Styracosterna
| Ankylopollexia Temporal range: Late Jurassic–Late Cretaceous, 156–66 Ma |
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|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | †Ornithischia |
| Suborder: | †Ornithopoda |
| Clade: | †Dryomorpha |
| Clade: |
†Ankylopollexia Sereno, 1986 |
| Subgroups | |
Ankylopollexia is an extinct clade of dinosaurs within the order Ornithischia that lived from the Late Jurassic to the Late Cretaceous. It is considered a more derived clade of iguanodontians and contains the subgroup Styracosterna and Hadrosauriformes. The name stems from the Greek word, “ankylos”, meaning stiff, fused, and the Latin word, “pollex”, meaning thumb. Originally described in 1986 by Sereno, this most likely synapomorphic feature of a conical thumb spine defines the clade. Many ankylopollexians have not yet been placed in the phylogeny because of the lack of data on the specimens or simply just not analyzed yet. One of the most famous and most derived members of the Ankylopollexia clade is the Iguanodon.
First appearing around 156 million years ago, Ankylopollexia died out as a clade around 65.5 million years ago. Mostly found in China, Eastern and Western Europe, and the Western United States, ankyllopolexians not have been found in Africa or South America. Even though they grew to be quite large, comparable to some carnivorous dinosaurs, they were herbivorous iguanodontians. Most ankylopollexians were bipedal. However, most, also when grazing or moving slowly, would stand on all fours because of their shorter forelimbs.
As a member of the order Ornithischia, the ankylopollexia had a pubis bone that points down and towards the tail. The ischium pointed forward to support the abdomen and is now parallel to the pubis as well. Both the ischium and the pubis are parallel to the vertebral column. This pelvic structure is sturdier compared to other orders in Dinosauria. Also, ornithischians, in general, have a smaller anteorbital fenestra. Characteristic of ornithischians, many ankylopollexians probably had cheek-like structures to hold food in their mouths. They could have been muscular or non-muscular tissue.
As mentioned before, most ankylopollexians were bipedal. There are a few exceptions to this rule, including the Mantellisaurus. Because of its short forelimbs and short body, Mantellisaurus was bipedal when moving, but when standing or moving slowly, it used its forelimbs to balance itself.
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Wikipedia