Scientists Discovered a Dinosaur Ancestor Called the 'Antarctic King'

Antarctanax shackletoni, or the “Antarctic king,” is an iguana-sized ancestor to dinosaurs and modern crocodiles.
Artist Adrienne Stroup’s rendering of AAntarctanax shackletoni and other mammals.

Scientists discovered a 250-million-year-old, iguana-sized dinosaur ancestor in Antarctica, according to findings published in the Journal of Vertebrate Paleontology on Thursday.

The new species was named Antarctanax shackletoni. The first part of the name means “Antarctic king,” and the second part pays tribute to Ernest Shackleton, the twentieth-century explorer who named the Fremouw Formation, the rock formation in the Transantarctic Mountains of Antarctica where the species was excavated by lead author Brandon Peecook in a 2010-2011 Antarctic expedition, during the austral summer. The study was authored by Peecock as well as scientists from the University of Washington and the University of the Witwatersrand in Johannesburg.


Antarctanax lived during the early Triassic period, a few thousand years after the end-Permian mass extinction event, when 70 percent of land-dwelling life on earth went extinct. The Antarctic king belonged to the archosaur reptile group, the ancestor of dinosaurs and modern crocodiles. Archosaurs blossomed following the devastation of the end-Permian extinction, but paleontologists still don’t know exactly what enabled them to thrive while most life on earth died out.

The typical story of the early Triassic period, Peecook told Motherboard, is one of gradual recovery. Paleontologists thought life emerged slowly, recuperating steadily from the end-Permian extinction event. But, Peecook said, the Antarctic king indicates that life may have recovered more quickly than previously thought.

“In and of itself, [ Antarctanax shackletoni] not a surprising animal—it looks like what an animal should look like if it’s that kind of thing at that time,” Peecook said. “But it’s underlining this bigger point that the ancestors of things like dinosaurs and crocodiles are a part of this really explosive radiation [of life], right after this awful earth history event.”

Antarctanax shackletoni’s unearthed bones include its vertebrae, leg and feet bones, and ribs. Although they didn’t find a skull with teeth, the researchers are confident that the reptile was a carnivore. “We know pretty confidently where it fits on the tree of life alongside the archosaurs, and everything around it is carnivorous,” Peecook said.


The Antarctic king lived during a time when Antarctica was still connected to Pangea, the supercontinent that once connected all seven of today’s continents. Despite being located close to the poles, according to Peecook, the Antarctic environment for Antarctanax shackletoni was warm due to greenhouse atmospheric heating. Non-flowing conifer species, ferns, and several other species of ancient lizards have been discovered in Antarctica, and they would have lived alongside the Antarctic king.

“There definitely were a lot of little carnivores in that [Antarctic] forest,” Peecook said. “Some of the amphibians were getting about as big as Antarctanax, and almost all amphibians are carnivores, too. So there’d be a lot of little guys probably eating each other, eating the young, eating insects.”

The fact that Antarctica was still connected to Pangea meant that the Fremouw Formation, where the species was found, was adjacent to areas like Australia, southern Africa, and South America.

Peecook told Motherboard that species like the Antarctic king make Antarctica a treasure trove for paleontologists. “It’s a lot of raw discovery, and it’s such an adventure,” Peecook told Motherboard.

“It’s very cool to be a part of the Antarctic discovery story, because it’s still so new,” Peecook said. “Antarctica is one of the last places on Earth where if you send scientists, we’re always gonna come back with ten exciting things to talk about. There’s so much we don’t know.”