Seymouriamorpha

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Seymouriamorpha
Seymouria

Seymouria

Temporal occurrence
Oberkarbon to Oberperm
323.2 to 258 million years
Locations
  • Europe, Russia, Central Asia, North America
Systematics
Chordates (chordata)
Vertebrates (vertebrata)
Land vertebrates (Tetrapoda)
Reptiliomorpha
Seymouriamorpha
Scientific name
Seymouriamorpha
Watson , 1917

The Seymouriamorpha are an extinct group of early terrestrial vertebrates whose fossil remains have been found in Europe, Russia, Central Asia, and North America.

A distinction is made between three families, the terrestrial Seymouriidae known from North America , the Discosauriscidae , which are only known from larval or neotene forms, and the Kotlassidae from the Upper Permian of Russia, which had once again adopted an aquatic way of life.

features

The Seymouriamorpha were about 50 to 100 cm long. Their axial skeleton is strong. The outer skull bones of adult animals were heavily carved through a hexagonal pattern. The palate was closed. The animals had ribs from the first cervical vertebra to the first caudal vertebra. The ribs of the chest region were reinforced. The spine was short, in front of the sacrum they had 24 to 28 vertebrae . The vertebrae had large, cylindrical pleurocentra and small, sickle-shaped intercentra and thus herald the development of the pleurocenter into the most important element of the vertebrae in the amniotes. The limbs were strong and stocky. The humerus and thigh bones were strongly built. The phalangeal formula of the forefoot is 2,3,4,4,3 or 2,3,4,5,3; that of the hind foot 2,3,4,5,3.

Larvale Seymouriamorpha and the Discosauriscidae had only a weakly ossified skeleton, three pairs of outer gills (handed down as carbonic shadows in the fossils) and lateral canals , as well as possibly also electroreceptors .

Seymouria
Discosauriscus

Systematics

For a long time, until the discovery of fossils of larval Seymouriamorphs, the Seymouriamorpha were regarded as the original group of the amniota or the most primitive amniotes. Other scientists saw them as amphibians. However, they are not closely related to today's amphibians ( Lissamphibia )

Benton places them together with the Diadectomorpha in the parent group of the amniotes

literature

  • Michael J. Benton : Paleontology of the vertebrates. Translation of the 3rd English edition by Hans-Ulrich Pfretzschner. Pfeil, Munich 2007, ISBN 978-3-89937-072-0 .
  • Robert L. Carroll : Paleontology and Evolution of the Vertebrates. Thieme, Stuttgart et al. 1993, ISBN 3-13-774401-6 .
  • Rainer Schorch: Early Tetrapoda in Wilfried Westheide & Reinhard Rieger: Special Zoology Part 2: Vertebrae and Skull Animals. Pages 306-310, 1st edition, Spektrum Akademischer Verlag Heidelberg • Berlin, 2004, ISBN 3-8274-0307-3

Web links

Commons : Seymouriamorpha  - collection of images, videos and audio files