[Gutenberg 31621] • Description of a New Softshell Turtle from the Southeastern United States

Trionyx muticus calvatusnew subspecies Gulf Coast Smooth Softshell Diagnosis and definition.—A subspecies of softshell turtle most closely allied to Trionyx muticus muticus but differing from that subspecies in having: (1) a juvenal pattern of large, circular spots, (2) no stripes on dorsal surface of snout, and (3) postocular stripe with thick, black borders immediately behind eye in adult males. T. m. calvatus resembles T. m. muticus, and differs from the several subspecies of Trionyx spinifer in having: (1) no enlarged tubercles on anterior edge of carapace, (2) no ridge projecting from nasal septum, and (3) a smooth dorsal surface on carapace in adult males. T. m. calvatus and T. m. muticus resemble T. ferox in having a smooth dorsal surface on carapace in adult males, but differ from T. ferox in having: (1) no tubercles along anterior edge of carapace, and (2) no ridge projecting from nasal septum. Description of holotype.—Carapace circular, widest at region of bridge; margin entire; dorsal surface smooth; anterior margin of carapace lacking tubercles; blunt vertebral ridge evident anteriorly; maximum length, 53.1 mm; greatest width, 46.3 mm; greatest depth, 11.5 mm. Plastron small, extending slightly farther forward than carapace; anterior lobe truncate with slight midventral indentation; posterior lobe rounded, sides forming acute angle; certain features of bony elements of plastron visible through overlying skin; width of bony bridge, 4.5 mm; maximum length of plastron, 37.5 mm. Head extended to level of eyes; head terminating in long, rounded, flexible snout; nostrils rounded with no ridges projecting from nasal septum; jaws closed, each covered by fleshy lips except anteriorly where horny portions of jaws are exposed; iris with dark stripe through pupil