What did the brachiosaurs eat?

Brontosaurus is an invalid name for Apatosaurus Excelsus. Apatosaurus was an herbivore, or plant eater. Because paleontologists don't know how high Apatosaurus held its head, they don't know what plants it would have most likely eaten. Plants that coexisted with Apatosaurus include conifers, cycads, ginkgoes, ferns, and horsetails.