Jan. 18—ALBUQUERQUE — A new species and genus of a toothy prehistoric fish has been discovered in Socorro County.

A paper, published in "Contributions from the Museum of Paleontology, University of Michigan" in December argues that an unusually large fish skull discovered several years ago is actually a new variety of the "demon-toothed fish," an early ray-finned fish that lived during the Paleozoic period several hundred million years ago.

"I haven't seen this in over eight years," said Susan Harris Thursday, turning a fossilized fish skull she discovered in Socorro County over in her hands.

About the size of a croissant, a rocky reddish surface shows hints of the skull within — a tooth here, a jawbone there. The fossil will be featured in the New Mexico Museum of Natural History and Science's upcoming Ancient Life exhibit, which is due to open Feb. 15.

The fossil is encased in layers of iron-rich calcium carbonate. Over time, like a grain of sand in an oyster becoming a pearl, layer upon layer builds up around a fossil or other nucleus, forming a concretion. The iron, which hardens the material, can make it difficult to mechanically clean the rock off of the fossil to better view the anatomy.

Enter the CT scan.

The fossil was lent to the University of Michigan for scanning, a non-invasive method of looking at fossils adopted relatively recently in paleontology. From there, a 3D model of the fossil was created, revealing its unique anatomy.

"When I saw the CT scan ... wow," said Spencer Lucas, the New Mexico Museum of Natural History and Science's director of paleontology and a co-author of the paper. "If you look at the fossil, you don't see a lot of anatomy right on the surface."

The 3D models will be a part of the exhibit along with the fossil.

Susan Harris, a self-taught fossil collector, found the specimen about eight years ago.The new genus and species will bear her name: Daemodontiscus harrisae. She tries to take a fossil-hunting trip every week.

It was a hot July day when Harris came across an outcrop of black shale in northern Socorro County.

There was evidence of prehistoric life, but no bones. Harris found several coprolites, or fossilized feces, and some plants.

Just before she left, she noticed a hard mass, or concretion, with what looked like randomly scattered teeth. It turned out to be a fish skull of a previously undiscovered genus and species.

When the skull's owner was still swimming, New Mexico was part of a supercontinent and located much closer to the equator. What is now desert was, at the time, a tropical coastal lake.

"I was in this hot, dry desert ... of course, I knew that I was in sediments that had been an ancient lake," Harris said. "But picking up a fish skull, that really makes it concrete. Wow, there really was a lake here, and then to imagine that this thing was once alive and swimming through a lake that existed above these shale sediments."

Harris had a feeling it was something special right away. The fish would have been about three feet long, with dozens of stiletto-sharp teeth on its jawbone and pointing horizontally on the palate.

Daemodontiscus, or demon-toothed fish, earned its name from its famous fangs. But the teeth, along with some other features, made Harris' find unusual.

In comparison, most early ray-finned fish would have been around 10 inches. At that size, the fish could have been a top predator in this coastal lake, Lucas said.

To this day, Harris says it's one of the best finds she's ever made.

Lucas stressed Harris will have a "big presence" in the upcoming exhibit. In addition to the fish skull, several of Harris' other finds will be part of the Ancient Life Hall.

"Susan is really one of the most accomplished fossil collectors associated with the museum," Lucas said. "She's been a volunteer for us for about 30 years, and she's made a lot of discoveries. This may be the most remarkable one, but we have a lot of important fossils she found, and some of the fossils in the hall, not just this fish, were ones she found."

Volunteers like Harris play an important role at the museum, said executive director Anthony Fiorillo.

"I have this guy [Lucas] who looks at 250 million years of Earth history," Fiorillo said. "One guy. If I had to rely on him for everything that was going in the hall, we would have a pretty empty hall. It's this kind of relationship that is a great example of the beauty of paleontology. ... It's the curiosity. That's the job of our museum, to inspire and nurture the public's curiosity about the stuff that's out there — and this is just a great example of it."