Capitalsaurus

Since I was down in Washington D.C. the other day, this article caught my eye - “Capitalsaurus,” A D.C. Dinosaur at Smithsonian.com. 

Now I know there are dinosaur fossils and trackways in the East in places like the Connecticut Valley in Connecticut and Massachusetts and the Newark Rift in New Jersey.  There are no dinosaur fossils in New York, but there is a famous set of therapod tracks excavated from Rockland County (the northern end of the Newark Rift) which now resides in the lobby of the New York State Museum in Albany.  Pennsylvania likewise has trackways, but no fossils thus far from the Gettysburg Rift.

These tracks and fossils are from Triassic-aged rift basins on the East coast (specifically those labeled 14-18 in the image at left).

The Triassic Period (around 200-250 million years ago) was the time the supercontinent of Pangaea began rifting apart.  Prior to this, the continent of Africa was connected to eastern North America.

The rift basins, shown in red at left, are essentially fossil "stretch marks" in the crust.  Further to the east, the crust broke, seafloor crust formed from ascending basaltic magma, and eventually opened up into the Atlantic Ocean as Africa drifted away.

 The figure at right shows how Pangaea rifted apart, formed an ocean basin as the two continents drifted away from each other, and left behind a rift basin (to the left of the ocean).

Since these rift basins are places where sediment accumulates, they are areas where fossils can be preserved and the Triassic Period was the initial time of the dinosaurs (which arose, lived, and died in the Mesozoic Era - a time consisting of the Triassic, Jurassic, and Cretaceous Periods).

Anyway, that's why we have some dinosaur trackways and fossils here in the eastern part of the U.S.

What I had not known, was that a dinosaur was once discovered in the heart of Washington, D.C.  It's not from a Triassic rift basin, but from significantly younger 100 million year old Cretaceous sediments formed when the area was swampy lowlands.

This dinosaur, informally dubbed Capitalsaurus, was discovered in 1898 when sewer workers were excavating at First and F Streets SE (see map) - the corner is now called Capitalsaurus Court.  What was found are a few vertebrae and bone fragments of a therapod (two-legged, meat-eating dinosaur).  The Smithsonian article, linked above, discusses some of the confusion about its correct classification.  Capitalsaurus is an informal name, not a scientific one, since it was not officially described in a peer-reviewed journal.  The District of Columbia, in the Official Dinosaur Designation Act of 1998, made Capitalsaurus the official dinosaur of D.C. (January 28 is Capitalsaurus Day).

This dinosaur is also supposedly described in the book Dinosaurs of the East Coast  by David Weishampel and Luther Young (The Johns Hopkins University Press , 1998) which is now on my "to read" list.

I should learn more about dinosaurs here in the east - I'm sure there are many interesting things about them I'm unaware of at present.

Below is an artist's conception of Capitalsaurus.  Take it with a big grain of salt given the fact that it's known from only a few vertebrae!