Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – _including humans_ – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my ~~shower thought~~ hypothesis. Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't _they_ considered amphibians too?

Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend _from_ Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).

![Tree](