Paraves is a clade of bird-esque dinosaurs that lived 120-160 million years ago. A recent study in the journal Evolution suggests that certain characteristics of paravians – the small size of these birds, their feathers, a fused bone in the wrist, as well as their wings – originated much early than paleontologists previously thought. Mark Puttick, of the University of Bristol in the United Kingdom, led the study that analyzed evolution of body size and forelimb length in dinosaurs closely related to birds and bird-like animals alive during the Mesozoic period.

20 million years before Archaeopteryx, dozens of dinosaurs were found to be light and winged, though not flapping their wings.

High rates of evolution of the ancestors of paravians – mostly reduction in body size – led to smaller bodies and a larger forelimb in these dinosaurs over time. This explains similarities between paravians and early birds. Puttick’s study found that paravian miniaturization did not coincide with forelimb elongation. The study did, however, identify increased rate of evolution of forelimbs and body size when paravians originated, a novel finding.

The study further determined new methods to analyze size changes in history; whereas before only a rough guess was available. They found that the size and wings of birds’ ancestors evolved much sooner than birds did – paravians were trying out new modes of flight during the Late Jurassic and Early Cretaceous periods. Puttick comments that “The origin of birds used to be seen as a rapid transition, but now we know that the key characteristics we associate with them arose much earlier.”

There were several conclusions: scant evidence for increased rate of evolution within or leading to birds from paravians. They also concluded that bone changes associated with flight, reduced body size, and an elongated forelimb occurred before birds originated, but changes in bone structure won’t be able to tell us the origin of flight. Finally, though most studies on the origin of Aves (birds) deal with whether flight began on the ground or in the trees, this study found structures consistent with the notion that paravians were experimenting with different modes of flight, including gliding and parachuting.

Source: Puttick, M. N., Thomas, G. H., & Benton, M. J. (2014). High rates of evolution preceded the origin of birds. Evolution. doi/10.1111/evo.12363/

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Published On: April 9, 2014

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