Cteniogenys antiquus (Gilmore 1928) Late Jurassic, ~150mya, ~50 cm in length phylogenetically and chronologically preceded Champsosaurus, but was phylogenetically closer to Lazarussuchus, which represented a more terrestrial line of choristoderes with origins close to Youngoides romeri (UC1528).

Distinct from Youngoides romeri, the skull of Cteniogenys was narrower and had a shallower rostrum and a cranium that leaned posteriorly. The nares were dorsally oriented, but remained at the tip of the snout. The rostrum was lower than half the height of the orbit. The maxilla extended to the dorsal rim of the rostrum in lateral view. The upper temporal fenestra was elongated. The shorter teeth were set more closely to one another. The transverse processes of the pterygoid were greatly reduced.

The post-crania is poorly known.

Cteniogenys provides clues as to how the bizarre skull of Champsosaurus had its genesis, but also retains many of the same morphologies seen in predecessor taxa, Youngoides and Youngina.

Coeruleodraco jurassicus (Matumoto, Dong, Wang and Evans 2018; Late Jurassic) nests between Cteniogenys and Philydrosaurus in the LRT.

Philydrosaurus proseilus (Gao and Fox 2005, Early Cretaceous, scale bar = 2 cm) is another basal choristodere with distinct ridges on the skull over the orbits. The lateral temporal fenestra is reported as closed, but the low-resolution image provided appears to show lateral temporal fenestra. It was scored without them. The cervicals do not decrease toward the skull. The right skull (above) does not seem to accurately reflect the fossil. Higher resolution images have been requested. Several juveniles were found associated with the presumed mother.

Gao K-Q and Fox RC 2005. A new choristodere (Reptilia: Diapsida) from the Lower Cretaceous of western Liaoning Province, China, and phylogenetic relationships of Monjurosuchidae. Zoological Journal of the Linnean Society 145 (3): 427–444.

Gilmore CW 1928. Fossil lizards of North America. Memoirs of the National Academy of Sciences 22(3):1-201.

Foster JR and Trujillo KC 2000. New occurrences of Cteniogenys (Reptilia, Choristodera) in the Late Jurassic of Wyoming and South Dakota. Brigham Young University Geology Studies 45:11-18.

Matsumoto R, Dong L, Wang Y and Evans SE 2019. The first record of a nearly complete choristodere (Reptilia: Diapsida) from the Upper Jurassic of Hebei Province, People’s Republic of China, Journal of Systematic Palaeontology
DOI:10.1080/14772019.2018.1494220

wiki/Cteniogenys
wiki/Philydrosaurus
wiki/Coeruleodraco