【古生物学】オーストラリアに到達していたティタノサウルス

A newly identified genus and species of Australian sauropod - a large herbivorous dinosaur with a long neck and tail - and the first cranial remains of an Australian sauropod are described in a paper in Scientific Reports this week. The two specimens from the Late Cretaceous period (approximately 95 million years ago) may help to shed light on how these dinosaurs arrived in Australia.

Stephen Poropat and colleagues describe two specimens of sauropod, including a new species - Savannasaurus elliottorum - found in the Winton Formation of Queensland, northeast Australia. The authors conclude that both sauropods were members of a group of dinosaurs called titanosaurs on the basis of their anatomy and a phylogenetic analysis of their evolutionary relationships.

The authors’ analysis of the prehistoric distribution of this group of dinosaurs suggests that Australian sauropods represent remnants of clades which were found around the world during the Early Cretaceous (around 125 million years ago). They propose that these lineages would have originated in South America and entered Australasia by crossing Antarctica. However, floral evidence suggests that a climatic barrier existed between Antarctica and South America between 120 million and 110 million years ago. The authors hypothesize that the appearance of titanosaurs in Australia around 105 million years ago may have been facilitated by a period of warming that removed the barrier between Antarctica and South America.