Thursday, January 28, 2010

More evidence for bird-dino link

An illustration depicting dinosaur Sinosauropteryx in true color, with a striped tail and orange back feathers
Sinosauropteryx is the first fossil dinosaur to have its color scientifically established.
Illustration courtesy James Robins
Chris Sloan
Published January 27, 2010

Pigments have been found in fossil dinosaurs for the first time, a new study says.

The discovery may prove once and for all that dinosaurs' hairlike filaments—sometimes called dino fuzz—are related to bird feathers, paleontologists announced today. (Pictures: Dinosaur True Colors Revealed by Feather Find.)

The finding may also open up a new world of prehistoric color, illuminating the role of color in dinosaur behavior and allowing the first accurately colored dinosaur re-creations, according to the study team, led by Fucheng Zhang of China's Institute for Vertebrate Paleontology.

The team identified fossilized melanosomes—pigment-bearing organelles—in the feathers and filament-like structures of fossil birds and dinosaurs from northeastern China.

Found in the feathers of living birds, the nano-size packets of pigment—a hundred melanosomes can fit across a human hair—were first reported in fossil bird feathers in 2008.

That year, Yale graduate student Jakob Vinther and colleagues, using a scanning electron microscope, discovered melanosomes in the dark bands of a hundred-million-year-old feather. In 2009 Vinther's group went on to show that another fossilized feather would have been iridescent in a living bird, due to microscopic light-refracting surfaces created by stacked melanosomes.

These earlier findings proved it was possible for melanosomes from dinosaur times to survive in fossils.
But until now no one had found the pigments in dinosaurs—other than birds, which many paleontologists consider to be dinosaurs. And no one had used melanosome shape and density to infer color.

End of Dinosaur-Bird Debate?

Even as the hundred-million-year-old bird melanosomes were being announced in 2008, the team behind the January 2010 report was using a scanning electron microscope to study minute details of feathered birds and dinosaurs found in Liaoning Province, China, a region famous for yielding thousands of exquisitely preserved animals that lived between 131 and 120 million years ago (prehistoric time line).

The Liaoning project put the team in a unique position to attempt the first melanosome discovery in dinosaurs.
"When we saw the Vinther paper, we said, Hey, look at this—and we found melanosomes immediately," said study co-author Mike Benton, a paleontologist at the University of Bristol in England.

The new study, published online today by the journal Nature, is "scientifically sound," said Hans Dieter-Sues, a paleontologist at the Smithsonian Institution's National Museum of Natural History in Washington, D.C., who was not involved in the research.

"I think the researchers really are looking at the fossilized remnants of melanosomes," he added in his email.
Among the fossil dinosaurs studied were several that were preserved with dino fuzz, such as the turkey-size carnivore Sinosauropteryx.

Some researchers argue that these controversial hairlike filaments, each about the width of a human hair, are fossilized internal collagen and not related to feathers.

The results reported today show that the filaments are packed with melanosomes in the same way as modern feathers.

"These filaments are probably the evolutionary precursors of true feathers," Benton said.

The Smithsonian's Sues added, "I think that one can safely say that this find invalidates some recent attempts to deny the existence of protofeathers in birdlike dinosaurs by claiming (without compelling evidence) that they are degraded collagen fibers."

University of Maryland paleontologist Thomas Holtz agreed, saying it's now up to skeptics "to either prove that internal collagen structures have melanosomes or melanosome-like elements—or to accept that dinosaurs had protofeathers."

Will this end the controversy about dino fuzz?

"It will definitely help end the debate," said Zhonghe Zhou, director of the Institute for Vertebrate Paleontology and a participant in the study.

"But there are still many issues that need to be further investigated," Zhou said. "What we've done here is to provide another line of evidence that the fiberlike filaments found in some dinosaurs are indeed protofeathers."
As for whether the discovery more securely establishes the evolutionary connection between dinosaurs and modern birds, the University of Maryland's Holtz said that, for him, previous, nonfeather discoveries had already settled the debate.

"I don't see that bonds already as strong as diamond links need any strengthening," said Holtz, who was not involved in the study.

(Related: "New Feathered Dinosaur Found; Adds to Bird-Dino Theory.")

A New World of Dinosaur Color
The discovery of melanosomes in fossil feathers also opens a window onto the previously unknown world of prehistoric color, because melanosomes contain the color-associated pigment melanin.
The two most common types of melanin found in modern birds are eumelanin, associated with black and grey feathers, and phaeomelanin, found in reddish brown to yellow feathers.

Melanosomes of both types were found during the new study, providing "the first empirical evidence for reconstructing the colors and color patterning" in dinosaurs and Chinese fossil birds, Zhang and his colleagues write.

For example, the 125-million-year-old early bird Confuciusornis was found to have color variation between blacks and browns in a single feather. And dark areas in Sinosauropteryx's tail were "absolutely packed with phaeomelanosomes," said Benton—a finding that led the team to propose that the dinosaur's tail was striped with "chestnut to rufous [reddish brown] tones."

The University of Maryland's Holtz said, "It seems reasonable to infer that the same size and shape melanosomes in dinosaurs would have resulted in the same colors as in modern birds."

But while melanosomes produce many feather colors, they can't make them all. Many bright feather colors, such as flamingo pink and canary yellow, are related to the foods birds eat.

And Sues, of the Smithsonian, said, "I would perhaps caution about direct inferences concerning coloration because the coloration on many present-day animals quickly changes after death as the color pigments degrade chemically."

Despite these limitations, the melanosome discoveries appear to mark the dawn of a new era for understanding the role of color in prehistoric worlds. Feather color in dinosaurs, for example, may reveal whether color patterns were useful for camouflage or peacock-like courtship displays, and if there were color differences between the sexes, as in many modern birds.

By searching for melanosomes and melanin not only in fossil feathers but also in other melanin-rich tissues, such as skin and hair, scientists, for the first time, won't have to guess at the colors of extinct creatures.
"All of the color reconstructions we made in the past were speculative," study co-author Zhou said. "Now we can add color to the ancient world and provide truly scientific reconstructions of extinct animals."

The University of Maryland's Holtz is "looking forward to the first really well-supported painting" of the many dinosaurs, lizards, and mammals of Liaoning. Still, he said, "I feel a little bit sorry for the paleo-artists, who've had a relatively open book as to how they colored dinosaurs.

"Now we've moved this idea of dinosaur color out of the realm of art and into the realm of science."

Wednesday, January 27, 2010

Dinosaur Extinction Grounded Ancient Birds, New Research Finds

Emus. New research suggests that ancestors of the African ostrich, Australasian emu plus cassowary, South American rheas and New Zealand moa became flightless independently, in close association with the extinction of the dinosaurs about 65 million years ago. (Credit: iStockphoto/John Carnemolla)

Dinosaur Extinction Grounded Ancient Birds, New Research Finds

ScienceDaily (Jan. 26, 2010) — An abundance of food and lack of predators following the extinction of dinosaurs saw previously flighted birds fatten up and become flightless, according to new research from The Australian National University.

The study, led by Dr Matthew Phillips, an ARC Postdoctoral Fellow at the ANU Research School of Biology, looked at the mitochondrial genome sequences of the now-extinct giant moa birds of New Zealand. To their surprise, the researchers found that rather than having a flightless relative, their closest relatives are the small flying tinamous of South America.

Their molecular dating study suggests that the ancestors of the African ostrich, Australasian emu plus cassowary, South American rheas and New Zealand moa became flightless independently, in close association with the extinction of the dinosaurs about 65 million years ago.

"Many of the world's largest flightless birds, known as ratites, were thought to have shared a common flightless ancestor. We followed up on recent uncertainty surrounding this assumption," said Dr Phillips.
"Our study suggests that the flighted ancestors of ratites appear to have been ground-feeding birds that ran well. So the extinction of the dinosaurs likely lifted predation pressures that had previously selected for flight and its necessary constraint, small size. Lifting of this pressure and more abundant foraging opportunities would then have selected for larger size and consequent loss of flight."

The finding of independent origins of flightlessness also solves a mystery of how these flightless birds dispersed across the world over marine barriers -- their ancestors flew. "Ratite birds have been thought of as relics of the former Gondwanan supercontinent, which combined Africa, South America, Australia, Antarctica, New Zealand, India and Madagascar," said Dr Phillips. "Not only have we shown that the separate ratite lineages evolved too recently to have been on Gondwana before its continents drifted apart, but from our analyses we infer that at least ostriches, and possibly ratites as a whole, have their origins in the northern continents."

The researchers' paper is published in this month's issue of the journal Systematic Biology.
 Story Source:
Adapted from materials provided by Australian National University.

Journal Reference:
  1. Phillips et al. Tinamous and Moa Flock Together: Mitochondrial Genome Sequence Analysis Reveals Independent Losses of Flight among Ratites. Systematic Biology, 2010; 59 (1): 90 DOI: 10.1093/sysbio/syp079

Australian National University. "Dinosaur Extinction Grounded Ancient Birds, New Research Finds." ScienceDaily 26 January 2010. 27 January 2010 <­ /releases/2010/01/100126105429.htm>.

Wednesday, January 20, 2010

Happy Penguin Awareness Day!!!!

Penguin Cupcakes
Originally uploaded by *kimmie*


Wear something black and white!
Read a book on penguins!
Donate to your favorite penguin charity!
Visit a penguin at the zoo or aquarium! 
Make a post about your favorite penguin!

See the penguin---be the penguin. ;-)

Penguin Cupcakes by *kimmie*.

Saturday, January 16, 2010

Alligators Breathe Like Birds


Computerized tomographic (CT) X-ray images of side and top views of a 24-pound American alligator, with 3-D renderings of the bones and of airways or bronchi within the lungs. The windpipe and first-tier of bronchi are not shown. A University of Utah study found that air flows in one direction through a gator's lungs. It flows from the first-tier bronchi through second-tier bronchi (blue), then through tube-like third-tier parabronchi (not shown) and then back through other second-tier bronchi (forest green). (Credit: C.G. Farmer and Kent Sanders, University of Utah.)

Alligators Breathe Like Birds, Study Finds

ScienceDaily (Jan. 15, 2010)University of Utah scientists discovered that air flows in one direction as it loops through the lungs of alligators, just as it does in birds. The study suggests this breathing method may have helped the dinosaurs' ancestors dominate Earth after the planet's worst mass extinction 251 million years ago.
Before and until about 20 million years after the extinction -- called "the Great Dying" or the Permian-Triassic extinction -- mammal-like reptiles known as synapsids were the largest land animals on Earth.
The extinction killed 70 percent of land life and 96 percent of sea life. As the planet recovered during the next 20 million years, archosaurs (Greek for "ruling lizards") became Earth's dominant land animals. They evolved into two major branches on the tree of life: crocodilians, or ancestors of crocodiles and alligators, and a branch that produced flying pterosaurs, dinosaurs and eventually birds, which technically are archosaurs.
By demonstrating one-way or "unidirectional" airflow within the lungs of alligators, the new study -- published in the Jan. 15 issue of the journal Science -- means that such a breathing pattern likely evolved before 246 million years ago, when crocodilians split from the branch of the archosaur family tree that led to pterosaurs, dinosaurs and birds.
That, in turn, means one-way airflow evolved in archosaurs earlier than once thought, and may explain why those animals came to dominance in the Early Triassic Period, after the extinction and when the recovering ecosystem was warm and dry, with oxygen levels perhaps as low as 12 percent of the air compared with 21 percent today.
"The real importance of this air-flow discovery in gators is it may explain the turnover in fauna between the Permian and the Triassic, with the synapsids losing their dominance and being supplanted by these archosaurs," says C.G. Farmer, the study's principal author and an assistant professor of biology at the University of Utah. "That's the major reason this is important scientifically."
Even with much less oxygen in the atmosphere, "many archosaurs, such as pterosaurs, apparently were capable of sustaining vigorous exercise," she adds. "Lung design may have played a key role in this capacity because the lung is the first step in the cascade of oxygen from the atmosphere to the animal's tissues, where it is used to burn fuel for energy."
Farmer emphasized the discovery does not explain why dinosaurs, which first arose roughly 230 million years ago, eventually outcompeted other archosaurs.
Farmer conducted the study -- funded by the National Science Foundation -- with Kent Sanders, an associate professor of radiology at the University of Utah School of Medicine. They performed CT scans of a 4-foot-long, 24-pound alligator.
'The Great Dying' -- Decline of the Synapsids, Rise of the Archosaurs

The synapsids -- which technically include modern mammals -- occupied ecological niches for large animals before the Permian-Triassic extinction.
"Some got up to be bear-sized," says Farmer. Some were meat-eaters, others ate plants. They were four-footed and had features suggesting they were endurance runners. Their limbs were directly under their body instead of sprawling outward like a lizard's legs. There is evidence they cared for their young.
The cause of the mass extinction 251 million years ago is unknown; theories include massive volcanism, an asteroid hitting Earth and upwelling of methane gas that had been frozen in seafloor ice.
"A few of the synapsids survived the mass extinction to re-establish their dominance in the early Triassic, and the lineage eventually gave rise to mammals in the Late Triassic," says Farmer. "However, the recovery of life in the aftermath of the extinction involved a gradual turnover of the dominant terrestrial vertebrate lineage, with the archosaurs supplanting the synapsids by the Late Triassic."
From then until the dinosaurs died out 65 million years ago, any land animal longer than about 3 feet was an archosaur, says Farmer, while mammal-like synapsid survivors "were teeny little things hiding in cracks. It was not until the die-off of the large dinosaurs 65 million years ago that mammals made a comeback and started occupying body sizes larger than an opossum."
No one knows much about the archosaur that was the common ancestor of crocodilians and of pterosaurs, dinosaurs and birds, Farmer says.
It probably was "a small, relatively agile, insect-eating animal," Farmer says. Illustrations of early archosaurs look like large lizards.
"Our data provide evidence that unidirectional flow [of air in the lungs] predates the origin of pterosaurs, dinosaurs and birds, and evolved in the common ancestor of the crocodilian and bird [and pterosaur and dinosaur] lineages," Farmer says.
Cul-de-sacs or Loops for Airflow

In the lungs of humans and other mammals, airflow is like the tides. When we inhale, the air moves through numerous tiers of progressively smaller, branching airways, or bronchi, until dead-ending in the smallest chambers, cul-de-sacs named alveoli, where oxygen enters the blood and carbon dioxide moves from the blood into the lungs.
It long has been known that airflow in birds is unidirectional, and some scientists suggest it also was that way in dinosaurs.
In modern birds, the lungs' gas exchange units are not alveoli, but tubes known as "parabronchi," through which air flows in one direction before exiting the lung. Farmer says this lung design helps birds fly at altitudes that would "render mammals comatose."
Some researchers have argued that unidirectional airflow evolved after crocodilians split from the archosaur family tree, arising among pterosaurs and theropod dinosaurs, the primarily meat-eating group that included Tyrannosaurus rex. Others have argued it arose only among coelurosaurs, a group of dinosaurs that also includes T. rex and feathered dinosaurs.
Unidirectional air flow in birds long has been attributed to air sacs in the lungs. But Farmer disagrees, since gators don't have air sacs, and says it's due to aerodynamic "valves" within the lungs. She believes air sacs help birds redistribute weight to control their pitch and roll during flight. Farmer says many scientists simply assume air sacs are needed for unidirectional airflow, and have pooh-poohed assertions to the contrary.
"They cannot argue with this data," she says. "I have three lines of evidence. If they don't believe it, they need to get an alligator and make their own measurements."
Assessing Airflow in Alligators

Farmer did three experiments to demonstrate one-way airflow in alligators' lungs:
  • She performed surgery on six anesthetized alligators and inserted flow meters called thermistors into the lungs to measure airflow speed and direction.
  • Farmer pumped air in and out of lungs removed from four dead alligators sent to her by a wildlife refuge in Louisiana. The flow was monitored, showing the air kept going the same direction to loop through various tiers of bronchi and back to the trachea.
  • Using lungs from another dead gator, she pushed and pulled water with tiny fluorescent beads through the lungs, making movies showing the unidirectional flow.
Farmer says the fact gator lungs still had unidirectional flow after being removed shows unidirectional airflow is caused by aerodynamic valves within the lungs, and not by some other factor, like air sacs or the liver, which acts like a piston to aid breathing.
How does air loop through an alligator's multichambered lungs?
Inhaled air enters the trachea, or windpipe, and then flows into two primary bronchi, or airways. Each of those primary bronchi enters a lung.
From those primary airways, the bronchi then branch into a second tier of narrower airways. Inflowing air jets past or bypasses the first branch in each lung because the branch makes a hairpin turn away from the direction of airflow, creating an aerodynamic valve. Instead, the air flows into other second-tier bronchi and then into numerous, tiny, third-tier airways named parabronchi, where oxygen enters the blood and carbon dioxide leaves it.
The air, still moving in one direction, then flows from the parabronchi into the bypassed second-tier bronchi and back to the first-tier bronchi, completing a one-way loop through the lungs before being exhaled through the windpipe.

Story Source:
Adapted from materials provided by University of Utah.

University of Utah. "Alligators Breathe Like Birds, Study Finds." ScienceDaily 15 January 2010. 16 January 2010 <­ /releases/2010/01/100114143014.htm>.