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Re: Sauropod rearing (was Sauropod Energetics (Peristaltic pump))



Scott wrote:

I heartily welcome Kent's suggestion that we engage in what would constitute evidence for sauropod rearing or lack thereof.

And THAT question is what I think is really going to be fun to do, IF there is some care given to the development of the arguments for or against, and not just alternately ducking and lobbing volleys between opposing sides. There's often too much of the latter on even the simplest of issues. If I err towards overly long responses, it's not for pedantry (as a public university professor I already have students paying to listen to my very words. Rather, it's because I'm trying to lay out ideas carefully.)


Now, regarding my ladder analogy, one of this august readership, a distinguished, often disarmingly funny and irreverent practitioner of paleontology ... "Jim", let's call him ... wrote back to me off-DML:

I know this experience well. I have been married nearly 28 years to a woman who is fanatical about my cleaning out the gutters of our roof every fall. Enough said.... :-)

Now, did "Jim" really get it? I think so, but Scott didn't. So let me just touch up a few points.


Scott says:

I think this analogy has several flaws; ... can anyone cite a single paper that correlates high EQ (which tends to be associated with behavior flexibility and the ability to learn new responses to novel situations) with locomotor adeptness? If not, let's please end this pernicious myth.

and to which, in full agreement, I deeply bow in Scott's general direction (not 180 degrees away, as in a similar quote from Monty Python and the HG):


http://faultgame.com/images/mp-fart.wav

and I now regret using the word "clever", and to have thus roused thoughts of EQ in our Scott, for indeed the required motor strategies would not likely require the reptilian homologues of neocortices, and cleverness, and such like. I imagine if I were a professional painter, after a while even I could become adept at moving upright- and-extended extension ladders AND chew gum at the same time. So enough said, and I thank Scott for lopping off the head of that potential red herring.

So then Scott raises another point, and in response I again bow most deeply and heartily:

Vertebrates use a number of sensory apparatus to judge balance and motion. Because my organs of balance where not at the top of the ladder, I lacked the good physical feedback that a sauropod head would have swaying at 6 meters off the ground. Also, the arc at the top of the ladder (or a head on the end of a neck) moves much more, providing better quality data prior to reaching the point of disaterous disequilibrium.

Yes. Here's really all I want to get across. I'll try to be brief: The sauropod has three primary sources of information with which to actively control its bipedal stance (we're assuming its not plop sitting on its tail, as that forms a tripod, if it could tolerate it, and largely puts to rest the balance problem).


Control Information 1: The first is to monitor the magnitude and locus of the ground reaction forces GRF in the left and right hind legs. Hint to self: if my left leg isn't carrying any weight (negligible ground reaction force GRF as indicated by feeling little squash in the left heel pad), I am probably leaning to the right too much so watch it! That sort of neural feedback control program could be done in the spinal cord without even going up to the brain. Pitching forward and backwards could also be controlled "just" by monitoring the locus of the GRF within the pes (again, a clue about pitching forward or backward that doesn't require interrupting the boss's lunch up at the pointy end of this thing). Maybe sauropods could stand up on their hind limbs without even HAVING a brain (or while having a drained brain) much as the much-celebrated decerebrated cat can still walk.

Control information 2: The vestibular organs. Of course, the semicircular canals would alert the brain "eek, we're pitching to the left, cap'n!" But that's the easy part. The difficult problem that slips by the vestibular organs are the very slow accelerations that don't tickle the hairs much. Amusement flight simulators seem so real, and real airplanes have been casually rolled in the sea on dark and stormy nights, and ladders have swayed way over and nearly crashed on the birdbath because of SLOW accelerations that were subliminal and not picked up by cross-checking with the third main source of information, vision:

Control Information 3: The third is visual. Things drifting to the left suggest that you are going to the right. Or, the wind is blowing them to the left and you are standing still. Note to self: be sure to check with what the vestibular organs are telling you, because if you are wrong, and you are actually standing still and things outside ARE moving, then you will look silly to pitch yourself over because you miss-read a visual cue. That's just what (human, not goat) kids do when they are walking at the beach at a certain young age: a wave washes up from the side and the kid, who was just walking along holding balance just fine, suddenly, voluntarily, pitches over into the water. Embarrassingly, the visual input is being trusted TOO much, without integrating it with the vestibular clues to balance. I'm not making this up. I'm actually a vision scientist, at least that's where I got most of my training. The point is, vision is real important to standing up, especially if you are holding a ladder above you, or you are essentially a ladder.

My final point is that these three sources of information: pressure pad and stretch receptors in the pes and limbs + vestibular + visual need to be integrated. It doesn't take a lot of smarts, as lots of lower vertebrates, and many presidents, can do it. It just takes some central integration (i.e. in the itty bitty brain). Now, getting back to size (NO! not as in EQ). The itty bitty head of an African Grey Parrot has been known to think more intelligently than the Big Head of FEMA, but still, motor control within the cerebellum would seem to take a lot of integration, because there is a big mass to keep under control down below (again, FEMA comes to mind).

Thanks Scott, for tripping over the ladder analogy. I do agree that it is now broken (much like the broken analogy between giraffe neck and Camarasaurus neck :) But it still is useful (the ladder analogy, not the giraffe one :)

So maybe sauropods did have the brain power (either in the rump, the spine, or the head) to stand up for what it needed to do (something we can't say about some large government bodies), and let's paleo- neuro-behavioral speculation not distract us from thinking about the biomechanical issues.

- Kent