a·pat·o·saur·us 
(ə-păt′ə-sôrəs) or a·pat·o·saur (ə-pătə-sôr′)
(ə-păt′ə-sôrəs) or a·pat·o·saur (ə-pătə-sôr′)n.
A very large herbivorous sauropod dinosaur of the genus Apatosaurus of the Jurassic Period, having a long neck and tail and a small head.
[New Latin Apatosaurus, unreal lizard, genus name : Greek apatē, untruth, lie + Greek sauros, lizard.]