Maryland's Geologic Features
Marylands Dinosaurs
contact: Dale Shelton (dshelton@mgs.md.gov)
Dinosaurs inhabited Maryland through much of their 160 million-year history. While dinosaurs were not as abundant or diverse in this area as other regions in the U.S., the Maryland population included a interesting range of species. At least twelve species of "terrible lizards" roamed the ancient Maryland landscape from the Late Triassic (228 million years ago) to the Late Cretaceous (70 mya). Maryland's climate and topography during this 158 million year period varied widely, from a tropical, volcanic lowland to a shallow, warm, sea teaming with life.
These conditions were perfect for the deposition and preservation of animal remains which would eventually become fossils. The bones, shells and other decay-resistant body parts of land and sea creatures, and even plants, were rapidly buried in alluvial sediments that were washed into these low-lying areas. If the remains were not destroyed by scavengers, bacteria or erosion, they eventually became fossilized. The sediments which surrounded these remains eventually turned to rock through the process of lithification. The animal remains within the sediments became petrified as the sediments turned to rock.. While not all fossils are petrified, dinosaurs fossils in Maryland are. These fossils have remained in place for millions of year until erosion, or humans, uncover them.
Dr. Christopher Johnston was the first to record dinosaur fossils in Maryland. The fossils, reported in 1859, consisted of teeth recovered from a Bladensburg iron mine. See Astrodon johnstoni: the Maryland State Dinosaur for more information on this species. Since that first report of dinosaur fossils, hundreds of bones, teeth, footprints and other remains have been found in Maryland, mostly by amateur paleontologists and bone hunters.
Dinosaur fossils are found in rocks in central Maryland. These rocks are from the Mesozoic era, between the Triassic and Cretaceous periods. Most of the specimens are found in the Arundel Clay (Lower Cretaceous), the Severn and Mt. Laurel Formations (Upper Cretaceous), and the Gettysburg Shale (Upper Triassic). Rocks from the Jurassic period are either not exposed or missing in Maryland.
For more information on Maryland dinosaurs, use the following links:
