Britannica
Sources used in this answer
How were saurischian dinosaurs different from ornithischian dinosaurs?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Jurassic Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Jurassic Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The primary distinction between saurischian ("lizard-hipped") and ornithischian ("bird-hipped") dinosaurs lies in the configuration of their pelvis.12
- Pelvic Structure: In saurischians, the pubic bone points down and forward, a condition similar to that of typical reptiles. In contrast, ornithischians possess a pubic bone with a large portion that points down and toward the tail, a configuration that superficially resembles the pelvis of birds.3142
- Dietary Habits: All known ornithischians were herbivorous, often featuring specialized adaptations such as a toothless horny beak for nipping vegetation and powerful cheek teeth for grinding. Saurischians include both carnivorous theropods and herbivorous sauropodomorphs.435
- Anatomical Features: Ornithischians are further distinguished by the presence of a unique bone at the tip of the lower jaw called the predentary. Saurischians share a distinct suite of features, including elongated posterior neck vertebrae and a specific hand structure where the second finger is the longest.45
While their names suggest a relationship to birds, birds actually evolved from theropod saurischian dinosaurs, not from the "bird-hipped" ornithischians.34