Reconstructing ancient terrestrial ecosystems in the Southern United States presents a unique challenge for paleontology. While dinosaur fossils are abundant in western North America, the eastern states, including Mississippi, offer a more complex picture. Dinosaurs did roam this region during their final epoch, but the geological record makes finding their remains difficult. The evidence is scattered and fragmented, reflecting the unique coastal environment that existed millions of years ago.
The Late Cretaceous Mississippi Environment
During the Late Cretaceous Period, North America’s geography was drastically different than it is today. The Western Interior Seaway, a vast body of water, split the continent in two, creating the western landmass Laramidia and the eastern landmass Appalachia. Mississippi was situated along the western edge of Appalachia.
Most of the state was submerged beneath this warm, shallow sea, which extended from the Gulf of Mexico north to the Arctic Ocean. This explains why the bulk of Mississippi’s fossil record consists of marine life, such as mosasaurs and various species of sharks. Terrestrial dinosaur fossils are rare because the state’s land area was limited to a narrow, low-lying coastal plain, which was a challenging environment for fossil preservation.
Defining the Dinosaur Residents
Paleontologists have confirmed the presence of several major dinosaur groups that inhabited Mississippi’s narrow coastal plain. The most common terrestrial finds belong to the Hadrosauridae, or duck-billed dinosaurs. These large, plant-eating herbivores are represented by fragmentary fossils, including cheek teeth, jaw fragments, and toe bones, indicating they were a regular part of the coastal ecosystem.
Tyrannosauroids, the clade of carnivorous theropods, were also present. The Mississippi finds are not from the largest species, but are isolated teeth from smaller, unidentified relatives that served as apex predators. The state also hosted smaller, lightly built theropods, such as the Ornithomimids, often called “ostrich dinosaurs” due to their similar build. These fast-moving dinosaurs likely fed on small animals, eggs, and plants.
Evidence for even more unique dinosaurs includes the discovery of a ceratopsid tooth in the Owl Creek Formation. This find marks the first reported horned dinosaur in eastern North America, suggesting a more diverse fauna existed in Appalachia than previously thought. The major groups confirmed in Mississippi include:
- Hadrosauridae (Duck-billed dinosaurs)
- Tyrannosauroids (Apex predators)
- Ornithomimids (Ostrich dinosaurs)
- Ceratopsidae (Horned dinosaurs)
The Nature of Fossil Evidence in Mississippi
The fossil evidence for dinosaurs in Mississippi consists primarily of isolated fragments, such as shed teeth or single bones, rather than the nearly complete skeletons found in western states. This is a direct consequence of the environment, as land animal carcasses rarely remained on the coastal plain long enough to be preserved intact.
Instead, dinosaurs that died near the coast or rivers were often washed out to sea by storm surges or swollen river systems. Once in the marine environment, the remains would float, break apart, and settle into the ocean sediment. This process, known as taphonomy, explains why terrestrial fossils are often found mixed with abundant marine fossils in formations like the Demopolis Chalk and the Eutaw Formation.
The primary geological units yielding these dinosaur fossils are the Ripley Formation and the Owl Creek Formation, both dating to the latest Cretaceous. The fragmented nature of these discoveries requires paleontologists to use microfossil techniques, analyzing isolated teeth and bone splinters to identify the species that lived on this ancient sliver of land.