Lizard-hipped vs Bird-hipped Dinosaurs

Dinosaurs are often categorized as lizard-hipped (Saurischians) or bird-hipped (Ornithiscians). Sauros is Greek for Lizard and Ornith from Greek meaning bird. Interestingly, birds are thought to be descendants of lizard hipped dinosaurs, rather than bird hipped dinosaurs. The difference between these two types of dinosaurs is in the pubis bone, a part of the hip bone. The pubis in Saurischians points forward, while the pubis in Ornithiscians points backwards. Interestingly, birds seemed to have descended from the Saurischians, despite having a hip structure more similar to the Ornithiscians. Below, the picture depicts the two hip structures between Saurischians and Ornithscians. “A” points to the lizard-hipped dinosaur and “B” points to the bird-hipped dinosaur. “C” corresponds with “A” and “D” corresponds with “B.” The pubis bone is depicted in orange and easily shows the difference in the directions that the pubis bone is facing in the two different type of dinosaurs. Some notable lizard hipped dinosaurs include T-Rex, Apatosaurus, and Allosaurus. On the other hand, examples of bird hipped dinosaurs include Iguanadon, Triceratops, and Stegosaurus.


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