Cteniogenys is a genus of choristodere, a morphologically diverse group of aquatic reptiles. It had a wide distribution temporally and geographically, from the Middle Jurassic and Late Jurassic of western Europe, to the Late Jurassic-age Morrison Formation of western North America, to the Late Cretaceous of Alberta, Canada. The genus was named in 1928 by Charles W. Gilmore, from a lower jaw collected during the late 1800s by Othniel Charles Marsh's workers at Como Bluff. He tentatively described the genus as a lizard, noting that it could instead be a frog. New material from Europe permitted Susan Evans to reevalute it as an early choristodere in 1989. To date it is only known from fragmentary specimens. Morrison Formation Cteniogenys were 25 to 50 centimeters (9.8 to 20 in) long, and prob