- Sphenacodontia
Taxobox
name = Sphenacodontia
fossil_range = LatestPennsylvanian to MiddlePermian (non-therapsid; non-mammalian)
image_width = 230px
image_caption = "Pantelosaurus "
regnum =Animal ia
phylum = Chordata
classis =Synapsid a
ordo =Pelycosaur ia
unranked_familia =Eupelycosauria
subdivision_ranks = Genera and Clades
subdivision = See taxonomySphenacodontia is the name given to the
clade that includes theSphenacodontidae and all their descendants (including mammals). They first appear during theLate Pennsylvanian epoch. The defining characteristics include a thickening of themaxilla visible on its internal surface, above the large front (caniniform) teeth; and thepremaxilla ry teeth being set in deep sockets. All other (sister group and more primitive) synapsid clades have teeth that are set in shallow sockets.Basal Sphenacodontia constitute a transitional
evolution ary series from earlypelycosaur s to ancestraltherapsid s (which in turn were the ancestors of more advanced forms and finally themammal s). One might say that the Sphenacodontians are proto-therapsids.Taxonomy and Phylogeny
* Class
Synapsida
* ORDER PELYCOSAURIA
** SuborderEupelycosauria
*** Sphenacodontia (incl.paraphyletic Sphenacodontidae)
**** "Haptodus "
***** "Palaeohatteria "
****** "Pantelosaurus "
******* "Cutleria "
********Sphenacodontoidea
********* FamilySphenacodontidae ("sensu stricto ")
********** "Ctenospondylus "
********** "Dimetrodon "
********** "Secodontosaurus "
********** "Sphenacodon "
********* FamilyTetraceratops idae
********** "'ORDER THERAPSIDA
*********** "'ClassMammalia References
* Laurin, M. and Reisz, R. R., 1997, [http://tolweb.org/accessory/Synapsid_Classification_&_Apomorphies?acc_id=466 Autapomorphies of the main clades of synapsids] -
Tree of Life Web Project ee also
*
Evolution of mammals External links
* [http://www.palaeos.com/Vertebrates/Units/Unit390/400.html Synapsida: Sphenacodontia]
Wikimedia Foundation. 2010.