Sphenacodontia
230px-Pantelosaurus.jpg
Karakteristik utamanya adalah penebalan maksilla pada permukaan wajah diatas gigi depan yang besar (taring) dan gigi premaksilla berdiri di rongga yang dalam. Sementara synapsida selapn sphenacodontia memiliki gigi premaksila yang berdiri di rongga yang dangkal.
Pohon utama berpisah dari fosil transisi, Haptodus Garnettensis. KEmudian berpisah lagi dengan Paleohatteria, kemudian Pantelosaurus. Terisisa dua cabang utama
Cutleria
Sphenacodontoidea

referensi:
Hopson JA (1991), Systematics of the nonmammalian Synapsida and implications for patterns of evolution in synapsids, in H-P Schultze & L Trueb [eds], Origins of the Higher Groups of Tetrapods: Controversy and Consensus. Comstock, pp. 635-693
Lucas SG (2006), Global Permian tetrapod biostratigraphy and biochronology, in SG Lucas, G Cassinis & JW Schneider (eds.). Non-Marine Permian Biostratigraphy and Biochronology. Geol. Soc. Lond. Spec. Publ. 265: 65-93.
Modesto SP (1994), The Lower Permian synapsid Glaucosaurus from Texas. Paleontology 37: 51–60
Modesto SP & RR Reisz (1990a), Taxonomic status of Edaphosaurus raymondi Case. J. Paleontol. 64: 1049-1051.
Reisz RR (1972), Pelycosaurian reptiles from the Middle Pennsylvanian of North America. Bull. Mus. Comp. Zool. 144: 27-62.
Rubidge BS & CA Sidor (2001), Evolutionary patterns among Permo-Triassic therapsids. Ann. Rev. Ecol. Syst. 32: 449-480.

Sumber gambar : http://en.wikipedia.org/wiki/Sphenacodontia

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