Friday, January 29, 2010

Feathered Dinosaurs

I have posted extensively on what we call dawn age reptiles. These are critters that are at home in swamps and deep water and are mostly aquatic.  I avoided talking about the later reptiles for the nonce.

The niche occupied by dawn age reptiles immediately solved a huge problem of temperature control.  They lived almost exclusively in water and avoided the whole issue.  Even our old friend Nessie fitted nicely into the oceanic version of this niche.

However, the minute we allow these critters to stray away from water, it is necessary to think about temperature control.  Exposed skin does a poor job of controlling temperature.  We do not go out and work naked in either the mid day sun or the dead of winter without serious consequences.

Every critter exploiting a wider range of temperature using any vigor must be insulated.  Basking is not an activity.  This has meant hair or feathers.

Not surprisingly, these late reptiles are showing signs of using feathers.  This probably thinned out as they became large.  The internal mass by itself would then be largely sufficient.  Down and feathers would be necessary for the young in any case.  I think that the default mode for active advanced reptiles included down and feathers as a pre condition to leaving the swamps.

I think this story is only beginning to be told.

Dinosaur Sported Colorful Feathers
By Jeanna Bryner, LiveScience Managing Editor
posted: 27 January 2010 01:01 pm ET

A meat-eating dinosaur called Sinosauropteryx likely sported a rim of colored feathers on its head, down its back and tail when it lived some 120 million years ago. The tail probably had a striped pattern of orange and white. Credit: © Chuang Zhao and Lida Xing.
Our image of what dinosaurs looked like has just been colorized, thanks to fossilized feather remains showing one meat-eating beast sported a striped tail of white and gingery bands.

Not only do the results paint a jazzier picture of the ancient giants, they also confirm the presence of real feathers, not just "feather-like" or bristly structures, in some meat-eating dinosaurs called theropods, the scientists say. The finding has implications for understanding the origin of feathers, since scientists think birds evolved from a group of theropods called maniraptors, some 150 million years ago during the Jurassic period.

"Our research provides extraordinary insights into the origin of feathers," said Mike Benton, a professor of paleontology at the University of Bristol. "In particular, it helps to resolve a long-standing debate about the original function of feathers — whether they were used for flight, insulation, or display. We now know that feathers came before wings, so feathers did not originate as flight structures."
Rather, feathers were likely used for color display at first, he added.
Specifically, Benton and his colleagues found remains of melanosomes, which are tiny structures enclosing pigments that are embedded within the structure of feathers. Melanosomes are responsible, in part, for the colors exhibited by the feathers of some modern-day birds, such as zebra finch feathers.
The team looked at melanosomes from remains of theropods and primitive birds using a scanning electron microscope, finding melanosomes for reddish-brown to yellow pigment and those for black-grey pigment. While the remains didn't include actual pigments, the researchers matched the shapes of these melanosomes with those found in the feathers of today's birds to figure out the color. 

The pattern of the melanosome structures suggested the theropod Sinosauropteryx had simple bristles with alternating white and ginger, or chestnut-colored rings down its tail. And the early bird Confuciusornis had patches of white, black and orange-brown coloring on parts of its body.

"There's a very clear rim of feathers running down the top of the head kind of like a Mohican [Native American headdress] all the way down the back and along the tail," Benton said, referring to feathers on Sinosauropteryx, which lived some 120 million years ago.

In the past, some have suggested that what scientists assumed were fossilized feathers were actually bits of tissue.

"These bristles really are feathers," Benton said during a press briefing yesterday on the discovery. "If they were bits of skin or connective tissue or something else they would not contain melanosomes."

No comments: