Fossil birds from the time of dinosaurs (Eoenatiornis, left, and Hongshanornis, right) showing they had diverse types of leg. (Credit: Roger Close)
A radical shortening of their bony tails over 100 million years ago enabled the earliest birds to develop versatile legs that gave them an evolutionary edge, a new study shows. A team led by Oxford University scientists examined fossils of the earliest birds from the Cretaceous Period, 145 - 66 million years ago, when early birds such as Confuciusornis, Eoenantiornis and Hongshanornis lived alongside their dinosaur kin. At that point birds had already evolved powered flight, necessitating changes to their forelimbs, and the team investigated how this new lifestyle related to changes in their hind limbs (legs). The team made detailed measurements of early bird fossils from all over the world, including China, North America and South America. An analysis of this data showed that the loss of their long bony tails, which occurred after flight had evolved, led to an explosion of diversity in the hind limbs of early birds, prefiguring the amazing variety of talons, stilts and other specialised hind limbs that have helped to make modern birds so successful. A report of the research is published this week in Proceedings of the Royal Society B . 'These early birds were not as sophisticated as the birds we know today - if modern birds have evolved to be like stealth bombers then these were more like biplanes,' said Dr Roger Benson of Oxford University's Department of Earth Sciences, who led the research.
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