Youngina? BPI 2871 (Gow 1975) Late Triassic, ~210 mya, is one of many Youngina specimens basal to larger clades. This one is derived from Proterosuchus and basal to Champsosaurus and Cteniogenys. It was thus the earliest known choristodere.

The rostrum was low and long. The maxilla was ventrally convex with small sharp teeth. There is no trace of an antorbital fenestra. This specimen did not live at the same time as the other Youngina specimens of the Late Permian.

Elachistosuchus huenei MB.R. 4520 (Museum für Naturkunde Berlin, Berlin, Germany; Gow 1975, Janensch 1949, Sobral et al 2015) Late Triassic, Norian ~210 mya) was considered a pseudosuchian archosaur, a rhychocephalian lepidosaur, a sister to the gliding lepidosaurifomr, Coelurosauravus and a sister to the Choristodera. Only the last is correct as this taxon is also a sister to BPI 2871. Elachistosuchus has a larger orbit and straight maxilla ventral margin among only a few other distinct traits.

Tchoiria klauseni (IGM 1/8) (Ksepka, Gao and Norell 2005) nests at the base of the large, long snouted Choristodera. It demonstrates the reduction of the postorbital and enlargement of the postfrontal to contact with the squamosal along with the separation of the nasal (pink) and prefrontal (brownl. The ascending process of the premaxilla (yellow) is mislabeled as a nasal (above).

Gow CE 1975. The morphology and relationships of Youngina capensis Broom and Prolacerta broomi Parrington. Palaeontologia Africana, 18:89-131.

Janensch W 1949. Ein neues Reptil aus dem Keuper von Halberstadt. N Jb Mineral Geol Palaeont B. 1949:225–242.

Ksepka DT, Gao K-Q and Norell MA 2005. A New Choristodere from the Cretaceous of Mongolia. American Museum of Novitates 3468, 22 pp.

Sobral G, Sues H-D & Müller J 2015. Anatomy of the Enigmatic Reptile Elachistosuchus huenei Janensch, 1949 (Reptilia: Diapsida) from the Upper Triassic of Germany and Its Relevance for the Origin of Sauria. PLoS ONE 10(9): e0135114. doi:10.1371/journal.pone.0135114

wiki/Youngina
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