The Evolution Of Bird, Like Dinosaurs, May Have Occurred Long Before Archaeopteryx
Archaeopteryx, which means early bird or original bird, was long considered to have evolved rapidly from dinosaurs. But scientists have now discovered that the transition of dinosaurs from being hulky meat -eaters to developing feathered wings and shrinking in size happened slowly over time. Scientist Mark Puttick and his colleagues investigated the evolution rates of two key characteristics needed for flight: body size and forelimb length.
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"We were really surprised to discover that the key size shifts happened at the same time, at
the origin of Paraves. This was at least 20 million years before the first bird, the famous Archaeopteryx, and it shows that flight in birds arose through several evolutionary steps", said Puttick, according to a press release Sunday.
Paraves includes dinosaurs closely related to birds. In order to fly, it was important for the dinosaurs to be small and light and evidence suggests that there were a whole lot of little dinosaurs that were lightweight and had wings of one sort or another. Most were gliders or parachutists, spreading their feathered wings, but not flapping them. "Out of all these flappers and gliders, only the birds seem to have been capable of powered flight," said co-author Mike Benton, Professor of Vertebrate Palaeontology at Bristol. "But you wouldn't have picked out Archaeopteryx as the founder of a remarkable new group."
The scientists arrived at these conclusions by applying new numerical methods that calculate the rate of evolution of different characteristics across a whole evolutionary tree, and identify where bursts of fast evolution occurred.
Dr. Gavin Thomas of the University of Sheffield said, "Up to now you could only have guessed roughly where the major evolutionary transitions occurred but the new methods pinpoint the size changes. The small size of birds and their long wings originated long before birds themselves did."
Until the 1990s, based on the fossils of Archaeopteryx, it was thought that birds had originated rapidly, marking a major transition from dinosaurs. But the discovery of non-avian dinosaur fossils with well -preserved feathers in China, gave rise to the theory that Archaeopteryx evolved later and was only one of a large number of small, flying dinosaurs.
"The origin of birds used to be seen as a rapid transition," said Mark Puttick, "but now we know that the key characteristics we associate with them arose much earlier."
Above photo courtesy of Shutterstock
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