Neorhynchoplax elongata, Rahayu & Ng, 2004

Rahayu, Dwi Listyo & Ng, Peter K. L., 2004, The Hymenosomatidae (Crustacea, Decapoda, Brachyura) of Timika (Irian Jaya, Indonesia), Zoosystema 26 (1), pp. 87-94 : 89-91

Neorhynchoplax elongata n. sp.

( Fig. 1 )

HOLOTYPE. — Indonesia. Kamora , intertidal, mud substrate in mangrove area, 22.IX.2001, coll. I. Ermayanti, ovigerous 2.7 × 4.0 mm ( MZB).

ETYMOLOGY. — The name alludes to the elongated carapace of the species.

DESCRIPTION

Female holotype

Carapace ( Fig. 1A ) longer than broad, width two thirds length (including rostrum); carapace surrounded by distinct, complete rim; dorsal surface almost flat, with distinct gastrocardiac, cervical and thoracic grooves; cervical and thoracic grooves branched; anterolateral margin smooth. Rostrum trilobate, with three large, sharp teeth, median longest, not continuous with dorsal surface of carapace. Eyestalk prominent, distinctly visible dorsally.

Third maxillipeds ( Fig. 1B ) cover two thirds of mouth field when closed; ischium subequal in length to merus along outer lateral edge, sparsely setose on inner lateral edge of both merus and ischium. Inner lateral margins of ischium meeting when closed; palp not longer than merus; exopod much longer than merus.

Chelipeds ( Fig. 1C ) equal, stouter than ambulatory legs; outer surface pubescent; fingers slender, same length as palm, cutting edges slightly serrat- ed. Dactylus and fixed finger slightly gaping proximally when closed. Palm, carpus and merus with tuft of setae on upper margins.

Ambulatory legs (pereiopods 2-5) slender. Dactylus much shorter than propodus, with tips sharply hooked, row of six teeth ventrally, ventral edge more densely lined with long and short setae. Propodus more than twice length of carpus, merus slightly shorter than propodus. Propodus, carpus and merus with scarce short setae.

Female abdomen ( Fig. 1E ) oval, convex, covers entire sternum, three-segmented, segments 3-5 fused, pleotelson sharply triangular.

REMARKS

Neorhynchoplax elongata n. sp. is remarkable within the genus in its long trilobate rostrum, with the lateral carapace margin not possessing any teeth or spines. In these characters, it closely resembles N. inachoides ( Alcock, 1900) , described on the basis of only one male specimen (6.0 × 8.5 mm) from Calcutta, India. Neorhynchoplax elongata n. sp., however, can easily be distinguished from N. inachoides in having an evenly ovate carapace (vs pyriform), the lateral rostral spines been relatively shorter and diverging obliquely outwards (vs longer and subparallel with median spine) and the relatively shorter ambulatory legs (cf. Alcock 1900: 389; Alcock & MacGilchrist 1905: pl. LXV fig. 1).

At present this species is only known from the type locality in Kamora, Irian Jaya, Indonesia.

Figures

FIG. 1. — Neorhynchoplax elongata n. sp., holotype 2.7 × 4.0 mm (MZB); A, carapace; B, left third maxilliped; C, abdomen; D, right cheliped; E, left third pereiopod. Scale bars: 1.0 mm.