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.