Information from FAO Species Identification Guide Western Central Atlantic
Smooth butterfly ray - Gymnura micrura
Diagnostic characters: Medium to large-sized stingrays (maximum disc width over 2 m). Body strongly depressed, with head, trunk, and broadly expanded pectoral fins forming rhomboid disc. Disc at least 1.5 times broad as long. Tail very slender and short (shorter than disc), distinctly demarcated from disc. Pectoral fins continuous along sides of head, not forming subrostral lobes or cephalic fins. Eyes and spiracles on top of head. Some species have spiracular tentacles. Snout obtuse and angular. Nasal curtains are broadly expanded and continuous across narrow isthmus in front of mouth and are smooth-edged (with rare exceptions). Mouth is slightly arched and lacks papillae on floor. Jaws bear many small teeth in bands. Caudal fin always absent, dorsal fin absent in all Western Central Atlantic representatives. Pectoral fins extend distinctly posterior to origin of pelvic fins. Pelvic fins are moderately laterally expanded and not divided into anterior and posterior lobes. Some species have 1 or more long, serrated spines. Tail with longitudinal folds on upper and/or lower surfaces. Skin of upper side naked in most species, but with a variable number of tubercles in large individuals of others. Colour: Dorsal surface grey, brown, light green, or purplish, with vermiculate patterns of lighter and darker shades, and cross-bands on tail; ventral surface whitish, with grey disc outline.
Size: Maximum size 90 to 120 cm disc width; males mature at 42 cm disc width, females mature at 50 cm disc width, and neonates 16 to 22 cm at birth.
Habitat, biology, and fisheries: Benthic along the coast over sandy bottoms, but also occurs in estuaries. Food consists of bivalve molluscs, crustaceans including mysids, shrimps, crabs, and ray-finned fishes.
Distribution: Recorded from Chesapeake Bay to Brazil, and common in Gulf of Mexico, but unrecorded from the greater and Lesser Antilles. Records of Gymnuramicrura from the eastern Atlantic, and Indian and Pacific Oceans probably refer to other species.