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TOPIC: Hunting Dinosaurs


L

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RE: Hunting Dinosaurs
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Children and toddlers are invited to the Museum of the Rockies' annual dinosaur egg hunt, set for 10 a.m. Saturday,...
Over 6,000 dinosaur eggs will be available to find, including 50 golden eggs with special dinosaur prizes in honour of the museum's 50th anniversary.

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L

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Dinosaur nest
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The Chinese government is conducting an investigation into the sale of a rare fossilised dinosaur nest, reportedly discovered in China, for 420,000 U.S. dollars at an auction in Los Angeles, according to the Ministry of Foreign Affairs.

"The Chinese government attaches great importance to the sale and is conducting an investigation into it" - Qin Gang, foreign ministry spokesman.

An unusually well-preserved 65 million-year-old dinosaur nest containing fossilised eggs was sold by auction house Bonhams & Butterfields on December 4.

Source: Xinhua

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Raptor egg nest
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Free Image Hosting at www.ImageShack.us

This photo released by Bonhams and Butterfields shows a well-preserved 65 million-year-old fossilised raptor egg nest with embryonic remains, from the Cretaceous period.

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L

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Dinosaur nest
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An exceptionally well-preserved 65-million year-old fossilised dinosaur nest with some broken eggs exposing tiny skeletons is up for auction in Los Angeles on Sunday.
The nest of raptors, fierce predatory dinosaurs, is expected to fetch between $180 000 and $200 000.

"It is probably one of the finest dinosaur egg nests in the world. For the tiny skeletons still to be inside the eggs, folded up beautifully like this, means that they had to be almost ready to hatch" - Thomas Lindgren, consulting director of Natural History for auctioneers Bonhams and Butterfields.

Lindgren said the 22-egg nest, encased in sandstone and containing 10 complete embryos, originated in China. It had been in the hands of private collectors in Asia for the past 20 years before being sold to an American.

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L

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RE: Hunting Dinosaurs
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They dominated the Earth for 150 million years, but we know little about how they reproduced. Now, a band of brave scientists is trying to find out.

They were massive, lumbering creatures who were masters of all they surveyed. And while they may have been some of the most successful ceatures to have ever lived, few palaeontologists can tell you how they moved heaven and earth. How did the 'terrible lizards' have sex without crushing one another or becoming hopelessly tangled?

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-- Edited by Blobrana at 21:50, 2006-09-10

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Tyrannosaur survivorship
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A massive dinosaur death bed in Alberta has helped map out the animal's life span and thrown doubt on long-held theories about how one species lived, says new research conducted in part at the University of Alberta.

"One of the surprises to me was that the overall pattern of survivorship fits closer to an attritional model rather than the catastrophic model we were expecting. Hopefully this will help us to unravel the cause of death of so many carnivores at one location. It's also surprising that something like this study has never been done before"- Dr. Phillip Currie, world-renowned palaeontologist and professor in the University of Alberta's Department of Biological Sciences.

For decades, scientists believed dinosaurs were bigger versions of living reptiles but this new research, published in the current issue of Science, shows that the life pattern of the Albertosaurus is closer to that of living large mammals. The pattern also shows that if the Albertosaurus lived until the age of two, he enjoyed a low death rate until the teenage years when mortality increased.

In 1910, a collecting party from the American Museum of Natural History floated down Alberta's Red Deer River. Led by Barnum Brown, they excavated skeletons of nine individuals of Albertosaurus sarcophagus from a single quarry. It is the best evidence that exists to suggest that tyrannosaurids may have been gregarious, or pack, animals. The almost complete lack of herbivore bones from the excavation suggests that this was probably not a predator trap. Recognizing the importance of the site, Currie led an expedition in 1997 to try to find Brown's original quarry and returned annually with a group from the Royal Tyrrell Museum of Palaeontology to excavate the site. The number of Albertosaurus individuals is now known to be at least 22, which range from two to almost 10 metres in total length.

For this latest paper, Currie collaborated with Dr. Gregory Erickson from Florida State University to produce the first age-standardized ecological life table for a non-avian dinosaur population. They selected fibulae or metatarsals from individuals and used growth line counts to estimate ages at death.

They found that the complex survivorship pattern is remarkably similar to that seen in living large mammals. High newborn mortality rates due to predation alone subside once a threshold size is reached and it appears that such a threshold was reached by age two in Albertosaurus sarcophagus, say the research team. The mortality rates remained low until about the 13th year of life, at which point they reached total lengths of six metres or 60 per cent of their maximum recorded size. At that point, mortality rates escalated to more than 23 per cent a year.
70% of the animals surviving to two years of age were still alive at age 13, which would help explain why so few bones of young adults have been found.

"One implication of these findings is that the previously mysterious rarity of sub-adult tyrannosaur specimens is due to their exceptionally low mortality rates" - Dr. Phillip Currie.

Some people have speculated that tyrannosaurs must have rocketed to adult size in a few years or less, leaving only a small fraction of development that juveniles could have contributed to the fossil record.

"However, this notion is inconsistent with our growth curve. Instead, we suggest that these young animals simply had low mortality, just like older juveniles and subadults of most large terrestrial mammals today"

The estimated survivorship curve also provides a possible explanation for the rarity of individual giants--just two per cent of the population lived long enough to attain maximal size and age for the species.

Source

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Cold-blooded Dinosaurs
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The debate over whether dinosaurs were cold-blooded like modern reptiles, or warm-blooded like us, may finally have been settled. According to some elegant biophysics, they were both depending on how big they were.

Dinosaurs were built like reptiles, so scientists originally assumed they were "cold-blooded", seeking or avoiding sunlight to control their temperature as modern reptiles do.
But more recently, details of dinosaur anatomy have led some to argue that they actively regulated their temperature, as mammals do. But other researchers contend that dinosaurs did not actively regulate temperature, but lost the heat generated by their metabolism so slowly that they stayed warm anyway.
Now Jamie Gillooly and colleagues at the University of Florida at Gainesville, US, say both the first and last groups may be right.

The speed at which certain crucial biochemical reactions common to all life take place depends on temperature. Gillooly's team found that this relationship means that a few constant values, arranged in a simple equation, can describe the relationship between temperature, metabolic or growth rate, and body mass. And the equation works across a very wide range of creatures from plankton to blue whales.
They decided to apply their equation to eight species of dinosaurs, ranging in size from 12 kilograms to 13 tonnes. To do so, they needed information on growth rates measured by other researchers from the annual rings seen in dinosaur bones and body mass estimates at different ages. According to their equation, the body mass during maximum growth, combined with the growth rate, can be used to calculate temperature.

And it turns out that the bigger the dinosaur, the hotter it was. The smaller species were indeed like modern reptiles, with body temperatures around 25C the ambient environmental temperature for their era.
But as dinosaurs got bigger, and the ratio of their surface area to their volume fell, they became less efficient at dissipating metabolic heat especially as they surpassed 600 kg. The 13-tonne Apatosaurus (formerly Brontosaurus) reached 41C. This is pretty hot compared to humans, at a mere 37C.

In crucial support of the researchers' ideas, 11 species of the modern crocodile family, ranging from 32 kg to 1000 kg, exactly fit the curve charting the relationship between size and temperature in the dinosaurs.
Extrapolating the curve to the biggest dinosaur, Sauroposeidon, gives a body temperature of 48C the limit at which normal tissue begins to break down. This suggests the upper size limit on dinosaurs was decided by body temperature.
Gillooly says his team's conclusions suggest that juvenile Apatosaurus had body temperatures 20C less than their parents. So while young dinosaurs sunbathed like modern lizards," perhaps the larger dinosaurs needed to seek out water or shade to cool off".

Gillooly hopes this modelling approach "could reveal aspects of the life of dinosaurs which might be tested using fossils".

Source NewScientist

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L

Posts: 131433
Date:
Hunting Dinosaurs
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One of the biggest of the meat-eating dinosaurs may have hunted in packs according to experts in Argentina.

At least seven T. rex-sized Mapusaurus roseae have been found together in the fossil-rich Patagonia region of the country.
A pack hunting strategy might have enabled the two-legged carnivore to overpower even bigger plant-eating "sauropod" dinosaurs.
Details of the discoveries appear in the scientific journal Geodiversitas.
Co-author Rodolfo Coria of the Carmen Funes Museum in Plaza Huincul, Argentina, said the dig showed evidence of social behaviour in Mapusaurus.

The excavation 24km south of Plaza Huincul found hundreds of bones from several Mapusaurs but none from any other creature. The evidence suggested the animals were together before they died.
Though it was possible they hunted in packs, there was no direct evidence for this.
Philip Currie of the University of Alberta in Canada speculated that pack hunting could have allowed Mapusaurs to prey on the biggest known dinosaur, Argentinasaurus, a 37.5 metre-long plant-eater.

It is not clear whether the animals cooperated in hunting, as wolves or lions do, or simply mobbed their prey or just gathered around after one of them made a kill.
Dr Currie said it was hard to say how long the biggest specimen was because no complete skeleton had been found. He estimated it may have measured about 12.3m from the snout to the tip of the tail.

Source BBC

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