Paleontologists divide the saurischian dinosaurs into two general groups: the sauropods and the carnivorous theropods (Theropoda). Both of these general groups contained numerous diverse species, which led to further subdivisions of these groups.

Like all classifications, there are differences from system to system, and there are continual debates and changes within each classification scheme. For example, in some classifications, the saurischians are divided into the theropods and the sauropodmorphs; the sauropodmorphs are further divided into the sauropods and prosauropods. But since the prosauropods died out early in the Jurassic period, other classifications concentrate mainly on the sauropods.

The general classification system used here is only one version: The sauropods in the Jurassic were subdivided into the diplodocids (Diplodocidae) and the brachiosaurids (Brachiosauridae); the camarasaurids (Camarasauridae) are either added as a subdivision of the brachiosaurs or are sometimes considered to be a separate group.

The theropods were subdivided into the ceratosaurs (Ceratosauria) and the tetanurans (Tetanurae); the tetanurans were further divided into the coelurosaurs (Coelurosauria) and carnosaurs (Carnosauria)—also known as the allosaurs (Allosauria). Some classification systems further divide the coelurosaurs into the ornithomimosaurs (Ornithomimids) and the maniraptorans (Maniraptora).