| "Labyrinthodonts"* Temporal range:
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|---|---|
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| Artist's conception of a Proterogyrinus, an anthracosaur | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Batrachomorpha |
| Subclass: | †Labyrinthodontia Owen, 1860 |
| Groups included | |
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| Cladistically included but traditionally excluded taxa | |
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"Labyrinthodontia" (Greek, 'maze-toothed') is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras (about 390 to 150 million years ago). Traditionally considered a subclass of the class Amphibia, modern classification systems recognize that labyrinthodonts are not a formal natural group (clade) exclusive of other tetrapods. Instead, they consistute an evolutionary grade (a paraphyletic group), ancestral to living tetrapods such as lissamphibians (modern amphibians) and amniotes (reptiles, mammals, and kin). "Labyrinthodont"-grade vertebrates evolved from lobe-finned fishes in the Devonian, though a formal boundary between fish and amphibian is difficult to define at this point in time.
"Labyrinthodont" generally refers to extinct four-limbed tetrapods with a large body size and a crocodile-like lifestyle. The name describes the pattern of infolding of the dentin and enamel of the teeth, which are often the only part of the creatures that fossilize. They are also distinguished by a broad, strongly-built skull roof composed of many small heavily-textured skull bones. "Labyrinthodonts" generally have complex multi-part vertebrae, and several classification schemes have utilized vertebrae to define subgroups.
Because labyrinthodonts do not form a monophyletic group, many modern researchers have abandoned the term. However, some have continued to use the group in their classifications, at least informally, pending more detailed study of their relationships.[1] Many authors prefer to simply use the term tetrapod, while others have re-defined the previously obsolete term Stegocephalia ("roof heads") as a cladistic alternative to "Labyrinthodontia" or "Tetrapoda".
- ^ Hall, Brian K., ed. (2007). Fins into limbs : evolution, development, and transformation ([Online-Ausg.]. ed.). Chicago: University of Chicago Press. p. 187. ISBN 978-0226313375.