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Study: Dinosaurs "Shrank" Regularly To Become Birds 138

An anonymous reader writes A new study suggests that large dinosaurs shrunk to small birds to survive over a period of around 50 million years. Aside from a few large species, most modern birds are predominantly tiny and look nothing at all like their prehistoric meat-eating ancestors. The evolutionary process that governed this transformation has not been well understood, but now researchers from the University of Adelaide in Australia have put together a detailed family tree mapping the evolution of therapod dinosaurs to the agile flying birds we see today. Their results indicated that meat-eating dinosaurs underwent several distinct periods of miniaturization over the last 50 million years which took them down from an average weight of 163kg to just 0.8kg before finally becoming modern birds.
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Study: Dinosaurs "Shrank" Regularly To Become Birds

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  • Makes Perfect Sense (Score:5, Interesting)

    by rmdingler ( 1955220 ) on Sunday August 03, 2014 @03:23PM (#47594953) Journal
    In times of extraordinary resources, an ecosystem's offspring are afforded the opportunity to grow larger, and larger is often a breeding advantage.

    In times of constriction of resources, those life forms with the minimal caloric needs tend to flourish.

    What a beautiful and strange World it must have been in the dinosaurs heyday to support a seven ton carnivore and a 50,000 to 100,000 kilo plant eater.

  • The Red Queen (Score:5, Interesting)

    by NoNonAlphaCharsHere ( 2201864 ) on Sunday August 03, 2014 @04:07PM (#47595145)
    I'm sorry, birds are the showiest class on the planet. Any theory about how they went from ~160Kg to ~1Kg in (only) 50 million years needs to have a healthy dose of sexual arms race to be plausible.
  • by Anonymous Coward on Sunday August 03, 2014 @04:20PM (#47595207)

    Because of the square cube law, gigantism is energetically expensive. The bigger an animal gets, the heavier it gets (disproportionately), and the more energy it needs to move. But size is relatively easy to tweak genetically, so making animals bigger to out compete their mating or territorial/predatory rivals must have been a solution which evolution hit on pretty quickly. But then evolution moved on, developing more sophisticated technology like feathers, hollow bones, and more powerful brains which could support flight and cooperative pack hunting, and gigantism became a relatively more expensive and less useful trait. Huge dinosaurs disappeared, for the same reason huge battleships did. Put a t-Rex into a forest with a pride of hungry lions. How long do you think the Rex would last?

    - Tristan

  • by Artifakt ( 700173 ) on Sunday August 03, 2014 @10:54PM (#47596549)

    There's also the argument that wings evolved from smaller structures which were held angled down to in turn hold the running bipod proto-bird (or advanced dinosaur) down when making sharp turns at high speeds (like automotive spoilers) . Strange as that idea sounds, if this actually worked, then it helps explain what's otherwise a pretty large gap - evolving flight. Arms races, as this one where the predators would be trying to outcorner their fleeing prey, and the prey would be trying to evade ever more agile predators, are often considered as explanations for complex evolutionary paths, and may well be true in this case, but it also means we would have an even harder time matching feathers to any specific climate data - as we don't know whether insualtion was the major advantage of the structures just because the animal didn't have the wing surface for actual flight..

Someday your prints will come. -- Kodak