Lizard-Like Dinosaur Relative Once Roamed Warm, Green Antarctica

“The midnight sun over Early Triassic Antarctica.” Along the banks of a river, three archosaur inhabitants of the dense Voltzia conifer forest cross paths: Antarctanax shackletoni sneaks up on an early titanopetran insect, Prolacerta lazes on a log, and an enigmatic large archosaur pursues two unsuspecting dicynodonts, Lystrosaurus maccaigi. (Copyright Adrienne Stroup, Field Museum)

(CN) – Scientists believe a recent fossil finding proves early relatives of dinosaurs and crocodiles once roamed the verdant forests of what is now ice-covered Antarctica.

Researchers describe their discovery of a new species of dinosaur – Antarctanax shackletoni – in a paper published Thursday in the Journal of Vertebrate Paleontology. The first half of its scientific name means Antarctic king while the second half is a nod to polar explorer Ernest Shackelton.

Paleontologists describe the incomplete fossil skeleton as an iguana-sized reptile that hunted bugs and relatives of early mammals and amphibians about 250 million years ago, when Antarctica was covered with forests and rivers.

“This new animal was an archosaur, an early relative of crocodiles and dinosaurs,” Field Museum researcher and lead author Brandon Peecook said in a statement. “On its own, it just looks a little like a lizard, but evolutionarily, it’s one of the first members of that big group. It tells us how dinosaurs and their closest relatives evolved and spread.”

Peecook and his co-authors Roger Smith of the University of Witwatersrand and the Iziko South African Museum, and Christian Sidor of the Burke Museum and University of Washington, say during this time period the temperature in Antarctica rarely dipped below freezing and was home to diverse wildlife.

“The more we find out about prehistoric Antarctica, the weirder it is,” Peecook said. “We thought that Antarctic animals would be similar to the ones that were living in southern Africa, since those landmasses were joined back then. But we’re finding that Antarctica’s wildlife is surprisingly unique.”

Earth’s largest mass extinction occurred about two million years before the Antarctic king lived. Climate change caused by volcanic eruptions killed 90 percent of all animal life. Scientists describe the years immediately after that extinction event as an evolutionary free-for-all.

Mass extinction wiped the slate clean and allowed new groups of animals to thrive. Archosaurs, including dinosaurs, were one of the groups that benefitted.

“Before the mass extinction, archosaurs were only found around the equator, but after it, they were everywhere,” Peecook says. “And Antarctica had a combination of these brand-new animals and stragglers of animals that were already extinct in most places – what paleontologists call ‘dead clades walking.’ You’ve got tomorrow’s animals and yesterday’s animals, co-habiting in a cool place.”

Peecook and his colleagues believe their fossil find supports the idea that Antarctica was a place of rapid evolution and diversification.

“The more different kinds of animals we find, the more we learn about the pattern of archosaurs taking over after the mass extinction,” Peecook said.

Despite the seemingly ancient age of artifacts, much of Antarctica is still relatively undiscovered according to researchers. “Antarctica is one of those places on Earth, like the bottom of the sea, where we’re still in the very early stages of exploration,” Peecook noted. “Antarctanax is our little part of discovering the history of Antarctica.”

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