Theriodontia
| Theriodontia | ||||||||||||
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Three members of the Theriodontia: |
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| Temporal occurrence | ||||||||||||
| Middle Perm to Upper Triassic | ||||||||||||
| 270.6 to 199.6 million years | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Theriodontia | ||||||||||||
| Owen , 1876 |
The Theriodontia ("animal teeth") are land vertebrates from the group of therapsids ("mammal-like reptiles"). They include three more highly developed, mainly carnivorous, groups. From one of them, the cynodontia , the mammals emerged.
features
Theriodonts were rather small to medium-sized and somewhat resembled the later predatory mammals. Primitive forms were more likely to be carnivores and insectivores, some more advanced forms also lived herbivores . The teeth are predatory and already differentiated, front incisors, one or more canines, rear molars, in the primitive forms pointed, in the higher with bumpy chewing surfaces. Palatine teeth were rarely present. The skull was flat, the mouth wide, the base of the skull straight, without a bend as in the Anomodontia . The top of the muzzle was horizontal with the nostrils. The dorsal process of the premaxillary was shortened. The roof of the skull narrowed between the skull windows and is narrower there than the width between the orbits . Quadratum and quadratojugale are shortened and lay in a depression of the squamosum (scaly bone ). The lower jaw had a coronoid process and, in the newer forms, provided a longer lever arm and more space for the temporalis muscle . The mandibular joint was perpendicular to the axis of the base of the skull and was level with the occiput and the row of teeth. The lower jaw bones following the dental were reduced, the canines of the lower jaw in relation to those of the upper jaw longer than in previous taxa. The legs stood vertically under the body and allowed the animals to run quickly.
In this group, mammalian-like body proportions developed with a strongly receding tail and a higher metabolic rate with endothermia .
Systematics
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Theriodontia
- Gorgonopsia
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Eutheriodontia
- Therocephalia
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Cynodontia
- Mammals (mammalia)
literature
- 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, 1970, ISBN 3-89432-797-9
Web links
- Palæos Theriodontia