Ichthyosaurs, second only to whales in size, thrived during the dinosaur age.
Their roots are unclear. Spitsbergen's Arctic fossils from 250 million years ago are revealing the rise of ichthyosaurs.
Siberian volcanism killed 90% of species in the Permian Period's worst mass extinction, leaving the eldest ichthyosaur 2 million years later.
The 11 tail vertebrae discovered indicate that the animal was about 10 feet (3 meters) long, making it a top predator.
Ichthyosaurs, like whales and other marine reptiles, emerged from terrestrial forebears.
Researchers thought 250 million-year-old ichthyosaurs would have been basic like their land-dwelling forebears.
This unnamed fossil showed advanced anatomy.
Kear said the intermediate ichthyosaur parent emerged sooner than expected.
On our July fossil-hunting trek to Spitsbergen, we will have to dig in even older rocks.