Prehistoric Birds May Have Used Four Wings to Fly

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Roughly 150 million years ago, birds began to evolve. The winged
creatures we see in the skies today descended from a group of dinosaurs
called theropods, which included tyrannosaurs, during a 54-million-year chunk of time known as the Jurassic period. Why the ability to fly evolved in some species is a difficult question to answer,
but scientists agree that wings came to be because they must have been
useful: they might have helped land-based animals leap into the air, or
helped gliding creatures who flapped their arms produce thrust.

As researchers continue to probe the origin of flight, studies of fossils have shown that theropods–particularly coelurosaurian dinosaurs,
which closely resemble modern birds—had large feathers on both their
fore limbs and hind limbs. However, extensive evidence for these leg
feathers didn’t exist in the earliest birds. But now, a new examination
of fossils reported today in the journal Science reveals several examples of this four-winged anatomy in modern birds’ oldest common ancestors.

Modern birds have two types of feathers:
vaned feathers that cover the outside of the body, and the down
feathers that grow underneath them. Researchers studying the
approximately 120 million-year-old fossils of 11 primitive birds from
the Shandong Tianyu Museum of Natural History in China found that one type of vaned plumage, also known as pennaceous feathers, was neatly preserved in skeletal fossils of these specimens, along each creatures’ hind limbs. After
this find, the researchers must have been flying high: The feathers of
birds’ wings, known as flight feathers, are long, stiff and
asymmetrically shaped pennaceous feathers, similar to those found in the
fossils. When fanned together, pennaceous feathers form the broad
surfaces of birds’ wingspans—without these surfaces, birds cannot stay
aloft.

Pennaceous feathers, which are composed of many flattened barbs,
existed in some winged dinosaurs. Finding them on the hind legs of early
birds suggests that before birds used two wings to fly, they may have
depended on four. Over millions of years, however, birds gradually lost
the feathers on this extra set of wings.

Written By: Marina Koren
continue to source article at blogs.smithsonianmag.com

1 COMMENT

  1. There was an earlier discussion on Dinosaur feathers on the old site;- http://old.richarddawkins.net/articles/587327-feather-evolution

    With this interesting 5 page article on feather evolution linked to it here:-

    http://ngm.nationalgeographic.com/2011/02/feathers/zimmer-text/1

    http://ngm.nationalgeographic.com/2011/02/feathers/clark-photography

    There is also an article on 4 winged Dinos here:-

    http://www.sciencenews

    A rethink of four-winged dinosaurs suggests that the much-debated hind wings stayed tucked under the body until deployed in the air for tight turns to dodge branches or chase prey.

    Just what a dinosaur did with well-developed feathers on all four of its limbs has been a puzzle since the 2003 unveiling of roughly 130-million-year-old Microraptor gui fossils from northeastern China.

    Interestingly the evolution of feathers can be illustrated in the fluffy barbules as chick embryos develop.

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