Petrolisthes elegantissimus, Werding, Bernd & Hiller, Alexandra, 2015

Werding, Bernd & Hiller, Alexandra, 2015, Description of a new species of Petrolisthes in the Indo-West Pacific with a redefinition of P. hastatus Stimpson, 1858 and resurrection of P. inermis (Heller, 1862) (Crustacea, Anomura, Porcellanidae), ZooKeys 516, pp. 95-108 : 101-103

Taxon classification Animalia Decapoda Porcellanidae

Petrolisthes elegantissimus sp. n. Figs 3and 4

Type material.

Indonesia. RMNH.CRUS.D.56374, holotype, male, CL 8.9 mm × CW 8.7 mm, NW Guinea, Pulau Japen, coast near Sarawandori, leg. W. van Seroei, 24.2.1955. Paratypes: RMNH.CRUS.D.56408, 4 males, 5 females (3 ov), same data as holotype. RMNH.CRUS.D.56375, 2 males, CL 8.8 mm × CW 8.8 mm, and CL 6.3 mm × CW 6.0 mm, same data as holotype. Indonesia: Snellius Expedition. RMNH.CRUS.D.56376, 5 males, 3 females (ov), Los (near Misool), 3-6.10.1929; RMNH.CRUS.D.56377, 2 males, Wotap, (Pulau Wotap), Tanimbar Island, beach and reef, 20.-23.10.1929; RMNH.CRUS.D.56409, 3 males, 1 female (ov), Pelee near Misool, beach, 04.10.1929. SMF 48329, 1 male, 1 female (ov), CL 8.1 mm × CW 8.6 mm, Sissie near Misool, beach, 06.10.1929.

Measurements.

Largest male: CL 8.9 mm × CW 8.7 mm; largest female (ov): CL 8.1 mm × CW 8.6 mm.

Description.

Carapace as long as broad or slightly broader than long, invertedly heart-shaped, broadest at metabranchial level; dorsal surface granular, branchial regions with low striae on outer margin. Front strongly produced, sinuously trilobate; lateral lobes formed by the supra-ocular edge; rostrum dorsally with deep median sulcus extending beyond protogastric ridge; orbits shallow, nearly straight, outer orbital angle rounded, forming a shallow lobe extending to hepatic margin. Epibranchial angle distinct but without a notch or spine, continuing in a ridge along the branchial margin. Protogastric ridge, cervical grooves and regions well marked. Lateral walls with scattered, simple setae.

Telson (Fig. 4C) composed of 7 plates; lateral plates narrow; lateral margins of central plate emarginate.

Basal segment of antennular peduncle (Fig. 4B) with faint transverse rugae; anterior margin rounded, granular, with minute teeth at mesial and lateral corners.

First movable segment of antenna with a lamellar, spine-tipped lobe, second with a longitudinal granular crest extending proximally into a rounded tooth, third rounded, unarmed.

Chelipeds sub-equal, merus with transverse, low granules on dorsal surface; anterior margin armed distally with a prominent, spine-tipped lobe. Carpus straight, margins subparallel, about 4-5 times as long as broad; dorsal surface covered with small, verruciform granules; anterior margin armed with 3-5 irregularly-set, acute small teeth of similar size; posterior margin slightly curved outwards with larger granules forming a crest along the distal half of length extending in a prominent, curved, distal tooth. Chela large, slender, posterior margin weakly curved, unarmed; dorsal surface covered with low, spherical granules, with a low, median crest extending to the base of the dactylus; fingers unarmed, gape without or with very short pubescence.

Walking legs extremely long and slender. Ischium devoid of setae or with few scattered, plumose setae. Merus devoid of setae or with few simple setae, unarmed or with a varying number (1-4) of irregularly-set, sharp spines along anterior margin with a prominent postero-distal spine in L1, weakly developed or lacking in L2, and postero-distally rounded in L3. Carpus, propodus and dactylus with scattered, simple setae. Propodus with distal triplet of movable spinules, and one additional spine on median part of posterior margin. Dactylus with 3 movable spines on posterior margin.

Variation.

Large specimens normally present more elongate and narrower chelipeds than smaller ones. The teeth of the anterior margin of the cheliped carpus often varies in the same specimen in number and position.

Habitat.

Petrolisthes elegantissimus sp. n., like the other two species, seems to be a shallow water species.

Distribution.

Only known from a restricted region in eastern Indonesia.

Etymology.

The specific name is derived from the Latin elegans (tasteful, refined), referring to a more elegant and gracile general habitus compared with that of the related species, Petrolisthes hastatus and Petrolisthes inermis . The species name is an adjective in the nominative singular.