-
snout length ~1/3 disc widthdisc top ~no denticlestail: > disc, no row thornsUrotrygon microphthalmum, Smalleye Round Ray, Smalleye Round Stingray
-
snout length ~1/4 disc widthdisc top covered with denticlestail: > disc, 1 row thornsUrotrygon venezuelae, Venezuelan Round Ray, Venezuelan Round Stingray