Contusarma, new genus

Type species. Sesarma bocourti A. Milne-Edwards, 1869, by present designation. Gender neuter.

Diagnosis. Carapace subrectangular; frontal margin bilobed, gently deflexed, as wide as or slightly wider than posterior carapace margin; lateral margins of carapace with small epibranchial tooth, posterolateral part subparallel; regions of carapace clearly demarcated; postfrontal and epigastric crests separated by distinct grooves, margin straight, sharp or gently convex, regions clearly separated; basal articles of antenna and antennules clearly separated by septum formed by extension of front; dorsal margin of palm without any longitudinal pectinated ridge; outer surfaces of both chelae prominently flattened, covered with numerous squamate or low sharp granules; chelipedal dactylus relatively broad; inner surfaces of first to third ambulatory coxae with only scattered short setae between them, never arranged into dense tufts; male thoracic sternites 2–4 relatively narrow in adults, shallow but just visible suture between sternites 3 and 4; male sternopleonal cavity reaching three-quarters length of sternite 4 but not reaching sternite 2; pleonal locking mechanism formed by small angular projection on posterior edge of sternite 4 of sternopleonal cavity, no trace of tubercle on sternite 5; male thoracic sternite 5 smooth, without depression on anterior part; G1 relatively slender, long, chitinous part bent obliquely, relatively long. Vulva on anterior part of sternite 6, anterior edge just touching sternite 5; rim-like anterior and posterior sternal vulvar covers; opening short, cylindrical, slightly projecting, directed obliquely posteriorly.

Etymology. The name is derived from the combination of the Latin “contusus” for flattening surface, with the genus name Sesarma . This alludes to the flat chelae that the two included species use to help in burrowing. The gender is neuter.

Included species. Sesarma bocourti A. Milne-Edwards, 1869; Sesarma cheirogona Targioni Tozzetti, 1877 .

Remarks. The genus contains two species, Sesarma bocourti A. Milne-Edwards, 1869, and Sesarma cheirogona Targioni Tozzetti, 1877 . The latter has been treated as a junior synonym of S. bocourti for over a century, but a suite of small morphological characters as well as genetic data allow it to be recognised as a separate taxon (Fig. 59). The differences between these two species are discussed under Contusarma bocourti below.