From: gecko@zooid.guild.org (GECKO)
Newsgroups: talk.origins
Subject: Re: Category 4 / Other large animal anamolies
Date: 30 Jul 92 23:28:21 GMT

 
 Ted Holden writes: 
 
>In article <744@tdat.teradata.COM*, swf@teradata.com (Stanley Friesen) 
>writes: 
>* |In article <1992Jul23.183919.3071@desire.wright.edu> sbishop@desire 
>* |.wright.edu writes: 
>* | 
>* |So, what?  Falls can be fatal for horses, falls can be fatal for 
>* |giraffes, falls *can* be fatal for humans. 
>* 
> 
>* Oh yes, talking about giraffes, does ted know that giraffes' feet support 
>* more weight per square inch cross section than do those of elephants? 
>* [What, you mean *giraffes* exceed Holden's weightlifters limit? - yep]. 
> 
>* sarima@teradata.com                   (formerly tdatirv!sarima) 
>*   or 
>* Stanley.Friesen@ElSegundoCA.ncr.com 
> 
> 
>Actually, this only means that Friesxen does not COMPREHEND Holden's 
>weightlifters' limit.  The Holden number for a giraffe would be around 13, 
>nothing outrageous.  The Holden number referrs to muscular capabilities 
>vs the amount of weight a creature has to deal with.  Shoe size, bone size, 
>etc. are irrelevant. 
 
     If the Hokum number depends entirely on muscular capabilities 
     and ignores bone structure and dimensions, joint flexture, muscle 
     attachment sites, and so on, then it cannot be too accurate. Bone 
     size is not irrelevant; it is an important consideration when 
     calculating the maximum stress/weight an animal can withstand. 
 
     Robert T. Bakker has this to say on the matter (from "The Return of 
     The Dancing Dinosaurs", an article in Volume I of the symposium 
     _Dinosaurs Past and Present_): 
 
         "Were elephant-sized dinosaurs capable of much faster locomotion 
          than present-day elephants?  If the big quadrupeds were in fact 
          much faster than modern elephants of the same weight, then 
          dinosaurian limbs should be stronger and muscle mechanics more 
          powerful.  Experiments in limb physiology during the last two 
          decades have shown that one key function of muscle action is to 
          realign the forces incurred during locomotion so that the net 
          compression is directed along the long axes of the limb bones 
          (Basmajian 1964).  The maximum load a limb bone can resist is 
          largely dependent on the minimum shaft cross-section.  A 
          medium-size adult Triceratops had a body weight (calculated from 
          clay scale models) of about five metric tons, equal to that of a 
          large bull African elephant (the largest elephants and 
          Triceratops reached twice this weight; Table 1).  The 
          circumference of the humerus is about equal in the Triceratops 
          and elephant (Fig. 15), but the dinosaur femur is much thicker. 
          The maximum thrust from the hind leg, therefore, must have been 
          significantly larger.  The fastest gait of African elephants is 
          a running walk at about thirty kilometers per hour; the dinosaur 
          should have been faster if simple limb-shaft strength was the 
          limiting factor." 
 
 
     So much for dismissing bone size as an irrelevancy :-). 
 
     While I'm on the topic of elephants, and mammoths for that matter 
     (the skeletal construction of both is essentially the same), 
     regarding whether it is sheer weight or structural design that 
     determines if a large terrestrial vertebrate can gallop or not, 
     I would reiterate that (fanciful Paloelithic depictions or no) 
     mammoths were physically unable to gallop.  At the same time, 
     extinct creatures of comparable size WERE able to gallop, and 
     would still be able to gallop if they were alive today - attenuated 
     gravity is not necessary to explain their existence. 
 
     Another passage from page 214 of Bakker's book _The Dinosaur 
     Heresies_ is pertinent: 
 
          "A useful piece of evidence about the speed of dinosaurs can be 
           extracted from the angles of their joints.  Seen from the side, 
           a running rhino always exhibits greater flexture at the elbow, 
           knee, hip, and shoulder than does an elephant.  Elephants run 
           straight-legged, thigh lined up with shank and upper arm with 
           lower arm, so their legs look rather like mobile Doric columns. 
           Rhinos run with a more bent-legged stride and are consequently 
           faster than elephants - top speeds are thirty-five miles per 
           hour for the rhino, twenty-two for the elephant.  The rhino 
           owes its greater velocity precisely to the bounce it gets from 
           the stretching tendons at its joints each time its feet plant 
           down.  Flexing joints provide more of this bounce, and all the 
           big mammals that gallop are so jointed.  Elephants can never 
           get all their feet off the ground simultaneously, even at top 
           speed, and their fastest gait can best be labelled a running 
           walk.  If we could compare the angles in dinosaur joints to 
           those in these living mammals, we would have an important clue 
           to the bounciness of their gait and hence their speed." 
 
     and on page 217: 
 
           "Big gallopers today possess strong knee muscles that attach to 
            the kneecap and shank in such a way that the knee joint opens 
            and closes under tremendous muscular power.  A bony ridge, the 
            cnemial crest, marks the point of attachment for the knee 
            tendons, and one can directly gauge the muscle power of a knee 
            from the size of a cnemial crest.  Elephants, turtles, and 
            salamanders are all slowpokes in their body-size classes and 
            all have puny knee muscles and low cnemial crests on the shank 
            bone.  Rhinos have big cnemial crests, as do other large- 
            bodied gallopers, such as water buffalo, giraffe, bison, and 
            gaur.  Big crests would also mean big calf muscles." 
 
 
     Gregory S. Paul provides more insight on the issue (from "The Science 
     and Art of Restoring the Life Appearance of Dinosaurs and Their 
     Relatives", an article in Volume II of _Dinosaurs Past and Present_): 
 
            "Elephants and tortoises cannot run because they have very 
             strange limbs, with fixed ankles that cannot rotate more than 
             a few degrees.  The effects of this can be simulated by 
             trying to run on your heels alone.  Medium-sized and larger 
             animals with flexible ankles that can push the body into a 
             long, suspended phase can run; there are no exceptions." 
 
 
     What all this means is that if the modern elephant had a radically 
     different limb architecture more akin to that of a rhino (thicker 
     bones, flexible ankles, larger cnemial crests, bouncier joints, etc.) 
     then it WOULD be able to gallop on contemporary Earth without the 
     benefits of imaginary attenuated gravity; but it doesn't, and so it 
     cannot gallop.  And as the mammoth did not significantly differ from 
     the elephant in the aforementioned respects, it is logical to assume 
     that it could not gallop either. 
 
 
     That's more than enough for now... 
 
 
                                      - GECKO 
 

gecko@zooid.guild.org