Paleontologists have discovered a new species of dinosaur in Australia. The wide-hipped, long-necked, four-legged plant-eater was about half the length of a basketball court, and its shoulders stood as high as the hoop. Dinosaur fossils in Australia are exceedingly rare, and this discovery could help scientists understand how these massive creatures spread across the planet millions of years ago.

"There are entire lost worlds of dinosaurs waiting to be found."

David Elliott, now the chairman of the Australian Age of Dinosaurs Museum, stumbled across the fossils by chance in 2005. He was herding sheep in the northern Australian town of Winton when he discovered what he thought were fossilized limb bones. When his wife Judy Elliott fit two of the fossils together, they realized that the bones were in fact the toe of a massive, plant-eating dinosaur. The rest of the skeleton revealed that it was an entirely new species from the group of vegetarian dinosaurs called sauropods.

Today, after more than 10 years of work, a team of scientists led by Australian paleontologist Stephen Poropat officially published their discovery in the journal Scientific Reports. They named the species Savannasaurus elliottorum after the the Elliott family and the grassy region where they discovered it. This is an important discovery, says Matthew Lamanna, a curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pennsylvania who was not involved in this study. "Dinosaurs from Australia are extraordinarily rare, and most Australian dinosaurs are represented by just a few bits and pieces," he says.

By contrast, the Savannasaurus skeleton is one of the most complete sauropods to be discovered in Australia. Based on its skeleton, it was probably about 50 feet long, with a long neck and a wide, round body — weighing in at 40,000 pounds, as much as three African elephants combined, Poropat says. The researchers haven’t found any fossilized dung or teeth to determine what Savannasaurus ate, but it likely grew to that size on a low-quality vegetarian diet. That might be why the dinosaur was so wide across the middle: it needed a really long gut to extract the nutrients from its fibrous food.

Savannasaurus lived in Australia 95 million to 98 million years ago alongside two other titanosaurs. That places it squarely in the late Cretaceous, the last portion of the age of dinosaurs that started about 225 million years ago and ended when an asteroid careened into the Earth some 66 million years ago, driving the massive animals extinct.

"We’ve really only scratched the surface as to what’s there."

We don’t know how these dinosaurs spread to Australia, but during this time period, Australia was connected to South America by Antarctica. Because there aren’t any sauropod bones on Australia that are more than 105 million years old, the authors of the study suspect that the dinosaurs may have traveled there from South America via Antarctica during a warming period.

It’s also possible that sauropods were there, but their bones didn’t survive long enough to be found.

"It’s been bandied about whether or not this is a bias in the fossil record," Poropat says. "But given the thousands of fossils that have come out of these sediments, to not even have a single tooth of a sauropod, or a limb bone, or anything like that seems quite strange."

In the same paper, Poropat and his colleagues also published their discovery of a skull belonging to another Australian titanosaur, Diamantinasaurus matildae. This species was discovered in 2009, but finding the first Diamantinasaurus skull is an especially big deal because it meant the scientists could use it to place Diamantinasaurus more accurately on the dinosaur family tree. Right now, Poropat and his colleagues suspect that Savannasaurus and Diamantinasaurus were probably most closely related to each other than any other species. While the researchers convinced that the two are distinct species enough to name Savannasaurus, the paleontologists will need to find more specimens to be sure.

"Anytime you put a name on a dinosaur it’s a hypothesis — and it’s one that’s going to be tested and tested in the future, and we are hoping of course that Savannasaurus will stand the test of time," Poropat says.

"One of the most exciting things about this discovery — and others that have come from Australia in recent years — is we’ve really only scratched the surface as to what’s there," Lamanna says. "There are entire lost worlds of dinosaurs waiting to be found in Australia."