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Anthracosauria is a Paraphyly order of extinct reptile-like (in the broad sense) that flourished during the Carboniferous and Cisuralian periods, although precisely which species are included depends on one's definition of the taxon. "Anthracosauria" is sometimes used to refer to all more closely related to such as , , and , than to such as and . An equivalent term to this definition would be Reptiliomorpha. Anthracosauria has also been used to refer to a smaller group of large, crocodilian-like aquatic tetrapods also known as Embolomeri.
With cladistics things have changed again. Jacques Gauthier, Arnold Kluge and Rowe (1988) defined Anthracosauria as a clade including "Amniota plus all other tetrapods that are more closely related to amniotes than they are to amphibians" (Amphibia in turn was defined by these authors as a clade including Lissamphibia and those tetrapods that are more closely related to lissamphibians than they are to amniotes). Similarly, Michel Laurin (1996) uses the term in a Cladistics sense to refer to only the most advanced Reptiliomorpha. Thus his definition includes Diadectomorpha, Solenodonsauridae and the amniotes. As Ruta, Coates and Quicke (2003) pointed out, this definition is problematic, because, depending on the exact phylogenetic position of Lissamphibia within Tetrapoda, using it might lead to the situation where some taxa traditionally classified as anthracosaurs, including even the genus Anthracosaurus itself, wouldn't belong to Anthracosauria. Laurin (2001) created a different phylogenetic definition of Anthracosauria, defining it as "the largest clade that includes Anthracosaurus russelli but not Tailed frog". However, Michael Benton (2000, 2004) makes the anthracosaurs a paraphyletic order within the superorder Reptiliomorpha, along with the orders Seymouriamorpha and Diadectomorpha, thus making the Anthracosaurians the "lower" reptile-like amphibians. In his definition, the group encompass the Embolomeri, Chroniosuchia and possibly the family Gephyrostegidae.
Many studies since have suggested that anthracosaurs or embolomeres are likely closer to , but some recent studies either retain them as amphibians or argue that their relationships are still ambiguous and are more likely to be stem-tetrapods.
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