PALEONTOLOGY PUZZLE: Traskasaura sandrae – History’s Strangest Sea Monster, a Bizarre Mix of Primitive and Advanced Traits That Left Scientists Baffled!

A newly named elasmosaurid plesiosaur from Late Cretaceous Canada has stunned researchers with its unprecedented “mosaic” anatomy—part ancient throwback, part evolutionary innovation—revealing a predator unlike any other marine reptile.

Formally described in May 2025 in the Journal of Systematic Paleontology by Robin O’Keefe and colleagues, Traskasaura sandrae is the first elasmosaurid named from British Columbia. The 12-metre-long beast lived ~85 million years ago in the Santonian seas of Vancouver Island’s Haslam Formation.

The story began in 1988 when Michael and Heather Trask discovered the holotype along the Puntledge River. Two more specimens—a humerus and a juvenile skeleton—were later recovered. Long known informally as the “Puntledge River elasmosaur,” the fossils were declared British Columbia’s provincial fossil in 2023 before their true idenтιтy was solved.

What baffled scientists is Traskasaura’s strange blend of traits: a relatively narrow mandible with large, robust teeth (primitive, reminiscent of earlier forms like Libonectes) combined with derived features enabling powerful downward swimming and ambush hunting from above. Its heavy, crushing denтιтion suggests it targeted hard-shelled prey such as ammonites in a way no other elasmosaur could.

This unique suite of adaptations—primitive jaw mechanics paired with advanced locomotor specializations—allowed Traskasaura to exploit a novel ecological niche in the northern Pacific. Named in honour of the Trask family and Sandra Lee O’Keefe, the species finally gives the Pacific Northwest its own Mesozoic marine icon.

Far from just another long-necked plesiosaur, Traskasaura proves that even well-studied groups can hide extraordinary evolutionary surprises. The strangest sea monster in the fossil record has at last been unmasked.