Astrodon johnstoni officially became the State dinosaur on October 1, 1998. It lived during the early Cretaceous period, between 130 million and 95 million years ago, and was the first identified dinosaur in Maryland. It was one of the earliest dinosaur finds in the United States and the first sauropod described in North America. It is not always easy to tell the skeleton of a juvenile reptile from an adult. For a time, this led to confusion about the true size of Astrodon . Today, however, there is agreement that Astrodon johnstoni did grow to a length of 60 feet or more.

Teeth from this dinosaur were first discovered in Muirkirk, Maryland (Prince George's County) in 1858. The largest dinosaur bone ever found in Maryland was the leg bone of an Astrodon johnstoni, discovered in 1991 in a quarry in Muirkirk.

Tooth of Astrodon johnstoni

Astrodon was definitely vegetarian, but as with all dinosaurs it is difficult to be specific about the exact diet. It probably browsed conifers and low-growing plants. It probably was a forest dweller. Although its bones have been recovered from river deposits, if current ideas are correct, it did not spend its time in the water.

[Information & drawings courtesy of the Maryland Geological Survey]