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
Shishugou Formation dinosaur traps sporting a crest running from its nose to the back of its head. Its discovery was hailed by paleontologists as the earliest known remains of the tyrannosauroid clan that culminated with "Tyrannosaurus rex". Shishugou Formation dinosaur traps The Shishugou Formation dinosaur traps also known as death pits or death traps are found in the Shishugou Formation, located in the Junggar Basin within Xinjiang Province of northwestern China. They are a rich source of Jurassic Period dinosaur fossils, many of which were new species to palaeontology. The Junggar Basin is a large continental basin made up of fluviatile and lacustrine sediments