There are differences between Xenopus laevis and Silurana (Xenopus) tropicalis that makes them incompatible. Mostly, there are size and temperature differences, as well as generation times. In the genetics world, S. tropicalis will eventually replace X. laevis as a model organism because tropicalis has a simpler DNA structure and a much faster generation time.

X. laevis 10 cm 16-22 (C) 1-2 years
S. tropicalis 4-5 cm 25-30 (C) < 5 months

It is interesting to note that Silurana tropicalis is more closely related to the dwarf clawed frogs (genera Hymenochirus and Pseudohymenochirus) and the Surinam toads (genus Pipa) than to the African clawed frog (genus Xenopus). The Pipidae frogs are very primitive and proves that they were around when Africa and South America were connected.

Photo, left to right
S. tropicalis, X. laevis (M), X.laevis (F)

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