Garthambrus undulatus, Mclay, Colin L., 2009

Mclay, Colin L., 2009, Revision of the crab genus Garthambrus Ng, 1996, with the description of two new genera and discussion of the status of Tutankhamen Rathbun, 1925 (Crustacea: Brachyura: Parthenopidae), Zootaxa 2122, pp. 1-50 : 30-32

Garthambrus undulatus sp. nov.

( Figs 8 C, D, 15)

Type material. HOLOTYPE: male 44.4 x 29.0 mm (MNHN-B31867), New Caledonia, VOLSMAR, stn DW30, 22º17.0’S, 171º17.7’E, 550 m, 5 Jun 1989.

PARATYPES: male 41.3 x 27.3 mm (MNHN-B31868), New Caledonia, CHALCAL II, stn DW72, 24º54.50’S, 168º22.30’E, 527 m, 28 Oct 1986; 1 male 19.1 x 13.4 mm (MNHN-B31869), SMIB 8, stn DW151, 24º53.4’S, 168º21.4’E, 530–547 m, 27 Jan 1993.

Material examined. See type material.

Description. Carapace sub-pentagonal, wider than long, surface undulating, minutely granular with some eroded areas.

Median rostral tooth elongated, blunt, deflexed but slightly curving upwards near tip. Lateral rostral teeth truncated. Frontal region slightly concave, supraorbital margin slightly elevated. Protogastric region with pair of prominent, blunt tubercles behind eroded area. Mesogastric region with broad median ridge that extends to metagastric region. Hepatic region with 2 eroded areas behind orbits. Cardiac region with 2 blunt tubercles in line, separated by eroded area. Posterior diagonal ridge on anterior branchial area, with prominent sub-acute tubercle as dominant feature, anterior diagonal ridge scarcely evident. Posterior branchial area with sub-acute tubercle; branchiocardiac groove well marked by series of 3 pits. Total of 8 prominences on carapace.

Supraorbital margin minutely granular; strongly concave to well marked supraorbital suture. Suborbital margin ends in prominent tooth. Margins of orbits fringed with short setae. Hepatic margin with well developed, blunt posterior tooth with smaller tooth on posterior margin, small blunt tooth before notch. Anterior epibranchial margin with 11 or 12 blunt teeth of varying size, small granules in between. Last anterior epibranchial tooth long, curved upwards, bifid. Posterior epibranchial margin concave with tooth near posterior epibranchial corner. Tubercle on posterior branchial region overhangs margin. Posterior margin concave at each corner, with prominent sub-acute tubercle.

Epistome T-shaped, mostly flat except for depressed median area. Subhepatic region concave with fissure almost completely covered by granules. Pterygostomial area slightly concave, minutely granular. Subbranchial ridge not well developed. Cheliped-blocking mechanism involves stout proximal spine on posterior margin of merus, against large sub-branchial spine near base of cheliped. Depression on sternites 3, 4 Vshaped. Corners on sternite 4 depression marked by large tubercle with several smaller ones. Anterior epibranchial corners of sternites 5–7 with slightly raised, tuberculate ridges preceded by slight depression. Only sternal suture 6/7 is complete.

Eyes mobile, eyestalks granular, short, diameter same as cornea, articulated at right angles to body axis; margin of orbit ventrally incomplete, orbital fossa deep, formed by lateral, suborbital margin, around 80% of cornea concealed when eye folded.

Antennular article 1 mobile, 6-sided; article 2 much longer than wide, inserted medially, folded at oblique angle; article 3 much longer than wide; articles 3, 4 normally kept folded in antennular fossa.

Antennal article 1 (“urinal article”) mobile, wider than long, convex; article 2 (“basal article”) trapezoidal, convex, fixed to epistome, suborbital margin; articles 3, 4 mobile, longer than wide; flagellum as long as articles 3, 4 combined.

Medial edge of third maxilliped basis-ischium knife-like, meeting its opposite in mid-line. Longitudinal median concavity on basis-ischium. Merus wider than long, with 2 depressions separated by ridge. Lateral corner of merus covers distal end of exopod. Palp folded medially, last 2 articles concealed by merus; carpus, propodus, dactylus of decreasing size, upper distal corners of carpus, propodus slightly produced.

Inner margin of cheliped merus with 7 or 8 small blunt granules; outer margin with 7 or 8 sub-acute granules, distal 4 longer. Single, prominent sub-acute granule in middle of carpus. Outer margin of propodus armed with 8 or 9 granules, 5 longer than others. Inner border of propodus armed with 6 granules, last 3 longer, curving upwards towards base of dactyl. Upper border of dactyl with 4 sub-acute granules. Right cheliped (crusher) gaping, with only 2 distal teeth. Left cheliped (cutter) with only 4 weakly developed interlocking teeth. Male cheliped length 2x CW or 3x CL.

Ambulatory legs decreasing in length posteriorly. Tubercle formula for ambulatory legs: P2: merus 6/2, carpus 1/0, propodus 0/0; P3: merus 6/2; no tubercles on carpus or propodus; P4 merus 5/(5 + 1), carpus 0/0, propodus 3/0; P5: merus 5(4 + 2), carpus 0/0, propodus 3/3. All tubercles stout, blunt. Dactyli shorter than propodi, ending in horny claw.

Male abdomen finely granular, medially convex; segments 3–5 fused, sutures only evident at margins. Medial curved hook on segment 6. Abdominal locking mechanism with large, smooth tubercles on sternite 5 fitting into deep sockets on posterior corners of segment 6. Telson triangular, distinctly wider than long, distally rounded, small medial pit present. Female unknown.

G1 extends to middle of sternite 5, almost straight, narrowing distally, sperm aperture subterminal, directed medially, distal 10% covered by small, acute, proximally directed spines. G2 slightly longer than first, extending to middle of sternite 4, flagellum 46% of total length, twisted 90°. Transition from basal section of G2 to flagellum is not marked by notch. Ratio of length of G2/G1 = 1.15. Female unknown.

Distribution. Known only from New Caledonia.

Etymology. The species name refers to the smooth, undulating carapace surface of this species.

Remarks. Garthambrus undulatus and G. cidaris look similar due to the broad epibranchial tooth. However, G. undulatus can be distinguished from G. cidaris because the anterior epibranchial margin ends in a long lateral tooth that is bifurcated at the tip. In G. cidaris , the lateral tooth is shorter and the tip is not bifurcated. In addition, the tubercles on the dorsal surface of the carapace are paxilliform and more numerous in G. c i d a r i s, but blunt and less numerous in G. undulatus .

Figures

FIGURE 8. Gonopods. Garthambrus tani Ahyong, 2008: A, B, male 28.5 x 21.2 mm (MNHN), New Caledonia, VAUBAN, stn CB 113, 500 m, 12 Apr 1978. — Garthambrus undulatus sp. nov.: C, D, holotype, male 44.4 x 29.0 mm (MNHN), New Caledonia, VOLSMAR, stn DW 30, 22 ° 17.0 ’ S, 171 ° 17.7 ’ E, 550 m, 5 Jun 1989. A, C, left G 1; B, D, left G 2. Scale bar = 1 mm.