Pseudolambrus confragosus (Calman, 1900)

(Figs. 2C, 5A–G, 10D–H)

Lambrus (Parthenolambrus) confragosus Calman, 1900: 42, pl. 3 figs. 27, 28 (type locality: Torres Strait, Australia).— Flipse 1930: 48 (identification key), 87 (index).

Parthenope (Parthenolambrus) calappoides .— Rathbun 1906: 832 (list), 886, pl. 15 fig. 6 (in part).

Lambrus confragosus — Grant & McCulloch 1906: 32.

Parthenope (Pseudolambrus) confragosus — Serène 1968: 61 (list).

Pseudolambrus confragosus —Davie 2002: 389 (list).— Tan 2004: 367, figs. 96G, 101.— Ng et al. 2008: 131 (list).

Material examined. 1 male (22.2 × 18.0 mm) (IO/SS/BRC/00323), FORVSS stn. 38818, south of Great Nicobar Island, Nicobars, India, 6.65°N, 93.83°E, 56 m depth, chain bag dredge, coll. V.P. Padate, 16 August 2019 .

Description. Carapace subtriangular, 1.2 times as wide as long, widest at posterolateral angle, dorsal surface irregularly tuberculate (Figs. 2C, 5A); hepatic region inflated, with strongly projected, medially angled margin; gastric region with a tall median, distally tapering tubercle (Fig. 5B); hepatobranchial and gastrobranchial notches deep; cardiac region with anterior median tubercle 2.0 times as high as posterior median tubercle. Frontal margin relatively long, deflexed, ventral surface with 2 depressions (Fig. 5C); lateral margins distinctly granular, diverging anteriorly, subparallel posteriorly; posterolateral corners with blunt spines; posterior margin with granulate tubercles dorsally.

Antennules folding obliquely; basal antennal article short, article 4 margin with 2 mesial and 1 lateral teeth (Fig. 5C); epistome well-developed, posterior margin elevated, median portion with two rounded protuberances (Fig. 5C); mxp3 merus subquadrate, half as long as ischium, with median depression and irregularly arranged granules (Fig. 5D).

Chelipeds subequal, 1.7 times CL, merus outer margin with large teeth, inner margin with 3 large triangular teeth (Fig. 2C); carpus with dentate carinae on inner and outer margins; palm with large crested lobe at midlength of outer margin, dactylus half as long as palm, with toothed crest along proximal half (Fig. 5E). Pereopods 2–5 shorter than chelipeds, densely tomentose, outer margins of meri, carpi and propodi armed with larger teeth compared with inner margins (Fig. 5F).

Male pleon elongate sub-triangular, somites 3–5 fused, somite 6 longest, ventral surfaces of somites 3–5 with a transverse row of 4 granules each, that of somite 6 with median granule (Fig. 5G); telson bluntly triangular, twothirds as long as wide (Fig. 5G). G1 stout, nearly straight (Fig. 10D, G), distal portion blunt with subdistal ventral spinose patch, spines on mesial margin extending to proximal half (Fig. 10E–F). G2 shorter than G1 (Fig. 10H).

Colouration. Fresh specimen: Carapace brick red, chelipeds brick red with whitish bands on proximal half of merus and midlength of palm, fingers whitish with brown tips, pereopods whitish with brick red patch on meri (Fig. 2C).

Biology. The present specimen was collected from rocky substrate in the vicinity of crinoids, at 56 m depth. Known to inhabit coral and sponge colonies, and coarse calcareous sand in reefs (Laurie 1906; Tan 2004) at depths from 18–500 m (Tan 2004).

Remarks. Calman (1900) described Lambrus (Parthenolambrus) confragosus from a female collected from Torres Strait, Australia, on the basis of a highly rugged carapace, compressed dentiform hepatic prominences, and the flattened lamelliform lobes on the outer margin of the cheliped palm. According to Tan (2004), Pseudolambrus confragosus resembles P. tarpeius (Adams & White, 1849) in the carapace armed with irregular, granular tubercles, and the presence of granular tubercles on the dorsal surface of carapace posterior margin. However, it differs from P. tarpeius in having a narrower hepatic region, relatively more inflated epibranchial region, and the presence of a lamelliform lobe on the outer surface of cheliped palm (Fig. 5A, E) (versus broader hepatic region, relatively less inflated epibranchial region, and the absence of a lamelliform lobe on the outer surface of cheliped palm in P. tarpeius; see Tan 2004: fig. 104A). The Indian specimen conforms to the description of the holotype (Calman 1900) as well as subsequent descriptions (Laurie 1906; Rathbun 1906; Tan 2004) in the distinctly tubercular and rugged surface of the carapace and chelipeds. However, the ornamentation on the G1 differs from the G1 of a male specimen from the Balicasag Island, Philippines in the presence of a subdistal spiny patch on the ventral surface (Fig. 10D, E) (versus G1 with smooth ventral surface in the Philippine specimen; cf. Tan 2004: fig. 96G, H).

Geographical distribution. Torres Straits (Calman 1900), Sri Lanka (Laurie 1906), Australia (Grant & McCulloch 1906) and Hawaii (Rathbun 1906), Seychelles, Mauritius, Gulf of Aden, the Philippines and New Caledonia (Tan 2004); and Nicobars, India (present study). The present observation is the first record from Indian waters.