Caseasauria

Caseasaurs Temporal range: Late Carboniferous[1] - Middle Permian PreꞒ Ꞓ O S D C P T J K Pg N
Fossil skeleton of Cotylorhynchus romeri
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	†Caseasauria
Genera and Families
†Caseidae †Eothyrididae †?Phreatophasma

Caseasauria is one of the two main clades of early synapsids, the other being the Eupelycosauria. Caseasaurs are currently known only from the Late Carboniferous^[1] and the Permian, and include two superficially different families, the small insectivorous or carnivorous Eothyrididae, and the large herbivorous Caseidae. These two groups share a number of specialised features associated with the morphology of the snout and external naris.

The ancestor of caseasaurs can be traced back to an insect eating or an omnivorous reptile-like synapsid from the Pennsylvanian time of the Carboniferous, possibly resembling Archaeothyris, the earliest known synapsid. The caseasaurs were abundant during the later part of the Early Permian, but by the Middle Permian caseasaur diversity declined because the group was outcompeted by the more successful therapsids. The last caseasaurs became extinct at the end of the Guadelupian (Middle Permian).^[2]

Phylogeny

Most uncertainty in the phylogeny of synapsids lies among the earliest members of the group, including forms traditionally placed within Pelycosauria. As one of the earliest phylogenetic analyses, Brinkman & Eberth (1983) placed the family Varanopidae with Caseasauria as the most basal ofshoot of the synapsid lineage. Reisz (1986) removed Varanopidae from Caseasauria, placing it in a more derived position on the stem. While most analyses find Caseasauria to be the most basal synapsid clade, the analysis of Benson (2012) placed a clade containing Ophiacodontidae and Varanopidae as the most basal synapsids, with Caseasauria occupying a more derived position. Benson attributed this revised phylogeny to the inclusion of postcranial characteristics, or features of the skeleton other than the skull, in his analysis. When only cranial or skull features were included, Caseasauria remained the most basal synapsid clade. Below is a cladogram modified from the analysis of Benson (2012):^[3]

See also

• Evolution of mammals
• Vertebrate paleontology
• Permian tetrapods

References

• Reisz, R. R., 1986, Handbuch der Paläoherpetologie – Encyclopedia of Paleoherpetology, Part 17A Pelycosauria Verlag Dr. Friedrich Pfeil, ISBN 3-89937-032-5
• Laurin, M. and Reisz, R. R., 1997, Autapomorphies of the main clades of synapsids

External links

• Palaeos Vertebrates 390.100 Synapsida

Wikispecies has information related to: Caseasauria

Basal synapsids Kingdom: Animalia Phylum: Chordata Superclass: Tetrapoda Ophiacodontidae Archaeothyris Baldwinonus Clepsydrops Ophiacodon Stereophallodon Stereorhachis Varanosaurus Varanopidae Apsisaurus Archaeovenator ?Milosaurus ?Nitosaurus Pyozia Thrausmosaurus Mycterosaurinae Heleosaurus Mesenosaurus Mycterosaurus Varanodontinae Aerosaurus Elliotsmithia Ruthiromia Tambacarnifex Varanops Varanodon Watongia Caseasauria Eothyrididae Eothyris Oedaleops Caseidae Alierasaurus Angelosaurus Casea Caseoides Caseopsis Cotylorhynchus Ennatosaurus Eocasea Euromycter Ruthenosaurus Oromycter ?Phreatophasma Trichasaurus Edaphosauridae Edaphosaurus Glaucosaurus Ianthasaurus Lupeosaurus ?Xyrospondylus Sphenacodontia Haptodus Pantelosaurus Sphenacodontoidea Sphenacodontidae Ctenorhachis Cutleria wilmarthi Macromerion Secodontosaurus ?Steppesaurus ?Tappenosaurus Sphenacodontinae ?Bathygnathus Cryptovenator ?Ctenospondylus Dimetrodon ?Neosaurus Sphenacodon Therapsida Mammalia Others Bolosaurus Dimacrodon Echinerpeton Eosyodon Gorgodon Ianthodon Knoxosaurus ?Protoclepsydrops Related categories Pelycosaurs Synapsids