man, 1892 (Crustacea:
Brachyura: Thoracotremata: Sesarmidae) from Bintan Island,
Indonesia. Raffles Bulletin of Zoology, 62: 615–619.
Serène R (1968) Note préliminaire sur de nouvelles espèces deSesarma (Decapoda Brachyura). Bulletin du Muséum nationald’Histoire naturelle, Paris, 39(5): 1084–1095.
Serène R & Soh CL (1970) New Indo-Pacific genera allied to
Sesarma Say, 1877 (Brachyura, Decapoda, Crustacea). Treubia,
27(4): 387–416.
Tan HH & Ng PKL (2008) First record in Singapore of anepenthiphilous crab, Geosesarma perracae (Crustacea:
Decapoda: Sesarmidae). Nature in Singapore, 1: 201–205.
Tweedie MWF (1936) On the crabs of the family Grapsidae inthe collection of the Raffles Museum. Bulletin of the Raffles
Museum, 12: 44–70, figs. 1–3, pls. 14, 15.
Tweedie MWF (1940) New and interesting Malaysian species of
Sesarma and Utica (Crustacea, Brachyura). Bulletin of the
Raffles Museum, 16: 88–113, figs. 1–12, pl. 24.
Wood-Mason J (1871) Contribution to Indian Carcinology. — On
Indian and Malayan Telphusidæ, Part I. Journal of the Asiatic
Society of Bengal, 40(2): 189–207, 449–454, pls. 11–14, 17.
Yeo DCJ, Ng PKL, Cumberlidge N, Magalhães C, Daniels SR& Campos MR (2008) Global diversity of crabs (Crustacea:
Decapoda: Brachyura) in freshwater. In: Balian EV, Lévêque
C, Segers H & Martens K (eds.) Freshwater Animal Diversity
Assessment. Hydrobiologia, 595: 275–286.

242