Dinosaur Park

Park History

Although dinosaur discoveries are often associated with the western United States, significant fossils of dinosaurs and other prehistoric animals are also known from the east coast. In the 1800s and early 1900s, the Arundel clays in Prince George’s County were mined for siderite or iron ore. Iron furnaces located throughout the region melted down siderite to produce iron used in construction and manufacturing. In 1858, African American miners working in open pit mines were the first to discover dinosaur fossils in Maryland.

The group of advanced prehistoric reptiles known as dinosaurs was first recognized in 1842 by British anatomist Richard Owen based on very fragmentary fossils found in England. However, it was not until more complete dinosaur fossils were found in the United States, including in Prince George’s County, that scientists were able to reconstruct the true life appearance and diversity of these extinct animals.

Among the first scientists to explore the Muirkirk deposit in Prince George’s County was geologist Phillip Thomas Tyson. He brought some of the strange bones discovered in the iron mines to a meeting of the Maryland Academy of Sciences in 1859, where his colleagues identified them as dinosaurs. Famous 19th-century paleontologist Othneil Charles Marsh of Yale University was also interested in Maryland fossils. In the winter of 1887, he sent fossil collector John Bell Hatcher to search the iron mines. Hatcher recovered hundreds of fossils, including the remains of ancient turtles, crocodiles, and several dinosaur species. Fossil collecting at the Muirkirk deposit essentially stopped when the iron industry died out in the early twentieth century, but it was revived in the 1980s by paleontologists Peter Kranz and Tom Lipka.

Fossil discoveries continue to happen at Dinosaur Park today. Since October 2009, the Maryland National Capital Park and Planning Commission has protected the site from development and unrestricted collecting. Dinosaur Park serves as an outdoor laboratory where the public can work alongside paleontologists to help uncover the past. Hundreds of fossils discovered by visitors have been collected and cataloged to date, enhancing our knowledge about the ancient ecosystem that once existed here. Perhaps, you will make an important discovery on your next visit!

Dinosaur Park in Deep Time

Dinosaur Park isn’t the only place in Maryland where you can look for fossils. Our great state is also the home of the world-famous Calvert Cliffs, where legions of avocational and professional fossil hunters collect the shark teeth and shells found there. Not surprisingly, Dinosaur Park visitors often ask whether the two sites are related.

The Chesapeake Group rocks of the Calvert Cliffs and the Potomac Group rocks of Dinosaur Park are actually separated by 100 million years. The shark teeth commonly found at the Calvert Cliffs date from the Miocene epoch, around 15 to 20 million years ago. This is very old, to be sure – the entirety of human history could be repeated 2,000 times in the timespan between the Miocene and the present day. Nevertheless, Dinosaur Park fossils are much older. Dating to the early Cretaceous Period, our fossils are a mind-boggling 110 million years old.

The Earth and life upon it underwent numerous monumental changes between the Cretaceous and the Miocene. When dinosaurs roamed Maryland, eastern North America was sandwiched between a narrower, shallower version of the Atlantic Ocean and the Western Interior Seaway, a body of water that once split the continent in two. This contributed to a warmer, wetter climate than we know today, but it would not last. By the end of the Cretaceous 66 million years ago, North America had become cooler and drier, with more pronounced seasons. Meanwhile, the landscape was transformed by the proliferation of flowering plants, which make up more than 90% of all plant species today.

A mountain-sized asteroid struck the Gulf of Mexico 66 million years ago, wiping out the large dinosaurs and allowing mammals to take over as the dominant land animals. Aside from a hot spell 50 million years ago, the overall trend over the last 66 million years was toward a cooler climate (human industrial activity has reversed this trend in the last two centuries). At the start of the Miocene, a slight rise in sea level led to eastern Maryland being completely submerged under the Atlantic. This near-shore environment was home to sharks, whales, and sea cows, all of which are found at the Calvert Cliffs.

Anywhere we find fossils, we are looking at just one of an endless parade of ecosystems that have come and gone. Despite the drastic differences between Maryland’s Miocene and Early Cretaceous fossils, the past 110 million years is still but one tiny fraction of the 4.5 billion year age of the Earth. Deep time is almost unfathomably immense and takes place on a scale that we are not used to comprehending. Still, by comparing fossils of different ages, we gain valuable insight into our changing world. The study of past life gives us a long view of life on Earth and can help us predict how it might respond to today’s environmental changes.