Stegosauria
| Stegosaurians Temporal range: Middle Jurassic - Early Cretaceous, 165–125 Ma |
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| Mounted skeleton of Stegosaurus stenops, Natural History Museum, London | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | †Ornithischia |
| Clade: | †Eurypoda |
| Suborder: |
†Stegosauria Marsh, 1880 |
| Subgroups | |
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Craterosaurus? |
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Craterosaurus?
Jiangjunosaurus
Regnosaurus?
Paranthodon
Amargastegos
Huayangosauridae
Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europe and China, though one species (Kentrosaurus aethiopicus) is known to have lived in Africa. Their geographical origins are unclear; the earliest unequivocal stegosaurian, Huayangosaurus taibaii, lived in China.
Stegosaurians were armored dinosaurs (thyreophorans). Originally, they did not differ much from more primitive members of that group, being small, low-slung, running animals protected by armored scutes. An early evolutionary innovation was the development of tail spikes, or "thagomizers", as defensive weapons. Later species, belonging to a subgroup called the Stegosauridae, became larger, and developed long hindlimbs that no longer allowed them to run. This increased the importance of active defence by the thagomizer, which could ward off even large predators because the tail was in a higher position, pointing horizontally to the rear from the broad pelvis. Stegosaurids had complex arrays of spikes and plates running along their backs, hips and tails. Their necks became longer and their small heads became narrow, able to selectively bite off the best parts of cycads with their beaks. When these plant types declined in diversity, so did the stegosaurians, which became extinct during the first half of the Cretaceous period.
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Wikipedia