"Cartorhynchus" had poorly-ossified limbs in spite of its well-ossified skull and vertebrae.However, Motani and colleagues suggested in 2014 that it was still an adult because many early-diverging members of marine reptile lineages have poorly-ossified limbs through paedomorphosis (the retention of immature traits into adulthood), although they did not completely reject the possibility that it was a juvenile due to the existence of only one specimen.