Information from FAO Species Identification Guide Western Central Atlantic
Spiny butterfly ray - Gymnura altavela
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, light green, olive, purple, or dark brown, sometimes with a reddish cast, often marked with spots or lines; ventral surface white, sometimes with a bronze or rusty cast.
Size: Maximum size 208 cm disc width; males mature at about 101 cm disc width; neonates 38 cm to 44 cm disc
width at birth.
Habitat, biology, and fisheries: Butterfly rays are cosmopolitan in tropical and warm-temperate waters, usually inhabiting sandy and muddy bottoms in shallow coastal waters, including estuaries and river mouths. Benthic in shallow water to 55 m. Because they have very short tails compared to whiptailed stingrays (Dasyatidae), they pose little threat to people (some species even lack a caudal serrated spine). They are viviparous without placenta and feed primarily on crustaceans and clams. Species are often caught in bottom gill nets. Large specimens are marketed fresh and salted. Dorsal surface dark brown to lighter brown, with small darker or lighter spots and blotches scattered on disc; ventrally creamy white.