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Agonized pose tells of dinosaur death throes

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  • Agonized pose tells of dinosaur death throes

    Hello!

    This one is not directly linked to bird flu nor to biomolecular science but I really found it interesting as it open a new perspective about dinausaur's disapearance... who are now known as the birds' ancestors.

    Keep in mind the way some of the H5N1 dying birds' symptoms are described when reading it... ( neck twisted ... and so ) and don't refrain your imagination.

    This is just a theory but... remember that birds are the oldest influenza reservoir...anyway that's fascinating.


    http://www.berkeley.edu/news/media/r...ththroes.shtml

    Agonized pose tells of dinosaur death throes
    By Robert Sanders, Media Relations | 06 June 2007

    BERKELEY ? The peculiar pose of many fossilized dinosaurs, with wide-open mouth, head thrown back and recurved tail, likely resulted from the agonized death throes typical of brain damage and asphyxiation, according to two paleontologists.
    <table style="margin-left: 10px; margin-bottom: 6px;" summary="layout table for image placement" align="right" border="0" cellpadding="0" cellspacing="0" width="100"> <tbody><tr> <td>
    The earliest feathered dinosaur, Archaeopteryx (plumage not shown). Drawn from specimen at Humboldt Museum, Berlin. The skull is about six inches long.</td> </tr> </tbody></table> A classic example of the posture, which has puzzled paleontologists for ages, is the 150 million-year-old Archaeopteryx, the first-known example of a feathered dinosaur and the proposed link between dinosaurs and present-day birds.
    "Virtually all articulated specimens of Archaeopteryx are in this posture, exhibiting a classic pose of head thrown back, jaws open, back and tail reflexed backward and limbs contracted," said Kevin Padian, professor of integrative biology and curator in the Museum of Paleontology at the University of California, Berkeley. He and Cynthia Marshall Faux of the Museum of the Rockies published their findings in the March issue of the quarterly journal Paleobiology, which appeared this week.
    Dinosaurs and their relatives, ranging from the flying pterosaurs to Tyrannosaurus rex, as well as many early mammals, have been found exhibiting this posture. The explanation usually given by paleontologists is that the dinosaurs died in water and the currents drifted the bones into that position, or that rigor mortis or drying muscles, tendons and ligaments contorted the limbs.
    "I'm reading this in the literature and thinking, "This doesn't make any sense to me as a veterinarian,'" said lead author Faux (pronounced fox), a veterinarian-turned-paleontologist who also is a curatorial affiliate with Yale University's Peabody Museum. "Paleontologists aren't around sick and dying animals the way a veterinarian is, where you see this posture all the time in disease processes, in strychnine cases, in animals hit by a car or in some sort of extremis."
    Faux and Padian argue in Paleobiology that the dinosaurs died in this posture as a result of damage to the central nervous system. In fact, the posture is well known to neurologists as opisthotonus and is due to damage to the brain's cerebellum. In humans and animals, cerebellar damage can result from suffocation, meningitis, tetanus or poisoning, and typically accompanies a long, slow death.
    Some animals found in this posture may have suffocated in an ash fall during a volcanic eruption, consistent with the fact that many fossils are found in ash deposits, Faux and Padian said. But many other possibilities exist, including disease, brain trauma, severe bleeding, thiamine deficiency or poisoning.
    "This puts a whole new light on the mode of death of these animals, and interpretation of the places they died in," Padian said. "This explanation gives us clues to interpreting a great many fossil horizons we didn't understand before and tells us something dinosaurs experienced while dying, not after dying."
    Also, because the posture has been seen only in dinosaurs, pterosaurs and mammals, which are known or suspected to have had high metabolic rates, it appears to be a good indicator that the animal was warm blooded. Animals with lower metabolic rates, such as crocodiles and lizards, use less oxygen and so might have been less traumatically affected by hypoxia during death throes, Padian said.
    <table style="margin-right: 10px; margin-bottom: 6px;" summary="layout table for image placement" align="left" border="0" cellpadding="0" cellspacing="0" width="100"> <tbody><tr> <td>
    An ostrich-like dinosaur, Struthiomimus; in the classic posture indicative of brain damage and asphyxiation at death. Drawn from specimen at American Museum of Natural History. The skull is about a foot long.</td> </tr> </tbody></table> Padian acknowledged that many dinosaur fossils show signs that the animal died in water and the current tugged the body into an arched position, but currents cannot explain all the characteristics of an opisthotonic pose. By studying a large number of fully articulated fossil skeletons, he and Faux were able to distinguish animals that underwent post-mortem water transport, a non-biological or abiotic process, from those with the classic "dead-bird" posture, which they interpret to be the result of biological processes.
    Faux, who also works as a disaster veterinarian from her home in Lewiston, Idaho, set out to test other post-mortem processes - rigor mortis, which is the temporary stiffening of muscles after death; and the drying of muscles, tendons and ligaments - that some paleontologists credit with creating the opisthotonic posture.
    Working with a raptor recovery center, she obtained birds that were so badly injured they had to be euthanized - great horned owls, red-tailed hawks and falcons - and observed them during rigor mortis, checking periodically for eight to 10 hours to see if they moved during the process.
    "In horses and smaller animals, rigor mortis sets in within a couple of hours, so I just looked to see if they were moving or not," Faux said. "And they weren't moving. They were staying in whatever position I'd left them in. I thought, 'If birds aren't doing it, and I'd never observed a horse doing it, then why would dinosaurs be doing it?'"
    The idea that drying causes muscles or tendons to contract asymmetrically also didn't make sense, she said, based on her veterinary experience and an experiment she conducted with two euthanized red-tailed hawks, which she dried for two months in Styrofoam peanuts. Most joints have counterbalancing muscles that dry the same way, she said, so there was no reason to expect that the muscles would turn a joint during drying. She found no post-mortem movement. She also pinned beef tendons as they dried, and though they shrank a bit, they did not shrink enough even to dislodge the pins. Given these observations, it is hard to imagine how shrinking tendons or muscles could drag a heavy creature into a different position, the researchers noted.
    Padian pointed out, too, that all opisthotonic dinosaurs are very well preserved, meaning they evidently did not sit out in the open for long, or scavengers would have quickly scattered the bones. So, he wondered, how could they have been exposed long enough to dry out?
    The only explanation that makes sense, they concluded, is central nervous system damage. The cerebellum is responsible for fine muscle movement, controlling, for example, the body's antigravity muscles that keep the head upright. Once the cerebellum ceases to modulate the behavior of the antigravity muscles, Faux said, the muscles pull at full force, tipping the head and tail back, contracting the limbs and opening the mouth.
    Padian and Faux urge reanalysis of many fossil finds, referring, for example, to a mass death uncovered in Nebraska in the early 20th century. They argue that cerebellar dysfunction explains the opisthotonic posture of the numerous camel-like fossils better than does the common explanation - that the animals died in a stream and were washed into an eddy or backwater.
    The authors also point to a fossil of Allosaurus, a T rex-like animal, that displayed bone lesions suggestive of a bacterial infection that also can lead to meningitis, a disease that can produce opithotonus. The authors point out that their explanation of the opisthotonic posture in dinosaurs and other animals provides a way to assess the role played by microbes in evolution, whether through disease or through other processes such as algal blooms - so-called "red tides" - that can suffocate aquatic animals.
    This example and others "suggest that reevaluation may be in order for an untold number of paleoenvironments whose story has been at least partly explained on the basis of the death positions of many of their fossil vertebrates," the authors write in their Paleobiology paper.

  • #2
    Re: Agonized pose tells of dinosaur death throes

    Hi, Mingus! *wave*

    Thanks for this post. It IS really interesting. This researcher might be on to something. Interesting! Poor dinosaurs.
    ...when you have eliminated the impossible, whatever remains, however improbable, must be the truth. - Sherlock Holmes

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    • #3
      Re: Agonized pose tells of dinosaur death throes

      thank you, mingus
      you can read stefan jay gould , about paleonthology
      it 's funny and really interesting

      Comment


      • #4
        Re: Agonized pose tells of dinosaur death throes

        Imagine yourself millions years ago at the end of the Dinosaurs era...

        Dinosaurs occupy almost every ecological niche and fill all the earth and all ecosystems in place.

        A catastrophic astronomical phenomenon from outer-space destroy the course of the climatic routine on earth.
        For years after the meteorite falloff, a series of disastrous winter put most of the species in danger.

        ( Just a bubble )

        The eruption of the Tamboro in Indonesia in 1815 is known to have sprayed in the earth's atmosphere enough powder to cause the next winter in 1816 the worst summer never seen from man memory at that time, in the middle of the little ice age. It have been called -- The year without a summer -- or -- Eighteen hundred and froze to death --.
        Several unusual cold winter also followed. It totally scrap the crop for that year and the price of food market raise for years.

        It is known to have been the last major large scale famine in the occidental world since today.

        So just imagine what could have done a gigantic meteor like the one who is believe to put dinosaurs in danger.
        Year Without a Summer - Wikipedia, the free encyclopedia

        (Ok end of the bubble )

        So the major part of the species was probably too much populated for the resources then available on the planet.

        A successive wave of diseases followed first to restablished that natural balance...

        So now let me please speculate freely from that point because it is the reason of my fascination.

        - Dinausaur are the ancestor of todays birds, more and more scientific data suggest this.
        - All thoses species where from the same animal branch, so they had several biological similarities between each other.

        At that point an apportunist virus may have take the advantage of one of thoses well spread biological feature like the a-2,3 gal linkage...

        The species the most susceptible to that virus soon died in mass than some of them ... probably the winged branch of the dinausaur reign like the archeopteryx survive with a higher rate but at the expense of being a better host for the virus, incubating the virus at higher viral load...
        a little bit like the modern birds to wich they soon because the ancestor.

        At that time, who knows if the virus that will become the ancestor of modern flu is or is not already segmented ? Probably not, millions years has to followed...

        After the Official dinausaur extinction, mammals did not rule over the earth right away...

        No, it is now known that a era domined by many speacies of predators bird that don't fly all of them in the Austrich familly.

        And they rule over the world until a carnivourous mammals family ancestor of the the wolfes or the fox took control over the ecosystems top of the food chain.

        So now, we got on modern days two major animals group, the birds who have developped the ability to resist to the influenza class virus, and the mammals who have low susceptibility to those virus and to a restricted type of...

        Anyway ... That's why I posted it here in the Lab, because it is just plain speculative vision of the evolution from that time to our time.

        You don't have to beleive it ... but i like it.




        Last edited by Mingus; June 30, 2007, 08:25 AM.

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        • #5
          Re: Agonized pose tells of dinosaur death throes

          Gigantoraptor erlianensis stood more than 16 feet (five meters) tall and weighed a ton and a half, or roughly 1,400 kilograms. Featuring a toothless beak on its head and a short tail for balance, the enormous birdlike dinosaur measured more than 26 feet (eight meters) in length. Living more than 65 million years ago at the end of the Cretaceous period, this big bird precursor has complicated the seemingly shrinking descent from Archaeopteryx to the modern sparrow.

          Paleontologist Xing Xu of Beijing's Institute of Vertebrate Paleontology and Paleoanthropology and colleagues discovered the animal while prospecting for fossils in the Erlian Basin of the Gobi Desert in north-central China. Based on its size, the paleontologists initially classified it as member of the tyrannosaur lineage, but bits of beak, leg and other bones revealed that it more properly belonged to the oviraptorosauria group, heretofore a grouping of small, feathered creatures weighing only a few pounds. "It is the largest known beaked dinosaur," Xu says. Adds paleontologist Mark Norell of the American Museum of Natural History in New York City: "I was just flabbergasted when I saw it because it was so big."

          The finding complicates the evolutionary descent of birds from dinosaurs. "Progressively from within advanced theropods you get smaller and smaller towards birds," Norell says. But "after some species originate and spring off the bird line, you get secondary gigantism."

          No one can say why for sure. "Big size has some advantages such as having fewer predators and having more food resources that are unavailable for small animals," Xu notes. But he adds that early oviraptorosaurs, this animal's ancestors, "are among the smallest dinosaurs."

          Science Image: Gigantoraptor-skeleton-with-man
          Image: LI RONGSHAN/IVPP
          BIG DINO: The birdlike dinosaur stood as tall as fearsome T. rex, shown here next to a five-foot seven-inch tall man, and may have shared that predator's taste for meat.
          "Maybe it's something about the environment," Norell speculates. "This is a very nascent stage of starting to understand the evolutionary dynamics of the animal."

          Already, Gigantoraptor is proving very odd, according to the paper detailing the find published in Nature. It bears a ridged humerus (upper arm bone) never before observed in a dinosaur as well as an enormous but birdlike femur (thighbone). "Maybe it has some sort of birdlike running mechanism," Xu says. Norell adds: "We don't know the biomechanical advantage this would confer. But I don't think it's hopping around at that size."

          It also is not clear whether the creature was feathered, though Xu speculates it was like most other animals in its lineage. If so, it would be by far the largest known feathered animal of all time, tripling the mass of Stirton's thunderbird, which lived in Australia roughly eight million years ago. "Certainly the babies would have had to have feathers until they reached thermal regulation with the environment," Norell notes.

          So what did this prehistoric "Big Bird" eat? Another mystery, as the animal bore no teeth in its jaw, had a small head and long neck (common in herbivores) but also sharp claws (common in carnivores). "[It] could be omnivorous," Xu says. Norell adds: "Lots of things that have no teeth like hawks and eagles are pretty efficient carnivores." It seems the world of dinosaurs?and bird ancestors?was as diverse as that of their latter-day descendants.

          http://www.sciam.com/article.cfm?cha...34D5E8&ref=rss

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