It seems that many people who keep African bullfrogs are having diffiulties telling the two species apart. First, the popular names are confusing. In Africa, Pyxicephalus adspursus , the "African Bullfrog (in U.S.)" is known as the Giant Bullfrog, while its smaller cousin, Pyxicephalus edulis is known as the African Bullfrog. The second problem is the assignment of new scientific names.
Subfamily: Pyxicephalinae
Genus: Pyxicephalus
* Species: Pyxicephalus adspersus Tschudi, 1838
**Synonym: Pyxicephalus adspersus adspersus Parry, 1982
*Species: Pyxicephalus edulis Peters, 1854
**Synonym: Pyxicephalus adspersus angusticeps Parry, 1982
Source: Frost, Darrel R. 2010. Amphibian Species of the World: an Online Reference. Version 5.4 (8 April, 2010). Electronic Database accessible at Amphibian Species of the World
American Museum of Natural History, New York, USA.
OK, time to eliminate the confusion.
Pyxicephalus adspersus
- Upper jaw withour irregular vertical pale bars
- No white spot on tympanum (ear drum)
- No pale interorbital bar
- Distance from eye to tympanum is about twice the diameter of the eye
Pyxicephalus edulis
- Upper jaw with irregular pale bars
- White spot on tympanum
- Distance from eye to tympanum is about the same as the diameter of the eye
There is a third species, Pyxicephalus obbianus (Calabresi's Bullfrog) that I have not seen in the pet tade and is endemic to Somalia. At one time, the genus Pyxicephalus had about 12 species, most of the smaller species moving into the genus Tomopterna (or sand frogs, native to Africa and India).
I hope this helps