The newly-discovered footprints of theropod and ornithopod dinosaurs date back to the Early Cretaceous epoch, over 120 million years ago, when Australia was still connected to Antarctica.
Melissa Lowery and Anthony Martin examine a dinosaur track. Image credit: Ruth Schowalter.
The Early Cretaceous dinosaur footprints were discovered in the Wonthaggi Formation south of Melbourne, Australia.
They include 18 tracks made by medium to large theropods (0.8-1.9 m hip heights) and four tracks made by small ornithopod dinosaurs (40-48 cm hip heights).
“These numerous tracks are the best evidence yet that these former polar environments supported large carnivores,” said Emory University’s Professor Anthony Martin.
“The large theropods would likely have fed on prey such as smaller dinosaurs, fish and turtles.”
“The hip height of that theropod would have been about the same as the full height of a tall, modern-day human.”
“The Australian state of Victoria’s rocky coastal strata mark where the ancient supercontinent Gondwana began to break up around 100 million years ago, separating Australia from Antarctica.”
“The polar environment at that time was a rift valley with braided rivers.”
“Although the mean annual air temperature was higher during the Cretaceous than today, during the polar winters the ecosystems experienced deep freezing temperatures and months of darkness.”
“The Wonthaggi Formation has yielded one of the best assemblages of polar dinosaur body fossils in the southern hemisphere, but most of these remains are small fragments of bones and teeth.”
“These fragments may have been carried to the site where they were buried by torrential spring floods.”
“Our find of so many theropod tracks, however, confirms that a variety of dinosaurs actually lived and walked on the ground where their bones were found.”
“Dinosaur tracks are actually much more common at the site than we previously realized.”
The theropod footprints in the Wonthaggi Formation range in length from 18 to 47 cm (7-18.5 inches).
They are distinguished by relatively thin toes tipped with sharp claws.
The ornithopod footprints range in size from 10 to 18 cm (4-7 inches).
The range in sizes of the tracks suggests a mix of juvenile and adult ornithopods and theropods.
“That indicates that these dinosaurs may have nested and raised their young in the polar environment,” Professor Martin said.
The discovery is reported in a paper in the Alcheringa, an Australasian Journal of Palaeontology.
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Anthony J. Martin et al. Polar dinosaur tracks of the Wonthaggi Formation (Lower Cretaceous), Victoria, Australia and their palaeontological significance. Alcheringa, an Australasian Journal of Palaeontology, published online September 8, 2024; doi: 10.1080/03115518.2024.2392498
Source : Breaking Science News