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Image of Capitalsaurus Court street sign with autumn leaves in the background
Capitalsaurus Court street sign with autumn leaves in the background. Image by the author.

A Dinosaur on Capitol Hill?

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This post was written by Claire D’Mura, Reference and Research Specialist in the Library’s Science Section.

We think of Washington, D.C. as a place rich with history. The Library of Congress itself stands as a historic institution with a purpose to collect, preserve and share its archive of historic items, many of which are very old. But, like so many things, “old” is a relative notion. The Library’s ever famous Gutenberg Bible is from 1455, but the oldest items in the library are even older than that. The oldest items are cuneiform tablets, dating from as early as 2144 B.C. It’s hard enough for our minds to grasp what life was like 4,000 years ago, when those tablets were created. Or that modern humans have only existed for around 200,000 years. What about further back than that? Say 110 million years ago? That history has remained elusive, buried deep under the marble monuments of the National Mall.

Recently, something unexpected made me consider this prehistoric story. Last autumn, I was taking a walk, taking in the last of the lovely fall leaves. I saw a street, glowing yellow with ginkgo leaves, which looked like it might offer an enticing stroll. I almost turned, but decided I’d check out the park straight ahead, instead. Just a second later, something more unusual than fall leaves caught my eye; I was heading on to “Capitalsaurus Court.” Surely this wasn’t a real designation, right? Turns out, it is an officially designated place and commemorates the site where the first fossilized dinosaur bones found in D.C. were unearthed. The city even celebrated “Capitalsaurus Day” on January 28th, 2001. Since it’s almost January 28th, it seems like a good time to learn more about Capitalsaurus.

In January of 1898, crews working on upgrading the sewer system along F St. between 1st and 2nd St. SE (just a few blocks south of the Capitol) discovered a rock that clearly wasn’t just a rock. It was handed over to the Smithsonian, where it was identified as a vertebra from an unknown creature. There were other bone fragments found, but the vertebra was the most well-formed, albeit in rough shape. With not much to go on, the specimen was given the identifier USNM 3049, and filed away.

The specimen didn’t see the light of day again until paleontologist Richard Swann Lull examined it as part of the 1911 Maryland Geological Survey. The specimen was found in what is known as the Arundel formation, a 60 mile band of clay deposits extending from Cecil County, Maryland, southwest to Washington, D.C. Lull thought the vertebra seemed most similar to specimens of the Creosaurus atrox, a theropod, similar to a Tyrannosaurus, but a bit smaller. He designated it as a new species, Creosaurus potens. In his report, he noted, “this vertebra represents by far the largest carnivore known from the Arundel formation.” And that was that, until Charles Gilmore took an interest in the specimen, nearly a decade later.

Image of Charles Gilmore, Curator of Vertebrate Paleontology at the Smithsonian Institution, standing behind diplodochus vertebra.
Professor Charles Gilmore, Curator of Vertebrate Paleontology at the Smithsonian Institution, standing behind Diplodochus vertebra. Library of Congress Prints and Photographs Division.

University of Wyoming professor Charles Whitney Gilmore joined the Smithsonian in 1903, first as a preparator and, in 1924, becoming the Curator of Vertebrate Paleontology. In 1920, Gilmore called into question the entire Creosaurus genus and argued that the species in the genus should all be classified as Allosaurus. But, he also noted that the USNM 3049 vertebra wasn’t an Allosaurus. Instead, he classified it as Dryptosaurus, another theropod like the Allosaurus and Tyrannosaurus, but with the distinguishing characteristic of longer arms and oversized claws. Gilmore specifically noted the specimen as Dryptosaurus ? potens, with the question mark included due to the high degree of uncertainty.

The fossil was again abandoned, until the 1980s, when Dr. Peter Michael Kranz came to Washington, D.C. Much had changed in paleontology since the time Gilmore had hesitantly classified USNM 3049 as a Dryptosaurus. Kranz assessed that the Dryptosaurus designation also wasn’t a fit, and instead suggested USNM 3049 was a new dinosaur species. In an article in the April 1990 issue of Washingtonian Magazine, Kranz coined the name “Capitalsaurus.” That this naming was initially announced in the Washingtonian, as opposed to a scientific journal, spoke to Kranz’s passion for bringing science education to the public.

In 1998, Kranz and a troop of 5th and 6th graders from Smothers Elementary School lobbied the D.C. Council to make “Capitalsaurus” the District dinosaur (“Making No Bones About Their Goal,” Washington Post. April 29, 1998). What followed was a series of legislative actions, which solidified the Capitalsaurus’ place in D.C. lore. The Official Dinosaur Act of 1998 was brought to a vote and passed, making the “Capitalsaurus” the official dinosaur of the District of Columbia on September 30, 1998. The following year, the site of the discovery, the 100 block of F St. SE, was designated “Capitalsaurus Court.” In 2001, Mayor Anthony Williams declared January 28th, 2001, the 103rd anniversary of the original discovery, as “Capitalsaurus Day.”

The name “Capitalsaurus” has never been formally accepted by paleontologists, and remains an unofficial term, scientifically speaking. To this date, only two dinosaur fossils have been discovered in the city of Washington, D.C., with the other being a thighbone from an Astrodon (a long-necked, plant-eating sauropod), discovered during construction of a water filtration plant in Northwest D.C. The two dinosaurs of D.C. are from the Early Cretaceous period. They are the only Early Cretaceous dinosaurs found east of the Mississippi and the only dinosaurs found in the Arundel Formation, which dates from that time.

Why are there so few dino fossils discovered in this area? These dinosaurs surely weren’t wayward souls wandering alone through the terrain of the Cretaceous. Dinosaur fossils on the East Coast are found much more sporadically than in the American West, where many of the celebrity dinosaurs, like Tyrannosaurus, Triceratops and Apatosaurus, come from.

Historical geology map of the Washington, D.C. area, including parts of Virginia and Maryland
Historical geology sheet, Maryland–District of Columbia–Virginia, Washington quadrangle. Library of Congress Geography and Map Division.

The reason for the relative scarcity of fossils found on the East Coast is due to the environmental conditions existing between the time of the dinosaur’s death and the time of its discovery. For fossils to form, the environment must be perfect…for a very, very long time. For the first step of fossilization, a creature’s remains must land in a place where they are quickly covered up and deprived of oxygen, significantly slowing decomposition. This most often happens in places with large and frequent deposits of sediment, such as lakes, rivers, and floodplains. During the Early Cretaceous period, the environment of the Capital area was similar to that of the Mississippi Delta today, facilitating the efficient burial of remains. Then, over millions of years, minerals in the surrounding mud seep into the remains, gradually replacing organic material until it is entirely stone.

Once a creature is successfully buried and preserved as a fossil, for us to learn about it, it must also find its way to the surface. In the Western United States, exposure to wind, runoff from rain, and the lack of thick vegetation has led to large areas where fossils have re-emerged and humans can (sometimes literally) stumble upon them. On the eastern side of the country, however, lush vegetation does not allow for this erosion, keeping the lower layers of the Earth buried. As a result, dinosaur fossils typically don’t find their way to the surface and have mostly been found as a byproduct of mining and construction projects.

According to David Weishampel and Luther Young, authors of Dinosaurs of the East Coast, “In the two hundred years since the search began, only a handful of partial dinosaur skeletons have been found in the East, and not a trace of these animals is known from the last two-thirds of the Jurassic Period, some 180 to 140 million years ago (Ma). West Virginia, Rhode Island, Maine, Vermont, and New Hampshire have yielded no dinosaur fossils at all” (Weishampel & Young, p.2). There are fossils of other periods, particularly of marine life, but the dinosaur record is notably sparse. This gap in the middle and late Jurassic period indicates that conditions were either not conducive to fossil formation, or that something afterwards destroyed what had been forming.

Despite the scarcity of and inherent difficulties in finding East Coast dinosaur fossils, the search continues. Weishampel noted in his 2006 paper “Another Look at the Dinosaurs of the East Coast of North America,” that the rate of paleontological discoveries has increased globally since 1980, including in the Eastern United States, though discoveries there remain scant and specimens incomplete.

Capitalsaurus may not be a “real”, formally named dinosaur, but its presence reminds us that this place hasn’t always been the concrete jungle it is today. This mysterious dinosaur carries a measure of levity and curiosity and invites us into the very real history and science of paleontology.

If reading this has sparked your curiosity about dinosaurs, check out our guide, Dinosaurs and Paleontology: A Resource Guide.

Learn more about the dinosaurs of the East Coast with the following books and articles:

Read about an early illustration of a dinosaur from a 19th century children’s book: Peter Parley and his Pictures: the First Illustration of Dinosaurs for American Children.

Read about Federal Archaeological laws since 1906 from the Law Library of Congress.

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  1. This was an enjoyable read! I remember many times seeing and speaking with Dr. Kranz when he came to the Science Reading Room at the Library.

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