Bull. Natl. Mus. Nat. Sci., Ser. A, 33(4), pp. 147–152, December 21, 2007

Two Species of the Family Parthenopidae (Crustacea, Decapoda,Brachyura) from the Kermadec Islands in the South Pacific
Masatsune Takeda1,2 and Richard Webber3
1

Teikyo Heisei University, 2289 Uruido, Ichihara-shi, Chiba, 290–0193 Japan
E-mail: takeda-m@thu.ac.jp
2
National Museum of Nature and Science, 3–23–1 Hyakunin-cho, Shinjuku-ku, Tokyo, 169–0073 Japan
E-mail: takeda@kahaku.go.jp
3Museum of New Zealand Te Papa Tongarewa, PO Box 467, Wellington, New ZealandE-mail: rickw@tepapa.govt.nz

Abstract Two species of the family Parthenopidae (Crustacea, Decapoda, Brachyura), Platylambrus allisoni (Garth, 1992) and Pseudolambrus constrictus sp. nov., are recorded from the Kermadec Islands in the South Pacific based on specimens in the collections of the Museum of New
Zealand Te Papa Tongarewa. Platylambrus allisoni, previously known only from a male specimen
from the deep sea off Easter Island, is characteristic in having the carapace ornamented with stellate granules fusing into solid, smooth, symmetrically arranged masses and ridges on the gastric,cardiac, branchial and anterolateral regions. Pseudolambrus constrictus is closest to Ps. calappoides (Adams and White, 1848), but readily distinguished from it by the different contour of its
carapace which has a distinct constriction at the anterior end of the hepatic margin and the front
not strongly inclined.
Key words : New species, Parthenopidae, parthenopid crabs, Pseudolambrus, Platylambrus allisoni, Kermadec Islands, New Zealand.

The bulk of brachyuran specimens from theKermadec Islands in the collections of the Museum of New Zealand Te Papa Tongarewa werestudied by Takeda and Webber (2006), and recently Komatsu and Takeda (2007) reported on
three species of the family Leucosiidae. In thispaper, two species of the family Parthenopidae,Platylambrus allisoni (Garth, 1992) andPseudolambrus constrictus sp. nov., are recorded;
a female specimen identified as Pl. allisoni is thesecond record since the original description, anda male specimen described as Ps. constrictus is
the holotype of the new species. This is the firstrecord of parthenopid crabs in the Kermadec Islands. Both specimens are deposited at the Museum of New Zealand Te Papa Tongarewa (MNZ).
In the descriptions and remarks on eachspecies, the breadth and length of the carapace
are abbreviated as CB and CL, respectively.

Genus Platylambrus Stimpson, 1871
Platylambrus allisoni (Garth, 1992)(Fig. 1)

Material examined. Kermadec Is., 1800 m
northwest of Raoul I. (29°13.96S, 177°52.84
W), 567–530 m deep; 1 female (MNZ CR.
011248); 13 September 1976; R. V. Acheron.
Remarks. The female examined has a carapace of 12.0 mm CB and 9.6 mm CL. The specimen agrees well with the description and figuresof a male from Easter Island recorded by Garth(1992) who reported on six species of Platylambrus from the South Pacific. The carapace is typically Platylambrus-shaped, but quite characteristic in having stellate granules fusing into solid,smooth, symmetrically arranged masses andridges on the gastric, cardiac, branchial and posterolateral regions, unlike all other congenericspecies.

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Masatsune Takeda and Richard Webber

Fig. 1.

Platylambrus allisoni (Garth), female (MNZ CR. 011248), CB12.0 mm.

Distribution. Platylambrus allisoni was previously known only by the holotype male taken
at a depth of 591 m off Easter Island. This newrecord extends the known distribution of thespecies through more than 70° of longitude (butat similar latitude), from the eastern to the western South Pacific.
Genus Pseudolambrus Paul’son, 1875
Pseudolambrus constrictus sp. nov.
(Figs. 2, 3)

Material examined. Kermadec Is., beween
Dayrell and Chanter Islands, Herald Islets(29°15S, 177°50.9W.), 31–45 m deep; 1 male,holotype (MNZ CR. 011247); 11 September
1976; R. V. Acheron.
Description. CB, 7.6 mm; CL, 6.8 mm. Carapace including rostrum triangular, only slightly
wider than long, not convex dorsally as a whole,with a wide branchial depression at each side ofcardiac region; surface of smooth appearance
under unaided eye, but eroded with small depressions of variable shapes and sizes. Gastric region

prominent, convex dorsally, undivided, armed
with a blunt tubercle at metagastric part; posterior slope of metagastric tubercle distinctly
sunken, connected with cardiac region through alongitudinal low, saddle-like ridge. Cardiac region rounded, convex, lower than gastric region,eroded, blunt at its tip. Intestinal region not
sharply demarcated from cardiac region, widening posteriorly toward posterior margin of carapace.
Front prominent, protruding obliquely downward as a triangular flattened lobe beyond orbits,with a shallow depression between orbits; tip offront thick, blunt, its median lower part compressed, with a depression, forming anterior partof antennular septum. Inner part of upper orbital
margin long, granulated, only weakly concave
laterally; outer part directed weakly forward outside of small notch; two short, longitudinal linear
ridges on outer part of upper orbital margin, aridge from external orbital angle, and two orthree ridges on lower orbital margin; external orbital angle not distinctly formed, being confluent
with anterior end of carapace margin; this anteri-Parthenopid Crabs from the Kermadec Islands

149

Fig. 2. Pseudolambrus constrictus sp. nov., holotype male (MNZ CR. 011247), CB 7.6 mm, dorsal (A) and ventral (B) views.

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Masatsune Takeda and Richard Webber

Fig. 3. Pseudolambrus constrictus sp. nov., holotype male (MNZ CR. 011247). Carapace (A), left frontorbital
region (B) in ventral view, right chela (C) in dorsal view, right third (D) and fourth (E) ambulatory legs in
dorsal view, left first pleopod (F) in ventral view, distal part of the same (G) in sternal view.

or part of carapace margin behind external orbital angle almost longitudinal, weakly convex
outward, as long as distance between internal andexternal orbital angles. Anterior slope of hepatic
margin of carapace retreating obliquely outward
at an angle of ca. 130 degrees with carapace margin behind external orbital angle; posterior slope
obliquely convergent, making smoothly convex
hepatic margin; hepatic region sunken as awhole, weakly convex dorsally, narrowing toward
bridge between gastric and cardiac regions.

Branchial region distinctly depressed inside athick, prominent submarginal ridge that is erodedon its dorsal surface; branchial margin of carapace much lower than its submarginal ridge, serrated by serial triangular teeth, isolated anteriorly
from hepatic margin by a notch, continuing toposterior margin of carapace as a wide, weakly
convex posterolateral lobe. Median third of posterior margin of carapace weakly convex posteriorly, eroded, as wide as distance between upper
orbital margins; posterior margin of carapace lat-Parthenopid Crabs from the Kermadec Islands

eral to median third divided into three lobes; median lobe twice as wide as inner lobe, one third
as wide as posterolateral lobe.
Chelipeds not long, unequal in size, right cheliped larger. Merus concealed for its proximal
half beneath carapace, distal half curving more
forward and outward, with flattened inner surface; median part of anterior margin excavated,
together with depressions at inner margin of carpus and upper part of proximal half of palm,
forming a large concavity; three lobular, triangular teeth fitting to form lower margin of the large
concavity, when the cheliped is flexed; posterior
margin of merus serrated with several teeth along
its proximal two thirds, and distal third with twolobes. Outer surface of carpus and upper surfaceof palm smooth, but outer upper surface of palm
ornamented with rough reticulation of linear
ridges, short furrows and depressions; lower halfof outer surface of palm roughened with clustersof granules; lower margin of palm armed withsharp teeth. Immovable finger armed with threeprominent cutting teeth, a longitudinal ridge withsome granules on outer surface, and some sharp
teeth on basal half of lower margin. Movable finger subequal in length to upper margin of palm,armed with two rows of clusters of granules onouter surface, and with three high, granulated
teeth with smaller teeth between them on margins. Outer upper surface of palm with twohumps, proximal one being larger; inner upper
margin of palm armed with five prominent teeth
with small marginal granules; inner surfaces ofteeth flattened, smooth, not separated from innersurface of palm. Inner surfaces of palm and basal
halves of both fingers smooth, studded with scattered granules of good size.
Ambulatory legs comparatively stout, flattened. Meri somewhat narrower distally, with tricarinate margins, one carina anteriorly and twoposteriorly; each anterior margin armed with several granules of good size, or rather tubercles,with obtuse tips; in first two pairs of legs granules on both anterior and posterior margins
small; in last two pairs of legs proximal two teethon each posterior upper margin prominent, and151

distinctly lobular in last pair. In first three pairsof legs each carpus armed with three teeth on anterior margin and three teeth on upper surface;
distal tooth of each anterior margin large and distinctly lobulate; in last pair of legs upper surfaceof merus smooth, flattened, with a small lobe anda prominent lobe at proximal and distal ends, respectively; distal end of lower margin lobate.
Each propodus of first three ambulatory legs
armed with a prominent lobe on median part ofanterior margin, and with two tubercles tippedwith setae on posterior margin; each upper surface provided with one large tubercle and one
small tubercle on proximal half, three or four
small teeth in a longitudinal line on distal half; inlast pair of legs, posterior margin of propodus
armed with three tubercles, median one of which
is much larger than others and distinctly lobate;
upper surface with a small tubercle at medianpart.
Abdomen narrow, seven-segmented. First segment short, almost obscured under posterior margin of carapace; second segment with a transverse, granulated ridge, abdomen bending at thissegment; third to fifth segments roughened withgranules, each provided with a transverse, granulated ridge; main part of sixth segment occupied
by a transverse, short, high ridge; terminal segment flattened, with only scattered sharp granulesof variable sizes.
Male first pleopod well developed, stout, flattened for its whole length, subtruncate at its distal end which is surrounded by setae. Secondpleopod sharply pointed at its tip, about half as
long as first pleopod.
Etymology. The name refers to the distinctiveand characteristic constriction in the carapace between the anterior and posterior ends of the hepatic margin of the carapace.
Remarks. The new species is closest toPseudolambrus calappoides (Adams and White,1848) which is widely distributed in the IndoWest Pacific from Japan to the Red Sea(Paul’son, 1875; Alcock, 1895; Sakai, 1976; Daiand Yang, 1991). During the present study, a female (12.4 mm CB9.7 mm CL) and a juvenile

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Masatsune Takeda and Richard Webber(7.7 mm CB6.4 mm CL) of P. calappoides from
50–70 m deep off Wakayama Prefecture on thePacific coast of central Japan (NSMT-Cr 6929)
were examined for direct comparison.
In P. calappoides the general outline of thecarapace is rounded-triangular in dorsal view,
and, in this respect, similar to that of the newspecies, but there are some distinctive differences. 1) In P. calappoides, the anterolateral margin of the carapace is without a constriction behind the orbit. The hepatic margin appears continuous with the infraorbital margin, without adistinct notch, whereas, in the new species, thehepatic and infraorbital margins are discontinuous and separated by a deep angle which createsa conspicuous constriction behind the orbit in
dorsal view, 2) In P. calappoides, the front is almost perpendicular, its tip is armed with a pair ofsmall, side-by-side tubercles, and the dorsal surface of the front is provided with a wide depression that narrows posteriorly toward the gastricregion, between the orbits. In the new species, on
the other hand, the rostrum is weakly deflexed,obtusely angled at its tip, which is without distinct tubercles, and the rostrum is also flattened
dorsally and has only a shallow depression between the orbits, 3) In P. calappoides, the metagastric part of the gastric region and the cardiac
region are each armed with a blunt tubercle. In P.
constrictus, there is no marked tubercle on thecardiac region, but a blunt tubercle is present on
the metagastric part, 4) In P. calappoides, thebranchial region is without a distinct submarginalridge but is raised for its outer two thirds with thedorsal surface inclined slowly toward the outermargin. The inner one third of the branchial region is depressed and lower than both the cardiac
region and the outer two thirds of the branchialregion. In P. constrictus, however, the whole surface of the branchial region is depressed, proximal to a strongly raised submarginal ridge.
Pseudolambrus tuberculatus Flipse, 1930,
from the Sulu Archipelago, is also similar to thenew species in the triangular appearance of its
carapace, and especially the flattened front, butagain, there is no postorbital constriction, and adistinct hepatic margin cannot be detected. In addition, the upper margins of the palms and movable fingers in P. tuberculatus are not dentate,and both margins of the ambulatory legs are notlobate.
Acknowledgements
This study was made possible under the financial support of the National Museum of Natureand Science, Tokyo.
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