Synapsida

Belongs within: Batrachosauria.
Contains: Sphenacodontidae.

The Synapsida are the total group for mammals—that is, mammals and all fossil animals more closely related to mammals than to reptiles. The most basal synapsids, the Permian ‘pelycosaurs’, were still fairly ‘reptilian’ in their general appearance, and include such well-known exemplars as the carnivorous Dimetrodon and the herbivorous Edaphosaurus.

The Caseidae were a group of sometimes massive herbivores with barrel-shaped bodies and relatively small heads. Edaphosaurus was a genus of similarly large herbivores with a high sail running along the back (Dixon 2007).

Synapomorphies (Kemp 1988): Temporal fenestra bounded above by squamosal and postorbital; occipital plate broad and tilted forwards; post-temporal fenestra small; postparietal single and median; septomaxilla with broad base and dorsal process; medial process of jugal sutured to pterygoid, ectopterygoid primitively present.

<==Synapsida [Edaphosauria, Ophiacodontia, Pelycosauria, Sphenacodontia, Theromorpha, Theropsida]
    |--+--EothyrididaeK88
    |  |    |--Eothyris parkeyi Romer 1937R61b, B93
    |  |    `--Oedaleops campi Langston 1965B93
    |  `--CaseidaeK88
    |       |  i. s.: ‘Pantylus’ coicodus Cope 1896R69
    |       |--Ennatosaurus tecton Efremov 1956B93
    |       |--Casea Williston 1910D07
    |       |    |--C. broilii Williston 1910B93
    |       |    `--C. rutenaD07
    |       |--Cotylorhynchus Stovall 1937D07
    |       |    |--C. hancockiD07
    |       |    `--C. romeriD07
    |       |--TrichasaurusSPR66
    |       |--CaseoidesSPR66
    |       |--CaseopsisSPR66
    |       |--AngelosaurusSPR66
    |       |--PhreatophasmaSPR66
    |       `--GlaucosaurusSPR66
    `--+--VaranopseidaeK88
       |    |--Basicranodon fortsillensisM06
       |    |--Archaeovenator hamiltonensisD-SMS06
       |    |--Elliotsmithia longicepsMS01
       |    |--Aerosaurus greenleeorum Romer 1937B93
       |    |--Varanodon agilis Olson 1965B93
       |    |--Mesenosaurus [Mesenosauridae]D-SMS06
       |    |    `--M. romeri Efremov 1940B93
       |    `--Varanops Williston 1914D07
       |         `--V. brevirostrisN85
       `--+--+--SphenacodontidaeK88
          |  `--Edaphosaurus Cope 1882C07 [incl. Naosaurus Cope 1886C07; EdaphosauridaeK88, Naosaurinae]
          |       |--*E. pogonias Cope 1882C07
          |       |--E. boanergesSPR66
          |       |--E. cruciger (Cope 1878) [=Dimetrodon cruciger, *Naosaurus cruciger]C07
          |       |--E. claviger (Cope 1886) [=Naosaurus claviger]C07
          |       |--E. microdus Cope 1884 [=Naosaurus microdus]C07
          |       |--‘Naosaurus’ mirabilis Fritsch 1883C07
          |       `--E. raymondi (Case 1908)B93
          `--Ophiacodontidae [Clepsydropidae, Clepsydropinae]K88
               |--Archaeothyris florensis Reisz 1972B93
               |--Varanosaurus Broili 1904R61b, C07
               |    `--*V. acutirostris Broili 1904C07
               |--Ophiacodon Marsh 1878D07
               |    |--O. major Romer & Price 1940B93
               |    |--O. mirusD07
               |    |--O. navajovicusD07
               |    |--O. retroversusD07
               |    |--O. trangualaD07
               |    |--O. uniformisD07
               |    `--O. watsoniD07
               |--Stereorhachis dominansR61a
               |--Embolophorus fritillus Cope 1878C07
               |--Metamosaurus fossatus Cope 1878C07
               |--Bathygnathus borealis Leidy 1854C07
               |--Tomicosaurus Case 1907C07
               |--Ctenosaurus koeneni v. Huene 1902C07
               `--Clepsydrops Cope 1875R61a, C07
                    |--*C. colletti Cope 1875 (n. d.)C07
                    |--C. magnus Romer 1961R61a
                    |--C. natalis Cope 1878C07
                    |--C. pedunculatus Cope 1877 (n. d.)C07
                    `--C. vinslovii Cope 1877 (n. d.)C07

Synapsida incertae sedis:
  ProtoclepsydropsLR95
  PariotichidaeC07
    |--Pariotichus brachiopsC07
    `--Ectocynodon ordinatusC07
  PoliosauridaeC07
    |--Archaeobelus vellicatus Cope 1877C07
    |--Pleuristion brachycoelous Case 1902–1903C07
    |--Callibrachion gaudryi Boule & Glengeaud 1893C07
    |--Stereorachis dominans Gaudry 1880C07
    |--Poliosaurus Case 1907C07
    |    `--*P. uniformis (Cope 1878) [=Theropleura uniformis]C07
    |--Elcabrosaurus Case 1907C07
    |    `--*E. baldwini Case 1907C07
    |--Anomosaurus v. Huene 1902C07
    |    `--A. strunzi v. Huene 1905C07
    `--Theropleura [incl. Diopeus Cope 1892]C07
         |--*T. retroversa Cope 1878 (see below for synonymy)C07
         `--T. grandis Case 1907C07
  NitosauridaeSPR66
    |--DelorhynchusSPR66
    |--NitosaurusSPR66
    `--Mycterosaurus longicepsR61b, M06

*Theropleura retroversa Cope 1878 [incl. Clepsydrops leptocephalus Cope 1884, *Diopeus leptocephalus, Theropleura triangulata Cope 1878]^C07

*Type species of generic name indicated

References

[B93] Benton, M. J. 1993. Reptilia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 681–715. Chapman & Hall: London.

[C07] Case, E. C. 1907. Revision of the Pelycosauria of North America. Carnegie Institute of Washington Publication 55: 1–176, 35 pls.

[D-SMS06] Dias-da-Silva, S., S. P. Modesto & C. L. Schultz. 2006. New material of Procolophon (Parareptilia: Procolophonoidea) from the Lower Triassic of Brazil, with remarks on the ages of the Sanga do Cabral and Buena Vista formations of South America. Canadian Journal of Earth Sciences 43: 1685–1693.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[K88] Kemp, T. S. 1988. Interrelationships of the Synapsida. In: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods vol. 2. Mammals pp. 1–22. Clarendon Press: Oxford.

[LR95] Laurin, M., & R. R. Reisz. 1995. A reevaluation of early amniote phylogeny. Zoological Journal of the Linnean Society 113: 165–223.

[M06] Modesto, S. P. 2006. The cranial skeleton of the Early Permian aquatic reptile Mesosaurus tenuidens: implications for relationships and palaeobiology. Zoological Journal of the Linnean Society 146: 345–368.

[MS01] Modesto, S. P., & R. M. H. Smith. 2001. A new Late Permian captorhinid reptile: a first record from the South African Karoo. Journal of Vertebrate Paleontology 21 (3): 405–409.

[N85] Norman, D. 1985. The Illustrated Encyclopedia of Dinosaurs. Salamander Books: London.

[R61a] Romer, A. S. 1961a. A large ophiacodont pelycosaur from the Pennsylvanian of the Pittsburgh region. Breviora 144: 1–7.

[R61b] Romer, A. S. 1961b. Synapsid evolution and dentition. In: Vandebroek, G. (ed.) International Colloquium on the Evolution of Lower and Non Specialized Mammals. Koninklijke Vlaames Academie voor Wetenschappen, Letteren en Schone Kunsten van Belgie—Klasse der Wetenschapen 1961 (1): 9–56.

[R69] Romer, A. S. 1969. The cranial anatomy of the Permian amphibian Pantylus. Breviora 314: 1–37.

[SPR66] Stovall, J. W., L. I. Price & A. S. Romer. 1966. The postcranial skeleton of the giant Permian pelycosaur Cotylorhynchus romeri. Bulletin of the Museum of Comparative Zoology 135 (1): 1–30.