NOVOROSTRUM, NEW GENUS (DECAPODA: ANOMURA: PORCELLANIDAE), WITH DESCRIPTIONS OF THREE RELATED SPECIES

Abstract

A new porcellanid genus, Novorostrum, is proposed for three species, Petrolisthes indicus de Man, 1893 (type species), and two new species, N. decorocrus and N. phuketensis, with detailed descriptions provided for each species. This genus is distinguishable from other porcellanid genera by the combination of the following characteristics: (1) the carapace with uneven gastric and branchial regions, with each region divided into several parts by grooves and sinuses; (2) the distinctly trilobate rostrum, its median lobe with lateral elevations; and (3) the ocular peduncle distinctly broader than the cornea in dorsal view. Novorostrum decorocrus, new species, has been treated as an intraspecific variation of N. indicum (as Petrolisthes indicus) by Nakasone and Miyake (1968). However, their specimens possess several distinct morphological features recognized as specifically valid. They are: (1) the subtrapezoidal carapace in dorsal view; (2) the carpus of the chelipeds with small spinelike teeth on the dorsoflexor margin; (3) the chela, and the merus, carpus, and propodus of the ambulatory legs with blunt teeth on the extensor margin; and (4) the chela provided with a weak, crenulated longitudinal ridge along the extensor margin on the dorsal surface. The second new species, N. phuketensis, is distinguished from N. indicum and N. decorocrus by the following: (1) the median lobe of the rostrum with weak lateral elevations; and (2) the subtriangular dorsal extension onto the cornea of the ocular peduncles.