Odontochelys semitestacea (Li et al. 2008) Lower Carnian, Late Triassic ~225 mya, 40cm in length, was originally considered the most primitive and oldest turtle, surpassing the previous oldest turtle, Proganochelys. Here, Odontochelys was derived from a sister taxon to Sclerosaurus and was a sister to the soft shell turtle, Trionyx.
Living turtles and their kin have an anterior naris, a wider rounder gape, a shorter postorbital, a longer supratemporal a higher maxilla, medial internal nares, longer pedal phalanges and many other traits not found in Odontochelys.
Distinct from Milleretta (RC70), the skull of Odontochelys had a longer post orbital areas and a shorter rostrum. The nares were within a naris length of the orbit. In dorsal view the jawline was medially pinched. The pineal opening was absent. Teeth were retained. No other turtle has teeth.
The scapula was a narrow strut and leaned anteriorly. The limbs were longer, especially the forelimbs.
Distinct from Sclerosaurus, the cervicals of Odontochelys were longer and smaller. Only nine dorsal vertebrae were present as in the unrelated Eunotosaurus. The ribs were broad with intercostal plates. A plastron and hypoischium were present.