Talk about a giant find. Paleontologists have dug up the fossil remains of two enormous long-necked dinosaurs in Queensland, Australia. One of them, Savannasaurus elliottorum, represents a species that's new to science; the other specimen, Diamantinasaurus matildae, features the first skull fragments found for any Australian sauropod.
The roughly 95-million-year-old fossils, described in the journal Scientific Reports, offer clues about how these sauropod dinosaurs first arrived Down Under.
"A new dinosaur like Wade, or Savannasaurus, will allow us to work out how these dinosaurs evolved through time, how they responded to climatic changes, and also how they responded to changes in the positions of the continents as well," lead author Stephen Poropat, a vertebrate paleontologist at the Australian Age of Dinosaurs Museum in Winton, Queensland, said in a video interview.
This specimen of Savannasaurus elliottorum (nicknamed "Wade" for Australian paleontologist Mary Wade) was discovered in 2005 by study coauthor David Elliott, who co-founded the dinosaur museum.
Elliott had been herding sheep in western Queensland when he came across a pile of fossilized bone fragments. At the time, he'd hoped that he'd discovered some kind of theropod (a group whose members include the velociraptor and Tyrannosaurus rex) but he soon realized it was a much bigger find.
"It turned out to be just as good, because it is a totally new species of sauropod — and it's quite unlike most of the other ones around the world too," Elliott said in a video interview. "It's very, very different."
Titanosaurs are the heavyweights of the long-necked sauropods; Savannasaurus elliottorum, for example, stretched to half the length of a basketball court, with a long neck and comparatively short tail. Even though it was just a medium-sized titanosaur, it was also "the most rotund sauropod we have found so far," Poropat said in a statement.
Scientists think that the two enormous species actually managed to somehow share resources — perhaps eating different plants, or at different times of the day. But they aren't clear on how the animals got to Australia in the first place.
They may have been able to cross from South America to Australia through Antarctica (all of which were connected at the time), but the plant record shows that there was what the study called a "sharp climatic barrier" that probably kept them out until about 105 million years ago. While much of the Earth was quite warm at that time, there were still relative cold spots that would have kept the sauropods from venturing into Antarctica.
But the dinosaurs clearly made it — and the researchers think it's because an episode of global warming eventually helped thaw out those cold spots, which "would have enabled sauropods to disperse from South America, across Antarctica, to Australia via a set of suitable habitats," they wrote.
The mystery of the titanosaurs has yet to be solved, however; Wade is just the fifth type of sauropod that's ever been discovered in Australia, Poropat pointed out. Scientists say they'll need much more fossil evidence before they can properly fill in the blanks in their history and migration patterns.
"Given the very patchy nature of the Early Cretaceous fossil record, especially in East Gondwana," the study authors wrote, "considerable further work is required before the complex biogeographic history of the Australian Cretaceous terrestrial vertebrate fauna can be unraveled."
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