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Sphenacodontia
Sphenacodontia
is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes Haptodus
Haptodus
baylei, Haptodus
Haptodus
garnettensis and Sphenacodon
Sphenacodon
ferox, but not Edaphosaurus
Edaphosaurus
pogonias".[1] They first appear during the Late Pennsylvanian epoch. Basal Sphenacodontia
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.

Contents

1 Characteristics 2 Classification 3 See also 4 References 5 External links

Characteristics[edit] The defining characteristics include a thickening of the maxilla visible on its internal surface, above the large front (caniniform) teeth; and the premaxillary teeth being set in deep sockets. All other (sister group and more primitive) synapsid clades have teeth that are set in shallow sockets. Classification[edit]

Haptodus, from Latest Carboniferous
Carboniferous
to Early Permian

Secodontosaurus, Early Permian

The following taxonomy follows Fröbisch et al. (2011) and Benson (in press) unless otherwise noted.[1][2] Class Synapsida

Eupelycosauria

Sphenacodontia

†Haptodus †Ianthodon †Palaeohatteria †Pantelosaurus Sphenacodontoidea

See also[edit]

Evolution
Evolution
of mammals

References[edit]

^ a b Benson, R.J. (2012). "Interrelationships of basal synapsids: cranial and postcranial morphological partitions suggest different topologies". Journal of Systematic Palaeontology. in press. doi:10.1080/14772019.2011.631042.  ^ Jörg Fröbisch, Rainer R. Schoch, Johannes Müller, Thomas Schindler and Dieter Schweiss (2011). "A new basal sphenacodontid synapsid from the Late Carboniferous
Carboniferous
of the Saar-Nahe Basin, Germany" (PDF). Acta Palaeontologica Polonica. 56 (1): 113–120. doi:10.4202/app.2010.0039. CS1 maint: Uses authors parameter (link)

Laurin, M. and Reisz, R. R., 1997, Autapomorphies of the main clades of synapsids - Tree of Life Web Project

External links[edit]

Synapsida: Sphenacodontia

v t e

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 Ianthodon Pantelosaurus

Sphenacodontoidea

Sphenacodontidae

Ctenorhachis Cutleria wilmarthi Macromerion Secodontosaurus  ?Steppesaurus  ?Tappenosaurus

Sphenacodontinae

 ?Bathygnathus Cryptovenator  ?Ctenospondylus Dimetrodon  ?Neosaurus Sphenacodon

Therapsida

Biarmosuchia Dinocephalia Anomodontia Theriodontia

Others

Bolosaurus Dimacrodon Echinerpeton Eosyodon Gorgodon Knoxosaurus  ?Protoclepsydrops

Related categories

Pelycosaurs Synapsids

Taxon identifiers

Wd: Q930410 EoL: 13075926 Fossil

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