Flying gave the birds access to many new habitats, and an adaptive radiation took place. We see the results of this rapid evolution in the Chinese fossils from the Lower Cretaceous, which are more varied, and mostly more advanced, than "Archaeopteryx". There are now 31 different bird genera from the Lower Cretaceous of China. It is also clear, from the tail feathers of "Confuciusornis" (one of the Chinese fossils), that some of these birds were already using feathers for signalling and display, just as they do today. Like heat regulation, using feathers for display may be much earlier than flight. "Confuciusornis" is the fifth oldest bird fossil, about 25 million years after "Archaeopteryx".
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