[2][3][4] It lived in what is now the eastern United States during the Early Cretaceous period, and fossils have been found in the Arundel Formation, which has been dated through palynomorphs to the Albian about 112 to 110 million years ago.

They had been found in Latchford's open iron ore pit in the Arundel Formation at Swampoodle near Muirkirk in Prince George's County, Maryland.

Tyson let them be studied by the dentist Christopher Johnston, professor at the Baltimore Dental College, who cut one tooth in half and thereby discovered a characteristic star-formed cross-section.

However, he did not attach a specific epithet, so Joseph Leidy is credited with naming Astrodon johnstoni (the type species) in 1865, with as holotype specimen YPM 798.

[11] The Arundel Formation of Maryland has been dated through palynomorphs to the Albian stage of the Early Cretaceous period, about 112 million years ago.

Scientists have used biostratigraphic data and the fact that it shares several of the same genera as the Trinity Group of Texas, to surmise that this formation was laid down during the Albian stage of the Early Cretaceous Period, approximately 110 mya.

In what is now Maryland, Astrodon shared its paleoenvironment with dinosaurs such as coelurosaurians, the ankylosaurian Priconodon crassus, the nodosaurid Propanoplosaurus marylandicus,[15] a possible basal ceratopsian, and potentially the ornithopod Tenontosaurus.

[18] Trace fossils included theropod tracks known as Eubrontes and others assigned to the ichnogenus Pteraichinus belonging to a pterosaur, which demonstrate that these animals were present in abundance.

In prehistoric Oklahoma, Astrodon lived alongside other dinosaurs, such as the sauropod Sauroposeidon proteles, the dromaeosaurid Deinonychus antirrhopus and the carnosaur Acrocanthosaurus atokensis.

A life-sized Astrodon model (featuring a wound on its left rear leg) is displayed in the Terror of the South exhibit on the third floor of the North Carolina Museum of Natural Sciences.