Hi Frank:
Thanks for another great article

Although, I have never kept the dwarfs, I am very interested in the evolutionary study of the family Pipidae. The dwarf frogs (genus Hymenochirus) are more closely related to the South American Pipa than to the larger African clawed frogs, Xenopus. So it looks like Pipa, Hymenochirus and possibly the poorly known Pseudhymenochirus belong to the subfamily Pipinae. Xenopus belongs to the subfamily Xenopodinae. To make matters more confusing, Xenopus tropicalis and X. epitropicalis have been moved to the genus Silurana (new subfamily Siluraninae) and they are also more related to Pipa than to Xenopus. Fossilized Xenopus have been found in South America. I cannot think of a better example to show that Africa and South America were once one continent