New Species of Ichthyosaur Reveals the Ancient Marine Reptile Went Extinct Much Later Than Thought

New analysis of fossils of an ancient, swimming sea reptile known an ichthyosaur reveals not only a new species of the creature, but corrects a previously misunderstood timeline of the ichthyosaur's existence.

Ichthyosaurs, deep-diving animals with enormous eyeballs that could grow up to 20 meters (66 feet) in length, are well known from hundreds of fossil records dating back to the time of the dinosaurs, but the old line of thought traced the creatures' decline through multiple extinction events during the Jurassic period. These successive events were thought to have killed all ichthyosaurs except those strongly adapted for fast-swimming life in the open ocean. Due to this pattern, it has been assumed that ichthyosaurs were constantly and rapidly evolving to be ever-faster open-water swimmers; seemingly, there was no 'stasis' in their long evolutionary history, according to a release from the University of Southampton.

But the latest study of an ichthyosaur specimen found in the 1950s contradicts the long-standing view of ichthyosaur history.

Before the fossil's precise age could be determined, the ichthyosaur expert who found the specimen, Robert Appleby, died.

"Robert Appleby recognized that the specimen was significant, but unfortunately died before resolving the precise age of the fossil, which he realized was critical," said Jeff Liston of National Museums Scotland and manager of the research project. "So continuation of the study fell to a new generation of researchers." 

That new generation reports that the specimen Appleby found in the Kurdistan region of Iraq is in fact a new species, which they named Malawania anachronus, which means 'out of time swimmer'.

Ichthyosaurs were through to have gone extinct in the Early Jurassic period, but the Malawania is Cretaceous in age, suggesting the species was among the last survivors of a group in decline.

This type of ichthyosaur did not seem to have changed much between the Early Jurassic and the Cretaceous, a very rare evolutionary stasis not normally seen in the evolution of marine reptiles, the researchers report.

"Malawania's discovery is similar to that of the coelacanth in the 1930s: it represents an animal that seems 'out of time' for its age. This 'living fossil' of its time demonstrates the existence of a lineage that we had never even imagined. Maybe the existence of such Jurassic-style ichthyosaurs in the Cretaceous has been missed because they always lived in the Middle-East, a region that has previously yielded only a single, very fragmentary ichthyosaur fossil," said Valentin Fischer of the University of Liege in Belgium, the study's lead author.

Strangely, the Malawania specimen was almost lost, had it not been for geologists, who spotted the fossil in an odd place.

"Preserved within a large, flat slab of rock, it was being used as a stepping stone on a mule track," said co-author Darren Naish of the University of Southampton. "Luckily, the geologists realized its potential importance and took it back to the UK, where it remains today."