Paralomis nivosa, Hall, Sally & Thatje, Sven, 2009

Hall, Sally & Thatje, Sven, 2009, Four new species of the family Lithodidae (Decapoda: Anomura) from the collections of the National Museum of Natural History, Smithsonian Institution, Zootaxa 2302, pp. 31-47 : 39-42

Paralomis nivosa n. sp.

( Figs 5 , 6 )

Material examined. Philippines: Palawan passage 10°57’45”N, 118°38’15”E, 27.12. 1908, 685 m: female holotype CL 30 mm, collected on the 1907–1908 ‘Albatross’ expedition to the Philippines ( USNM 1122581).

Etymology. This species is named nivosa , which is the Latin for snow-like or snowy. The name alludes to the fact that the carapace is angular and resembles a snowflake in dorsal view.

Description of holotype. Carapace angular in outline, with distinct angle at hepatic region ( Fig. 6 a). Gastric and branchial regions of similar size and moderately convex; cardiac region slightly sunken in comparison. Inflated whelt towards posterior of branchial regions and at medial entrance to cervical groove. Intestinal region flattened to posterior margin. Surface of carapace covered in low, rounded tubercles, each with a thick ring of short setae around sides and rounded non-setose apex ( Fig. 5 b). A few instances of clustered tubercles on gastric and cardiac regions. No spines or particularly prominent tubercles on dorsal surface. Lateral edges rounded and covered with similar ornamentation as dorsally. Five sharp spines on anterolateral portion of carapace: two on anterior margin; one on hepatic region, and two on anterior branchial margin. No spines on posterior or posterolateral branchial margin.

Rostrum pedunculate and wide, almost covering eyestalks in dorsal view. Base of rostrum dorsally covered in tubercles, similar to rest of dorsal carapace. Two short, sharp spines at end of this rostral prominence, at level of corneae. Median spine of rostrum extending beyond corneae; slightly keeled ventrally, and strongly curved upward ( Figs 6 b, d).

Eyestalks with several dorsal spines, one very long and extending past cornea ( Fig 6 e). Antennal acicle long, with one long medial spine, five long outer spines, and four short spines on internal surface. Several spinules on dorsal surface of acicle. All spines with uniform coverage of short setae along their length.

Cheliped carpus with a series of 4 enlarged spines on internal angle and a few tubercles on other surfaces. Very few spinules on surface of chelae palms, none on fingers. Fingers with row of clusters of setae external to cutting surfaces, and several setae on mobile finger.

Pereiopods uniformly covered with tubercles, with some prominent sharp spines as on lateral margins. Merus of pereiopod 4 about half carapace length and 1.5 times length of propodus, with rounded crosssection. Five prominent spines on dorsal anterior edge, and several sharp spinules on ventral posterior edge of walking leg meri. Sharp spinules covering carpus and propodus. Dactylus slightly shorter than propodus and compressed in cross-section. One or two spines in articulating region, but smooth surfaces elsewhere. With 5 short, black needle-like spines on ventral side of dactylus, as well as several tufts of setae.

Abdomen of holotype female asymmetrical, although with very little ‘right-hand skew’ — telson almost in line with body axis ( Fig. 5 a). Mid portion of second abdominal segment prominent in dorsal view. Medial and paired lateral plates on each abdominal segment 3–5. Marginal plates on left side separate from lateral plates. Surface of abdominal plates with low tubercles similar to those found dorsally.

Remarks. The dorsal ornamentation in Paralomis nivosa n.sp. is very similar to P. haigae Eldredge, 1976 ( Fig 5 c), and P. d o f l e i n i Balss, 1911 and this feature allies these three species within Paralomis . This specimen is a small adult; 30 mm in carapace length. Direct comparison with similar sized specimens of P. haigae and P. dofleini have been made at the USNM and Muséum National d’Histoire Naturelle, Paris (MNHN).

P. n i v o s a has several sharp spines on the lateral borders, dorsally on the rostrum, and on the legs. There is no indication of any spines laterally in P. haigae or P. dofleini , with the exception of one on the anterior margin. No specimens of P. haigae studied have spines dorsally on the rostrum. The outline of the carapace in P. n i v o s a is quite angular, whereas in P. h a i g a e, the carapace is more rounded.

The rostrum in P. haigae and P. d o f l e i n i has a wide base, which ends in a blunt prominence above a short, straight ventral spine. In P. n i v o s a, the ventral spine is very prominent and curved upward.

Figures

FIGURE 5. Paralomis nivosa n. sp. a, b, d – f: female holotype, 30 mm CL (USNM 1122581), Philippines, Palawan passage, 10 ° 57 ’ 45 ” N, 118 ° 38 ’ 15 ” E, 685 m. (a) abdomen. (b) mid-branchial carapace ornamentation, dorsal. (d) part of right ocular peduncle visible below rostrum, dorsal (e) whole organism, dorsal. (f) carapace lateral spine, dorsal. Paralomis haigae Eldredge. e: female 43.8 mm CL (MNHN-Pg 4274), Samoa. (e) whole organism, dorsal. Scale bar = 1 mm for a – d; 5 mm for e, f.

FIGURE 6. Paralomis nivosa n. sp. a – f: female holotype, 30 mm CL (USNM 1122581), Philippines, Palawan passage, 10 ° 57 ’ 45 ” N, 118 ° 38 ’ 15 ” E, 685 m. (a) carapace, dorsal. (b) rostral spines, dorsal. (c) right chela, lateral. (d) rostrum, lateral. (e) antennal acicle, frontal. (f) left chela, lateral. Scale bar = 5 mm for a; 1 mm for b – f