ISU researchers solve mystery of ancient fish

Idaho State University researchers said Wednesday that they had solved some of the mysteries surrounding the spiral teeth of the ancient fish Helicoprion.

Helicoprion roamed the seas that once covered southeastern Idaho, as well as Wyoming and Utah.

The fossils of this 270-million-year-old fish have long mystified scientists because, for the most part, the only remains of the fish are its teeth because its skeletal system was made of cartilage, which doesn’t preserve well. No one could determine how these teeth – that look similar to a spiral saw blade – fit into a prehistoric fish with a poor fossil record, long assumed to be a species of a shark, according to a news release.

“New CT scans of a unique specimen from Idaho show the spiral of teeth within the jaws of the animal, giving new information on what the animal looked like, how it ate,” said Leif Tapanila, principal investigator of the study, who is an ISU associate professor of Geosciences and Idaho Museum of Natural History division head and research curator.

In the museum’s Idaho Virtualization Laboratory, Tapanila and his colleagues have virtual reconstructions of the Helicoprion’s jaws that clear up the biggest mystery surrounding these teeth.

“We were able to answer where the set of teeth fit in the animal,” Tapanila said. “They fit in the back of the mouth, right next to the back joint of the jaw. We were able to refute that it might have been located at the front of the jaw.”

Located in the back of the jaw, the teeth were “saw-like,” with the jaw creating a rolling-back and slicing mechanism. The Helicoprion also likely ate soft-tissued prey such as squid, rather that hunting creatures with hard shells.

The university wants the public to see the researchers’ findings. Idaho Museum of Natural History officials said the museum has the largest public collection of Helicoprion spiral-teeth fossils in the world. And using the new information, is creating a full-bodied reconstruction of a modest-sized, 13-foot long Helicoprion, which probably grew as long as 25 feet.

This model will be part of the museum’s new Helicoprion exhibit that will open this summer, which includes artwork by Ray Troll, a scientific illustrator as well as fine arts artist.