Testudinata

Testudinata is the group of all tetrapods with a true turtle shell. It includes both modern turtles (Testudines) and many of their extinct, shelled relatives (stem-turtles), though excluding Odontochelys and Eorhynchochelys, which are placed in the more inclusive Pantestudines.

Testudinata Temporal range: Late Triassic – Holocene, 210–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N Possible Early and Middle Triassic records in the form of fossil tracks[1]
Skeleton of Proganochelys quenstedti, American Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Pantestudines
Clade:	Testudinata Klein, 1760[2]
Subgroups[3]
†Chinlechelys †Proterochersis? †Proganochelys Rhaptochelydia Gaffney & Kitching, 1994[4] †Proterochersis? †Australochelyidae †Australochelys †Palaeochersis †Waluchelys Mesochelydia

History

It was first coined as the group containing turtles by Jacob Theodor Klein in 1760. In 1832-1836, Thomas Bell wrote a book describing the Testudinata, which summarizes all the world's turtles, living and extinct, illustrated by forty plates by Jane S. Bell, James de Carle Sowerby and Edward Lear.^[5] It was first defined in the modern sense by Joyce and colleagues in 2004.^[2][6] While the ancestral condition for the clade is thought to be terrestrial, members of the subclade Mesochelydia, which contains almost all known testudinatans from the Jurassic onwards, are thought to be ancestrally aquatic.^[7]

Classification

The cladogram below follows an analysis by Jérémy Anquetin in 2012.^[6]

	†Odontochelys  Testudinata  †Proterochersis †Proganochelys †Palaeochersis †Australochelys †Kayentachelys †Indochelys †Sichuanchelys †Chengyuchelys †Chuannanchelys †Eileanchelys †Heckerochelys †Condorchelys †Naomichelys †Otwayemys †Mongolochelys  †Meiolaniidae  †Niolamia †Ninjemys †Meiolania †Kallokibotion Testudines (modern turtles)

References

1. Asher J. Lichtig; Spencer G. Lucas; Hendrik Klein & David M. Lovelace (2018). "Triassic turtle tracks and the origin of turtles". Historical Biology: An International Journal of Paleobiology. 30 (8): 1112–1122. doi:10.1080/08912963.2017.1339037. S2CID 133893011.
2. Joyce, Walter G.; Parham, James F. & Gauthier, Jacques Armand (2004). "Developing a protocol for the conversion of rank-based taxon names to phylogenetically defined clade names, as exemplified by turtles" (PDF). Journal of Paleontology. 78 (5): 989–1013. doi:10.1666/0022-3360(2004)078<0989:DAPFTC>2.0.CO;2. S2CID 15078337.
3. Sterli, Juliana; Martínez, Ricardo N.; Cerda, Ignacio A. & Apaldetti, Cecilia (6 August 2020). "Appearances can be deceptive: bizarre shell microanatomy and histology in a new Triassic turtle (Testudinata) from Argentina at the dawn of turtles". Papers in Palaeontology. 7 (2): 1097–1132. doi:10.1002/spp2.1334. S2CID 225515560.
4. Gaffney, Eugene S. & Kitching, James William (1995). "The morphology and relationships of Australochelys, an early Jurassic turtle from South Africa". American Museum Novitates (3130): 1–29. hdl:2246/3666.
5. Bell, Thomas (1832–1836). A Monograph of the Testudinata.
6. Anquetin, J. R. M. (2012). "Reassessment of the phylogenetic interrelationships of basal turtles (Testudinata)". Journal of Systematic Palaeontology. 10: 3–45. doi:10.1080/14772019.2011.558928. S2CID 85295987.
7. Sterli, Juliana; de la Fuente, Marcelo S.; Rougier, Guillermo W. (2018-07-04). "New remains of Condorchelys antiqua (Testudinata) from the Early-Middle Jurassic of Patagonia: anatomy, phylogeny, and paedomorphosis in the early evolution of turtles". Journal of Vertebrate Paleontology. 38 (4): (1)–(17). doi:10.1080/02724634.2018.1480112. hdl:11336/99525. ISSN 0272-4634. S2CID 109556104.