User:Kurthu2/sandbox

Studies on [adaptive radiation] typically search for an “early-burst” signal of diversification under the idea that diversification within clades should slow over time as niches are occupied. Analyses done on earlier dinosaur species support this early-burst model of adaptive radiation, beginning in the [Triassic] period. However, this did not hold true for one clade known as Maniraptora, which includes all dinosaurs closer to birds than to ornithomimids and contains dinosaurs that survived to modern-day birds. Rather than showing a strong early-burst evolution in body size, this clade consolidated around a single adaptive center. Unlike its dinosaur ancestors, precursors to modern-day birds combined that characteristic with a high, steady rate of evolution, both in undirected body-size evolution and other forms of ecological adaptations to their environment. This could be a central reason why modern-day birds have significantly higher rates of ecological diversity compared to non-avian dinosaur species.

One hypothesis as to how modern birds survived the Cretaceous-Paloegene mass extinction when other dinosaur species did not could be related to their ability to adaptively radiate. Due to the fact that the avian ancestors of modern birds did not take up all of the niche space where other species did fill up their niche space, birds could have been able to produce a higher level of ecological diversity and innovation that helped them to faster adapt to different environments. These rates of evolution could in part be due to their small body sizes.

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