It was a huge, meat-eating dinosaur from the late Jurassic period , about 156 million to 135 million years ago. It was a theropod that lived in what is now the western United States. Apatosaurus was a huge sauropod from the Jurassic period . An apomorphy is a new genetic characteristic to a clade .
Feathers are an apomorphy for birds.
Fossil footprints have been found in Canada. It had a long neck, a long powerful tail, a small head, and a bulky body. It was similar to Camarasaurus . A partial fossil was found in Spain. It was named by Sanz, Buscalioni, Casanovi and Santafe in 1987.