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Thursday, May 26, 2011
New Paper on Kaiika Maxwelli Published
Kaiika maxwelli, a new Early Eocene archaic penguin (Sphenisciformes, Aves) from Waihao Valley, South Canterbury, New Zealand
New Zealand Journal of Geology and Geophysics
Volume 54, Issue 1, March 2011, Pages 43 - 51
Authors:
RE Fordycea; DB Thomasa
DOI: 10.1080/00288306.2011.536521
Abstract
Kaiika maxwelli is a new species of archaic fossil penguin from the Kauru Formation (Waipawan-Mangaorapan, Early Eocene) of the southern Canterbury Basin, Waihao River, South Canterbury, New Zealand. Kaiika maxwelli is represented by a well-preserved large and robust humerus, in which the broad m. scapulotricipitalis tendon sulcus, sigmoidal shaft and vestigial supracondylar process are similar to those of the basal penguin Waimanu, but differs from Waimanu and other penguins by having a deeply incised ventral tubercle and a smoothly curved profile of the deltoid crest and head. Humeral length suggests a body length of 1.3 m comparable to that of an emperor penguin, indicating that large penguins lived at a time of global warmth. This is the first significant fossil penguin named from pre-Bortonian (Middle Eocene) strata of the southern Canterbury Basin. Kaiika maxwelli is only the seventh species of fossil penguin reportedly older than Middle Eocene.
Friday, May 20, 2011
China Fossil Shows Bird, Crocodile Family Trees Split Earlier Than Thought
ScienceDaily (May 19, 2011) —
A fossil unearthed in China in the 1970s of a creature that died about
247 million years ago, originally thought to be a distant relative of
both birds and crocodiles, turns out to have come from the crocodile
family tree after it had already split from the bird family tree,
according to research led by a University of Washington paleontologist.
The only known specimen of Xilousuchus sapingensis has been reexamined and is now classified as an archosaur. Archosaurs, characterized by skulls with long, narrow snouts and teeth set in sockets, include dinosaurs as well as crocodiles and birds.
The new examination dates the X. sapingensis specimen to the early Triassic period, 247 million to 252 million years ago, said Sterling Nesbitt, a UW postdoctoral researcher in biology. That means the creature lived just a short geological time after the largest mass extinction in Earth's history, 252 million years ago at the end of the Permian period, when as much as 95 percent of marine life and 70 percent of land creatures perished. The evidence, he said, places X. sapingensis on the crocodile side of the archosaur family tree.
"We're marching closer and closer to the Permian-Triassic boundary with the origin of archosaurs," Nesbitt said. "And today the archosaurs are still the dominant land vertebrate, when you look at the diversity of birds."
The work could sharpen debate among paleontologists about whether archosaurs existed before the Permian period and survived the extinction event, or if only archosaur precursors were on the scene before the end of the Permian.
"Archosaurs might have survived the extinction or they might have been a product of the recovery from the extinction," Nesbitt said.
The research is published May 17 online in Earth and Environmental Science Transactions of the Royal Society of Edinburgh, a journal of Cambridge University in the United Kingdom.
Co-authors are Jun Liu of the American Museum of Natural History in New York and Chun Li of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China. Nesbitt did most of his work on the project while a postdoctoral researcher at the University of Texas at Austin.
The X. sapingensis specimen -- a skull and 10 vertebrae -- was found in the Heshanggou Formation in northern China, an area with deposits that date from the early and mid-Triassic period, from 252 million to 230 million years ago, and further back, before the mass extinction.
The fossil was originally classified as an archosauriform, a "cousin" of archosaurs, rather than a true archosaur, but that was before the discovery of more complete early archosaur specimens from other parts of the Triassic period. The researchers examined bones from the specimen in detail, comparing them to those from the closest relatives of archosaurs, and discovered that X. sapingensis differed from virtually every archosauriform.
Among their findings was that bones at the tip of the jaw that bear the teeth likely were not downturned as much as originally thought when the specimen was first described in the 1980s. They also found that neural spines of the neck formed the forward part of a sail similar to that found on another ancient archosaur called Arizonasaurus, a very close relative of Xilousuchus found in Arizona.
The family trees of birds and crocodiles meet somewhere in the early Triassic and archosauriforms are the closest cousin to those archosaurs, Nesbitt said. But the new research places X. sapingensis firmly within the archosaur family tree, providing evidence that the early members of the crocodile and bird family trees evolved earlier than previously thought.
"This animal is closer to a crocodile, but it's not a crocodile. If you saw it today you wouldn't think it was a crocodile, especially not with a sail on its back," he said.
The research was funded by the National Science Foundation, the Society of Vertebrate Paleontology, the American Museum of Natural History and the Chinese Academy of Sciences.
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Washington. The original article was written by Vince Stricherz.
University of Washington (2011, May 19). China fossil shows bird, crocodile family trees split earlier than thought. ScienceDaily. Retrieved May 20, 2011, from http://www.sciencedaily.com /releases/2011/05/110518151822.htm
Friday, May 13, 2011
Penguins' Oxygen Trick: How They Survive Deep Dives
Jennifer Welsh, LiveScience Staff Writer
Date: 12 May 2011
 |
|
An Emperor penguin dives through a hole into the water below Antarctica's McMurdo Sound sea ice. CREDIT: Emily Stone, National Science Foundation |
The penguins can switch between two modes of oxygen use — either starving their muscles or giving them an extra shot of oxygen to keep them working — to achieve their amazing dives.
"It appears that there's a little bit of plasticity or variability in what they do when they are diving," said study researcher Cassondra Williams of the University of California in San Diego. "It's much more complicated than we thought." [Infographic: The Ocean's Deepest Divers]
To figure out how penguins survive deep dives on a single breath of air, the researchers designed special probes to monitor the levels of oxygen in the penguins' muscles during their dives off McMurdo Sound, Antarctica. The results are based on three emperor penguins and 50 dives, which ranged from 23 to 210 feet (7 to 64 meters) in depth, which lasted from 2.3 to 11.4 minutes.
"They have two different patterns they can opt for while they are diving," Williams told LiveScience. "In one, they appear to cut off blood flow completely to the muscle, leaving it to rely on its own supplies, which leaves the blood oxygen for the rest of the body, like the brain and the heart."
In other dives, the researchers saw a plateau after the initial oxygen drop. They believe that the penguin is selectively sending extra oxygen from the blood into the muscles, so they don't get tired. They can only do this for a limited time, though, until blood oxygen levels become too low for the rest of the body. Eventually the penguins need to come up for air.
Cutting off the oxygen supply to the muscles forces them to start making energy using "anaerobic" respiration, which is done without oxygen. It has a downfall, though; it produces a byproduct called lactic acid that can be toxic in high doses.
If the penguins let the lactic acid accumulate in their muscles, it takes longer to recuperate after a long dive, the researchers believe. This may be why on some dives the penguins send extra oxygen. For example, an extra oxygen shot might be beneficial if the penguins are taking
several dives during a short stint to, say, chase down a school of fish and don't want to lose the feeding opportunity while they spend additional time on the ice recuperating.
"They don't want to hit their aerobic limit and accumulate lactic acid, but it's not clear how or why they do that," Williams said.
The study was published May 12 in the Journal of Experimental Biology.
Source
Thursday, May 12, 2011
Why Global Warming Spells Disaster For Adélie Penguins (VIDEO)
by: Kristina Chew
The Western Antarctic Peninsula is one of the most rapidly warming areas on the earth: In just the past half-century, its temperatures have risen by 10.8 degrees Fahrenheit. Adélie penguins rely on the ice to live and global warming is taking its toll on their numbers, though not exactly in ways one might think.
Indeed, Adélie penguin colonies on the Antarctic Peninsula, on the northern edge of Antarctica, have declined by 90 percent, and the only colony of emperor penguins that once lived there is now extinct. But it turns out that elsewhere, specifically in the Ross Sea, a southern extension of the Pacific Ocean, Adélie colonies have been growing significantly, as winter sea ice cover grows there.
Indeed, climate change has benefited penguins in some ways, as the New York Times observes:
Other factors including consumers' taste for Chilean sea bass have
also helped the Ross Sea penguins' survival. Fishing fleets and a
fishery in the Ross Sea have encroached on the last refuge of the fish,
lessening the Adélie penguins' competition for food.
Despite this, the fate of the penguins seems sealed. As the boundary of the sea ice retreats south, the penguins' chances for survival diminishes. Global warming has also had a drastic effect on the food chain: A recent study in the Proceedings of the National Academy of Sciences has found that the warmer temperatures are killing off as much as 80 percent of the phytoplankton that grow under ice floes and the krill, a staple of the penguin diet.
Further, temperatures are rising in the Ross Sea: The average summer temperature at McMurdo Station, the American research base on Ross Island, has gone up 2.7 degrees Fahrenheit in the past 30 years, which is more than the global average. As the ice pack melts, the Ross Sea penguins will have no choice but to "shift their range farther south toward the pole."
David Ainley, an ecologist with the consulting firm H. T. Harvey and Associates who has been studying Ross Sea penguins for 40 years, notes that the penguins "appear to need light -- if only twilight -- to forage and navigate, and as comfort against predators." As the Adélie penguins have to go further south as the pack ice retreats, they may face extinction not only because their habitat is gone, but because of an "unshakable fear of darkness" -- because they find themselves living in a dark part of the world far from where they once made their colonies.
This video shows Adélie penguins on Ross Island, their home for the time being.
Source
The Western Antarctic Peninsula is one of the most rapidly warming areas on the earth: In just the past half-century, its temperatures have risen by 10.8 degrees Fahrenheit. Adélie penguins rely on the ice to live and global warming is taking its toll on their numbers, though not exactly in ways one might think.
Indeed, Adélie penguin colonies on the Antarctic Peninsula, on the northern edge of Antarctica, have declined by 90 percent, and the only colony of emperor penguins that once lived there is now extinct. But it turns out that elsewhere, specifically in the Ross Sea, a southern extension of the Pacific Ocean, Adélie colonies have been growing significantly, as winter sea ice cover grows there.
Indeed, climate change has benefited penguins in some ways, as the New York Times observes:
...in the Ross Sea a reverse trend is
occurring: Winter sea ice cover is growing, and Adélie populations are
actually thriving. The Cape Royds colony grew more than 10 percent every
year, until 2001, when an iceberg roughly the size of Jamaica calved
off the Ross Sea ice shelf and forced residents to move 70 kilometers
north to find open water. (The iceberg broke up in 2006, and the colony
of 1,400 breeding pairs is now recovering robustly.) Across Ross Island,
the Adélie colony at Cape Crozier -- one of the largest known, with an
estimated 230,000 breeding pairs -- has increased by about 20 percent.
Climate change has created a paradise for
some pack ice penguin colonies and a purgatory for others, but the
long-term fate of all Adélie and emperor penguins seems sealed, as
relentless warming eventually pulls their rug of sea ice out from under
them. Some scientists attribute the recent sea ice growth in the Ross
Sea to the persistent ozone hole, a legacy of the human use of
chlorofluorocarbons that cools the upper atmosphere over the continent,
increasing the temperature difference with the lower atmosphere and
equator, and over the last 30 years has delivered significantly brisker
westerly winds in the summer and autumn. The warming of Earth's middle
latitudes is having a similar effect, increasing that temperature
difference and sending stronger winds that push sea ice off the coast
and expose pockets of open water, called polynyas, that give nesting
Adélie penguins easier access to food.
Despite this, the fate of the penguins seems sealed. As the boundary of the sea ice retreats south, the penguins' chances for survival diminishes. Global warming has also had a drastic effect on the food chain: A recent study in the Proceedings of the National Academy of Sciences has found that the warmer temperatures are killing off as much as 80 percent of the phytoplankton that grow under ice floes and the krill, a staple of the penguin diet.
Further, temperatures are rising in the Ross Sea: The average summer temperature at McMurdo Station, the American research base on Ross Island, has gone up 2.7 degrees Fahrenheit in the past 30 years, which is more than the global average. As the ice pack melts, the Ross Sea penguins will have no choice but to "shift their range farther south toward the pole."
David Ainley, an ecologist with the consulting firm H. T. Harvey and Associates who has been studying Ross Sea penguins for 40 years, notes that the penguins "appear to need light -- if only twilight -- to forage and navigate, and as comfort against predators." As the Adélie penguins have to go further south as the pack ice retreats, they may face extinction not only because their habitat is gone, but because of an "unshakable fear of darkness" -- because they find themselves living in a dark part of the world far from where they once made their colonies.
This video shows Adélie penguins on Ross Island, their home for the time being.
Source
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