According to a University of Oxford press release dated August 13, a research team led by scientists from the prestigious British university discovered that, after examining fossils from the Cretaceous Period (145-66 million years ago), a fundamental shortening of the bony tails of the earliest birds caused the development of versatile legs and gave these animals an evolutionary edge. The findings are reported this week in the Proceedings of the Royal Society B, under the title, “Rates of dinosaur limb evolution provide evidence for exceptional radiation in Mesozoic birds.”
“Birds are the most diverse living tetrapod group and are a model of large-scale adaptive radiation. Neontological studies suggest a radiation within the avian crown group, long after the origin of flight. However, deep time patterns of bird evolution remain obscure because only limited fossil data have been considered,” wrote the researchers in the study’s abstract.
It was during the Cretaceous Period that the earliest birds, such as Confuciusornis, Eoenantiornis, and Hongshanornis lived alongside their dinosaur kin. Because birds had already achieved powered flight by this point, the dramatic changes to birds’ forelimbs caused an equally dramatic change to the hind legs. The scientists took interest in the lifestyle change, and embarked on a study to determine the relationship between the changes in the fore and hind legs.
Following the detailed analysis of early bird fossils from China, North America, South America, and in various other locations around the world, the team of scientists discovered that the loss of long, bony tails led to an incredible explosion of diverse hind legs and limbs, such as talons and stilts.
According to Doctor Roger Benson of Oxford Unversity, “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. Yet what surprised us was that despite some still having primitive traits, such as teeth, these early birds display an incredibly diverse array of versatile legs.”
Doctor Benson added, “Our work shows that, whilst they may have started off as just another type of dinosaur, birds quickly made a rather special evolutionary breakthrough that gave them abilities and advantages that their dinosaur cousins didn’t have. Key to this special ‘birdness’ was losing the long bony dinosaur tail – as soon as this happened it freed up their legs to evolve to become highly versatile and adaptable tools that opened up new ecological niches.”
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