Saturday, June 29, 2013

How 'Parrot Dinosaur' Switched from Four Feet to Two as It Grew

A Psittacosaurus skeleton cast in the permanent collection of The Children’s Museum of Indianapolis. (Credit: Photo by Michelle Pemberton, via Wikimedia Commons (Creative Commons license))

June 28, 2013 — Tracking the growth of dinosaurs and how they changed as they grew is difficult. Using a combination of biomechanical analysis and bone histology, palaeontologists from Beijing, Bristol, and Bonn have shown how one of the best-known dinosaurs switched from four feet to two as it grew.

Psittacosaurus, the 'parrot dinosaur' is known from more than 1000 specimens from the Cretaceous, 100 million years ago, of China and other parts of east Asia. As part of his PhD thesis at the University of Bristol, Qi Zhao, now on the staff of the Institute for Vertebrate Paleontology in Beijing, carried out the intricate study on bones of babies, juveniles and adults.

Dr Zhao said: "Some of the bones from baby Psittacosaurus were only a few millimetres across, so I had to handle them extremely carefully to be able to make useful bone sections. I also had to be sure to cause as little damage to these valuable specimens as possible."

With special permission from the Beijing Institute, Zhao sectioned two arm and two leg bones from 16 individual dinosaurs, ranging in age from less than one year to 10 years old, or fully-grown. He did the intricate sectioning work in a special palaeohistology laboratory in Bonn, Germany,
The one-year-olds had long arms and short legs, and scuttled about on all fours soon after hatching. The bone sections showed that the arm bones were growing fastest when the animals were ages one to three years. Then, from four to six years, arm growth slowed down, and the leg bones showed a massive growth spurt, meaning they ended up twice as long as the arms, necessary for an animal that stood up on its hind legs as an adult.

Professor Xing Xu of the Beijing Institute, one of Dr Zhao's thesis supervisors, said: "This remarkable study, the first of its kind, shows how much information is locked in the bones of dinosaurs. We are delighted the study worked so well, and see many ways to use the new methods to understand even more about the astonishing lives of the dinosaurs."

Professor Mike Benton of the University of Bristol, Dr Zhao's other PhD supervisor, said: "These kinds of studies can also throw light on the evolution of a dinosaur like Psittacosaurus. Having four-legged babies and juveniles suggests that at some time in their ancestry, both juveniles and adults were also four-legged, and Psittacosaurus and dinosaurs in general became secondarily bipedal."

The paper is published in Nature Communications.

Story Source:
The above story is reprinted from materials provided by University of Bristol.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Qi Zhao, Michael J. Benton, Corwin Sullivan, P. Martin Sander, Xing Xu. Histology and postural change during the growth of the ceratopsian dinosaur Psittacosaurus lujiatunensis. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3079

University of Bristol (2013, June 28). How 'parrot dinosaur' switched from four feet to two as it grew. ScienceDaily. Retrieved June 29, 2013, from­ /releases/2013/06/130628092147.htm

Thursday, June 13, 2013

X-Rays Reveal New Picture of 'Dinobird' Plumage Patterns

Artist's illustration of how Archaeopteryx may have looked sporting its new pigmentation. (Credit: Image courtesy of Manchester University) 
June 11, 2013 — The first complete chemical analysis of feathers from Archaeopteryx, a famous fossil linking dinosaurs and birds, reveals that the feathers of this early bird were patterned - light in colour, with a dark edge and tip to the feather ­­- rather than all black, as previously thought.

The findings came from X-ray experiments undertaken by a team from the University of Manchester, working with colleagues at the US Department of Energy's (DOE) SLAC National Accelerator Laboratory. The scientists were able to find chemical traces of the original 'dinobird' and dilute traces of plumage pigments in the 150 million-year-old fossil.

"This is a big leap forward in our understanding of the evolution of plumage and also the preservation of feathers," said Dr Phil Manning, a palaeontologist at The University of Manchester and lead author of the report in the June 13 issue of the Journal of Analytical Atomic Spectrometry (Royal Society of Chemistry).

Only 11 specimens of Archaeopteryx have been found, the first one consisting of a single feather. Until a few years ago, researchers thought minerals would have replaced all the bones and tissues of the original animal during fossilisation, leaving no chemical traces behind, but two recently developed methods have turned up more information about the dinobird and its plumage.

The first is the discovery of melanosomes - microscopic 'biological paint pot' structures in which pigment was once made, but are still visible in some rare fossil feathers. A team led by researchers at Brown University announced last year that an analysis of melanosomes in the single Archaeopteryx feather indicated it was black. They identified the feather as a covert - a type of feather that covers the primary and secondary wing feathers - and said its heavy pigmentation may have strengthened it against the wear and tear of flight, as it does in modern birds.

However, that study examined melanosomes from just a few locations in the fossilised feather, explained SLAC's Dr Uwe Bergmann: "It's actually quite a beautiful paper," he said, "but they took just tiny samples of the feather, not the whole thing."

The second is a method that Drs Bergmann, Manning and Roy Wogelius have developed for rapidly scanning entire fossils and analysing their chemistry with an X-ray beam at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL) in the USA.

Over the past three years, the team used this method to discover chemical traces locked in the dinobird's bones, feathers and in the surrounding rock, as well as pigments from the fossilised feathers of two specimens of another species of early bird. This allowed the team to recreate the plumage pattern of an extinct bird for the very first time.

In the latest study, the team scanned the entire fossil of the first Archaeopteryx feather with the SSRL X-ray beam. They found trace-metals that have been shown to be associated with pigment and organic sulphur compounds that could only have come from the animal's original feathers.
"The fact that these compounds have been preserved in-place for 150 million years is extraordinary," said Dr Manning said. "Together, these chemical traces show that the feather was light in colour with areas of darker pigment along one edge and on the tip.

"Scans of a second fossilised Archaeopteryx, known as the Berlin counterpart, also show that the trace-metal inventory supported the same plumage pigmentation pattern."

Co-author Dr Roy Wogelius, also based in Manchester's School of Earth, Atmospheric and Environmental Sciences, said: "This work refines our understanding of pigment patterning in perhaps the most important known fossil. Our technique shows that complex patterns were present even at the very earliest steps in the evolution of birds."

The team's results show that the chemical analysis provided by synchrotron X-ray sources, such as SSRL, is crucial when studying the fossil remains of such pivotal species. The plumage patterns can begin to help scientists review their possible role in the courtship, reproduction and evolution of birds and possibly shed new light on their health, eating habits and environment.

Dr Manning added: "It is remarkable that x-rays brighter than a million suns can shed new light on our understanding of the processes that have locked elements in place for such vast periods of time. Ultimately, this research might help inform scientists on the mechanisms acting during long-term burial, from animal remains to hazardous waste. The fossil record has potential to provide the experimental hindsight required in such studies."

The research team included scientists from The University of Manchester (UK); SLAC (USA); the Black Hills Institute of Geological Research in South Dakota (USA); and the Museum für Naturkunde in Berlin (Germany), which provided the stunning Archaeopteryx fossils for analysis.

Story Source:
The above story is reprinted from materials provided by Manchester University.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Phillip. L. Manning, Nicholas P. Edwards, Roy A. Wogelius, Uwe Bergmann, Holly E. Barden, Peter L. Larson, Daniela Schwarz-Wings, Victoria M. Egerton, Dimosthenis Sokaras, Roberto A. Mori, William I. Sellers. Synchrotron-based chemical imaging reveals plumage patterns in a 150 million year old early bird. Journal of Analytical Atomic Spectrometry, 2013; DOI: 10.1039/C3JA50077B

Manchester University (2013, June 11). X-rays reveal new picture of 'dinobird' plumage patterns. ScienceDaily. Retrieved June 13, 2013, from­ /releases/2013/06/130611204530.htm

Monday, June 3, 2013

Return to boom times? Cape Royds penguin colony shows signs of bouncing back

Photo Credit: Peter Rejcek
The Adélie penguin colony at Cape Royds once numbered 4,200 breeding pairs. It dropped during the 2000s but there are signs the population may be bouncing back.

The Adélie penguin boomtown known as Cape Royds went bust in the 2000s. Now there are signs that a recovery is under way.
The volcanic rocky headland on Ross Island has always been a sleepy place compared to the other Adélie penguin colonies in the region. It represents the farthest south Adélies have dared to set up breeding grounds.

By the turn of the century, about 4,200 breeding pairs made nests at Cape Royds. Then came the march of the icebergs, big tabular slabs of ice that blocked McMurdo Sound from the rest of the Ross Sea External Non-U.S. government site. Sea ice increased dramatically in the region. Royds became even more isolated, and life untenable except for the most hardy of the flightless seabirds.

“It’s starting to recover,” said David Ainley External Non-U.S. government site, senior ecologist at San Francisco Bay Area ecological consulting firm, H.T. Harvey and Associates External Non-U.S. government site.

Photo Credit: Peter Rejcek
Scientist David Ainley surveys the Adélie colony at Cape Royds.
Ainley is the principal investigator for a long-term project External Non-U.S. government site trying to understand factors behind the population dynamics and trends at Royds and other colonies in the Ross Sea region.

Every day or two he leaves his field camp — a semi-permanent structure that serves as kitchen, lounge and office, along with a few expedition tents — and walks among the squawking birds. Binoculars and yellow-covered notebook in hand, he records his observations, looking for birds that he, and others of his team have banded over the years.

Ainley’s research into penguin ecology and population dynamics goes back to the 1970s. Yet Antarctica’s iconic bird still surprises him.

“They’re kind of perplexing,” he said, a wisp of a grin under his white mustache.
Take the penguin diaspora and recent homecoming of the young adults that had been out to sea in recent years.

Ainley had expected it would take time before the colony could recover its numbers, which had dropped to about 1,400 breeding pairs by the summer of 2010-11. Even then, young birds around age 4 were starting to trickle back. [See previous article — Population pressures: Changes in Ross Sea environment, fishery cause demographic shift in species.]

This season, the number of known-age birds banded by the scientists doubled, from 35 to 72 nests. In the worst years, barely 20 nests could be found amongst the crowd. Still, many didn’t breed, though they showed up at their usual guano-stained spots, going through the motion of playing house.
“As they get older, they spend more and more time at the colony,” Ainley said.

Photo Credit: Peter Rejcek
Adult Adélie penguins care for a chick, while a second begins to break free of an egg.
One significant change that appears to be at play: The average breeding age of the Ross Island penguins has crept up from between ages 4 and 5 to ages 6 and 7.

Ainley and co-principal investigators Katie Dugger and Grant Ballard External Non-U.S. government site believe that may be due to the increasing sea ice in the region. While the icebergs may be long gone, change in climate is increasing the extent and duration of sea ice in the Ross Sea sector of the Southern Ocean.

That takes the penguins farther and farther away in winter as they ride a huge sea ice merry-go-round. The researchers learned this by attaching geo-locator tags to birds that had just fledged chicks in several seasons. Being farther away in spring means later arrival — especially for young birds that act like tardy teenagers anyway — to the extent that many don’t arrive in time to lay eggs.

However, the populations at most of the other Ross Sea colonies under study are increasing — a puzzle that Ainley blames on a commercial fishery that is removing a primary competitor from the ocean: the Antarctic toothfish.

Photo Credit: Peter Rejcek
Adelie penguins on their nests at Cape Royds. Mount Erebus, an active volcano, is in the background.
A long-lived species that can weigh in excess of 100 kilograms, the Antarctic toothfish is sold as Chilean sea bass at restaurants and supermarkets. One of its primary prey is Antarctic silverfish, Pleuragramma antarcticum. The penguins also favor this herring-sized fish, which may be more plentiful with fewer top predators around thanks to the dozen fishing vessels that ply the Ross Sea every summer.

“That’s why we think the penguin population is increasing. …Things are changing, and it doesn’t appear to be because of climate,” said Ainley, who has advocated creating a marine protected area for the Ross Sea. Previous analyses showed that colony sizes drop when there is very extensive winter sea ice.

Proposals among the international community have fallen short of what Ainley would like to see happen. A New Zealand-based documentary called The Last Ocean External Non-U.S. government site follows his and others’ efforts to conserve the Ross Sea ecosystem.

“It’s not too late if they stop or seriously slow the fishing right now,” he said. “It would still be less impacted than anywhere else. It would take 20 years to recover, if it did recover, given that the environment is changing.”

NSF-funded research in this story: David Ainley, H.T. Harvey and Associates, Award No. 0944411 External U.S. government site; Grant Ballard, PRBO, Award No. 0944141 External U.S. government site; and Katie Dugger, Oregon State University, Award No. 0944358 External U.S. government site.