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But do they have a two-chambered heart? Birds have a 4 chambered one and crocodiles have a 3 chambered one, which IIRC, is in some ways more complex that's very

• ncmncm 7y ago
  Apparently the current view is that crocs abandoned one of their chambers, which seems to me an astonishing thing to achieve. We can probably assume that the croc relatives that lived in trees or thundered across the tundra had four-chambered hearts. I gather most of them were taken by the mass extinction early in Jurassic era that opened the way for the dinosaurs. The crocs we have now must have all evolved from little caiman-like things, all their bigger relatives done in by the K-T event.