'', an embolomere As originally defined by
Säve-Söderbergh in 1934, the anthracosaurs are a group of usually large aquatic Amphibia from the Carboniferous and lower Permian. As defined by
Alfred Sherwood Romer however, the anthracosaurs include all non-amniote "
labyrinthodont"
reptile-like amphibians, and Säve-Söderbergh's definition is more equivalent to Romer's suborder
Embolomeri. This definition was also used by
Edwin H. Colbert and
Robert L. Carroll in their textbooks of Vertebrate Palaeontology (Colbert 1969, Carroll 1988). Dr A. L. Panchen however preferred Säve-Söderbergh's original definition of Antracosauria in his
Handbuch der Paläoherpetologie, 1970. With
cladistics things have changed again.
Gauthier,
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
cladistic sense to refer to only the most advanced
reptile-like amphibians. 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
Ascaphus truei". 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
reptiliomorphs closer to
amniotes, 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. ==Etymology==