According to new research from the Universities of Bristol and
Sheffield into the Paraves, the key characteristics that allow birds to fly,
their wings and small size, arose much earlier than previously thought. The
first birds and their closest dinosaurian relatives lived 160 to 120 million
years ago. Mark Puttick from the University of Bristol and colleagues investigated the rates of evolution of the two key characteristics that preceded flight: body size and forelimb length. In order to fly, hulking meat-eating dinosaurs had to shrink in size and grow much longer arms to support their feathered wings.
ADVERTISEMENT
<!–/* * Replace all instances of INSERT_RANDOM_NUMBER_HERE with
* a generated random number (or timestamp).
*
* The backup image section of this tag has been generated for use on a
* non-SSL page. If this tag is to be placed on an SSL page, change the
* 'http://ad10.walklightmedia.net/delivery/…'
* to
* 'https://ad10.walklightmedia.net/delivery/…'
*
* This noscript section of this tag only shows image banners. There
* is no width or height in these banners, so if you want these tags to
* allocate space for the ad before it shows, you will need to add this
* information to the tag.
*
* If you do not want to deal with the intricities of the noscript
* section, delete the tag (from … to ). On
* average, the noscript tag is called from less than 1% of internet
* users.
*/–>
… to
“We were really surprised to discover that the key size
shifts happened at the same time, at the origin of Paraves,” said Puttick
of Bristol’s School of Earth Sciences. ”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.”
Being small and light is important for a flyer, and it now seems
a whole group of dozens of little dinosaurs 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 study applied 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.
“Up to now you could only have guessed roughly where the
major evolutionary transitions occurred,” said Dr. Gavin Thomas of the
University of Sheffield, “but the new methods pinpoint the size changes.
The small size of birds and their long wings originated long before birds
themselves did.”
Birds owe their success to their flight, wings and feathers.
Until the 1990s, when the first feathered dinosaurs were found in China,
birds were thought to have originated rapidly, marking a major transition from
dinosaurs. Now, we know that Archaeopteryx was only one of a large
number of small, flying dinosaurs.
“The
origin of birds used to be seen as a rapid transition,” said Puttick,
“but now we know that the key characteristics we associate with them arose
much earlier.”
Read
more at the University
of Bristol.
Archaeopteryx render via Shutterstock.