STEGOSAURIA
CLASSIFICATION
Animalia: Vertebrata: Tetrapoda: Sauropsida: Archosauromorpha:
Ornithodira: Dinosauria: Ornithischia: Thyreophora
CLADOGRAM:
—Stegosauria “Stegosaurus‘ taxon” == {Stegosaurus + Ankylosaurus}
| INCERTAE SEDIS:
| unnamed form (partial arm bones) — Aalenian? — Scotland
| Changtusaurus
| Craterosaurus
| Gigantspinosaurus
| “Katsuyamakensaurus”
| Regnosaurus
|?-Hesperosaurus
|–Huayangosauridae == {Huayangosaurus > Stegosaurus}
| `–Huayangosaurus
`–Stegosauridae == {Stegosaurus > Huayangosaurus}
| INCERTAE SEDIS:
| unnamed form — late Late Jurassic — U.S.A.
| indeterminate material — Hauterivian — Argentina
| Monkonosaurus
| Yingshanosaurus
|–Dacentrurus
`–+–Kentrosaurus
`–+–Chialingosaurus
|–Chungkingosaurus
`–Stegosaurinae
| INCERTAE SEDIS:
| cf. Lexovisaurus (fragmentary skeleton) — middle Callovian — Germany
|–Lexovisaurus
|?-Paranthodon
|–Tuojiangosaurus
`–Stegosaurini
|–Stegosaurus
`–Wuerhosaurus
ESSAY
| “ROOFED REPTILES”:These primarily Jurassic herbivores had two rows of plates and/or spikes going down the back. Although the spikes, which were usually found on the tail, were certainly used for defense, the exact purpose of the plates is unknown. They could not have made very effective armor, since they left the sides completely exposed. Perhaps they performed a similar function to the sails of Spinosaurus, Ouranosaurus, and Rebbachisaurus, whatever that function was (possibly heat regulation, sexual display, or both). T HE END:Stegosaurs did not last to the end of the Mesozoic Era, but died out during the Cretaceous Period, possibly due to competition from other ornithischian herbivores or from a change in flora (the transition from gymnosperms to angiosperms) which they could not adapt to. One creature which was thought to be a Late Cretaceous stegosaur (Dravidosaurus) has turned out to be a plesiosaur! (This is not the only time marine vertebrate remains have been mistaken for stegosaur remains — the plates of Lexovisaurus durobrivensis turned out to be gill rakers from a fish!) |
