Carettochelys insculpta (Ramsay 1886; 70 cm) is the extant pig-nosed turtle. Unlike any other species of freshwater turtle, the feet are flippers, like the related marine sea turtle Dermochelys. The carapace is not scaly, but leathery, but it remains domed and the solid plastron is strongly connected to the carapace.

Brinkman, Rabi and Zhao 2017 nested Carettochelys basal to soft shell turtles, but the large reptile tree nests it with the leatherback turtle, Dermochelys.

Like the soft-shell turtle, Trionyx, the soft nose tissue extends slighly from the skull by convergence.

Dermochelys coriacea (Vandelli 1761, originally Testudo; Blainville 1816) is the extant leatherback turtle, which nests with Carettochelys. It lacks a bony shell, replaced by thick, oily, leathery skin. The mouth and esophagus are filled with backward pointing spikes arising from toothess jaws. Here a juvenile skull demonstrates the elevation and lengthening of the postorbital region in the adult.

Brinkman D, Rabi M and Zhao L-J 2017. Lower Cretaceous fossils from China shed light on the ancestral body plan of crown soft-shell turtles (Trionychidae, Cryptodira). Nature Scientific Reports 7(6719).

Gaffney ES 1979. Comparative cranial morphology of recent and fossil turtles. Bulletin of the American Museum of Natural History 164(2):65-376.

Ramsay EP 1886. On a new genus and species of fresh water tortoise from the Fly River, New Guinea. Proceedings of the Linnaean Society of New South Wales (2) 1: 158-162.

wiki/Carettochelys
wiki/Dermochelys