Therocephalia
| Therocephalia | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Middle Perm to Middle Triassic | ||||||||||||
| 268 to 237 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Therocephalia | ||||||||||||
| Broom , 1905 |
The Therocephalia are an extinct group of terrestrial vertebrates from the group of Therapsiden ("mammal-like reptiles"). They first appeared in South Africa's fossil deposits from the Middle Permian . They were most rich in shape in Upper Perm, from which there are finds from southern Africa, Russia and China. They became rarer in the Triassic . There are finds from the Lower and Middle Triassic of the Antarctic.
The Therocephalia were large, mainly predatory carnivores or small insectivores. Some sub-Triassic forms, such as Bauria from South Africa, were herbivorous .
features
Therocephalic skulls were relatively large, massive, and long, but relatively low. The muzzle was broad, with large canines and simple, conical molars, which could also be missing.
The jaw muscles reached over the skull and left only a narrow sagittal ridge formed by the parietal bones between the two upward-facing windows of the skull . This is the main difference from the skulls of the Gorgonopids . Some forms of therocephalia had a fully developed secondary palate, a feature they share with the cynodonts but, as there are differences in detail, evolved independently of them. The skull window and orbit could flow together. The cheekbone was never wide.
The lumbar vertebrae had small, thin ribs. The iliac bone had finger-like extensions at its rear end. Her limbs were long. Some forms had mammalian body proportions and a severely degenerated tail. The phalangeal formula was 2.3.3.3.3 and thus corresponds to that of mammals.
Systematics
External system
The family relationships are illustrated by the following cladogram:
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Internal system
Kuhn gives seven families and 55 genera for Therocephalia and 9 more families and 45 genera for Bauriamorphs. The early Therocephalia were originally classified as Pristerognathidae, but later recognized as a paraphyletic group and divided into the short-snouted Lycosuchidae and the long-snouted Scylacosauridae. Another former Therocephalic family, the Scaloposauridae, were composed mainly of juvenile specimens of different genera. All further developed therocephalic forms form the taxon Eutherocephalia, including the hyena-like Whaitsiidae and the herbivorous Baurioidea.
- Lycosuchidae
- Scylacosauridae
- Eutherocephalia
- Whaitsiidae
- Moschorhinidae (= Euchambersiidae)
- Baurioidea
literature
- Thomas S. Kemp: The Origin & Evolution of Mammals. Oxford University Press, Oxford 2005. ISBN 0198507615 .
- Michael J. Benton : Paleontology of the vertebrates. 2007, ISBN 3899370724
- Robert L. Carroll : Paleontology and Evolution of the Vertebrates , Thieme, Stuttgart (1993), ISBN 3-13774-401-6
- Oskar Kuhn : The mammal-like reptiles . A. Ziemsen Verlag, 2003, ISBN 3-89432-797-9
Web links
- Palæos Therocephalia
Individual evidence
- ↑ Bruce S. Rubidge & Christian A. Sidor: Evolutionary patterns among permo-triassic Therapsids. Annu. Rev. Ecol. Syst. 2001. 32: 449-80 Complete PDF