Antarctica was not always a frozen wasteland – 250 million years ago, it was covered with forests and rivers, and the temperature rarely dropped below freezing. It was also home to several wildlife, including the first dinosaur relatives. Scientists have just discovered the newest member of that family – a reptile the size of an iguana whose name means "Antarctic king."
"This new animal was an archosaur, an early relative of crocodiles and dinosaurs," says Brandon Peecook, a researcher at the Field Museum and the lead author of a study on the subject. Journal of Vertebrate Paleontology describing the new species. "By itself, it looks like a lizard, but evolutionarily it is one of the first members of this great group. It tells us how the dinosaurs and their closest relatives evolved and spread. "
The fossil skeleton is incomplete, but paleontologists still have a good notion of the animal, called Antarctanax Shackletoni (the former means "Antarctic king", the latter is a nod to the polar explorer Ernest Shackleton). Based on their similarities with other fossil animals, 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) assume that Antarctanax was a carnivore that hunted insects, primitive mammalian relatives and amphibians.
The most interesting thing about Antarctanax, however, is where they lived and when. "The more we find out about prehistoric Antarctica, the stranger it is," says Peecook, who is also affiliated with the Burke Museum. "We thought that the Antarctic animals would be similar to those living in southern Africa, since these masses of land were gathered at the time. But we are finding that Antarctic wildlife is surprisingly unique. "
About two million years ago Antarctanax lived – a blink of an eye in geological time – Earth suffered its greatest mass extinction of all time. Climate change, caused by volcanic eruptions, killed 90% of all animal life. The years immediately after that extinction event were an evolutionary runaway – with the tombstone cleared by mass extinction, new groups of animals competed to fill in the gaps. Arcosaurs, including dinosaurs, were one of the groups that experienced tremendous growth. "Before mass extinction, archosaurs were only found around the equator, but then they were everywhere," says Peecook. "And Antarctica had a combination of these new and misplaced animals from animals that were already extinct in most places – what paleontologists call dead walking dead. You have tomorrow's animals and animals from yesterday, cohabiting in a cool place. "
The fact that scientists have discovered Antarctanax helps to reinforce the idea that Antarctica was a place of rapid evolution and diversification after mass extinction. "The more different types of animals we encounter, the more we learn about the pattern of archosaurs taking over after mass extinction," Peecook notes.
"Antarctica is one of those places on Earth, like the seabed, where we are still in the early stages of exploration," says Peecook. "Antarctanax is our small part of discovering the history of Antarctica. "