Odontochelys semitestacea is the oldest known turtle to have been discovered. It is the only known species in the genus Odontochelys and the family Odontochelyidae. The species was first described from three 220 million year-old specimens excavated in Triassic deposits originating from Guizhou, China. It is likely that Odontochelys was aquatic, as the fossil specimens were found in marine deposits rife with conodonts and ammonites. It is theorized that the primitive turtle frequented shallow marine waters close to shore.