Chhapgarus, Ng & Trivedi & Bhat, 2022

Ng, Ngan Kee, Trivedi, Jigneshkumar & Bhat, Mithila, 2022, Redescription of Pseudograpsus intermedius Chhapgar, 1955 (Decapoda, Brachyura, Varunidae) from India, Zootaxa 5209 (1), pp. 127-138 : 130

Chhapgarus n. gen.

Type species. Pseudograpsus intermedius Chhapgar, 1955 , by present designation.

Description. Carapace squarish, dorsal surface covered with short, brown setae; regions well defined, convex; frontal margin slightly convex, straight; anterolateral margin subcristate with three teeth including first orbital tooth; posterolateral margins not sharply demarcated from anterolateral margin, concave at branchial region, distinctly subparallel; orbits small, eyes completely filling orbit. Third maxillipeds short, stout; small, distinct rhomboidal gape when closed, palp short, with short setae; exopod with short flagellum. Epistome broad, flat, posterior margin entire. Inner surface of chela with granules, setose. Ambulatory legs long, slender with short setae, stout dactyli. Lateral margins of thoracic sternites 4–5 finely granulated; anterior sternal plates without any medial grooves. Male pleon narrowly triangular, with 7 free segments (6 somites plus telson). Female pleon ovate, very broad. G1 stout, gently curving outwards, terminal lobe elongate, slightly curved.

Etymology. The new genus is named in honor of Dr. Boman Framji Chhapgar for his valuable contributions to the study of crustacean fauna of Gujarat and Maharashtra States, India. Gender: masculine.

Remarks. The description of the genus Pseudograpsus provided by H. Milne Edwards (1837) is brief that has been updated by Ng et al. (2002). In his description, H. Milne Edwards (1837: 81) named two species as belonging to the genus, Pseudograpsus viz. P. pencilliger (Latreille, 1817) , and P. pallipes H. Milne Edwards, 1837 . No type species was designated. Holthuis (1977) was the first to validly select Cancer penicilliger Latreille, 1817 , as the type species (see also Ng & Nakasone 1993: 2). Cancer penicilliger was later synonymized under the senior name, Pseudograpsus setosus (see Ng et al. 2002). The genus Pseudograpsus has a long history of association with Hemigrapsus and Brachynotus (see Tesch 1918; McLay & Schubart 2004; Ng et al. 2002). This association is now being studied in-depth (in preparation). Balss (1934) synonymized P. erythraeus Kossmann, 1894 , under P. elongatus . Ng & Nakasone (1993) transferred P. laniger to their new genus, Scutumara Ng & Nakasone, 1993 , with a comment that the genus Pseudograpsus needs to be revised.

The genus, Pseudograpsus , currently comprises of five species viz. P. setosus (Fabricius, 1778) (= P. pencilliger (Latreille, 1817) , type species); P. crassus A. Milne-Edwards, 1868 , P. albus Stimpson, 1858 , P. elongatus A. Milne-Edwards, 1873 , and P. intermedius Chhapgar, 1955 . Out of these five species, P. intermedius varies from other species of Pseudograpsus s.s. in having setae on the carapace, chela having soft setae on outer surface, broad and stout ambulatory legs and differences in morphology of reproductive structures, hence Chhapgarus n. gen. is established for Pseudograpsus intermedius Chhapgar, 1955 . Interestingly, C. intermedius comb. nov. inhabits the mid-intertidal zone in mangrove habitats ( Chhapgar 1955), while species of Pseudograpsus s.s. are found in freshwater streams and/or under pebbles/coral sand habitats along beaches ( Tesch 1918; Balss 1922; H.T. Shih, pers. comm). The morphological differences between Chhapgarus n. gen. and Pseudograpsus are given in Table 1 .

Chhapgarus n. gen., also shows similarity to Utica White, 1847 in having setae on the carapace surface and outer surface of chela, but differs from the latter in the following characters: carapace squarish (versus distinctly quadrangular in Utica ); gastric region without “V” shaped ridge (versus prominent “V” shaped ridge on gastric region in Utica ); branchial region without horizontal ridge (versus horizontal setose granulated ridge present across the branchial region in Utica ).