Dinosaur Debate Gets Cooking – Science News

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Life stories written in mammal bones are being used to debunk a key argument for cold-bloodedness in dinosaurs.


Annual growth lines etched in the femurs of 115 wild warm-blooded mammals such as giraffes, reindeer and gazelles are similar to those previously seen in the bones of reptiles and dinosaurs, researchers report online June 27 in Nature.

“People always said that mammals do not show these lines,” says study lead author Meike Köhler, a paleontologist at the University of Barcelona in Spain. This assumption is “like a myth that’s going around; you read it everywhere,” she says. “But people haven’t really studied mammals.”

In dinosaurs and reptiles, yearly cycles of growth and nutrition are stamped in the bones like the rings of a tree. In fat months, animals pack on blood vessel-rich bone tissue, and in lean months they skimp, laying down only thin sheets. Under a microscope, the slender sheets of bone look like dark lines. Because these “lines of arrested growth” or “rest lines” stripe the bones of both dinosaurs and reptiles, some scientists assumed that dinosaurs, like reptiles, were cold-blooded. But the new work shows that warm-blooded mammals have banded bones, too.

Written By: Meghan Rosen
continue to source article at sciencenews.org

7 COMMENTS

  1. Seasonal cycles of growth are hardly surprising, when we consider that in the tropics there are wet and dry seasons with abundance and famine, while in the temperate and polar regions many mammals cyclically build up reserves, and then hibernate.

  2. The myth memes are always more potent because they hit first and are always easier to understand, reinforcing an existing belief. 

    “The Nazis were atheists”, for example (one I’ve had to debate often recently). It’s simply a myth and is perpetuated by the fact that it got going early on and preyed on the belief that evil-doers are always non believers.

    “dinosaurs are cold blooded” is a simple fallacy that no one bothered to fact check and it’s perpetuated because seeing dinosaurs as vicious, mindless eating machines is very easy.

    Reminds me of a simple word problem that most people fudge on the first go because they didn’t take their time to read it fully and comprehend what was being said. People have an innate desire to latch onto an immediate answer that is both simple and confirms a previously held bias.

    In short, people are reactionary to new information and credulous to old information. The world turns.

  3. The whole thing in the osteoclast/osteoblast carbonic acid equilibrium cycle? ( with chlorine ion motive power? ) As mammals, or predating mammal bone breakdown/buildup cycles? What exactly do bird bones do here?

  4.  It would be interesting to compare traditional open field single-suckle beef cattle with intensively fed, indoor barley-beef production, -  in which maturity is reached over a year earlier – (ie in less than half the time).
    A similar possible comparison could be made with pig production methods.

  5. It’s not even as if cold- and warm-bloodedness are remotely helpful descriptions in any case, because “cold-blooded reptiles” don’t actually have cold blood. They just gain their heat from external sources like the sun, so it’s more appropriate to call them ectotherms. Indeed, reptiles can sometimes have warmer blood than warm-blooded mammals thanks to this mechanism!

    Animals have too many ways of regulating their body temperatures to reduce them to an unrepresentative dichotomy. For instance, some dinosaurs were most likely gigantotherms, i.e. so voluminous compared with their surface areas that they retain heat simply due to their massive size. Others, especially the small feathered theropods, could have been endotherms (i.e. their bodies have homeostatic systems for generating their own temperature, like mammals), and plated dinosaurs were possibly ectotherms that used their plates as solar panels.

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