Colossoemys is the nomen dubium of an extinct genus of alligatoroid crocodilian. Based on fossils found in the Solimões Formation, the finds were assigned to Emys macrococcygeanus, a turtle that would have inhabited the Amazon Basin of South America during the Pleistocene epoch.[1] The genus was originally named on the basis of two large procoelous vertebrae, a pubis, and a plastral fragment (likely to be from a turtle rather than a crocodilian).[2] The paucity of material associated with the genus has led Colossoemys to be considered a nomen dubium.[1]