Arkansas holds a unique record of prehistoric life, though it lacks the reputation for dinosaur fossil discoveries found in the American West. The state’s geological history, marked by extensive shallow seas during the Mesozoic Era, made the discovery of dinosaur body fossils rare. Few areas preserve the correct age and environment, revealing a sparse but fascinating ecosystem.
Confirmed Dinosaur Species and Evidence
The most compelling evidence for a specific dinosaur species in Arkansas is the single, scientifically confirmed bone discovery of Arkansaurus fridayi. Designated the official state dinosaur, it is known only from a partial right hind foot found in 1972 near Lockesburg by Joe B. Friday. The fossil bones consist of three metatarsals, four phalanges, and three claws, representing the only formally described dinosaur skeletal remains from the state.
Arkansaurus was a bipedal theropod belonging to the Ornithomimosauria group, often called “ostrich-mimic” dinosaurs. Based on related species, it was likely a fast-running, lightly built, omnivorous animal standing 6 to 15 feet tall. The foot bones were recovered from the Early Cretaceous Trinity Group and formally described in 2018, nearly five decades after discovery. While Arkansaurus is the only named species, other fragmentary bones and teeth have been found, suggesting the presence of large and small theropods and armored ankylosaurs.
The Cretaceous Period Context
The scarcity of dinosaur bones in Arkansas is largely explained by the state’s environment during the Mesozoic Era. For much of the Cretaceous Period, a vast inland sea covered the southern and eastern portions of the state. This expansive body of water preserved marine life far more often than terrestrial dinosaurs.
Land-dwelling fossils are concentrated in the southwestern part of the state, where the Early Cretaceous Trinity Group formations are exposed. This region was a coastal plain and river delta environment situated along the ancient Gulf Coast. These geological formations, including the Holly Creek and De Queen Formations, consist of shallow-water deposits like sandstone, claystone, and limestone. These deposits are suitable for preserving the remains of creatures that lived on the shoreline or in semi-aquatic habitats.
Other Prehistoric Life in Arkansas
Though skeletal dinosaur remains are rare, abundant trace fossils confirm that large dinosaurs frequently traversed the area. Thousands of dinosaur tracks, or trackways, have been uncovered in the gypsum mines near Nashville, Arkansas, within the Trinity Group. These trackways include the enormous, circular footprints of four-legged, long-necked herbivorous sauropods, and the three-toed tracks of large theropods.
The coastal plain environment also preserved a diverse array of non-dinosaur fauna from the Early Cretaceous. This included small vertebrates like frogs, turtles, crocodilians, and a new species of skink (Sciroseps pawhuskai). The ancient seaway was home to formidable marine reptiles during the Late Cretaceous, with fossil evidence of mosasaurs, such as Platecarpus, and the long-necked plesiosaur Elasmosaurus. These marine predators, along with various sharks and fish, inhabited the warm, shallow waters covering the region.