A bone discovered as far back as 1985 on the Antarctic Peninsula has now been officially identified as the first known dinosaur fossil ever found on the Antarctic continent. The vertebra comes from a titanosaur, a group of long-necked sauropods that included some of the largest land animals in Earth’s history.
The fossil was discovered by Dr Mike Thomson, a geologist with the British Antarctic Survey (BAS), during an expedition to James Ross Island. The aim of his work was to map the rock strata of the region and thereby lay the foundations for the chronological classification of future fossil finds. Thomson suspected even then that the bone came from a large reptile.
It was not until decades later that Dr Mark Evans, a palaeontologist and head of the BAS’s geological collections and laboratories, examined the fossil more closely. He identified it as a tail vertebra from a titanosaur.
“This fossil was found by Dr Mike Thomson, one of the true pioneers of Antarctic geology,” explained Evans. A look at his notebooks shows that Thomson already knew it was a large reptile. This makes it all the more special to be able to confirm the find 40 years later.
A small representative of the titanosaurs
Titanosaurs were among the largest dinosaurs in Earth’s history, with some species weighing more than 15 tonnes. However, with an estimated length of six to seven metres, the Antarctic specimen was comparatively small.
The vertebra was found in the Santa Marta Formation, a marine rock layer dating from the late Cretaceous period, around 82 million years ago. It is so far the only known dinosaur fossil from Antarctica to have come from this formation. Researchers believe that after the animal’s death, the bone ended up in the sea, sank to the seabed and became fossilised there.
New clues to their distribution
The discovery provides important clues as to how dinosaurs spread across the southern continents. Professor Paul Barrett of the Natural History Museum in London points out that no titanosaurs are known from Australia to date, and there is only limited evidence from New Zealand. The discovery in Antarctica could suggest that these animals spread further across the landmasses, which were connected at that time.
82 million years ago, Antarctica was not an ice-covered continent. Lush temperate forests covered large parts of the region, and the climate was considerably warmer than it is today.
Due to its thick ice sheet, Antarctica still has the lowest number of known dinosaur fossils of any continent. However, researchers believe that numerous further traces of the region’s former biodiversity remain hidden in the rock.
The study ‘A titanosaurian sauropod dinosaur from the Late Cretaceous of Antarctica’ was published in the journal *Acta Palaeontologica Polonica*.
Rosamaria Kubny, PolarJournal