Labyrinthodontia
From Freepedia
A Labyrinthodont (Greek, "maze-toothed") is any member of an extinct superorder or subclass (Labyrinthodontia) of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times (about 350 to 210 million years ago). The name describes the pattern of infolding of the dentine and enamel of the teeth, which are often all of the creatures that survives. They are also distinguished by a heavy solid skull, and complex vertebrae, the structure of which is useful in older classifications of the group.
The traditional classification (e.g. Romer 1966, also repeated in Colbert 1969, and Carroll 1988) has three orders:
- Ichthyostegalia (primitive ancestral forms (e.g. Ichthyostega) - Late Devonian only)
- Temnospondyli (common, sometimes large, flat-headed forms with either strong or secondarily weak vertebrae and limbs - Carboniferous to Triassic - e.g. Eryops (later Jurassic and Cretaceous fossils were found) - originally considered ancestral to Anura (frogs)
- Anthracosauria (deep skulls, strong vertebrae but weak limbs, evolving towards and ancestral to reptiles - Carboniferous and Permian - e.g. Seymouria)
A good summary (with diagram) of characteristics and main evolutionary trends of the above three orders is given in Colbert 1969 pp.102-103.
The grouping "Labyrinthodonts" has since been largely discarded as paraphyletic, that is, artificially composed of organisms that have separate genealogies, and thus not a valid taxon. The groups that have usually been placed within Labyrinthodontia, are currently variously classified as basal tetrapods, non-amniote Reptiliomorpha and as a monophyletic or paraphyletic Temnospondyli, according to cladistic analysis.
References
- Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
- Colbert, E. H., (1969), Evolution of the Vertebrates, John Wiley & Sons Inc (2nd ed.)
- Romer, A. S., (1947, revised ed. 1966) Vertebrate Paleontology, University of Chicago Press, Chicago
External links
See also
- Tetrapod
- Temnospondyli
- Batrachosauria
- Reptiliomorpha
- Amphibian
- Prehistoric amphibian
- Ichthyostega
- Eryops
- Prehistoric life
Categories: Paleontology | Amphibians | Devonian | Fossils | Mesozoic | Paleozoic
