Stegosauridae Temporal range: Middle Jurassic - Early Cretaceous, 170–100 Ma |
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Life restoration of Stegosaurus stenops | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Superorder: | Dinosauria |
Order: | †Ornithischia |
Suborder: | †Stegosauria |
Superfamily: | †Stegosauroidea |
Family: | †Stegosauridae Marsh, 1880 |
Type species | |
†Stegosaurus stenops Marsh, 1877 |
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Subgroups | |
Stegosauridae is a family of stegosauria, large thyreophorans. They lived longer than other Stegosaurs; while all Huayangosauridae and most of basal stegosaurs died out in Tithonian - Kimmeridgian, stegosauridae survived till Middle Cretaceous. They are usually characterized by triangular plates on their back. These plates were not as hard as the plates of Huayangosauridae, so perhaps they were used only for display.[1]
However there are several exemptions:Dacentrurus,[2] Lexovisaurus and Kentrosaurus have also spikes on their back.
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In the family tree of Thyreophora, Stegosauridae are right in the middle. Some paleontologists, propose a theory that they evolved from dinosaurs like Scelidosaurus.[3] They state that in early stegosaurs, like Huayangosaurus, plates are relatively small, while in Stegosaurus, the most advanced member of the family, they are very large. Perhaps bony plates of stegosaurs evolved from scutes of Scelidosaurus[4] or its relatives.
Scelidosaurus, etc.↓ *↓
Lexovisaurus and other primitive stegosaurs↓ *Ankylosauria
Stegosaurids were usually large and powerful dinosaurs. Their front legs were shorter than their rear making them slow - moving dinosaurs. When Othniel Charles Marsh first found Stegosaurus, he portrayed him with very short front legs and neck. But new evidence says that they had relatively long these body parts.[3] New discoveries suggest that in them was present sexual dimorphism.[5]
In 2010 Miriam Reichel from Switzerland[6] using software "ZBrush" created two Stegosaurus teeth digital models: one was serrated, and another lacked serrations. He proved that Stegosaurus had rhamphotheca. Also he found that stegosaurs was capable of biting small branches.
He also suggested that the same data could be applied to other Stegosauridae.
Stegosaurids are usually divided into two main subfamilies: Dacentrurinae and Stegosaurinae.[7] Stegosaurinae are usually characterized by large sizes. The earliest stegosaur is thought to be Lexovisaurus[8] from Bathonian of England. There was found a massive femur of the juvenile Lexovisaurus.
This is a list of stegosaurian genera by classification and location:
Suborder Thyreophora
Infraorder Stegosauria
A cladogramm by Kenneth Carpenter.[11]
Stegosauridae └──┬─?Chungkingosaurus └──┬──Chialingosaurus └──┬──┬──Wuerhosaurus │ └──┬──Dacentrurus │ └──Hesperosaurus └──┬──Tuojiangosaurus └──┬──┬──Kentrosaurus │ └──Lexovisaurus[12] └──┬──Stegosaurus stenops └──S. ungulatus (=?S. armatus)
He states, that Wuerhosaurus and Hesperosaurus are more closely related to Tuojiangosaurus and Dacentrurus, than to Stegosaurus. However, Thomas Holtz thinks that Hypsirophus, Stegosaurus, Hesperosaurus and Wuerhosaurus form a subfamily-Stegosaurinae.[7]
Cladogramm by Holtz et al.
Stegosauridae └──┬──┬──Dacentrurinae │ └──┬──Dacentrurus │ └──Miragaia └──┬──Stegosaurinae └──┬──┬──Wuerhosaurus │ └──Hesperosaurus └──┬──Stegosaurus └──Hypsirophus
Most of primitive stegosaurids, such as Lexovisaurus, Kentrosaurus, and Tuojiangosaurus, are characterized by triangular plates running along their backs and reduced lateral osteoderms.[13] Some of them like Kentrosaurus, also had spines on second half of their back and postorbital horns.[14]
Today are known only 2 members of Dacentrurinae: Dacentrurus and Miragaia.[15] They usually have long back spines and necks.