A new species of marine reptile from the Triassic period has been identified from fossils found in southeastern Alaska, the United States.
An artist’s depiction of Gunakadeit joseeae. Image credit: Ray Troll.
Thalattosaurs (meaning ‘ocean lizards’) were among several reptile lineages that adapted to marine life in the Mesozoic era.
They grew to lengths of up to 3-4 m (10-13 feet) and lived in equatorial oceans worldwide until they died out near the end of the Triassic period.
“Thalattosaurs were among the first groups of land-dwelling reptiles to readapt to life in the ocean,” said Dr. Neil Kelley, a paleontologist at Vanderbilt University.
“They thrived for tens of millions of years, but their fossils are relatively rare so the new specimen helps fill an important gap in the story of their evolution and eventual extinction.”
The newly-identified species is a small-bodied (estimated total length 75-90 cm, or 2.5-3 feet) thalattosaur.
Named Gunakadeit joseeae, it lived about 220 million years ago (Norian division of the Triassic period).
“When you find a new species, one of the things you want to do is tell people where you think it fits in the family tree. We decided to start from scratch on the family tree,” said Dr. Patrick Druckenmiller, director and earth sciences curator at the University of Alaska Museum of the North.
“We were surprised when we identified where Gunakadeit joseeae landed,” he added.
“It was so specialized and weird, we thought it might be out at the furthest branches of the tree. Instead it’s a relatively primitive type of thalattosaur that survived late into the existence of the group.”
Holotype specimen of Gunakadeit joseeae in right lateral view. Image credit: Druckenmiller et al, doi: 10.1038/s41598-020-57939-2.
The fossilized remains of Gunakadeit joseeae — a nearly complete skeleton including the skull – were recovered from the Norian sediments of Keku Islands, Alaska.
The specimen is the most complete thalattosaur ever found in North America.
“When we saw the fossil’s skull, we could tell right away that it was something new because of its extremely pointed snout, which was likely an adaptation for the shallow marine environment where it lived,” the researchers said.
“It was probably poking its pointy schnoz into cracks and crevices in coral reefs and feeding on soft-bodied critters,” Dr. Druckenmiller said.
“Its specialization may have been what ultimately led to its extinction.”
“We think these animals were highly specialized to feed in the shallow water environments, but when the sea levels dropped and food sources changed, they had nowhere to go.”
A paper describing Gunakadeit joseeae was published in the journal Scientific Reports.
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P.S. Druckenmiller et al. 2020. An articulated Late Triassic (Norian) thalattosauroid from Alaska and ecomorphology and extinction of Thalattosauria. Sci Rep 10, 1746; doi: 10.1038/s41598-020-57939-2
