TRACKING DOWN CLUES TO THE ORIGIN OF ARKANSAS’ ONLY DINOSAUR FOSSILS

FAYETTEVILLE, Ark. — A University of Arkansas graduate student is taking steps to identify and characterize the remains of the right foot of the only dinosaur fossils found in Arkansas.

ReBecca Hunt, undergraduate student in the department of geosciences, presented some of her findings at a recent meeting of the Society of Vertebrate Paleontology in Norman, Okla.

Robert Friday, a farmer from Sevier County in Southwest Arkansas, discovered the fossils on his farm near Lockesburg, Ark., in 1972. The fossils have been named Arkansaurus fridayi in honor of the place and the person who found them.

A close look at the site revealed three foot bones, three toe bones and two claws. The fossils date back to the early Cretaceous and appear to resemble the late Jurassic theropod Ornitholestes, a possible descendant of the Arkansas dinosaur. But its identity and origins remain a mystery.

"It doesn’t look exactly like anything discovered so far," Hunt said, so it is possible that the fossils represent a new specimen.

Hunt tried to narrow down the field of candidates by studying the fossilized foot in relation to tracks at other sites. To do so, she first had to determine whether or not cartilage might have added to the length of the feet, creating longer tracks. Cartilage does not become fossilized and disappears after the animal dies.

To estimate the amount of cartilage that might have been present, she dissected the feet of emus and alligators, two of the closest living relatives of dinosaurs. She found that the two animals had very little cartilage in the foot area, and that, when scaled to the size of the Arkansaurus fridayi fossil foot, the addition of possible cartilage caused no elongation.

Having determined the approximate shape of the foot, Hunt began to look at track sites in other places for clues to the dinosaur’s identity. She found a possible candidate at Dinosaur Valley State Park near Glen Rose, Texas, where molds of the actual foot of a dinosaur became imprinted in the earth during this time.

Arkansaurus fridayi would have roamed about 120 million years ago, walking upright on two legs, searching for prey. Although parts of Arkansas were under water at that time, there was enough land to support a hunter such as this creature.

Dinosaur fossils are a rare find east of Kansas, which at one time lay under a vast ocean. In the West, the uplift of the Rocky Mountains caused a lot of deposition that proved conducive to fossil preservation, but no such geologic processes took place in the Eastern United States.

"To become a fossil, a creature has to be buried in just the right conditions," Hunt said.

The Arkansaurus fridayi fossils have been examined by James Quinn, a former professor at the University of Arkansas, and by Dan Chure, a paleontologist with Dinosaur National Monument. Hunt herself became interested in the fossils after a conversation with James Kirkland, a paleontologist at Utah State University at last year’s society of Vertebrate Paleontology meeting.

But so far, much remains unknown about Arkansas’ only dinosaur fossil. Hunt hopes to bring more information about this creature to light.

For more information about this early Cretaceous creature, please see http://www.rockhoundingar.com/dino.html