The African bullfrogs are composed of morphologically very different genres. There are no outward similarities that you could use them as a synapomorphy for the delimitation of other families. One feature that is missing the genera of this family, is lobed, median tongue extension, occurring in many Old World frogs, among which are also the Pyxicephalidae closely related Petropedetidae and Phrynobatrachidae. In contrast to the difficult external diagnosis of the molecular genetic findings clearly supports a close relationship of the genera within the family Pyxicephalidae.
The genera Pyxicephalus and Aubria are very large and stocky. Together they form the subfamily Pyxicephalinae. In the second subfamily, the Cacosterninae that resemble only the genera Amietia and Strongylopus the Real frogs in size and appearance. The other members of this subfamily are very small in general. In Microbatrachella, Nothophryne and Poyntonia the Omosternum ( the front part of the sternum ) and the connection between procoracoid and clavicle is hardly ossified.
Systematics and Taxonomy
While still in 2005, the African bullfrogs, with almost the same level of genera, as now, as a sub- family of the family Ranidae had been counted, almost all subfamilies of Ranidae were in 2006 collected for own families in an extensive study of Darrel Frost and others. The African bullfrogs were then further divided into two subfamilies. The sister group of the Pyxicephalidae are the Petropedetidae with which they were sometimes combined into the superfamily Pyxicephaloidea.
The African bullfrogs include two subfamilies with 13 genera.
- Subfamily Cacosterninae Amietia Dubois, 1987 ( 16 species)
- Anhydrophryne Hewitt, 1919 ( 3 types)
- Arthroleptella Hewitt, 1926 (7 species)
- Cacosternum Boulenger, 1887 ( 15 species )
- Microbatrachella Hewitt, 1926 ( 1 species )
- Natalobatrachus Hewitt & Methuen, 1912 ( 1 species )
- Nothophryne Poynton, 1963 ( 1 species )
- Poyntonia Channing & Boycott, 1989 ( 1 species )
- Strongylopus Tschudi, 1838 ( 11 species)
- Tomopterna Duméril & Bibron, 1841 (15 species)
- Aubria Boulenger, 1917 ( 2 species)
- Pyxicephalus Tschudi, 1838 ( 4 species)
The monotypic genus Ericabatrachus ( with the only kind Ericabatrachus baleensis ) is difficult to classify and is provided by Darrel R. Frost in the family of African bullfrogs, in other classifications in the vicinity of the Petropedetidae. According to a recent analysis, the inclusion is justified in the Petropedetidae.