A taxonomic revision of the freshwater crab genusBarytelphusaAlcock, 1909 (Decapoda: Brachyura: Gecarcinucidae), with descriptions of a new genus and three new species

Abstract

The taxonomy of the gecarcinucid crab genus Barytelphusa Alcock, 1909, native to peninsular India, is revised. The genus was formerly known from as many as 13 species and four varieties. We examined their name-bearing type specimens, and to stabilise their taxonomy, designated lectotypes for Potamon (Potamonautes) jacquemontiRathbun, 1905, Thelphusa guerini H. Milne Edwards, 1853, and Telphusa pocockianaHenderson, 1893, and a neotype for Thelphusa cunicularis Westwood in Sykes, 1836. With most of the species already assigned to other genera in previous works, we restrict Barytelphusa s. str. further to only two species, i.e., Barytelphusa cunicularis (Westwood in Sykes, 1836), and a new species described herein, Barytelphusa inflatasp. nov.Potamon (Potamonautes) jacquemonti, the type species of the genus, is here synonymised with Barytelphusa cunicularis. A new genus, Barusagen. nov., is established to accommodate two species placed previously in Barytelphusa (Thelphusa guerini and Paratelphusa (Barytelphusa) mccanniChopra & Das, 1935) and two new species (Barusa gracillimasp. nov. (type species) and Barusa obesasp. nov.). Thelphusa planata A. Milne-Edwards, 1869, and Telphusa pocockiana remain as junior synonyms of Barusa guerini (H. Milne Edwards, 1853) comb. nov.Barusagen. nov. resembles Barytelphusa but can be differentiated by several significant characters of the carapace, antennae, cheliped, male pleon, and male first gonopod. Identification keys to the species of both genera are provided. The taxonomy of Potamon napaeum Alcock, 1909, placed previously in Barytelphusa, and more recently in TravancorianaBott, 1969, is also clarified, and the species is now reassigned to MaydelliathelphusaBott, 1969.

Morphological and molecular identification of the freshwater crab, Barytelphusa cunicularis from Kanniyakumari, India

“…During these years, there have been several instances where the members of the genus Barythelphusa have been subjected to "inclusion-exclusion" changes and synonymizations, contributing to inconsistencies in the phylogenetic status of the genus. In a recent account, Pati and Yeo (2022) epibranchial tooth relatively distinct and blunt, at the level of postorbital cristae, with distinct cleft; cervical grooves deep, relatively long, reaching the level of postorbital cristae; incomplete frontal medial triangle, with only dorsal margin, while the lateral margins were indistinguishable; relatively long antennae, subequal in length to eyestalks. Third maxilliped exopod with well-developed flagellum, equal or exceeding in length to merus.…”

“…G1 relatively short, with short terminal segment, ~0.6× length of subterminal segment. G2 distinctly shorter than G1, with the distal segment conspicuously short, ~0.2× length of basal segment (Pati and Yeo, 2022). The morphometric cues with respect to the CW:CL and CW:CH ratio given by Pati and Sharma (2014) have also been relevant to distinctly identify the genus.…”