Why don't giraffes have necks as long as a brachiosaurus?

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10 Responses to “Why don't giraffes have necks as long as a brachiosaurus?”

  1. bzishi says:

    And why doesn’t a giraffe have wings? Wouldn’t that make it easier to get to the high up foliage?

  2. PJG Hendry says:

    This planet was spinning faster in those days.

  3. BWJones says:

    The cervical vertebrae of the brachiosaurus are absolutely phenomenal.  The world’s largest articulated skeleton is a brachiosaurus in the Museum Für Naturkunde in Berlin.  Check out that brachiosaurus!  http://prometheus.med.utah.edu/~bwjones/2012/07/museum-fur-naturkunde-berlin/

  4. GawainLavers says:

    “We think of giraffes as long-necked creates…”

    Only in the bible belt…sorry, had to be said.

  5. John Randolph says:

    There was a Nature or Science article some time ago that looked at the energetics of sauropods having such long necks.  It turns out that pumping blood to the brain actually takes a lot of energy, but it was compensated by the fact that the sauropod could graze over a larger area with the long neck without moving, making it energetically favorable for the animal.

  6. BillStewart2012 says:

    Giraffes are tall enough for most of the available food sources in their native regions.  Browsing from trees gives them access to an ecological niche that didn’t have much competition, and being tall makes it easier to see predators.  Extra height wouldn’t get them significantly more food, but would make it tougher for their hearts to get blood to their heads, so it’s not a win.

    • Gatto says:

      It feels easy to explain evolution, seeing why an adaption works; and, it’s definitely easy to invent adaptions that seem like wins, but don’t actually happen in practice. If they did have longer necks, maybe they’d be able to reach more trees without moving, or some such.
      What’s cool about the paper is they bothered to analyze actual physiological reasons, and that it turn may even yield new insights, and new ideas. ( plus, hey: Giraffes! )

  7. Theranthrope says:

    You also have to consider that sauropods had more time to evolve light-but-strong vertebrae compared to azdarchids: 

    Azdarchids had only 65 million years to evolve from something roughly the size of a opossum at the time of the Cretaceous–Paleogene mass-extinction event, compared to 100 million years for the super-heavy sauropodomorphs of late-Jurassic and 185 million years for the super-heavy Titanosaurs of the late-Cretaceous to evolve from a small (chicken- or turkey- sized) bipedal carnivorous archosaur after the Permian–Triassic mass-extinction event (the “Great Dying”).

    It’s an apples-to-oranges comparison: A giraffe’s dinosaur contemporary isn’t Brachiosaurus, but probably something similar to the prosaropod Plateosaurus

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