1. Apatosaurus (ăp'ətəsôr`əs, ā'păt'ə–), [Gr.,=deceptive lizard], quadruped saurischian dinosaur dinosaur [Gr., = terrible lizard], extinct land reptile of the Mesozoic era

2. In sauropsid species, the Cervical vertebrae bear Cervical ribs.In lizards and saurischian dinosaurs, the Cervical ribs are large; in birds, they are small