In August 1972, Joe B. Friday discovered the remains of the right hind foot of a dinosaur in a shallow pit on his land in Lockesburg (Sevier County). He found the bones in rocks belonging to the Lower Cretaceous Trinity Group, which consists of deposits of clay, sand, gravel, limestone, and the evaporite minerals gypsum and celestite. Friday donated the bones to the University of Arkansas at Fayetteville (UA), where they are kept in the University Museum Collections at the Arkansas Archeological Survey.

UA professor James Harrison Quinn gave the bones the informal name “Arkansaurus fridayi” in 1973. He cleaned and assembled the bones and compared them to the feet of two similar-appearing dinosaurs previously described in the scientific literature. He constructed clay models of the missing bones to complete a partial foot. Casts of the foot may be viewed at the Arkansas Geological Survey (AGS) and the Museum of Discovery, both in Little Rock (Pulaski County).

“Arkansaurus fridayi” is a type of bipedal coelurosaur dinosaur, a group of theropods that includes the subgroups Tyrannosauridae, Ornithomimidae, and Maniraptora. Its nearest relative was thought by Quinn to be an Ornithomimus, a bird or ostrich-like dinosaur, and a 2003 study by Rebecca Hunt still regards this dinosaur as an unknown species. This is due in part to a poor record of theropods in the eastern United States and the lack of a complete skeleton with which to make comparisons.

The foot bones of “Arkansaurus fridayi” are the only dinosaur bones found in Arkansas that have been brought to the attention of the scientific community. The bones were found in Early Cretaceous age rocks from approximately 146 to 100 million years ago. The only other evidence of dinosaurs in Arkansas is a trackway site that was found by strip mining for gypsum near Nashville (Howard County). This trackway was made by large four-legged herbivorous dinosaurs. “Arkansaurus fridayi” was much smaller, walked on two legs, and was probably carnivorous. Other dinosaur bones similar to “Arkansaurus fridayi” have been found in Utah, Montana, and Maryland. Scientific evidence from these fossils suggests that these dinosaurs were small, lightly built, gracile dinosaurs that were predatory in nature.

Scientific Classification of “Arkansaurus fridayi”

 For additional information:
Braden, Angela K. The Arkansas Dinosaur “Arkansaurus fridayi”. Little Rock: Arkansas Geological Commission, 1998.

Holtz, Thomas R. “Phylogenetic Taxonomy of the Coelurosauria (Dinosauria: Theropoda).” Journal of Paleontology 70 (1996): 536–538.

Hunt, ReBecca K., Daniel Chure, and Leo Carson Davis. “An Early Cretaceous Theropod Foot from Southwestern Arkansas.” Proceedings Journal of the Arkansas Undergraduate Research Conference 10 (2003): 87–103.

Kirkland, James I., Brooks B. Britt, Christopher H. Whittle, Scott K. Madsen, and Donald L. Burge. A Small Coelurosaurian Theropod from the Yellow Cat Member of the Cedar Mountain Formation (Lower Cretaceous, Barremian) of Eastern Utah in Lower and Middle Cretaceous Terrestrial Ecosystems. Bulletin No. 14. Albuquerque: New Mexico Museum of Natural History and Science, 1998,

Pittman, Jeffrey G., and David D. Gillett. “Tracking the Arkansas Dinosaurs.” Special issue, The Arkansas Naturalist 2 (March 1984).

Angela Chandler
Arkansas Geological Survey