Apatosaurus "Apatosaurus" may have been more solitary than other Morrison Formation dinosaurs. Fossils of the genus have only been found in the upper levels of the formation. Those of "Apatosaurus ajax" are known exclusively from the upper Brushy Basin Member, about 152–151 mya. "A.louisae" fossils are rare, known only from one site in the upper Brushy Basin Member; they date to the late Kimmeridgian stage, about 151mya. Additional "Apatosaurus" remains are known from similarly aged or slightly younger rocks, but they have not been identified as any particular species, and thus may instead belong to "Brontosaurus". The Morrison Formation records a
Dinosaur Footprints Reservation four distinct types of two-legged dinosaur, are present in the sandstone outcrops. Additional fossils that have been found at the site or nearby include invertebrate burrows, fish, and plants (including charcoalified logs and leaves). The parallel orientation of many of the dinosaur trackways was among the first lines of evidence used to support the novel theory that dinosaurs traveled in packs or groups. As the name implies, fossil footprints are this park's main attraction. They were formed during the Early Jurassic period (approximately 200 million years ago) when what is now the Connecticut River Valley was a subtropical region filled