Wednesday, June 23, 2010

Hold Your Head High, Brachiosaurus

One of the recent debates in paleontology has concerned the neck posture of the sauropods. Such titanic creatures are completely absent from land today, so it's natural for them to be puzzled over.

Walking With Dinosaurs, the 1999 documentary, featured herds of Diplodocus with their heads held basically parallel to the ground, reflecting some paleontologists' supposition that for the beasts to raise them much higher would have been an unbearable strain, requiring blood pressure too high for their hearts to bear. The SV-POW! team has weighed in with a strong argument to the contrary, based on the evidence provided by living animals - a fantastic summary is available here. Rather than a straight horizontal line, they argue that it made more sense for sauropods like Diplodocus and Apatosaurus to hold their heads at a gentle curve, with the heads well above their bodies.

Examining the Chinese early Cretaceous sauropod Euhelopus, Andreas Christian from the University of Flensberg has concluded that it was especially adapted for high browsing, a conclusion that likely bears true for similar sauropods, notably the ever-popular Brachiosaurus.


Euhelopus, via wikimedia commons.

As you can see in the above reconstruction, Euhelopus is similar to Brachiosaurus in its marked differences from the standard-issue, Flintstones-style "brontosaur." The front legs are longer than the back, and the tail is shorter. In all, the profile is more giraffe-like. Christian's paper suggests that this posture, while requiring considerable effort to pump blood up through the neck, was less expensive than grazing over a broader area - holding its head at a 90 degree angle from the horizontal for five minutes required only about half of the energy expenditure as walking a hundred meters. He also found that the stresses on the neck vertebra were lower in as Euhelopus held its neck more erect. Christian concludes that "raising the neck... may have been less expensive for a sauropod like Euhelopus or Brachiosaurus than walking a long distance. During a food shortage, raising the neck was probably even essential for surviving: it is better to get little than nothing at all." Not an earth-shattering discovery, but one that adds to our understanding of how such a magnificent adaptation made sense for these animals.

8 comments:

  1. I really like this reconstruction, the patterning and neck/tail spines seem logical for the animal.

    Nice to get news on the neck issue too, there seems to be more support for the neck up position lately.

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  2. These recent neck posture studies have been really interesting. Though I didn't find them in any way surprising. Given that the neck and head are the most vulnerable parts of a sauropod, it would be a very bad idea to keep them permanently just in the bite height of a large theropod. They must have been able to rise the head at least temporarily when being attacked. An adult sauropod would have been quite safe from predators otherwise, but just one good bite in the tiny head... dead.

    Or at least that's what I have come to think. I might, of course, be wrong.

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  3. This reminds me of the old-school drawing of a Brachiosaurus standing on the bottom of a lake, with only the top of his head sticking out over the water-s surface. It is amazing how influential artist's reconstructions become in shaping our view of these creatures.

    Every time I see a pack of crows fighting over some roadkill, I think to myself "Those are dinosaurs, they look and act just like dinosaurs!". Then I recall that much modern reconstruction, such as the JP movies, uses birds as the model for the dinosaur behavior, so I am only recycling this model back on itself.

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  4. OP - I'm really interested in those spines on various sauropods. Species identifiers, I'd guess. Maybe I'll need to do a post on those sometime soon...

    P - You should check out some of the stuff in the Vintage Dinosaur Art flickr pool. One of my favorite memes in old paleoart and childrens' book illustrations was exactly that - helpless sauropods having their necks eaten by theropods! Classic technique.

    Scott - I wonder if smaller theropods used to gang up on larger ones, like the blackbirds that chase crows?

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  5. Yes, but biting at the neck does not always work out the way the theropod would have intended, as depicted here:

    http://www.topatoco.com/merchant.mvc?Screen=PROD&Store_Code=TO&Product_Code=WN-DINOBITE&Category_Code=006

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  6. That shirt is freaking incredible! But I'm afraid of the implication that a theropod chowing down on a sauropod is cannibalism... if that's true I get all cannibalistic everytime I eat a burger.

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  7. It's not cannibalism if you don't share the same Order.

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  8. Only eating your own species is cannibalism, says Wikipedia: http://en.wikipedia.org/wiki/Cannibalism_%28zoology%29

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