兽脚亚目食肉恐龙是早期的有翼和羽的恐龙，其主要靠后足行走且不会飞行。

Theropods were early winged and feathered dinosaurs that walked mainly on their hind legs and were incapable of flight.

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䴙䴘目鸟类有独特的食羽行为，但对进入消化道后羽毛的功能、消化机理等存疑及争议颇多。

Grebes have a unique feather-eating behavior, but there are many suspicion and dispute on the mechanism of the digestion process and the function of feathers in the digestive tract.

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