Edaphosaurus
| Edaphosaurus | ||||||||||||
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Skeleton reconstruction of Edaphosaurus boanerges in New York's American Museum of Natural History |
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| Temporal occurrence | ||||||||||||
| Upper Carboniferous to Lower Permian | ||||||||||||
| 305 to 272.5 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Edaphosaurus | ||||||||||||
| Cope , 1882 | ||||||||||||
Edaphosaurus ("plaster lizard", to gr. Edaphos - plaster, ground; sauros - lizard) is an extinct genus of pelycosaurs (Pelycosauria), the older of the two taxa of the synapsids . Edaphosaurus was one of the first known terrestrial vertebrates (Tetrapoda) to feed on plants . The type species is E. pogonias from the Lower Permian of Texas .
Edaphosauridae
The Edaphosaurids, listed as a family in classical nomenclature , consisted of only two genera, both of which were herbivores (herbivores). Ianthasaurus had a different type of dentition, which was very similar to that of the carnivorous (carnivorous) Sphenacodontiden , the most famous representative of which is Dimetrodon . Therefore a sister group relationship of the two genera is assumed. The Edaphosaurids were next to the Diadectidae , close relatives of the amniotes from the Carboniferous and Unterperm of Laurussia , the first known herbivores among the terrestrial vertebrates.
morphology
Edaphosaurus resembled today's monitor lizards and iguanas in its lizard-like appearance , but had relatively shorter legs. The largest of the nine known species were E. cruciger and E. pogonias , which reached a length of up to 3.2 meters. The trunk was - typical of a herbivore - barrel-shaped, the unusually small head broad and short and the caudal spine long and thick. The conical, short and wide teeth were present both on the edges of the jaws and over large areas on oval fields on the palate and the inside of the lower jaw. The unusual set of teeth was probably used for plucking and chopping soft plant material.
The most striking feature, however, were the enormously elongated spinous processes on the vertebrae of the trunk and cervical spine, which formed a spectacular large "sail", probably covered with skin. Such sails occurred in three of the six families of the Pelycosaurier, but occurred as a convergent development in other tetrapods. In contrast to related forms such as Dimetrodon , the spinous processes of the Edaphosaurids were connected to one another by "cross braces". An early find of an Edaphosaurus was originally described as Naosaurus ("ship's lizard ") because the connections on the extensions are reminiscent of the horizontal yards on a ship's mast.
Function of the dorsal sail
The function of the dorsal sail in the pelycosaurs has not been conclusively clarified. Thermoregulation , communication and camouflage are discussed, but these need not be mutually exclusive. Calculations of the importance of the sail in the heat balance show that the warming of the body took place at more than double the speed if the animal aligned the sail perpendicular to the incident sun rays in the morning. To cool off, Edaphosaurus aligned the sail in parallel or turned it into the wind. Recent examples of such a strategy of temperature control are found in desert lizards. In Edaphosaurus , the cross connections between the spinous processes possibly improved the heat dissipation of the sail. Tests in the wind tunnel showed that the turbulence caused by the cross connections in the air flowing past increased the thermoregulatory effectiveness of the sail, so that the sail could be smaller and flatter than without it. During the mating season , the sail may have been conspicuously colored and played a role in courtship .
literature
- Robert L. Carroll : Paleontology and Evolution of the Vertebrates. Thieme publishing house, Stuttgart. 1993.
- Martin Sander : Reptiles . Ferdinand Enke Verlag, Stuttgart, 1994
- S. Christopher Bennett: Aerodynamics and thermoregulatory function of the dorsal sail of Edaphosaurus . Paleobiology: Vol. 22, No. 4, pp. 496-506 (1996). ( Abstract )
Web links
- Palaeos.com (English)
- Introduction to the Pelycosaurs (English)