The evolution of mammal-like crocodyliforms in the Cretaceous Period of Gondwana.
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.
O'Connor
Patrick M
PM
Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, 228 Irvine Hall, Athens, Ohio 45701, USA. oconnorp@ohio.edu
Sertich
Joseph J W
JJ
Stevens
Nancy J
NJ
Roberts
Eric M
EM
Gottfried
Michael D
MD
Hieronymus
Tobin L
TL
Jinnah
Zubair A
ZA
Ridgely
Ryan
R
Ngasala
Sifa E
SE
Temba
Jesuit
J
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