Maryland holds a significant place in North American dinosaur discoveries. Far from the vast fossil beds of the American West, this Mid-Atlantic state has yielded some of the continent’s earliest and most important dinosaur finds. Its ancient landscapes were home to diverse prehistoric creatures, leaving clues that shape our understanding of life millions of years ago.
Maryland’s Dinosaur Legacy
Maryland’s paleontological history dates back to some of the earliest dinosaur discoveries in North America. In 1858, in an open-pit iron mine near Muirkirk, two unusual teeth were unearthed by Philip Tyson, then Maryland’s State Agricultural Chemist. These teeth were given to Dr. Christopher Johnston, a local physician and dentist, who examined them microscopically and published his findings in 1859, naming the species Astrodon for its star-like pattern.
The scientific description of Astrodon johnstoni came in 1865 by Joseph Leidy, a prominent American paleontologist. This marked a significant moment, as Astrodon johnstoni became the first sauropod dinosaur named from North America. This discovery occurred almost simultaneously with Leidy’s work on Hadrosaurus foulkii from New Jersey, establishing Maryland as a foundational site in the emerging field of paleontology. The importance of Astrodon johnstoni was recognized in 1998 when it was officially designated Maryland’s State Dinosaur.
Notable Maryland Dinosaurs
Among the dinosaurs that roamed ancient Maryland, Astrodon johnstoni stands out as the most recognized. This large, long-necked sauropod could reach lengths of 50 to 60 feet and weigh several tons. Its name, meaning “star tooth,” refers to the internal structure of its teeth. While some paleontologists previously classified similar fossils under the name Pleurocoelus, Astrodon has precedence and is considered the same animal, likely a type of brachiosaurid.
Beyond this towering herbivore, evidence suggests the presence of other dinosaurs. The large predatory theropod Acrocanthosaurus, a relative of the tyrannosaurs, is known from teeth and incomplete skeletal remains. This carnivore was a major predator in its ecosystem. Additionally, armored dinosaurs like Priconodon have been identified. Priconodon was a nodosaurid, a type of ankylosaur, characterized by its bony plates embedded in its skin.
Small, agile theropods, known as ornithomimids or “bird-mimic” dinosaurs, also inhabited the region. These creatures, such as Coelurus gracilis, were fast-moving and possibly feathered, resembling modern ostriches. Fragments of ornithopod dinosaurs, including a partial tooth possibly belonging to Tenontosaurus, suggest medium-sized, bipedal plant-eaters. The discovery of Propanoplosaurus, a nodosaur hatchling, reveals that young dinosaurs were preserved in Maryland’s ancient sediments.
The Prehistoric Maryland Environment
During the Early Cretaceous Period, approximately 115 million years ago, Maryland’s landscape was very different from today. It was characterized by a broad, low-lying coastal plain traversed by slow-moving rivers and swampy areas. This environment was part of a deltaic floodplain, experiencing a semi-tropical climate.
The plant life of this ancient ecosystem included conifers like redwood and cypress trees, and ferns, cycads, ginkgoes, and horsetails. Early ancestors of broadleaf trees, such as magnolias and sycamores, also appeared. This lush vegetation provided ample food for herbivorous dinosaurs and supported diverse prehistoric life, including turtles, crocodiles, and various fish species. The Arundel Formation, a clay-rich rock unit, preserves evidence of this freshwater fluvial environment, where animal and plant remains were deposited and fossilized.
Discovering Maryland’s Dinosaurs
Most of Maryland’s dinosaur fossils originate from the Arundel Clay Formation, part of the Potomac Group. This clay-rich sediment, once economically important for its iron ore, has since become important for its paleontological finds. The earliest finds were often incidental during iron mining operations in the mid-19th century.
Fossils found in Maryland include remains like teeth, bones, and even footprints. The fragmented nature of many specimens presents challenges for paleontologists, as complete skeletons are rare. Despite this, the work of early researchers like Othniel Charles Marsh and John Bell Hatcher in the late 1800s, who systematically collected hundreds of bones and teeth, advanced understanding of Maryland’s ancient fauna. Today, locations like Dinosaur Park in Laurel, Maryland, preserve active fossil sites where ongoing research and public engagement reveal new insights into the state’s dinosaur past.