Meeting Abstract
43.3 Wednesday, Jan. 5 Craniodental specialization in notosuchian Crocodyliformes: Linking morphology with ecology during the Cretaceous Period OCONNOR, P.M.*; SERTICH, J.J.W.; STEVENS, N.J.; Ohio Univ; Stony Brook Univ; Ohio Univ oconnorp@ohio.edu
Notosuchian crocodyliforms recovered from Cretaceous-age deposits have revealed a level of craniodental diversity not exhibited in extant Crocodylia. Tooth crowns ranging in shape from simple conical fangs to multicusped, complex molariforms are known within Notosuchia and have formed the basis for suggesting mammal-like feeding adaptations in these small-bodied, terrestrial crocodyliforms. Herein we report the discovery of a new species (Pakasuchus) of notosuchian that deviates significantly from more typical crocodyliform craniodental morphologies, exhibiting a short (~7 cm), broad skull, robust lower jaw, and extremely heterodont dentition. The presence of morphologically complex, complementary upper and lower molariform teeth indicates a degree of crown-crown contact during jaw adduction that is unmatched among crocodyliforms, illustrating a level of occlusal complexity convergent with that typified by mammals. Morphology of the elongate craniomandibular joint provides additional evidence for the specialized nature of jaw mobility in this form, with modeled movements limited to rotation and rostrocaudal translation of the lower jaw. Whereas proal kinematics have been hypothesized in other notosuchians, no other form exhibits this degree of corresponding molariform occlusal morphology. The organization of opposing molariform occlusal surfaces (e.g., canted occlusal surfaces) suggests that maximum crown-crown contact would have occurred during orthal and anterior (proal) displacement of the lower jaw during adduction. The presence of another small-bodied mammal-like crocodyliform in the Cretaceous of Gondwana is significant in that it suggests notosuchians likely filled niches and inhabited ecomorphospace otherwise occupied by mammals on Laurasian landmasses.
