Placodontia
| Placodontia | ||||||||||||
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Skull of Placochelys |
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| Temporal occurrence | ||||||||||||
| Triad | ||||||||||||
| 249.7 to 199.6 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Placodontia | ||||||||||||
| Cope , 1871 |
Placodontier or plaster- tooth lizard (Placodontia) were a marine reptile group of the Triassic . They lived in the Tethys and its tributaries in shallow regions near the coast.
They owe their name to their teeth, with which they could bite the hard shells of their food ( mussels , snails , brachiopods ). The teeth on the roof of the mouth had become large dental plates, while the teeth on the edge of the jaw were conical and blunt. Placodont animals were rarely more than two meters long.
The more primitive forms such as Placodus (traditionally summarized as "Placodontoidea") still had a partially movable trunk, a longer tail and, like today's crocodiles, moved by swimming snakes. Their front teeth were spatulate and were used to tear hard-shelled, often sessile animals from the ground. The skull was not yet as ossified as in the Cyamodontoidea, the bone sutures can still be seen. Front and rear legs show poor adaptation to marine life.
The placodon animals, which are summarized in the taxon Cyamodontoidea, were heavily armored to protect against their natural enemies. The shell is outwardly similar to that of the turtle and is composed of many polygonal bones. The skull is also very ossified.
Because of the lack of mobility of the trunk and the shorter tail, they were no longer able to swim in a snake. They probably moved, similar to today's sea turtles, by rowing their fin-like legs. The most extensive armor of this group was possessed by Henodus , who also closed the upper temple window, lost most of the teeth and replaced it with a horned beak. The placodon animals did not survive the end of the Triassic.
Systematics
- Placodontia
literature
- Robert L. Carroll : Paleontology and Evolution of the Vertebrates. Thieme, Stuttgart et al. 1993, ISBN 3-13-774401-6 .
- Martin Sander : Reptiles. 220 individual representations (= Haeckel library. Vol. 3). Enke, Stuttgart 1994, ISBN 3-432-26021-0 .
Web links
- Mikko's Phylogeny Archive Placodontia
- Oceans of Kansas Placodonts
Individual evidence
- ↑ Olivier Rieppel: Paraplacodus and the phylogeny of the Placodontia. Zoological Journal of the Linnean Society. Vol. 130, No. 4, 2000, pp. 365–359, doi: 10.1006 / zjls.2000.0232 (Open Access)