HIERARCHICAL CLASSIFICATION OF THE CLASS PROAMNIOTA+

HIERARCHICAL CLASSIFICATION OF THE CLASS PROAMNIOTA+[i]

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CLASS PROAMNIOTA LINKS

The following descriptions come from Benton (2005). The structure of the following system is also based, in part, on the phylogenetic treatment by Mikko’s Phylogeny Web (from the Finnish Museum of Natural History). Taxa in red are extinct.

CLASS PROAMNIOTA[i]+ (LEPOSPONDYLI + REPTILOMORPHA)
This is a taxonomy of two Subclasses, each with three orders. Reptilomorpha is the sister group to the amniotes.

SUBCLASS LEPOSPONDYLI
The synapomorphies that define this group include the loss of the supratemporal, and the vertebrae are cylindrical pleirocentra.
- ORDER MICROSAURIA
  - Small and mainly terrestrial animals, almost lizard-like. Some show secondary adaptations to water and others to burrowing in soil or leaf litter.
  - Carboniferous to lower Permian
  - Microbrachis, Pantylus, Tuditanus
- ORDER NECTRIDEA
  - Mainly aquatic and newt-like. Some developed large lateral wing-like extensions of their skulls that enlarged as they aged.
  - Upper Carboniferous (Pennsylvanian) to Permian
  - Sauropleura, Diplocaulus, Diploceraspis
- ORDER AISTOPODA
  - Very similar to snakes, the aistopods had many vertebrae and no limbs or limb girdle elements. Also, they seem to have been able to open their jaws very wide through extra joints in the skull.
  - Carboniferous and lower Permian
  - Aornerpeton, Ophiderpeton

SUBCLASS REPTILIOMORPHA (SISTER TO THE AMNIOTES)+
The synapomorphies for this subclass include premaxillae less than 1/2 of the skull width, and the vomers taper forward (Benton, 2005). They dominated terrestrial habitats from the Carboniferous to the Permian. This group also included the first known tetrapod herbivore.
- ORDER ANTHRACOSAURIA
  - Fish eating animals with elongate skulls, which seem to have been able to flex when opening the jaws. It had large vertebrae and a flat tail that could have been useful for swimming. Some had legs that were well developed and suited to rapid terrestrial movement, but later forms had reverted to a more aquatic existence.
  - Lower Carboniferous to Upper Carboniferous
  - Diplovertebron, Proterogyrinus, Pholiderpeton
- ORDER SEYMOURIAMORPHA
  - The seymouriomorphs were a diverse and powerful group of animals. The terrestrial forms held their bodies high off the ground. Aquatic forms had broad skulls and fed on fish. Upper Carboniferous (Pennsylvanian) to Upper Permian
  - Seymouria
- ORDER DIADECTOMORPHA
  - These were very close to the origin of the amniotes. Members of this group were among the first herbivorous tetrapods. One, Diadectes, was adapted to herbivory by having anterior nipping teeth and posterior crushing teeth. These animals were heavily built with very strong legs and limb girdles.
  - Upper Carboniferous (Pennsylvanian) to Lower Permian
  - Diadectes, Limnoscelis

[i] Benton (2005) united the Lepospondyli and Reptiliomorpha as subclasses under an unnamed class. I have attempted to provide a name that is appropriate and indicate the sister relationship with the Amniota. The name Proamniota means before the amniotes.

LITERATURE CITED

Benton, M. J. 2005. Vertebrate Paleontology. Third Edition. Blackwell Publishing, Malden, MA. [L]

Carrol, R. L. 2001. The origin and early radiation of terrestrial vertebrates. Journal of Paleontology. 75(6):1202-1213.

Clack, J.A. 2002. An early tetrapod from ‘Romer’s Gap’. Nature. 418: 72-76.

Laurin, M. 2002. Tetrapod phylogeny, amphibian origins, and the definition of the name Tetrapoda. Syst. Biol. 51: 364-369.

Laurin, M. and R.R. Reisz. 1995. A reevaluation of early amniote phylogeny. Zoological Journal of the Linnaean Society. 113: 165-223.

Marjanovic, D. and M. Laurin. 2007. Fossils, molecules, divergence times, and the origin of lissamphibians. Systematic Biology. 56 (3): 369-388.

Reisz, R.R. and H.D. Sues. 2000. Herbivory in Late Paleozoic and Triassic Terrestrial Vertebrates. pp 9-41. in: Evolution of Herbivory in Terrestrial Vertebrates, Cambridge Univ. Press., H.D. Sues, ed.. Herbivory in Late Paleozoic and Triassic Terrestrial Vertebrates. in: Sues, H. D., ed. Evolution of Herbivory in Terrestrial Vertebrates, Cambridge Univ. Press. pp 9-41.

Ruta, M., J.E. Jeffery, M.I. Coates. 2003. A supertree of early tetrapods. Proc. R. Soc. London. B. 270: 2507-2516.

By Jack R. Holt. Last revised: 01/20/2013

HIERARCHICAL CLASSIFICATION OF THE CLASS PROAMNIOTA+[i]

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