Friday, July 29, 2011

"Oldest Bird" knocked off its perch

Xing Lida and Liu Yi
An artist's conception shows how the birdlike dinosaur known as Xiaotingia zhengi might have looked.
The newfound fossil of a 155 million-year-old feathered dinosaur has led scientists to claim that Archaeopteryx, the species long held forth as the "oldest bird," is no bird at all.
Chinese researchers made the claim in Thursday's issue of the journal Nature, and an outside expert says the study "is likely to rock the paleontological community for years to come." Ohio University paleontologist Lawrence Witmer noted that the latest research, focusing on a fossil species dubbed Xiaotingia zhengi, comes 150 years after the discovery of Archaeopteryx, which marked a milestone in the study of the origin of birds.

"It's fitting that 150 years later, Archaeopteryx is right back at center stage," Witmer told me.
Xiaotingia was found by a collector in China's Liaoning Province, a hotbed for feathered-dino fossils, and sold to the Shandong Tianyu Museum of Nature. Paleontologists led by Xing Xu of the Chinese Academy of Sciences analyzed the fossil's skeletal measurements in detail and fed them into a computer database with  measurements from 89 fossilized dinosaur and bird species, including Archaeopteryx.
Without Xiaotingia, the computer analysis put Archaeopteryx on the evolutionary line leading to modern-day birds. But when Xiaotingia was included, Archaeopteryx was placed in a group of birdlike dinosaurs known as deinonychosaurs. The differences had to do with details such as the shape of the wishbone and the skull's snout.

Archaeopteryx was about the size of a modern-day crow, and Xiaotingia was as big as a chicken.

Xu et al., Nature
The fossil skeleton of Xiaotingia zhengi is splayed out in rock.
"If you just looked at Xiaotingia, you'd say, 'Oh, boy, another little feathered dinosaur from China,'" Thomas Holtz, a paleontologist at the University of Maryland at College Park who reviewed the study for Nature, told me. "In and of itself, it is not a particularly unusual animal. But the combination of traits, at least in their analysis, pulls Archaeopteryx over to the deinonychosaur side of things."
The researchers acknowledged that their reclassification was "only weakly supported by the available data," but they said this kind of fuzziness was to be expected when the fossils being analyzed are close to the common ancestor of now-extinct dinosaurs and modern birds. "This phenomenon is also seen in some other major transitions, including the origins of major mammalian groups," they wrote.

Witmer agreed: "We're looking at an origin, and consequently it's going to be messy."
The 150 million-year-old Archaeopteryx fossil, which was discovered in southern Germany in 1861, was long seen as the oldest evidence of a bird species because the rocky imprint bore traces of feathers. But over the past decade or two, many dinosaur fossils have been found with evidence of feathers — to the extent that some scientists have been able to figure out how the feathers were colored. As a result, some researchers have argued for years that Archaeopteryx should be reclassified.

In the past, creationists have used Archaeopteryx in their arguments against evolutionary theory, contending that birds always existed in their feathered form and did not evolve from dinosaurs. Evolution's critics may try to spin these latest findings to their advantage as well, Witmer said.
"It may well be they're going to suggest that we evolutionists don't know what we're doing," he told me. "In reality, it's just the opposite. It just shows what evolution is all about. A prediction of evolutionary theory is that it should be really hard for us to figure out what's going on in an origin."

Archaeopteryx's dethronement means the title of "oldest bird" could fall to other ancient species, such as Epidexipteryx hui, Jeholornis and Sapeornis, Witmer said. "They're not exactly household names," he noted. "These new characters have been known only for 10 years or less." Archaeopteryx, meanwhile, would be lumped in with Xiaotingia as well as another feathered-dino species called Anchiornis huxleyi.

G. Mayr / Senckenberg
An Archaeopteryx specimen highlights wing and tail feather impressions.
The renewed debate over Archaeopteryx's classification is far from finished. Holtze said he knew some researchers who were inclined to go with a completely different classification scheme, which would put the deinonychosaurs along with Archaeopteryx on the evolutionary line leading to modern-day birds.
The debate could also require a rethinking of how birds arose, and how features such as feathers and flight developed. Holtz said some paleontologists have suggested that Archaeopteryx was not a particularly good flier, and putting it in the deinonychosaur category would make more sense on that score. It may turn out that deinonychosaurs gradually evolved from so-so fliers into feathered but flightless animals. "They would have been nasty predatory analogs to ostriches," Holtz said.

Holtz acknowledged that Archaeopteryx "has been our image of what early birds are like, for the historical reason that it's been known for 150 years as having all these feathers." The fact that the fossil was found just two years after Charles Darwin published "On the Origin of Species" added to its image as an evolutionary icon. A dramatic change in that image might come as another scientific shock to folks who are already being told that there's no such thing as a brontosaur, and that Pluto no longer ranks among the solar system's major planets.

"To which I say, 'Get over it!'" Holtz said. "Science is about changing ideas based on evidence, not about ignoring evidence to conform to our comfortable ideas."


Thursday, July 14, 2011

Drag Reduction by Air Release Promotes Fast Ascent in Jumping Emperor Penguins paper download link

Drag reduction by air release promotes fast ascent in jumping emperor penguins—a novel hypothesis

John Davenport1,*, Roger N. Hughes2, Marc Shorten1, Poul S. Larsen3

1Department of Zoology, Ecology and Plant Science, University College Cork, Distillery Fields, North Mall, Cork, Ireland
2School of Biological Sciences, Bangor University, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
3Department of Mechanical Engineering, Fluid Mechanics Section, Technical University of Denmark, Building 403,
2800 Kgs. Lyngby, Denmark
ABSTRACT: To jump out of water onto sea ice, emperor penguins must achieve sufficient underwater speed to overcome the influence of gravity when they leave the water. The relevant combination of density and kinematic viscosity of air is much lower than for water. Injection of air into boundary layers (‘air lubrication’) has been used by engineers to speed movement of vehicles (ships, torpedoes) through sea water. Analysis of published and unpublished underwater film leads us to present a hypothesis that free-ranging emperor penguins employ air lubrication in achieving high, probably maximal, underwater speeds (mean ± SD: 5.3 ± 1.01 m s–1), prior to jumps. Here we show evidence that penguins dive to 15 to 20 m with air in their plumage and that this compressed air is released as the birds subsequently ascend whilst maintaining depressed feathers. Fine bubbles emerge continuously from the entire plumage, forming a smooth layer over the body and generating bubbly wakes behind the penguins. In several hours of film of hundreds of penguins, none were seen to swim rapidly upwards without bubbly wakes. Penguins descend and swim horizontally at about 2 m s–1; from simple physical models and calculations presented, we hypothesize that a significant proportion of the enhanced ascent speed is due to air lubrication reducing frictional and form drag, that ­buoyancy forces alone cannot explain the observed speeds, and that cavitation plays no part in ­bubble formation.

Download this paper HERE

Penguins Take to the Air!

Matt Walker | Wednesday, 13 July 2011
Leaping Emperor penguin (Image: Blue Planet, BBC)
An Emperor penguin leaps from the water (Image: Blue Planet, BBC)
Penguins can’t fly. But they can get airborne.
In fact, taking to the air, for even a brief instant, is actually a vital strategy penguins employ to avoid being eating by predators such as leopard seals or orcas.
Now scientists have worked out the secret technique that penguins use to get airborne. It involves wrapping their bodies in a cloak of air bubbles – and it turns out to be the same technique that engineers use to speed the movement of ships and torpedoes through water.
Another interesting aspect of the discovery is that it was made by scientists examining in minute detail footage shot for the programme Blue Planet, a landmark natural history series filmed by the BBC’s own Natural History Unit.

It sounds implausible that penguins might get airborne. These short, squat birds, which tend to live in the colder parts of the southern hemisphere, are renowned for their waddling walks and flapping flippers – which are famously great for swimming, but useless for flying.
But many species of penguin do take to the air.
Due to their body shape, and poor climbing ability, it is difficult for penguins to haul themselves ashore, especially onto rocky shorelines. And it can be almost impossible for a penguin to haul itself out from the ocean onto sea ice.

Emperor penguins create bubble trails (image: Blue Planet, BBC)
Emperor penguins create bubble trails (image: Blue Planet, BBC)
So penguins leap ashore: they swim at speed to the surface, burst through and briefly get airborne to clear the rocks or ice shelf, and land on their breast.
Smaller species, such as Adelie penguins, can leap 2-3 metres out of the water, landing unscathed onto broken rock. Bigger species, such as Emperor penguins (the largest of all), reach heights of 20 – 45 cm, but that is enough for them to leap out of holes in the ice and clear the ice’s edge.
But one aspect of this leaping behaviour has long puzzled biologists. As the birds swim toward the surface, they trail a wake of bubbles behind them. No one knew where these bubbles come from, or why there are there.
Five years ago, that began to change when a group of biologists met in a pub in Cork, the Irish Republic, before the start of a scientific symposium.

Professor Roger Hughes from Bangor University in Gwynedd recalled how he’d seen a wildlife film in which penguins trailed bubbles in this way and asked his colleague Professor John Davenport, of University College Cork, if he knew why they did so.
Adelie penguin
Adelie penguins leap high (image:
Professor Davenport did not, but set off to find out with his PhD student Marc Shorten.
Together they obtained footage from the BBC of its Blue Planet series, which filmed breaching penguins for its Frozen Seas episode.

(Watch below how Emperor penguins first evade a leopard seal, then when the coast is clear, they trail a wake of bubbles before leaping from the water)
The scientists slowed down this footage, analysing the speeds and angles of emperor penguins exiting the water, developing a basic biomechanical model of what was going on.
During this analysis, the researchers made some interesting discoveries. The bubbles of air being trailed by the penguins weren’t coming out of the birds’ lungs via the beak.
Instead, they were coming from the birds’ feathers.

“We were amazed to find that,” Professor Davenport tells me.
The researchers also realised that these air bubbles form a “coat” around the birds’ bodies as they rocket toward the surface at speeds of 19km an hour.
To investigate further, the three scientists teamed up with Professor Poul Larsen from the Danish Technical University in Lyngby, who brought his expertise in mathematics and fluid mechanics to the research.
The four scientists have now just published the results of their study.

The “coat of air bubbles” first noticed on the Blue Planet footage is indeed what enables the penguins to get air as they leap onto land.
Penguins have great control over their plumage, Professor Davenport tells me.
They raise their feathers to fill their plumage with air, then dive underwater. As the birds descend, the water pressure increases, decreasing the volume of the trapped air. At a depth of 15-20 metres, for example, the air volume has shrunk by up to 75%.

The birds now depress their feathers, locking them around the new, reduced air volume.
The penguin then swims vertically up as fast as it can, and the air in the plumage expands and pours through the feathers.
“Because the feathers are very complex, the pores through which the air emerges are very small so the bubbles are initially tiny. They coat the outer feather surface.”
Crucially, this coat of small air bubbles acts as a lubricant, drastically reducing drag, enabling the penguins to reach lift-off speeds.

This air insulation effect is known to boat architects and engineers. By placing a layer of air around a ship’s hull, or torpedo, for example, designers can dramatically reduce drag, and speed up the boat or weapon’s passage through the water as a result.
But “this process has never been thought of before as having a biological role,” says Professor Davenport.
The penguins also appear to have overcome one other issue that blights naval architects trying to exploit “air lubrication” underwater.

Emperor penguin (image: Blue Planet, BBC)
The moment before lift off (image: Blue Planet, BBC)
Although a coat of tiny bubbles dramatically reduces drag, it can also have a major slowing effect if the bubbles reach a ship or torpedo’s propeller. That’s because the propeller starts pushing against air not water.
However, a penguin’s flippers, its means of propulsion equivalent to the propeller, are held outside of the bubble clouds, so they are not affected.

This wonderful insight into how penguins leap out of the water has just been published in the Marine Ecology Progress Series journal.

It brings a whole new meaning to the expression “getting air”.


Monday, July 11, 2011

A New Book on My "Must Read" List--Pioneers in Penguin Science

'Empire of Ice': The scientific quests of the Antarctic explorers

In "Empire of Ice," Pulitzer Prize-winning author and historian Edward J. Larson looks at how dedication to science powered many of the Antarctic's most daring expeditions.

Special to The Seattle Times

'An Empire of Ice: Scott, Shackleton, and the Heroic Age of Antarctic Science'
by Edward J. Larson
Yale University Press, 326 pp., $28

Leaving in the pitch black of the Antarctic winter of 1911, Edward Wilson, Apsley Cherry-Garrard and Birdie Bowers set out to find penguins. They were part of Robert Falcon Scott's second Antarctic expedition. To reach the birds, they man-hauled two sledges carrying 750 pounds, which often led to them having to relay the overweight sledges, so that for each mile advanced, they walked three. Moonlight provided a little light, but still they dropped into unseen crevasses and bumped into ice hummocks. And it was rather chilly, with temperatures dropping to minus-75.8 degrees F.

When they arrived at the penguin colony, the men built a stone hut, covered by a canvas tent. They were able to collect a few birds and eggs before a blizzard hit. Trapped for days, Cherry-Garrard wrote that the wind "sounded like the rush of an express train through a tunnel." Everything was frozen, and when the wind took the tent, the men had to cower in their exposed bags.

Their return trip to their base was even worse. Having had little success at the penguin colony, they had to man-haul 16 hours a day in mostly darkness, and Cherry-Garrard's jaw chattered so violently he shattered all of his teeth.

This "worst journey in the world," as it came to be called, was not the only time Wilson had risked his life to observe Antarctic penguins. He had studied the birds on Scott's previous expedition. But all of the hardships were worth it because "they did it for science," writes Edward J. Larson, in his new book, "An Empire of Ice: Scott, Shackleton, and the Heroic Age of Antarctic Science."

Writing about Scott's and Ernest Shackleton's Antarctic expeditions is a cottage industry. New books analyzing everything from the men's leadership abilities to how and why their reputations have changed appear regularly.
To his credit, Pulitzer Prize-winner Larson offers a new take by looking at how science drove many of the expeditions. As he did in previous books such as "Summer for the Gods" and "Evolution's Workshop," Larson combines careful reading of the primary documents, a thorough knowledge of the players, and first-rate writing to produce a compelling book. That having been said, this book's main appeal will be to those already familiar with the expeditions and those interested in the history of science.

My only complaint is the maps. I appreciate that Larson used historic maps from the expeditions, but they are very hard to read and often filled with too much surplus data. The photographs, however, are a nice addition.
The men took their research seriously, often making incredible sacrifices in the name of science, whether it be meteorology, biology or geology. They did so in part because they were British and felt that as citizens of the leading nation of the world, it was their responsibility to be the first to penetrate the unknown realms, to study them, and to write lengthy descriptions of what had been found.

Larson effectively argues that although some may look derisively back at Scott and Shackleton as relics of the Edwardian age, their scientific work should be considered as "modern and forward-looking enterprises." After all, Antarctica has become "fundamentally a place of science," and these expeditions led the way.


Friday, July 8, 2011

Pterosaurs Not Driven Into Extinction by Birds, Study Reveals

New research finds that pterosaurs, flying reptiles from the time of the dinosaurs, were not driven to extinction by the birds, but in fact they continued to diversify and innovate for millions of years afterward. (Credit: iStockphoto/Linda Bucklin)

The Rise and Rise of the Flying Reptiles: Pterosaurs Not Driven Into Extinction by Birds, Study Reveals

ScienceDaily (July 7, 2011) — Pterosaurs, flying reptiles from the time of the dinosaurs, were not driven to extinction by the birds, but in fact they continued to diversify and innovate for millions of years afterwards.
A new study by Katy Prentice, done as part of her undergraduate degree (MSci in Palaeontology and Evolution) at the University of Bristol, shows that the pterosaurs evolved in a most unusual way, becoming more and more specialised through their 160 million years on Earth. The work is published in the Journal of Systematic Palaeontology.

"Usually, when a new group of animals or plants evolves, they quickly try out all the options. When we did this study, we thought pterosaurs would be the same," said Katy. "Pterosaurs were the first flying animals -- they appeared on Earth 50 million years before Archaeopteryx, the first bird -- and they were good at what they did. But the amazing thing is that they didn't really begin to evolve until after the birds had appeared."
Katy's study was done in conjunction with her supervisors, Dr Marcello Ruta and Professor Michael Benton. They looked at 50 different pterosaurs that ranged in size from a blackbird to the largest of all, Quetzalcoatlus, with a wingspan of 12 metres, four times the size of the largest flying bird today, the albatross. They tracked how all the pterosaur groups came and went through their history and recorded in detail their body shapes and adaptations.

The new work shows that pterosaurs remained conservative for 70 million years, and then started to experiment with all kinds of new modes of life. After birds emerged and became successful, the pterosaurs were not pushed to extinction, as had been suggested. It seems they responded to the new flyers by becoming larger and trying out new lifestyles. Many of the new lifestyle adaptations were seen in the pterosaurs skulls, as they adapted to feed on different food sources; some were seed-eaters, many ate fish, and later ones even lost their teeth. The rest of the body also showed a surprising amount of variation between different groups, when considering that the body forms have to retain many features to allow flight.

"Pterosaurs were at the height of their success about 125 million years ago, just as the birds became really diverse too," said Dr Marcello Ruta. "Our new numerical studies of all their physical features show they became three times as diverse in adaptations in the Early Cretaceous than they had been in the Jurassic, before Archaeopteryx and the birds appeared."

Pterosaurs dwindled and disappeared 65 million years during the mass extinction that killed the dinosaurs. In their day they had been a fair match for the birds, and the two groups divided up aerial ecospace between them, so avoiding conflict.

"We're delighted to see a student mastering some tough mathematical techniques, and coming up with such a clear-cut result," said Professor Michael Benton. "Palaeontologists have often speculated about the coming and going of different groups of animals through time, but the new study provides a set of objective measurements of the relative success and breadth of adaptation of pterosaurs through their long time on the Earth."
Further information can be found on the Palaeobiology and Biodiversity Research Group's website: The rise and rise of the flying reptiles (

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Bristol.

Journal Reference:
  1. Katherine C. Prentice, Marcello Ruta, Michael J. Benton. Evolution of morphological disparity in pterosaurs. Journal of Systematic Palaeontology, 2011; DOI: 10.1080/14772019.2011.565081

University of Bristol (2011, July 7). The rise and rise of the flying reptiles: Pterosaurs not driven into extinction by birds, study reveals. ScienceDaily. Retrieved July 8, 2011, from­ /releases/2011/07/110706101608.htm

Sunday, July 3, 2011

New Theory On Origin of Birds: Enlarged Skeletal Muscles

Ostriches in South Africa's Kruger National Park. A developmental biologist is proposing a new theory of the origin of birds, which traditionally has been thought to be driven by the evolution of flight. The new theory credits the emergence of enlarged skeletal muscles as the basis for their upright two-leggedness, which led to the opportunity for other adaptive changes like flying or swimming. (Credit: © David Garry / Fotolia)
ScienceDaily (July 2, 2011) — A developmental biologist at New York Medical College is proposing a new theory of the origin of birds, which traditionally has been thought to be driven by the evolution of flight. Instead, Stuart A. Newman, Ph.D., credits the emergence of enlarged skeletal muscles as the basis for their upright two-leggedness, which led to the opportunity for other adaptive changes like flying or swimming. And it is all based on the loss of a gene that is critical to the ability of other warm-blooded animals to generate heat for survival.

Dr. Newman, a professor of cell biology and anatomy, studies the diversity of life and how it got that way. His research has always centered on bird development, though this current study, "Thermogenesis, muscle hyperplasia, and the origin of birds," also draws from paleontology, genetics, and the physiology of fat.
Dr. Newman draws on earlier work from his laboratory that provided evidence for the loss, in the common dinosaur ancestors of birds and lizards, of the gene for uncoupling protein-1 (UCP1). The product of this gene is essential for the ability of "brown fat," tissue that protects newborns of mammals from hypothermia, to generate heat. In birds, heat generation is mainly a function of skeletal muscles.

"Unlike the scenario in which the evolution of flight is the driving force for the origin of birds, the muscle expansion theory does not require functionally operative intermediates in the transition to flight, swimming, or winglessness, nor does it require that all modern flightless birds, such as ostriches and penguins, had flying ancestors. It does suggest that the extinction of non-avian dinosaurs may have been related to a failure to evolve compensatory heat-generating mechanisms in face of the loss of UCP1," says the scientist

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by New York Medical College, via EurekAlert!, a service of AAAS.

Journal References:
  1. Stuart A. Newman. Thermogenesis, muscle hyperplasia, and the origin of birds. BioEssays, 2011; DOI: 10.1002/bies.201100061
  2. Nadejda V Mezentseva, Jaliya S Kumaratilake, Stuart A Newman. The brown adipocyte differentiation pathway in birds: An evolutionary road not taken. BMC Biology, 2008; 6 (1): 17 DOI: 10.1186/1741-7007-6-17

New York Medical College (2011, July 2). New theory on origin of birds: Enlarged skeletal muscles. ScienceDaily. Retrieved July 3, 2011, from­ /releases/2011/06/110622115317.htm