Gymnuridae
by J. D. McEachran and C. Capape
Medium to large rays (disc width to 4 m), the disc lozenge-shaped and broader than long; snout obtuse and little produced, head not elevated from disc; tail distinct from disc, very slender but much shorter than disc length, one or several serrated spines at base of tail in some species, as also keel along top of tail, but no membranous folds. Nostrils separated from mouth, but their front margins greatly expanded backward to meet across a narrow isthmus; mouth almost straight to arched, without papillae on floor. Spiracles well developed, with or without a tentacle-like process pointing back from inner margin. Pectoral fins attached to side of head, the finrays beginning at tip of snout; dorsal fin present or absent; caudal fin absent. Upper surfaces naked or with scattered thornlets.
Benthic on soft bottoms, generally in shallow tropical or warm temperate waters to 70 m, usually marine but some species entering estuaries; common in tropical inshore waters. Rather inactive, Iying partially covered with bottom substrate or swimming slowly over the bottom by undulating the margins of the pectoral fins. Feeding on fishes, crustaceans and molluscs. Ovoviviparous, the females containing 2-6 embryos.
Genera 1 (some authors recognize 2).
Recent revisions: on a regional basis only, e.g. Fowler (1941) and Bigelow and Schroeder (1953).