200-Million-Year-Old Swimming Reptile Fossil Discovered In Southeast Alaska

Artist’s depiction of Gunakadeit joseeae. Ray Troll ©2020

Madison Dapcevich 04 Feb 2020, 21:08

Once or twice a year, the lush Tongass National Forest in coastal Southeast Alaska experiences huge tidal fluctuations, exposing rocky intertidal zones that are otherwise submerged underwater. It was during one of these minus tides nearly a decade ago that Jim Baichtal, a geologist with the US Forest Service, went fossil hunting in the Keku Islands near the village of Kake.

Little did he know, his discovery would change what the scientific community knows about ancient marine reptiles that dashed through the world’s oceans hundreds of millions of years ago.

Baicthal had stumbled upon the most complete specimen of a pointy-snouted thalattosaur ever discovered in North America. For the first time, experts describe a newly added species Gunakadeit joseeae in Scientific Reports.

“Thalattosaurs were among the first groups of land-dwelling reptiles to readapt to life in the ocean,” said study co-author Neil Kelley of Vanderbilt University in a statement. “They thrived for tens of millions of years, but their fossils are relatively rare so this new specimen helps fill an important gap in the story of their evolution and eventual extinction.”

This fossil of Gunakadeit joseeae was found in Southeast Alaska. About two-thirds of the tail had already eroded away when the fossil was discovered. University of Alaska Museum of the North

Following its 2011 discovery, it would take experts at the University of Alaska Fairbanks several years to prepare the “weird” fossil for analysis. To properly place the new species in the phylogenetic tree, researchers analyzed dozens and dozens of detailed anatomic features from fossil specimens around the world and used computers to analyze information to determine potential relatives.  

“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,” said lead author Patrick Druckenmiller, director and earth sciences curator at the University of Alaska Museum of the North. “We decided to start from scratch on the family tree.”

Before G. joseeae was discovered, it had been two decades since the thalattosaur relationships on the family tree had been updated. Thalattosaurs lived primarily in equatorial oceans during the Triassic Period right around the time their distant dinosaur relatives were emerging. Despite their broad range, intact fossils are rare and the lack of finds has hampered efforts to fully understand their evolutionary history during a “time of profound marine ecological change.”

Scientists determined that G. joseeae represented a new taxon that expands existing knowledge about how the ancient reptiles fed, the habitat they lived in, and their eventual extinction. For starters, the reptile was relatively small and grew up to just 4 meters long (13 feet). The aquatic tetrapods were highly specialized and had a short, pointy snout that equipped them for survival in nearshore shallow marine environments – a characteristic that may have eventually led to their demise.

Gunakadeit, a sea monster of Tlingit legend, brings good fortune to those who see it. Robert Mills ©2020

“It was probably poking its pointy schnoz into cracks and crevices in coral reefs and feeding on soft-bodied critters,” said Druckenmiller. “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.”

In a nod to local Alaska Native culture, the scientists named the marine reptile after Gunakadeit, a Tlingit sea monster who brings good fortune to those who see it. In this case, finding the animal has led to a deeper understanding and new insight into the reptilian family tree.

“Gunakadeit expands the already striking morphological disparity seen in thalattosaurs, indicative of adaptation to a wide range of dietary and ecological roles,” conclude the authors.

From left, Gene Primaky, Jim Baichtal, and Patrick Druckenmiller stand in rising tidewater after the last of the two blocks was removed. Minutes later, the tide submerged the excavation site. Kevin May, UA Museum of the North

 

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