system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If two-legged dinosaurs evolved into birds, what happened to four-legged dinosaurs?
gpt
They went extinct, as did almost all of the two-legged dinosaurs as well. Not all theropods evolved into birds, only a single line that then branched out into all the species we know today. All the others, like T-rex or allosaurus, were simply dead-ends and have no living descendants today.