title: The evolution of mammal-like crocodyliforms in the Cretaceous Period of Gondwana.
abstract: Fossil crocodyliforms discovered in recent years have revealed a level of morphological and ecological diversity not exhibited by extant members of the group. This diversity is particularly notable among taxa of the Cretaceous Period (144-65 million years ago) recovered from former Gondwanan landmasses. Here we report the discovery of a new species of Cretaceous notosuchian crocodyliform from the Rukwa Rift Basin of southwestern Tanzania. This small-bodied form deviates significantly from more typical crocodyliform craniodental morphologies, having a short, broad skull, robust lower jaw, and a dentition with relatively few teeth that nonetheless show marked heterodonty. The presence of morphologically complex, complementary upper and lower molariform teeth suggests a degree of crown-crown contact during jaw adduction that is unmatched among known crocodyliforms, paralleling the level of occlusal complexity seen in mammals and their extinct relatives. The presence of another small-bodied mammal-like crocodyliform in the Cretaceous of Gondwana indicates that notosuchians probably filled niches and inhabited ecomorphospace that were otherwise occupied by mammals on northern continents.
authors.affiliation: Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, 228 Irvine Hall, Athens, Ohio 45701, USA. oconnorp@ohio.edu
authors.forename: Patrick M
authors.initials: PM
authors.lastname: O'Connor
authors.forename: Joseph J W
authors.initials: JJ
authors.lastname: Sertich
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Stevens
authors.forename: Eric M
authors.initials: EM
authors.lastname: Roberts
authors.forename: Michael D
authors.initials: MD
authors.lastname: Gottfried
authors.forename: Tobin L
authors.initials: TL
authors.lastname: Hieronymus
authors.forename: Zubair A
authors.initials: ZA
authors.lastname: Jinnah
authors.forename: Ryan
authors.initials: R
authors.lastname: Ridgely
authors.forename: Sifa E
authors.initials: SE
authors.lastname: Ngasala
authors.forename: Jesuit
authors.initials: J
authors.lastname: Temba
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003817:Dentition; D005580:Fossils; D049690:History, Ancient; D008322:Mammals / Q000033:anatomy & histology* / Q000145:classification* / Q000502:physiology; D010802:Phylogeny; D013636:Tanzania; D014057:Tomography, X-Ray Computed