Perichelydia
Perichelydia is a clade of stem-turtles known from the Middle Jurassic to Holocene. Alongside crown group Testudines, It also contains the Helochelydridae, which is known from the Cretaceous of Europe and North America, Sichuanchelyidae from the Middle Jurassic to Paleocene of Asia and Europe. Meiolaniformes, which is known from the Cretaceous to Holocene of South America Australia and Oceania, and Spoochelys, known from the Mid-Cretaceous Griman Creek Formation of Australia. While not included in the original definition Kallokibotion, from the Late Cretaceous of Europe is also considered part of this group. The clade was first named by Joyce in 2017, they are distinguished from the clade Mesochelydia by two characters, the presence of processus trochlearis oticum, and a closed interpterygoid vacuity
