Contusarma, Schubart & Ng, 2020

Schubart, Christoph D. & Ng, Peter K. L., 2020, Revision of the intertidal and semiterrestrial crab genera Chiromantes Gistel, 1848, and Pseudosesarma Serène & Soh, 1970 (Crustacea: Brachyura: Sesarmidae), using morphology and molecular phylogenetics, with the establishment of nine new genera and two new species, Raffles Bulletin of Zoology 68, pp. 891-994 : 952

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.

Figures

Fig. 59. Phylogenetic relationships among selected taxa of Sesarmidae (91 OTUs), including all representatives of Chiromantes and Pseudosesarma previous to current revision of these genera. In addition, several species of Bresedium and Sesarmops are considered, as the revision also involves some of their former members. Topology and confidence values were determined by means of a phylogenetic reconstruction based on 1,096 basepairs of mtDNA (16S-tRNALeu-ND1), conducted with MrBayes, GTR+I+G as substitution model, and Parasesarma plicatum as outgroup (midpoint rooting). Posterior probabilities were determined after 4 million generations with a burn-in of 25%. All species so far classified within Chiromantes (without obvious anterolateral teeth) are shaded in blue, whereas those species that used to be classified in Pseudosesarma (carrying at least one pair of anterolateral teeth) are shaded in yellow.