Stegopleurodon pteridion sp. nov.

urn:lsid:zoobank.org:act: 97E6134C-B0F4-4147-87E7-522E8BCD6545

Figs 13F, 14 A–C, 15A–D

Diagnosis

Carapace surface smooth, with 2 large lateral lobes; 1 postocular lobe with sharp anterior angle, 1 branchial lobe (Fig. 16A). Outer lateral border of branchial lobe thin, expanded above lateral border, forming wing-like structure. Dorsal surface with 2 convex regions: 1 small gastric swelling, 1 large cardiac one. Posterior part of cardiac convexity forms ridge joining posterior border of carapace. Male cheliped with propodus inflated, carinate on upper border; carpus squarish in cross-section with each angle carinate; merus triangular in cross-section, with each angle carinate. Ambulatory legs with merus, carpus, propodus enlarged, carinate on upper border; lower border of merus of P2–P5 each with 2 crested carinae with margin bearing setae-like spines; dactylus curved, sharp.

Etymology

The name ‘ pteridion ’ means ‘with wings’ in Greek. The name is treated as a Latin noun in apposition.

Material examined

Holotype

SOUTH CHINA SEA: ♂ (13.1 × 7.9 mm) (NTOU), northeast of Zhongsha, stn CP4156, 16°09.80′ N, 114°58.73′ E to 16°12.19′ N, 115°00.53′ E, 511– 505 m, 28 Jul. 2015, coll. ZHONGSHA 2015 Expedition.

Description

Small size species. Carapace pyriform. Pseudorostrum composed of 2 short dorsoventrally flattened parallel teeth with rounded edge. Supraorbital eave narrow, forming rounded anterior and posterior angles. Carapace surface smooth, with 2 large lateral lobes; 1 postocular lobe with sharp anterior angle, and 1 branchial lobe (Figs 13F, 14A). Outer lateral border of branchial lobe thin, expanded above lateral border, forming wing-like structure. Dorsal surface with 2 convex regions: 1 small gastric swelling, 1 large cardiac one (Figs 13F, 14A). Posterior part of cardiac convexity forms ridge joining posterior border of carapace.

Antennae shorter than pseudorostrum. Antennule retractable in deep fossae. Eyes with short cornea, rounded; anterior region of eye protected by supraorbital eave; postorbital plate forms a cavity protecting posterior region of eye. On lateral side of carapace, behind postocular plate, a series of long hooked setae. Basal antennal article flat, curved on proximal edge; distinct tubercle at base of basal antennal article (Fig. 14B). Epistome small. Pterygostomial region relatively large, smooth, with 2 distinct plates present (Fig. 14B). Buccal frame quadrangular, completely closed by third maxillipeds.

Male cheliped with propodus inflated, carinate on upper border; carpus squarish in cross-section with each angle carinate; merus triangular in cross-section, with each angle carinate. Ambulatory legs with merus, carpus, propodus enlarged, carinate on borders; merus triangular in cross-section, lower border of merus of P2–P5 each with 2 crested carinae with margin bearing spine-like setae; carpus with 2 carinae on anterior region, posterior region covered with setae; propodus with single carina on anterior region, posterior region covered with setae; dactylus curved, sharp, covered with setae except at tip.

Male thoracic sternum anteriorly deeply depressed, covered with setae, smooth when denuded; sternites 1–3 fused (Fig. 14B). Male abdomen with triangular telson and 6 free somites, widest at third. G1 straight, constricted distally (Fig. 15).

Colouration

In the fresh specimen, the carapace is orange with the chelipeds pinkish-orange; the first three pairs of ambulatory legs are pale orange, with the last pair entirely white (Fig. 13F).

Remarks

The new species fits well with the description of Stegopleurodon Richer de Forges & Ng, 2009, but it is clearly different from the only species known, S. planirostrum Richer de Forges & Ng, 2009, from New Caledonia (Richer de Forges & Ng 2009b). Stegopleurodon pteridion sp. nov. has thin anterolateral lobes (Fig. 14A, C), whereas those on S. planirostrum are thick and strong (cf. Richer de Forges & Ng 2009b: fig. 8A, C). Stegopleurodon planirostrum has a proportionately wider carapace than S. pteridion sp. nov. (Fig. 14A). In S. planirostrum, there are strong ridges on the carapace: one longitudinal and two transverse, forming a cross on the gastric and another on the cardiac region (cf. Richer de Forges & Ng 2009b: fig. 8A). In S. pteridion sp. nov., only one ridge is present on the posterior part of the carapace between the cardiac region and the posterior margin of the carapace (Fig. 14A, C).

Distribution

Only known from South China Sea.