During the Cretaceous period, as the supercontinent Gondwana was slowly drifting apart, an 1,800-mile rift valley stood between Australia and Antarctica. The now-vanished region, a rich forested floodplain, teemed with life—and an important fossil discovery is helping scientists learn more about a previously unknown dinosaur that once roamed through the area.
As Yasemin Saplakoglu reports for Live Science, researchers have analyzed five fossilized upper jaw bones found in Australia’s Gippsland Basin, along the coast of Victoria. The 125 million-year-old bones belong to a new species of ornithopod, a family of herbivorous dinosaurs characterized by their bird-like bipedal stance. The size of the jaw bones indicate that this new species was relatively small—“wallaby-sized,” as the researchers put it.
Writing in the Journal of Paleontology, the team dubs the dinosaur Galleonosaurus dorisae—a name inspired by the shape of the creature’s jaw, which resembles a galleon ship, and paleontologist Doris Seegets-Villiers, who wrote her Ph.D. thesis on the area where the fossils were found. Importantly, the fossil group included specimens from individuals ranging in age from young to mature, marking “the first time an age range has been identified from the jaws of an Australian dinosaur,” says Matthew Herne, lead study author and postdoctoral fellow at the University of New England.
Using 3D micro-CT scans, the researchers were able to take a close at the five jawbones and a tooth, according to Genelle Weule of Australia’s ABC News. They observed marked distinctions between Galleonosaurus dorisae and Qantassaurus intrepidus, the only other known ornithopod from the Gippsland region; Qantassaurus had a shorter and more robust snout than its cousin, leading the team to conclude that they likely fed on different plant types, which allowed them to co-exist.
Galleonosaurus was also found to be a close relative of Diluvicursor pickeringi, another small ornithopod that was also named by Herne and his colleagues, and found to the west of Gippsland. But Galleonosaurus is around 12 million years older than Diluvicursor, suggesting “that the evolutionary history of dinosaurs in the Australian-Antarctic rift had been lengthy,” Herne says.
The discovery of the Galleonosaurus fossils is indeed exciting to researchers because it offers a glimpse into life in the rift valley—“a lost world,” as Herne tells Weule. Millions of years ago, part of the rift was located within the Arctic Circle, but the climate was relatively warm, allowing plants and animals to thrive there.
“[S]mall dinosaurs, turtles, small mammals, small birds, flying reptiles, lungfish and aquatic reptiles, called plesiosaurs, all flourished in the rift environment,” Herne explains to Newsweek’s Hannah Osborne. “The canopy trees would have been families that are still present in Australia and South America—conifers related to Bunya pines, Monkey Puzzles and Huon pines. Early flowering plants [were also present], as well as many kinds of ferns and horsetails.”
Ultimately, the rift was split by the Southern Ocean. But traces of some of the species that once lived there have been preserved, thanks to miles of once-active volcanoes along the rift. “Sediments from these volcanoes were carried down huge rivers, where dinosaur bones and fallen foliage were mixed in—creating sedimentary basins that show life on Earth at the time,” Osborne writes.
By looking at fossils from these basins, experts can also get a better sense of how prehistoric creatures were moving across the globe. The new study, for instance, revealed that Galleonosaurus was closely related to ornithopods from Patagonia in South America, which suggests that a land bridge must have at one time connected South America and Australia, via Antarctica, Herne tells Live Science’s Saplakoglu. With new technologies, he adds, scientists are able to shine unprecedented light on “the mysterious world of dinosaur ecology—what they ate, how they moved and how they coexisted—and their evolutionary relationships with dinosaurs from other continents."