The Dinosaurs and Prehistoric Animals of Maryland

colorful dinosaur Ornithomimus Velox

Getty Images/james63

Considering how small it is, Maryland has an outsized geologic history: the fossils discovered in this state range all the way from the early Cambrian period to the end of the Cenozoic Era, a stretch of over 500 million years. Maryland is also somewhat unique in that its prehistory alternated between long stretches when it was submerged underwater and equally long stretches when its plains and forests were high and dry, allowing for the development of a wide range of terrestrial life, including dinosaurs. Read on to learn about the most important dinosaurs and prehistoric animals that once called Maryland home.

of 06



Wikimedia Commons/Dmitry Bogdanov

The official state dinosaur of Maryland, Astrodon was a 50-foot-long, 20-ton sauropod that may or may not have been the same dinosaur as Pleurocoelus (which, oddly enough, may itself have been the same dinosaur as Paluxysaurus, the official state dinosaur of Texas). Unfortunately, the importance of the poorly understood Astrodon is more historical than paleontological; two of its teeth were unearthed in Maryland in 1859, the first dinosaur fossils ever to be discovered in this state. 

of 06


Ankylosaur dinosaur, artwork
Example of an Ankylosaur dinosaur.


The recent discovery of Propanoplosaurus, in Maryland's Patuxent Formation, is important for two reasons. Not only is this the first undisputed nodosaur (a type of ankylosaur, or armored dinosaur) to be discovered on the eastern seaboard, but it's also the first-ever dinosaur hatchling to be identified from this region of the United States, measuring only about a foot from head to tail (it's unknown how big Propanoplosaurus would have been when fully grown).

of 06

Various Cretaceous Dinosaurs

Early Cretaceous life, artwork


Although Astrodon is Maryland's best-known dinosaur, this state has also yielded scattered fossils from the early and late Cretaceous period. The Potomac Group formation has yielded remnants of Dryptosaurus, Archaeornithomimus, and Coelurus, while the Severn Formation was populated by various unidentified hadrosaurs, or duck-billed dinosaurs, as well as a two-legged "bird mimic" theropod that may (or may not), have been a specimen of Ornithomimus.

of 06


Cetotherium, a prehistoric whale of Maryland
Wikimedia Commons

For all intents and purposes, Cetotherium (the "whale beast") can be considered a smaller, sleeker version of the modern gray whale, about one-third the length of its famous descendant and only a fraction of its weight. The odd thing about Maryland's Cetotherium specimen (which dates to about five million years ago, during the Pliocene epoch) is that the fossils of this prehistoric whale are much more common along the shores of the Pacific Rim (including California) than the Atlantic coast.

of 06

Various Megafauna Mammals

Giant beaver (Castoroides ohioensis) skeleton

Wikimedia Commons/C. Horwitz

Like other states in the union, Maryland was populated by a wide variety of mammal during the late Pleistocene epoch, on the cusp of the modern era — but these animals tended to be fairly petite, far from the rampaging Mammoths and Mastodons discovered to Maryland's south and west. A limestone deposit in the Allegany Hills preserves the evidence of prehistoric otters, porcupines, squirrels and tapirs, among other shaggy beasts, which lived in Maryland's woodlands thousands of years ago.

of 06



Getty Images/Colin Keates

The official state fossil of Maryland, Ecphora was a large, predatory sea snail of the Miocene epoch. If the phrase "predatory snail" strikes you as funny, don't laugh: Ecphora was equipped with a long, toothed "radula" that it used to bore into the shells of other snails and mollusks and suck out the tasty guts nestled inside. Maryland has also yielded numerous fossils of the small invertebrates of the Paleozoic Era, before life invaded dry land, including brachiopods and bryozoans.

mla apa chicago
Your Citation
Strauss, Bob. "The Dinosaurs and Prehistoric Animals of Maryland." ThoughtCo, Aug. 29, 2020, Strauss, Bob. (2020, August 29). The Dinosaurs and Prehistoric Animals of Maryland. Retrieved from Strauss, Bob. "The Dinosaurs and Prehistoric Animals of Maryland." ThoughtCo. (accessed June 6, 2023).