Seymouriamorpha

Seymouriamorpha
Fossil of Seymouria in the National Museum of Natural History
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Clade: Reptiliomorpha (?)
Order: †Seymouriamorpha
Watson, 1917
Subgroups

See text.

Seymouriamorpha are an extinct group of tetrapods (terrestrial vertebrates) known from the Carboniferous and Permian periods. They have long been considered stem-amniotes (reptiliomorphs), and most paleontologists still accept this point of view, but some analyses suggest that seymouriamorphs are stem-tetrapods (not more closely related to Amniota than to Lissamphibia). Seymouriamorphs are divided into three main groups: Kotlassiidae, Discosauriscidae, and Seymouriidae, which includes the best-known genus, Seymouria. The last seymouriamorphs became extinct by the end of the Permian.

Many seymouriamorphs were terrestrial or semi-aquatic. However, aquatic larvae bearing external gills and grooves from the lateral line belonging to the seymouriamorph family Discosauriscidae have been found, making seymouriamorphs unquestionably non-amniotes. As they matured, they became more terrestrial and reptile-like. They ranged from 30 cm (1 ft) long lizard-sized creatures to the 1.5 m (5 ft) long Enosuchus. If seymouriamorphs are reptiliomorphs, they were the distant relatives of amniotes.

They have been considered to be the makers of the trace fossils placed in the ichnogenus Amphisauropus.

Taxonomy

Cladogram based on Ruta, Jeffery, & Coates (2003):

Seymouriamorpha

Cladogram based on Klembara (2009) & Klembara (2010):

References

  1. ↑ Klembara, J.; Werneburg, R.; Mikudíková, M.; Šurka, J.; Štamberg, S. (2023). "The oldest records of the stem amniote Discosauriscus (Seymouriamorpha, Discosauriscidae) from the European Carboniferous-Permian boundary". Bulletin of Geosciences. 98 (3): 233–246. doi:10.3140/bull.geosci.1882.
  2. ↑ Laurin, Michel (2010). How Vertebrates Left the Water. Berkeley: University of California Press. ISBN 978-0-520-26647-6.
  3. ↑ Bulanov VV (2003). "Evolution and systematics of seymouriamorph parareptiles". Paleontological Journal. 37 (Supplement 1): 1–105.
  4. ↑ J. K. Klembara, The external gills and ornamentation of skull roof bones of the Lower Permian tetrapod Discosauriscus (Kuhn 1933) with remarks to its ontogeny. Palaontol. Z. 69, 265–281 (1995).
  5. ↑ Pardo, Jason D.; Mann, Arjan (2026-06-18). "Direct development of stem tetrapods across the fin-to-limb transition". Science. 392 (6804): 1292–1296. doi:10.1126/science.aeb7635. ISSN 0036-8075.
  6. ↑ Marchetti, Lorenzo; Mujal, Eudald; Bernardi, Massimo (January 2017). "An unusual Amphisauropus trackway and its implication for understanding seymouriamorph locomotion". Lethaia. 50 (1): 162–174. Bibcode:2017Letha..50..162M. doi:10.1111/let.12184.
  7. ↑ Olson, E. C. (1951). "Fauna of upper Vale and Choza: 1-5" (PDF). Fieldiana Geology. 10 (11): 89–128. doi:10.5962/bhl.title.3264.
  8. ↑ Ruta, M.; Jeffery, J. E.; Coates, M. I. (2003). "A supertree of early tetrapods". Proceedings of the Royal Society B. 270 (1532): 2507–16. doi:10.1098/rspb.2003.2524. PMC 1691537. PMID 14667343.
  9. ↑ Klembara, Jozef (2009). "The skeletal anatomy and relationships of a new discosauriscid seymouriamorph from the lower Permian of Moravia (Czech Republic)". Annals of Carnegie Museum. 77 (4): 451–483. doi:10.2992/0097-4463-77.4.451.
  10. ↑ Klembara, Jozef (2011). "The cranial anatomy, ontogeny, and relationships of Karpinskiosaurus secundus (Amalitzky) (Seymouriamorpha, Karpinskiosauridae) from the Upper Permian of European Russia" (PDF). Zoological Journal of the Linnean Society. 161 (1): 184–212. doi:10.1111/j.1096-3642.2009.00629.x.