A Megaraptor-like theropod (Dinosauria: Tetanurae) in Australia: support for faunal exchange across eastern and western Gondwana in the Mid-Cretaceous.
The fossil record of Australian dinosaurs in general, and theropods in particular, is extremely sparse. Here we describe an ulna from the Early Cretaceous Eumeralla Formation of Australia that shares unique autapomorphies with the South American theropod Megaraptor. We also present evidence for the spinosauroid affinities of Megaraptor. This ulna represents the first Australian non-avian theropod with unquestionable affinities to taxa from other Gondwanan landmasses, suggesting faunal interchange between eastern and western Gondwana during the Mid-Cretaceous. This evidence counters claims of Laurasian affinities for Early Cretaceous Australian dinosaur faunas, and for the existence of a geographical or climatic barrier isolating Australia from the other Gondwanan continents during this time. The temporal and geographical distribution of Megaraptor and the Eumeralla ulna is also inconsistent with traditional palaeogeographic models for the fragmentation of Gondwana, but compatible with several alternative models positing connections between South America and Antarctica in the Mid-Cretaceous.
Department of Geology, The Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, IL 60605, USA. smithnd@uchicago.edu
Nathan D
ND
Smith
Peter J
PJ
Makovicky
Federico L
FL
Agnolin
Martín D
MD
Ezcurra
Diego F
DF
Pais
Steven W
SW
Salisbury
D025041:Animal Migration; D000818:Animals; D001315:Australia; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification*; D005580:Fossils; D005843:Geography; D010802:Phylogeny; D011157:Population Dynamics; D014457:Ulna / Q000033:anatomy & histology