200 million-year-old sea lizard fossils discovered

The geologist found the most complete fossil of a pointed snout sea lizard Gunakadeit joseeae in North America.

G. joseeae fossils were discovered on Keku Islands, Alaska.(Photo: IFL Science).

Each year, the Tongass National Forest in southeastern Alaska experiences one or two major tidal fluctuations, exposing submerged reef areas. In such an event, geologist Jim Baichtal from the US Forest Service accidentally discovered the 200 million-year-old fossil skeleton of an entirely new species of sea lizard (thalattosaur) , named Gunakadeit joseeae. .

The specimen found on the Keku Islands, near Kake village, is the most complete fossil of a pointed muzzle thalattosaur in North America. The discovery, first published in Scientific Reports, changed the scientific community's understanding of ancient marine reptiles.

"Thalattosaur is one of the first land-based reptile groups to adapt to life in the ocean," Neil Kelley, co-author of research at Vanderbilt University, said in a statement. "They thrive for tens of millions of years but fossils are relatively rare, so new specimens have helped fill the gaps in their evolution and extinction."

Image of reconstruction of G. joseeae.(Graphic: Ray Trool).

Before G. joseeae was discovered, the relationship of the thalattosaur group in a phylogenetic tree was not updated for two decades. These ancient lizards lived mainly in equatorial oceans during the Three Gorges, around the same time as their distant dinosaur relatives. Despite its wide range of habitats, the scarcity of complete fossils has hindered efforts to fully understand their evolutionary history during periods of dramatic sea ecosystem change.

G. joseeae is a relatively small reptile compared to its contemporaries, when it was only about 4 m long. They have 4 legs, short snout, pointed and highly adaptable, allowing survival in shallow coastal waters.

According to the team, G. joseeae represents a new taxon, widening the morphological differences in lizard groups and changing scientists' understanding of how ancient reptiles eat, distribute and their ultimate extinction.

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