Hemitrygon Müller & Henle, 1838

Last, Peter R., Naylor, Gavin J. P. & Manjaji-Matsumoto, B. Mabel, 2016, A revised classification of the family Dasyatidae (Chondrichthyes: Myliobatiformes) based on new morphological and molecular insights, Zootaxa 4139 (3), pp. 345-368 : 355

Genus Hemitrygon Müller & Henle, 1838

Hemitrygon (subgenus of Trygon ) Müller & Henle, 1838:90. Type species Trygon bennettii Müller & Henle, 1841 ; by subsequent monotypy.

Definition. Small to medium-sized dasyatids (adults typically to 31–66 cm DW, 93 cm DW in H. fluviorum ) characterised by the following: depressed to robust, weakly rhombic to rhombic disc with pectoral-fin apex narrowly angular to broadly rounded; snout obtuse to broadly angular and moderately elongate (1.7–2.5 times combined orbit and spiracle length); eye small to very small and protruding slightly; nasal curtain typically broadly skirt shaped; mouth narrow, with 1–7 oral papillae (typically with 3 centrally); tail short and filamentous to long and whip-like (length 0.8–2.9 times DW), its base depressed oval and not especially broad; pelvic fins mediumsized to large, protruding slightly beyond disc; dorsal fold variably developed, typically low or reduced to form a ridge; ventral fold low with a short to long base; caudal sting close to tail base (distance from pectoral-fin insertion to caudal-sting base 1.9–2.6 times interspiracular width); median thorns on disc in a row, often poorly defined or absent; denticle band poorly defined, small, diffuse or absent; skin smooth or with a patchy coverage of denticles; scapular thorns small or absent; tail sometimes with large median thorns, otherwise smooth or partly covered with fine denticles; dorsal coloration plain; ventral surface white, disc margin sometimes yellow or orange; tail plain, usually black distally; estuarine/marine, Western Pacific.

Species. H. akajei (Müller & Henle, 1841) , H. bennetti (Müller & Henle, 1841) , H. fluviorum (Ogilby, 1908) , H. izuensis (Nishida & Nakaya, 1988) , H. laevigata (Chu, 1960) , H. laosensis (Roberts & Karnasuta, 1987) , H. longicauda (Last & White, 2013) , H. navarrae (Steindachner, 1892) , H. parvonigra ( Last & White, 2008) , and H. sinensis (Steindachner, 1892) .

Remarks. Resurrected genus and formerly a junior synonym of Dasyatis ( Kottelat, 2013) , it consists of 10 morphologically similar species formerly placed in Dasyatis . The group is under review (PL); some of the nominal species listed above may be synonyms but other un-named species appear to exist.