Reptiliomorpha is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with lissamphibians. It was defined by Michel Laurin (2001) and Vallin and Laurin (2004) as the largest clade that includes Homo sapiens but not Ascaphus truei.
FactsEditThe informal variant of the name, "reptiliomorphs", is also occasionally used to refer to stem-amniotes, i.e. a grade of reptile-like labyrinthodont tetrapods that are more closely related to amniotes than they are to lissamphibians, but are not amniotes themselves; the name is used in this meaning e.g. by Ruta, Coates and Quicke (2003). An alternative name, "Anthracosauria" is also commonly used for the group but is confusingly also used for the more primitive grade of reptiliomorphs by Benton.
As the exact phylogenetic position of Lissamphibia within Tetrapoda remains uncertain, it also remains controversial which fossil tetrapods are more closely related to amniotes than to lissamphibians, and thus, which ones of them were reptiliomorphs in any meaning of the word.
In Walking with... SeriesEditProterogyrinus and Seymouria. Proterogyrinus was featured during the Carboniferous period and reaching 2.3 m long, it was one of the dominant animals of its time. It was shown hunting Meganeura during a forest fire, and earlier one of them killed a giant Arthropleura by impaling it on a stump. By contrast, Seymouria was a much smaller animal, about 90 cm. in length, and it lived in the shadow of the first synapsids - the Pelycosaurs. A solitary Seymouria tried to rob a female Dimetrodon nest, but a wandering male Dimetrodon ambushed and killed it instead.
The first half of this episode features a labyrinthodont called Rhinesuchus - a distant cousin to the amphibians featured in the previous episode. It was depicted as one of the last representatives of the anthracosaur amphibians - most of them died out by the beginning of the Mesozoic. (The last giant amphibian (not a reptiliomorph) was Koolasuchus.)