Birds of today have femurs that bend backward and are nearly horizontal to the ground. This is needed to compensate for the extra weight of their heavily muscled wings. One thing that is a bit puzzling though is that the dinosaurs that modern birds evolved from stood upright with their feet directly under their center of mass. Scientists previously believed that the bird's ancestors so they crouched to balance their ever smaller tails.
A new study reconstructed many mostly complete skeletons of bird ancestors. They confirmed that the ancestors did start getting shorter tails, but that wasn't enough to completely explain why they crouched. Growth of the forelimbs that became wings had a much bigger role in the crouching. The crouched position may be good for takeoffs and landings, but the link between crouching and the evolution of flight is still not completely clear.
NOS themes:
Science is based on evidence: There are skeletons of dinosaurs and birds that can be compared for evidence.
Science is subject to debate and tentative: The researcher said: “I think this is a missing puzzle piece that future studies will be able to fill in using models like ours” , showing that as they find more evidence ideas can change.
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