Saurischia
Established by Seeley in lectures presented in 1887 but officialy published in 1888 when he devided Owen\'s dinosauria into two groups based on the form of the pelvis, the braincase, the vertebrae and the armor. Ornithischa and Saurischia are sister taxa, stem groups of Dinosauria, so every member of the Dinosauria must belong to one of these two groups.