Two individuals of Traskasaura sandrae hunt the ammonite Pachydiscus in the northern Pacific during the Late Cretaceous. Traskasaura sandrae, named today in the Journal of Systematic Paleontology, was declared the Provincial Fossil of British Columbia in 2023. Credit: Robert O Clark. CC BY.

The mystery of a ‘very odd’ elasmosaur has finally been solved: one of North America’s most famous fossils has been identified as a new species.

This primitive 85-million-year-old, 12 metre-long, fiercely predatory marine reptile is unlike any elasmosaur known to-date and hunted its prey from above.

A group of fossils of elasmosaurs have just been formally identified as belonging to a very odd new genus of the sea monster, unlike any previously known.

Long-necked and measuring in at 12 metres, Traskasaura sandrae – as it is officially named in a new study – possessed heavy, sharp, robust teeth, ideal for crushing.

The findings highlight Traskasaura as having a strange mix of primitive and derived traits unlike any other elasmosaur.

Its unique suite of adaptations enabled this plesiosaurto hunt prey from above. The findings suggest that the fierce marine reptile was perhaps one of the first plesiosaur taxa to do so.

The 85-million-year-old fossils are not new to science, though, far from it.

The first (now known to be) Traskasaura fossil was discovered from Late Cretaceous rocks in 1988 along the Puntledge River on Vancouver Island, British Columbia, Canada.

Since then, additional fossils have been recovered: an isolated right humerus and a well-preserved, juvenile skeleton comprising thorax, girdles and limbs.

All in all, three animals are part of the collection detailed in the new paper, all from the Haslam Formation of Vancouver Island.

Museum display of Traskasaura in The Courtenay and District Museum and Palaeontology Centre. Credit: The Courtenay and District Museum and Palaeontology Centre. CC BY.

Official fossil emblem

First described in 2002, the fossils recently became famous, having been adopted by the Province of British Columbia and declared as the official fossil emblem of British Columbia (‘the Provincial Fossil of British Columbia’).

Lead author Professor F Robin O’Keefe from Marshall University, in West Virginia, USA, said: “Plesiosaur fossils have been known for decades in British Columbia, however, the identity of the animal that left the fossils has remained a mystery, even as it were declared BC’s provincial fossil in 2023.

“Our new research published today finally solves this mystery.

“The scientific confusion concerning this taxon is understandable. It has a very odd mix of primitive and derived traits. The shoulder, in particular, is unlike any other plesiosaur I have ever seen, and I have seen a few.”

O’Keefe, who is an expert on marine reptiles from the age of dinosaurs, added: “With the naming of Traskasaura sandrae, the Pacific Northwest finally has Mesozoic reptile to call its own.

“Fittingly, a region known for its rich marine life today was host to strange and wonderful marine reptiles in the Age of Dinosaurs.”

He continued: “The fossil record is full of surprises. It is always gratifying to discover something unexpected.

“When I first saw the fossils and realised they represented a new taxon, I thought it might be related to other plesiosaurs from the Antarctic.

“My Chilean colleague Rodrigo Otero thought differently, and he was right; Traskasaura is a strange, convergently evolved, fascinating beast.”

Juvenile elasmosaur discovered 2020. Credit: The Courtenay and District Museum and Palaeontology Centre. CC BY.

Excellently preserved

In the initial, 2002 description of the fossils, experts were reluctant to erect a new genus based solely on the adult skeleton of the elasmosaur discovered.

Relatively few characters were ‘unambiguous’ on this particular skeleton.

However a new ‘excellently preserved’ partial skeleton enabled this latest international team of scientists from Canada, Chile, and the United States to shed much new light on the morphology of the Puntledge River elasmosaur – and eventually identify it as a new genus and species.

Traskasaura clearly had a very long neck – at least 36 well-preserved cervical vertebrae indicate at least 50 bones in the neck, and probably more.

And whilst not huge amounts are known about Traskasaura’s behaviour, the “fascinating and long list of autapomorphic characters” of the bones indicate strong capabilities for downward swimming.

O’Keefe believes the combination of its unusual features relate to its hunting style – where it would use this capability for downward swimming to dive upon its prey from above.

This prey was likely the abundant ammonites known from the region. These would have been a “good candidate – due to Traskasaura’s robust teeth, ideal, possibly, for crushing ammonite shells,” he explained.

Summarising their findings, the team says their hypothesis that the three individuals describe do not belong to the same taxon ‘does deserve consideration’.

However, all three individuals show diagnostic features of the new taxon, and therefore probably represent a single species.

The findings are published in the Journal of Systematic Palaeontology.