Dinosaurs lived during most of the Mesozoic Era, from 235 to 65 million years ago, on every continent on Earth. In Maryland, all three Mesozoic time periods in which dinosaurs lived are represented in the state's geology: Triassic, Jurassic, and Cretaceous. Maryland has produced more dinosaur bones than almost any other state east of the Mississippi River. Maryland's Dinosaur Trail occupies the geologic region running parallel to the Route 1 corridor between Washington and Baltimore, where rock layers about 100 million years old from the Early Cretaceous Period contain one of the largest concentrations of dinosaur fossils on the East Coast. Thousands of fossils have been found in the gray and red clays near Laurel, Maryland. In a section called Dinosaur Alley, fossils include predators resembling Acroncanthosaurus, small Deinonychus-like meat eaters, armored dinosaurs, Priconodon, duck bill-like Tentontosaur, and the Maryland state dinosaur, Astrodon johnstoni, a sauropod. One hundred million years ago, this area was a broad, flat delta with slow, curving rivers, and remains of dinosaurs, plants, and other animals were washed by floodwaters into oxbow lakes at sharp river bends, where they became trapped, were covered with sediment, and slowly fossilized. The fossils in the Muirkirk Deposit area come from these ancient oxbow lakes.
