The bone bed discovered at Dinosaur Park in Laurel, Md., seen above Tuesday, is the first of its kind found in Maryland since 1887. (Minh Connors/The Washington Post)
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Despite its name, Dinosaur Park in Laurel, Md., doesn’t look as though it would be the scene of the most significant discovery of dinosaur fossils in Maryland in almost 140 years. Tucked behind a modern industrial office park in a D.C. suburb, the fenced-in two-acre site is a rugged but rather ordinary-looking plot. There’s nothing Jurassic-y about it at all.

But at a news conference at the Prince George’s County park Wednesday, officials and paleontologists announced the April discovery of the largest theropod fossil in eastern North America, a three-foot-long shin bone they hypothesize is from Acrocanthosaurus, a spiny, sharp-toothed carnivore from the Early Cretaceous period — about 38 feet long.

The discovery of additional dinosaur fossils soon followed, a trove of prehistory wrested from ironstone and clay. More than 100 fossils, estimated to be 115 million years old, have been found so far in a dinosaur bone bed along what had once been a river. A bone bed is the term paleontologists use to describe a concentration of bones of one or more species within a geologic layer.

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The finding “marks a fundamental, extraordinary milestone in the field of paleontology and opens a window into our ancient world and to the species that once roamed this land,” Peter A. Shapiro, chairman of the Maryland-National Capital Park and Planning Commission, said at a news conference.

Additional fossils found, according to the county, included a tooth from an Astrodon johnstoni (the state dinosaur of Maryland), which ranged from 50 to 60 feet long, stood 30 feet tall and could weigh up to 20 tons; a tail vertebra from a 60-to-70-foot-long plant-eating sauropod; and a thigh bone of a small theropod, a meat-eating dinosaur the size of a chicken and a distant relative to Tyrannosaurus rex.

JP Hodnett, paleontologist with the Maryland-National Capital Park and Planning Commission and Prince George’s County, recalled his reaction when he realized the scale of the discovery at the park.

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“It was an expletive,” he said, laughing as he stood on a rocky hillside next to the theropod fossil. “No, it was very much like, ‘Oh, man, this is going to be huge.’ It literally is huge, not only in terms of the size of the animals that we’re dealing with but the significance of the find.”

Hodnett says there is great enthusiasm about the find from paleontologists across the country, particularly those in the western United States who are working with dinosaur remains of a similar age. “For us to find something that helps connect pieces is super exciting for them, especially because with some of the dinosaurs we are finding they are relatives to things that are found out West.”

Though the fossils were discovered in April, the process of finding them began almost a decade ago when a piece of heavy equipment accidentally broke off a rock face, exposing the fossil of a large dinosaur bone embedded in the stone. At the time, Hodnett said, the decision was made to let erosion take its course and see if more of the bone would be revealed. In 2018, Hodnett and his team began making plans to extract the bone from the rock, but those plans were eventually upended by the pandemic.

It wasn’t until 2021, as the team was digging around the back of the stone, that it began finding other dinosaur fossils. “That made us go, ‘Wait a minute — there’s something special going on here,’” Hodnett said.

Maryland’s first dinosaur bone bed was discovered in 1887, but there have not been any found since until this one.

Matthew Carrano, a paleontologist with the Smithsonian Institution, called the find “the most significant collection of dinosaur bones discovered along the Eastern Seaboard in the last hundred years.” Dinosaur fossils, Carrano said in a statement, “are exceptionally rare in the eastern US, and among these only Maryland has produced dinosaurs from the Early Cretaceous Period. Typically, only one or two bones are found at a time, so this new discovery of a bonebed of fossils is extremely important.”

Fossils are regularly found at Dinosaur Park, a county park open to the public on the first and third Saturdays of each month. It was created to encourage children and ordinary citizens to participate in digs, scour the ground and rocky outcropping for bones and be paleontologists for a day. But typically the finds are of small teeth or bones or of ancient vegetation, such as carbonized wood and seeds.

The larger and more varied new discoveries can provide a window for further research, paleontologists say.

“Our knowledge of the dinosaurs in the eastern part of North America has been lacking compared to what we know about in the West,” said Thomas Holtz, a dinosaur paleontologist at the University of Maryland. “But this site is helping to change that because finally we’re beginning to get multiple bones, some of whom represent probably the same individual. That would give us a lot more information than we have had in the past.”

Holtz said he had been coming to the location where the fossils were found for decades and was thrilled when he first learned of the recent find. Earlier this year, he brought his students over to work on the site rather than in a lab.

And the recent discoveries may only be the tip of the iceberg. Holtz said that while there are no guarantees that more bones will be found, he is hopeful that as the digging goes deeper into the hillside, more will emerge.

“We can’t say exactly what’s going to be there,” he said. “That’s part of the exploratory aspect of paleontology, because you don’t know what you’re going to find. But chances are looking really good that there are more finds to come.”

Indeed. Just a day before the news conference, the paleontologists at the site discovered an astrodon claw.