First ever dinosaur fossil discovered on Antarctica identified as a titanosaur

Today, Antarctica is known for its thick ice cap and extreme weather conditions, but travel back 70 million years and things were vastly different.

Back then, Earth’s southernmost continent hosted a thriving, forested ecosystem filled with a diversity of dinosaur life. Thanks to a fragmentary fossil vertebra this is now confirmed to have included titanosaurs, the group of dinosaurs that included the largest land animals ever to have existed.

The fossil was collected in 1985 during a British Antarctic Survey expedition to James Ross Island. This large island lies on the south-eastern side of the Antarctic Peninsula – the section of the continent that stretches out towards South America. During the expedition, researchers found numerous marine fossils, allowing them to accurately date the formation to the Late Cretaceous. Among these fossils was the vertebra of what was initially assumed to be a marine reptile.

However, a new paper has shown that this piece of bone actually came from a sauropod dinosaur. Professor Paul Barrett, one of our dinosaur researchers and a sauropod expert, helped to identify and describe the fossil.

“Believe it or not, this is the first bit of dinosaur ever discovered on Antarctica,” says Paul. “It was overlooked because I think it was misidentified while under harsh field conditions, but it is a sauropod and it’s only the second sauropod bone from the entire continent.”

The bone is too incomplete for the researchers to know what species it came from. But they can use its shape and size to suggest that it belonged to the titanosaur group and that the animal was likely six to seven metres long. Whether or not it was a juvenile, or this was its size as an adult, is equally impossible to know.

The analysis of the fossil has been published in the journal Acta Palaeontologica Polonica.

When Antarctica was green

During the Late Cretaceous, the Antarctic continent was still attached to the southern tip of South America. It was cloaked in rich temperate forests dominated by ferns, palms and conifers, perhaps not unlike the forests we see today on the island of Tasmania, just off Australia’s south-east coast.

Due to Antarctica being so far south, there would also have been dramatic swings in daylight hours, with all life being plunged into twilight during the winter months.

But despite the challenges, life here was thriving. About half a dozen dinosaur species have been described from the continent so far, although the real number is most certainly higher.

However, what we can see is that the full diversity of dinosaurs was present. On the forest floor there were small herbivores, such as Morrosaurus, armoured ankylosaurs, like Antarctopelta and two-legged predators, such as Imperobator. There would have been avian dinosaurs too, including an ancient relative of ducks and geese called Vegavis.

Although fossils are rare, these species were joined by some of the largest animals ever to walk on land – sauropod dinosaurs. Only one other sauropod bone has ever been found on Antarctica, making this newly identified specimen incredibly valuable.

Because of its fragmentary nature, there are lots of questions left to answer about this ancient animal. It seems most similar to a dinosaur from South America called Muyelensaurus, but it’s impossible to say if it’s the same species or a close relative.

One thing that’s certain is its geological age. That’s because it was found in rocks that formed in a marine environment. The ammonites the bone was found near help us precisely determine the age of the rock.

“It’s very precisely from a bit of the Late Cretaceous called the Campanian and it’s from the lowermost part of the Campanian,” explains Paul. “It’s quite precisely dated because it’s from marine rocks. The vertebra was found alongside bits of ammonite, and so this is an animal that would have floated out to sea after it died, perhaps washed out by a river.”

How did titanosaurs reach New Zealand?

The identification of this scrappy fossil could also help solve another mystery.

While sauropods have been found in Australia, we haven’t yet discovered any titanosaurs there. However, dinosaurs from this group of enormous animals are found in nearby New Zealand.

This latest fossil confirms that titanosaurs were also present on Antarctica.

“At the time, New Zealand was, weirdly, quite a long way away from Australia,” explains Paul. “It was closer to southern South America and the Antarctic Peninsula than it was to Australia, just because of the way the continents have moved around.”

“So, there was a region at the western end of Antarctica, where we’ve got the southern tip of South America, the Antarctic Peninsula and the ancient continent of Zealandia, all in the same general area.”

This means the Antarctic Peninsula was possibly how these huge dinosaurs were able to move from South America into New Zealand, while bypassing Australia entirely.

We’ll need more fossils and more evidence to confirm that this is what happened. But regardless, what was once thought to be a tiny scrap of marine reptile is now helping scientists to flesh out what this extreme, remote part of the world looked like tens of millions of years ago.