Spiny Stingray, Urotrygon munda
The Spiny Stingray, Urotrygon munda, whose common Spanish name is raya redonda aspera, is a species in the family Urotrygonidae, the American Round Stingrays, known as raya redondas Americanas in Mexico. Globally, there are thirteen species in the genus Urotrygon, of which five are found in Mexican waters, all in the Pacific.
These fish have rounded flat bodies with discs that are about equal in length and depth. They are a uniform light brown to yellowish brown color with tails having lighter edges. Their undersides are off white. Their discs have front margins that are straight to slightly convex. Their heads have a short weakly pointed snout. Their small eyes and spiracles are on top of their heads and their mouths, nostrils, and gill slits are on their ventral sides. Their slender tails are longer than the disc length and have an elongated oval caudal fin. They feature one or two rows of eighteen to thirty-two recurred spines along the mid-back that extend from mid-disc to the tail spine. They have one large venomous spine mid-tail. Their discs and tails are densely covered with relatively large, strong, and recurved denticles with star-like bases.
The Spiny Stingrays reside over and within coastal sandy and muddy bottoms at depths up to 260 feet. They are most abundant at depths less than 50 feet and move to greater depths during cold-water episodes. They are found in all Mexican waters of the Pacific but are absent from north of Magdalena Bay along the west coast of Baja.
The Spiny Stingrays have a maximum length of 40 cm (16 inches) with maximum disc widths of 24 cm (9.4 inches). They seek food by stirring the bottom sediment with their pectoral fins to dislodge small crustaceans, small fish, mussels, and worms on which they feed. Their pups are born alive and are miniature adults that are independent at birth. They are a rare and poorly studied species and as such very limited information is available about their behavioral patterns.
Due to the abundant presence of the large recurved spines and denticles on their disc and tail, the Spiny Stingray cannot be confused with any other species.