Astrodon was a genus of dinosaur from the Early Cretaceous Period (112 million years ago) that lived in what is now the eastern United States. It was related to the more widely-known Brachiosaurus. Two teeth of Astrodon were found in the Arundel Formation near Bladensburg, Maryland in 1859 by Christopher Johnston. The naming of the Astrodon, however, was not done until 1865 when Joseph Leidy gave it the type species name A. johnstoni. Astrodon would have been the second identified dinosaur in the United States if Johnston would have attached a scientific epithet to the discovery.

Adult Astrodons are estimated to have been more than 30 feet high and 60 feet in length. Most of the remains of Astrodon are from juvenile specimens. O.C. Marsh discovered bones in 1888 at the same formation that he named Pleurocoebus nanus and P. altus. However, in 1921 Charles W. Gilmore argued that the name Astrodon had priority and the bones were thus renamed to their appropriate genus. Today, Astrodon is sometimes considered a synonym of Pleurocoebus, but there is debate on which is the actual correct name for this genus. The two species named by Marsh, P. nanus and P. altus, are commonly described as different growth stages of A. johnstoni.

In 1998, A. johnstoni was named the state dinosaur of Maryland. Astrodon has also been used in the novel “˜Raptor Red’ by Robert T. Bakker, as the prey of Utahraptor.

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