Eli5: why are birds believed to be the descendants of the dinosaurs?
In: Earth Science
We know from DNA analyses that birds are most closely related to lizards and reptiles (particularly crocodiles and turtles), and we know many of those lizards and reptiles are essentially “cousins” of the dinosaurs that split off from the species that predated the dinosaurs.
Further, we know from the fossil record that therapod dinosaurs have a huge amount of physical features (particularly feathers, special bone structures, joints, etc.) that don’t appear in any other living creatures *except* for birds. Further, the closest structures to bird wings in the fossil record are the bone structures of the upper limbs of the therapods. And of course therapods incubated their eggs in a brooding behavior very similar to modern birds.
We also have fossils of creatures that seem to bridge the gap between the therapods and modern birds.
QED; birds are the descendants of the therapods.
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