Thursday, April 18, 2013

Dinosaur egg study supports evolutionary link between birds and dinosaurs

Darla Zelenitsky from the University of Calgary collaborated with David Varricchio at Montana State University to closely examined the shells of fossil eggs from a small meat-eating dinosaur called Troodon.
Published: Thursday, April 18, 2013
Jay Im (University of Calgary).
A small, bird-like North American dinosaur incubated its eggs in a similar way to brooding birds -- bolstering the evolutionary link between birds and dinosaurs, researchers at the University of Calgary and Montana State University study have found. Among the many mysteries paleontologists have tried to uncover is how dinosaurs hatched their young. Was it in eggs completely buried in nest materials, like crocodiles? Or was it in eggs in open or non-covered nests, like brooding birds?
Using egg clutches found in Alberta and Montana, researchers Darla Zelenitsky at the University of Calgary and David Varricchio at Montana State University closely examined the shells of fossil eggs from a small meat-eating dinosaur called Troodon.

In a finding published in the spring issue of Paleobiology, they concluded that this specific dinosaur species, which was known to lay its eggs almost vertically, would have only buried the egg bottoms in mud. "Based on our calculations, the eggshells of Troodon were very similar to those of brooding birds, which tells us that this dinosaur did not completely bury its eggs in nesting materials like crocodiles do," says study co-author Zelenitsky, assistant professor of geoscience. "Both the eggs and the surrounding sediments indicate only partial burial; thus an adult would have directly contacted the exposed parts of the eggs during incubation," says lead author Varricchio, associate professor of paleontology.

Varricchio says while the nesting style for Troodon is unusual, "there are similarities with a peculiar nester among birds called the Egyptian Plover that broods its eggs while they're partially buried in sandy substrate of the nest."

Paleontologists have always struggled to answer the question of how dinosaurs incubated their eggs, because of the scarcity of evidence for incubation behaviours. As dinosaurs' closest living relatives, crocodiles and birds offer some insights. Scientists know that crocodiles and birds that completely bury their eggs for hatching have eggs with many pores or holes in the eggshell, to allow for respiration. This is unlike brooding birds which don't bury their eggs; consequently, their eggs have far fewer pores.

The researchers counted and measured the pores in the shells of Troodon eggs to assess how water vapour would have been conducted through the shell compared with eggs from contemporary crocodiles, mound-nesting birds and brooding birds. They are optimistic their methods can be applied to other dinosaur species' fossil eggs to show how they may have been incubated. "For now, this particular study helps substantiate that some bird-like nesting behaviors evolved in meat-eating dinosaurs prior to the origin of birds. It also adds to the growing body of evidence that shows a close evolutionary relationship between birds and dinosaurs," Zelenitsky says.



Dinosaur embryos twitched in their eggs like those of modern birds

A collection of embryos fossilised at various ages in different nests reveals how dinosaurs developed in the egg
  • The Guardian,
Illustration of a dinosaur embryo inside its egg.
A Lufengosaurus dinosaur embryo inside its egg. Illustration: D. Mazierski
Dinosaur embryos moved around inside their eggs and grew in much the same way as those of modern animals such as birds, say scientists who have examined more than 200 fossilised bones from 190m-year-old embryos found in China.

The bones came from the genus known as Lufengosaurus, a long-necked dinosaur that could grow up to eight metres long, and were found among fragments of egg shells at a site near the city of Lufeng in Yunnan, south west China. They are the oldest dinosaur embryos ever found and seem to have come from several nests and from eggs at various stages of development. "Most of the time you get single glimpses of embryonic life in a dinosaur because they are preserved as a nest and all the eggs are in the same developmental stage," said Robert Reisz, a palaeontologist at the University of Toronto Mississauga, who led the team that analysed the bones. "Here we have a growth series of embryos, which allowed us to track how these animals grew."

The team's results are published in the journal Nature. Reisz's team focused their analysis on the largest bone, the femur. They found that, inside the eggs, these bones seemed to be growing very quickly, implying that their incubation period might have been relatively short.

Inside the bones is a honeycomb structure of "primary spaces". The larger these are, said Reisz, the faster the embryo would have grown. In addition, the scientists found that the bones were shaped inside the eggs, as they grew, as attached muscles pulled on them. "This suggests that dinosaurs, like modern birds, moved around inside their eggs," said Reisz. "It represents the first evidence of such movement in a dinosaur.


Tuesday, April 9, 2013

Free download - Excellent Adélie Penguin research paper

Research Article

Climate Change Winners: Receding Ice Fields Facilitate Colony Expansion and Altered Dynamics in an Adélie Penguin Metapopulation


  • Michelle A. LaRue mail,
  • David G. Ainley,
  • Matt Swanson,
  • Katie M. Dugger,
  • Phil O′B. Lyver,
  • Kerry Barton,
  • Grant Ballard    

  • PDF
  • Citation
  • XM
  • Friday, April 5, 2013

    Climate Change Winners: Adélie Penguin Population Expands as Ice Fields Recede

     Adélie penguin. The population size of an Adélie penguin colony on Antarctica’s Beaufort Island increased 84 percent as the ice fields retreated between 1958-2010, with the biggest change in the last three decades. (Credit: University of Minnesota)

    Apr. 3, 2013 — Adélie penguins may actually benefit from warmer global temperatures, the opposite of other polar species, according to a breakthrough study by an international team led by University of Minnesota Polar Geospatial Center researchers. The study provides key information affirming hypothetical projections about the continuing impact of environmental change.

    Researchers from the United States and New Zealand used a mix of old and new technology studying a combination of aerial photography beginning in 1958 and modern satellite imagery from the 2000s. They found that the population size of an Adélie penguin colony on Antarctica's Beaufort Island near the southern Ross Sea increased 84 percent (from 35,000 breeding pairs to 64,000 breeding pairs) as the ice fields retreated between 1958-2010, with the biggest change in the last three decades. The average summer temperature in that area increased about a half a degree Celsius per decade since the mid-1980s.

    The first-of-its-kind study was published today in PLOS ONE, a leading peer-reviewed scientific journal. The research affirms models published in 2010 projecting how south polar penguins will respond to changed habitat as Earth's atmosphere reaches 2 degrees Celsius above pre-industrial levels, a point that is rapidly approaching.

    The study showed that available habitat for Adélie penguins on the main portion of the Beaufort colony, on the south coast, increased 71 percent since 1958, with a 20 percent increase from 1983-2010. The extent of the snow and ice field to the north of the main colony did not change from 1958-1983, but then retreated 543 meters from 1983-2010.

    In addition to the overall population growth, researchers saw an increase in population density within the colony as it filled in what used to be unsuitable habitat covered in snow and ice. They also found that the emigration rates of birds banded as chicks on Beaufort Island to colonies on nearby Ross Island decreased after 2005 as available habitat on Beaufort increased, leading to altered dynamics of the population studied. "This research raises new questions about how Antarctic species are impacted by a changing environment," said Michelle LaRue, the paper's co-author and research fellow at the Polar Geospatial Center in the University of Minnesota's College of Science and Engineering. "This paper encourages all of us to take a second look at what we're seeing and find out if this type of habitat expansion is happening elsewhere to other populations of Adélie penguins or other species."

    Penguin expert and study co-author David Ainley, a lead author of an earlier study, agreed that this study gives researchers important new information. "We learned in previous research from 2001-2005 that it is a myth that penguins never move to a new colony in large numbers. When conditions are tough, they do," said Ainley, a senior marine wildlife ecologist with H.T. Harvey and Associates, an environmental consulting company in California. "This study at Beaufort and Ross Islands provides empirical evidence about how this penguin attribute will contribute to their response to climate change."

    Adélie penguins are common along the southern Antarctic coast. They are smaller than their Emperor penguin counterparts standing about 46 to 75 cm (18 to 30 inches) when upright and weighing about 4.5-5.4 kg (10-12 pounds). The Adélie penguin lives only where there is sea ice but needs the ice-free land to breed. Breeding pairs produce on average one chick per year and return to the same area to breed if conditions haven't changed.

    To determine changes in available nesting habitat in this study, researchers gathered aerial photos during the penguin incubation period in 1958, 1983 and 1993 and high-resolution satellite images from 2005 and 2010. Researchers overlaid the images exactly, lining up rocks and other geographical landmarks. They studied guano (penguin feces and urine) stains to determine the available habitat.
    In the future, researchers plan to use additional satellite imagery to look at other Adélie penguin populations to help understand the dynamics and environmental factors that influence regional populations. "This study brought together researchers from different academic disciplines who all contributed their expertise," LaRue said. "We had people who study climate change, spatial analysis, and wildlife population dynamics. This is how good science leads to results."

    In addition to LaRue and Ainley, other researchers involved in the study included Matt Swanson, a graduate student researcher at the University of Minnesota Polar Geospatial Center; Katie M. Dugger from Oregon State University; Phil O'B. Lyver from Landcare Research in New Zealand; Kerry Barton from Bartonk Solutions in New Zealand; and Grant Ballard from PRBO Conservation Science in California.

    The study was primarily funded by the National Science Foundation (NSF).

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

    Journal Reference:
    1. Michelle A. LaRue, David G. Ainley, Matt Swanson, Katie M. Dugger, Phil O′B. Lyver, Kerry Barton, Grant Ballard. Climate Change Winners: Receding Ice Fields Facilitate Colony Expansion and Altered Dynamics in an Adélie Penguin Metapopulation. PLoS ONE, 2013; 8 (4): e60568 DOI: 10.1371/journal.pone.0060568

    University of Minnesota (2013, April 3). Climate change winners: Adélie penguin population expands as ice fields recede. ScienceDaily. Retrieved April 5, 2013, from­ /releases/2013/04/130404092827.htm