Prehistoric Animals


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herbivorous dinosaur

Herbivorous dinosaurs

The age of the dinosaurs was, for the most part, characterized by a hot and humid climate. Abundant vegetation may have nourished thousands of dinosaur species. The herbivorous dinosaurs were of very different sizes and shapes. Among the saurischians and herbivorous ornithischians, there were quadrupeds and bipeds. As far as we know, all ornithischians were herbivores.


There are two categories of herbivorous saurischians: prosauropods and sauropods.


Sellosaurus prosauropod

The archaic prosauropods were medium to large, with a long neck and long tail, a rather small head and a large body. They were all quadrupeds, although some probably stood on their hind legs to eat, to defend themselves or to parade.


Diplodocus sauropod

The sauropods, which probably descended from prosauropods, were large to very large. Some were the largest animals that ever existed on Earth. They are recognizable by their very long tail and neck, barrel-shaped body and tiny head. To ensure their survival, prosauropods and sauropods had to transform huge amounts of nutrient-poor food. They managed to do this by tearing off the leaves and slings, which they swallowed directly without chewing and then fragmented in their gigantic stomach under the effect of fermentation. Gastroliths have been found in many sauropod stomachs. These stones, which were crushed by the stomach muscles, helped crush the very hard fibers of the plants.


Despite their great diversity, ornithischians were all herbivores. Among them are thyreophorans, including stegosaurs and ankylosaurs, ornithopods which include iguanodontians and hadrosaurids as well as marginocephalians (ceratopsians and pachycephalosaurs).


Stegosaurus thyreophor

All thyreophorans wore some sort of bone armor on their backs. In stegosaurs, this armor was in the form of a double row of plates and bony pikes protruding upwards. In the ankylosaurs, the back was covered with a mosaic of plates that sometimes descended to the flanks or to the belly. These plates, especially those of the perimeter, were bristling with spikes here and there. The weight of this armor required the animal to stand on all fours, but some of the primitive thyreophorans like Scutellosaurus were probably able to stand on two legs for short periods.



Ornithopods ("bird feet") owe their name to their three-fingered feet reminiscent of those of birds. Their size varied from the very small Heterodontosaurus to the hadrosaurids, which sometimes measured more than 10 meters in length. They were characterized by a relatively large head, a moderately long neck and long hind limbs. They moved on all fours and stood on both hind legs when necessary. They often had "ossified tendons" along the back, on the rump and along the tail, which probably helped to maintain the equilibrium of the tail and rear of the animal by making them more rigid and helped control certain movements.



The marginocephalians were characterized by a bone outgrowth on the circumference of their heads. The pachycephalosaurs displayed a series of protuberances and bumps, while their cousins, the ceratopsians, acquired a bony collar which later spread to the shoulders. The pachycephalosaurs probably used their heads as rams to defend themselves or to parade. The ceratopsians, almost all quadrupeds, had a very large head amplified by a cervical collar, horns and spikes on the face.

Different food processing strategies

The herbivorous ornithischians processed food differently from the saurischians. Some, like thyreophorans, cut their food into tiny pieces inside their mouth with their little sharp teeth; they could not grind their food, as the marginocephalians and ornithopods would later do with their batteries of teeth that acted as millstones.