Cretaceous Maryland

115 million years ago, Prince George's County was a flat coastal plain with winding rivers. The environment probably resembled parts of southern Louisiana today. Sharp bends in the rivers became detached and formed lakes or swamps called oxbows. Dinosaur Park is a remnant of one such oxbow. When the river flooded, debris flowing downstream, including dead plants and animals, would be deposited in and around the oxbow. There they became entombed in clay and became the fossils we find at Dinosaur Park today.

Climate Clues


Animal and plant fossils tell us what sort of organisms lived in Cretaceous Maryland, but they also provide important clues about the prehistoric climate. For example, some of the most common. fossils at Dinosaur Park are crocodile teeth and armor fragments. Modern crocodiles are ectothermic ("cold-blooded"), meaning that their body temperature is dependent on the air around them. This means that crocodiles can only live in areas without long periods of freezing temperatures. Since crocodiles were plentiful in ancient Maryland, the climate must have been warm and subtropical, similar to southern Louisiana where crocodilians live today.
Illustration of an Oxbow With Skeletal Remains of Dinosaur
Learn more about Cretaceous Maryland at the Smithsonian Museum of Natural History's Backyard Dinosaurs online exhibit.