Low Tide Reveals Rare Dinosaur Fossil

Low tides revealed this rare fossil find in Alaska. (Patrick Druckenmiller)

ANCHORAGE, Alaska – A team from the University of Alaska Museum of the North has succeeded in excavating the fossil of a rare, ancient marine reptile from rock that's usually covered by the tide.

Eugene Primaky, working for the USDA Forest Service Heritage Program out of Petersburg, spotted what he thought might be the bones of a fish or a branch while looking over an intertidal outcropping near Kake in Southeast Alaska in May. He gave it a kick. It didn't move.

Photos were sent to the museum's earth sciences curator, Patrick Druckenmiller, who quickly determined that it was the back end of a little-known sea-going reptile from the age of the dinosaurs called a thalattosaur, Greek for "sea lizard."

The fossil was found in a formation estimated to be 220 million years old. "Based on the age of the rocks and what I could see in the picture, I was 99 percent sure that's what it was," Druckenmiller said.

Druckenmiller and a colleague, Kevin May, traveled to the site in mid-June to collect the specimen. The site was exposed only during extreme low tides at certain times of year. The team faced a two-day window in which they had just four hours each day to remove the fossil. The next chance to do so wouldn't come until October.

Rock saws were used to hack into the layers surrounding the fossil. The workers managed to complete the excavation just five minutes before the site went underwater on the first day. But Druckenmiller spotted yet more bone penetrating the rock. A larger section was removed on the second day in hopes that it would contain the rest of the skeleton.

The two slabs, weighing 500 pounds, were shipped to Fairbanks. There, at the museum's fossil preparation lab at the museum, rock will be slowly chipped away to expose as much of the complete skeleton as still exists. The process will take several months.

Druckenmiller thinks that when the rock is finally removed it will reveal one of the best thalattosaur specimens ever found in North America and possibly anywhere else in the world. He hopes that the rest of the bones, including the skull, will be in the second chunk of rock and as well-preserved as the tail and hind bones first spotted by Primaky.

As it stands, the specimen is one of Alaska's most compete fossil vertebrates, according to a museum press release.

"This is the best preserved and the most articulated specimen of Triassic reptile I have been involved with," said Jim Baichtal, the Tongass National Forest geologist who sent the first photos to Fairbanks and participated in the fossil's extraction.

Inspecting the rest of the skeleton may reveal new information about reptiles of the era.

"It's reasonably complete and once we reveal more of the skeleton, we will be able to compare it to other thalattosaurs to see if it is a new species," said Druckenmiller. "We don't know what kind we have yet."

There are few available images of what a live one may have looked like, Druckenmiller said. But he compared it to an Endennosaurus, one of the 10 types of thalattosaurs so far identified.

An image at reptileevolution.com, a collaborative website created by paleontologists and museum personnel from around the world, shows the Endennosaurus as having a long eel-like tail, a long neck, a narrow, toothless, birdlike head and four short legs with clawed, possibly webbed, feet. The picture at the website of a skull of a Thalattosaurus -- the genus name for North American thalattosaurs -- shows a more robust head and small teeth.

At the website, the Endennosaurus is depicted in a posture that calls to mind a sea otter on land. Druckenmiller likens it to "a marine iguana or a crocodilian," living a "mostly aquatic" life. However, it appears that such creatures would have had no trouble going ashore and moving about on solid ground, even if they appeared somewhat clumsy.

A big thalattosaur might have stretched out to nine feet. Druckenmiller suspects this specimen will prove to be about half that size.