Iguana-Sized Reptile Dubbed ‘Antarctic King’ Ruled Continent Before Dinosaurs Emerged

Stock photo of a prehistoric fossil.
Oranzy Photography / Shutterstock

During the early years of the Triassic Era, the continent we now know as Antarctica was a forested area with a warm climate so different from the frozen conditions of present day. The location was also home to a diverse variety of prehistoric creatures, including an iguana-sized reptile that was among the ancestors of the dinosaurs that arrived millions of years later, as detailed in a study published Thursday in the Journal of Vertebrate Paleontology.

As explained by Live Science, the creature was named Antarctanax shackletoni, with the first part of the name being the Greek word for “Antarctic king,” and the second part being a tribute to Ernest Shackleton, the British polar explorer who discovered and named the Beardmore Glacier during a 1908 expedition. The animal, which is believed to have existed about 250 million years ago, was an archosaur, meaning it belonged to the same evolutionary group that eventually included dinosaurs, pterosaurs, and crocodiles.

Although scientists were only able to uncover a partial fossil, they were able to determine that A. shackletoni might have measured about four to five feet (1.2 to 1.5 meters) long as an adult. Per Gizmodo, analysis of the animal’s bones revealed that it was a carnivorous creature that consumed amphibians, proto-mammals, and bugs. Study lead author Brandon Peecook, a paleontologist at the Field Museum of Natural History, noted that A. shackletoni most likely lived on the ground, as inferred by the bones on its feet and spine.

“It doesn’t have any adaptations in its feet that would make us think it lived in the trees or that it’s a burrower,” Peecook told Live Science.

As Antarctica was home to a “warm [and] wet environment” where temperatures were seldom below freezing during the Triassic Era, the so-called “Antarctic king” was just one of the many animals that thrived in those prehistoric times. According to Peecook, Antarctica in the Triassic was also home to amphibians, cynodonts (mammal ancestors), dicynodonts (“mammal-like predators” with tusks and beaks), and other reptiles.

“We have evidence of widespread forests all over the place, and big rivers moving through those forests.”

Beyond its corroboration of previous findings that hinted at Antarctica’s warmer climate and ecological diversity in prehistoric years, the new study could also help scientists learn more about the evolution of archosaurs after the Permian mass extinction that took place about 252 million years ago. This event killed almost all forms of marine species and about 70 percent of vertebrates on land, and prior to the new study, researchers believed that it took several millions of years for Earth to be repopulated by new species. However, the discovery of A. shackletoni, per Live Science, suggests that it took just a “couple of million years” for archosaurs to diversify in the aftermath of the Permian mass extinction.

“A pattern we see over and over again with mass disturbances like the end-Permian mass extinction is that some of the animals who managed to survive quickly filled in the empty eco-spaces,” Peecook said in a separate interview with Gizmodo. “Archosaurs are a great example—a group of animals that were able to do practically everything. This clade just went totally ballistic.”