Academic identifying characteristics of ceratopsid dinosaurs: all plant-eating four-legged dinosaurs, which are characterized by horns of different sizes developed in different parts of the head.
Early horned dragons, Psittacosaurus
Since the parietal and scales extend backwards to form a folded neck shield, making the skull large, accounting for almost 1/3 of the length of the whole body, this structure also affects the changes in other parts of the skull: the temporal bone degenerates, the nose expands, the snout elongates into a pointed beak, the anterior forehole is reduced, the cheekbones are enlarged, and there are teeth in the primitive stage of the anterior maxilla. The inner nostrils are separated by a long hoe bone rod, and its posterior edge is the palatal bone, and the palatal foramen disappears. The beak-like process of the lower jaw develops, and the anti-articular process is small. Each dentition has 15 to 40 teeth. The crown has a serrated structure at the edge. There are longitudinal ridges on the inside of the upper teeth and on the outside of the lower teeth.
The spine is double-flat, with 9 cervical vertebrae, 12 dorsal vertebrae, and up to 11 recommended vertebrae. The distal end of the slender scapula is enlarged, the radial ulna is 2/3 of the humerus, the ulnar process is prominent, the forefoot is short and wide, and the development is normal. The intestinal bone is low and long, its bone process is larger, the posterior pubic process is degenerated, the distal ischial is bent, the hind limbs are longer than the forelimbs, the femur is thick, the V-toe of the hind foot is degenerated, and the terminal hoof-like claws are bent.
Horned dragons appeared later, evolved from ornithopods, their original type is cryptorhythosaurs found in Asia, and the progressive genus is the most found in North America, which is the standard fossil of the Late Cretaceous.
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