Temporal range: Late Pennsylvanian-Recent, 304–0 Ma
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3D restoration of Dimetrodon grandis, a sphenacodontid
Restoration of a pair of Alopecognathus angusticeps, a therocephalian therapsid
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Clade:
Synapsida
Clade:
Sphenacomorpha
Clade:
Sphenacodontia Romer & Price, 1940
Subgroups
†Haptodus[1]
†Hypselohaptodus[1]
†Ianthodon[2]
PantherapsidaSpindler, 2016[3]
†Kenomagnathus
†Tetraceratops
†Palaeohatteriidae
Sphenacodontoidea
†Shashajaia
†Sphenacodontidae
Therapsida
Sphenacodontia is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes Haptodus baylei, Haptodus garnettensis and Sphenacodon ferox, but not Edaphosaurus pogonias".[4] They first appear during the Late Pennsylvanian (Upper Carboniferous) epoch. From the end of the Carboniferous to the end of the Permian, most of them remained large, with only some secondarily becoming small in size.
Basal Sphenacodontia constitute a transitional evolutionary series from early pelycosaurs to ancestral therapsids (which in turn were the ancestors of more advanced forms and finally the mammals). One might say that the sphenacodontians are proto-therapsids (even though there is almost a 30-million-years gap between the separation of the ancestors of therapsids from other sphenacodontians and the first appearance of therapsids in the fossil record).
^ abSpindler, Frederik (15 August 2019). "Re-evaluation of an early sphenacodontian synapsid from the Lower Permian of England" (PDF). Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 111: 27–37. doi:10.1017/S175569101900015X. S2CID 202192911. Retrieved 8 October 2019.
^Cite error: The named reference Spindler2014 was invoked but never defined (see the help page).
^Spindler, F. 2016. Morphological description and taxonomic status of Palaeohatteria and Pantelosaurus (Synapsida: Sphenacodontia). Freiberger Forschungshefte C550(23): 1–57. https://www.researchgate.net/publication/321129043_Morphological_description_and_taxonomic_status_of_Palaeohatteria_and_Pantelosaurus_Synapsida_Sphenacodontia
^Cite error: The named reference BRJ12 was invoked but never defined (see the help page).
Sphenacodontia is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes Haptodus baylei...
salamanders. Therapsids evolved from "pelycosaurs", specifically within the Sphenacodontia, more than 279.5 million years ago. They replaced the "pelycosaurs"...
evolutionary gradation from primitive synapsid to early therapsid. The clade Sphenacodontia is used to designate the monophyletic group that includes sphenacodontids...
successively more basal clades such as Theriodontia, Therapsida and Sphenacodontia: Most uncertainty in the phylogeny of synapsids lies among the earliest...
considered more basal synapsids, falling outside clade Sphenacodontia. Within Sphenacodontia is the group Sphenacodontoidea, which in turn contains Sphenacodontidae...
Varanopidae Family Ophiacodontidae Family Edaphosauridae Infraorder Sphenacodontia Family Sphenacodontidae Order Therapsida Evolution of mammals List of...
2016. Morphological description and taxonomic status of (Synapsida: Sphenacodontia). Freiberger Forschungshefte C550(23): 1–57. https://www.researchgate...
and taxonomic status of Palaeohatteria and Pantelosaurus (Synapsida: Sphenacodontia). Freiberger Forschungshefte C550(23): 1–57. https://www.researchgate...
utoronto. Archived from the original on March 6, 2005. "Synapsida: Sphenacodontia: Secodontosaurus". Palaeos. Archived from the original on April 23,...
of Varanopidae within Synapsida and considered them as the suborder Sphenacodontia. Most phylogenetic analyses have place Varanopidae as a basal member...
Roberta Paton in 1974. In his 2015 dissertation revising the basal Sphenacodontia, Frederik Spindler demonstrated that H. garnettensis and H. grandis...
113–120. doi:10.4202/app.2010.0039. "Palaeos Vertebrates Synapsida: Sphenacodontia". Michel Laurin (1994). "Re-evaluation of Cutleria wilmarthi, an Early...
anatomy of the early synapsid Ianthodon schultzei (Sphenacomorpha: Sphenacodontia), and its evolutionary significance". Fossil Record. 18: 17–30. Currie...
first being Macromerion. Since then the assignment of Milosaurus to Sphenacodontia has been refuted. The name Milosaurus mccordi refers to Milo Flynn and...
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