Australia has a new sauropod dinosaur
Twenty-tonne Savannasaurus from western Queensland brings the number of named Australian sauropods to five.
PALAEONTOLOGISTS have described a new titanosaur sauropod, from a specimen first excavated in 2005. From the same region near Winton, they also report the first-known sauropod skull fragments from Australia, which they believe belonged to a known species, Diamantinasaurus.
The scientists, led by Dr Stephen Poropat of the Australian Age of Dinosaurs Museum (AAOD), studied the relationship of both Diamantinasaurus and new species Savannasaurus to similar dinosaurs from South America, and have made the first estimate of when titanosaurs migrated across the supercontinent of Gondwana to Australia.
David Elliott, grazier and AAOD founder, stumbled across the bones of Savannasaurus elliottorum while mustering sheep a decade ago. Later that year, a dig involving scientists from the Queensland Museum resulted in the collection of 17 pallets of bones that were encased in hard siltstone concretions.
Ten years of preparation and study finally revealed a new species, detailed in the journal Scientific Reports. The fossil – which includes parts of the backbone, legs, pelvis and tail – reveals a rotund, medium-sized sauropod that weighed 20 tonnes and was 12–15m long – half the length of a basketball court.
“Unfortunately, we do not have teeth or complete skulls for either Diamantinasaurus or Savannasaurus. However, because they were living in the same place at the same time, we suspect that they preferred different foods,” Stephen says. “The bigger belly of Savannasaurus might have... [allowed] it to process tougher or less nutritious vegetation.”
The scientists did discover a new fossil including the braincase (partial skull) of a Diamantinasaurus, which they believe was a close relative of the new species. Both lived on the Australian part of Gondwana 95 million years ago during the Late Cretaceous. Diamantinasaurus would have been more slender than Savannasaurus, but slightly larger, at an estimated 23t and 15–16m in length.
“This new Diamantinasaurus specimen has helped to fill several gaps in our knowledge,” Stephen says. “The braincase in particular has allowed us to refine Diamantinasaurus’s position on the sauropod family tree.”
Working alongside sauropod experts Dr Philip Mannion and Professor Paul Upchurch, Stephen was able to study how these Australian dinosaurs were related to sauropods from other parts of the world.The palaeontologists noted that they were similar to kinds of titanosaur common in South America 125 million years ago during the Early Cretaceous. They hypothesise that titanosaurs evolved in South America, but were unable to cross cold, high-latitude parts of the supercontinent until a warm spell. “We suspect that the ancestor of Savannasaurus was from South America, but that it could not and did not enter Australia until approximately 105 million years ago,” Paul says. “At this time, global average temperatures increased, allowing sauropods to traverse landmasses at polar latitudes.”
These more primitive sauropods then persisted in an isolated Australia while other kinds of titanosaur came to dominate South America.
Dr Phil Bell, at the University of New England in Armidale, says:“Every new specimen is potentially important. The description of these two specimens is exciting. Where Australia’s dinosaurs came from and when they arrived has long been a point of contention.”