Stephanie Pappas, LiveScience Senior Writer
A fossil that once lined a mule track in Iraq has revealed the surprising survival of a group of ichthyosaurs, marine reptiles that swam the seas more than 66 million years ago.
Researchers had previously believed that ichthyosaurs declined throughout the Jurassic Period, which lasted from 199 million to 145 million years ago, with the only survivors rapidly evolving to keep ahead of repeated extinction events. The new fossil, however, dates from the Cretaceous Period, which lasted from 145 million to 66 million years ago. It looks remarkably like its Jurassic brethren, revealing a surprising evolutionary statis.
The fossil "represents an animal that seems 'out of time' for its age," study researcher Valentin Fischer of the University of Liège in Belgium said in a statement.
Ichthyosaur evolution
Ichythyosaurs were dolphin-shaped swimming reptiles that gave birth to live young. They lived in the oceans at the same time dinosaurs were tromping around on land. Previously, researchers thought only one group of ichthyosaurs, called ophthalmosaurids, made it out of the Jurassic into the Cretaceous. The newly named fossil, dubbed Malawania anachronus, is a Cretaceous survivor that does not belong to the ophthalmosaurids, however. That means a "ghost lineage" of ichthyosaurs survived alongside the ophthalmosaurids, changing very little over millions of years.
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