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Walking quadrupeds (was: Re: Euoplocephalus walking)



On 20 Apr 97 at 9:03, Bettyc wrote:

> Grant Harding wrote:
> > How did Euoplocephalus walk? There are three ways for a quadroped
> > to walk: 1. Putting its front legs forward, then its back legs
> > forward
> 
> this can only be done at high speeds- animals like modern horses and
> cheetahs do this during the gallop.

Not quite. In the gallop (Or was that canter in English? At least I
mean what is called a galop in Dutch) a horse puts down its legs in
the following manner: rear-left, left-diagonal (so: rear-right and
front-left at the same time), front-right. After this there is a
moment that the animal has no leg touching the ground at all.  (The
description is of the right gallop; there are of course two 
possibilities, that mirror each other.)

In a very fast gallop (Dutch: rengalop) that left-diagonal can be 
expanded into a very fast succession of rear-right and front-left. So 
a slow gallop/canter is a three stroke movement and a (fast) gallop 
can be (or is) a four stroke movement.

> Otherwise it's such an unstable
> gait, the animal doing it would fall over.

This seems true. It seems a canter/gallop is generally a fast way of 
moving yourself around, comparable to fast running in bipedals like 
us humans. For heavy, slow moving animals a four stroke movement 
seems preferable, since you'll always be in a tripod arrangement (or 
on all fours) at any time, which is of course very stable.

> > 2. Putting its left legs forward, then its right legs forward
> 
> this is called pacing and modern animals that do this include the
> camel which does it at fairly slow speeds, and horses which do it at
> a faster speed (ever hear of a type of horse called the 'Pacer"?)

Not all horses can pace. Only a couple of kinds of horses can really 
walk like this (one example is the small kind from Iceland). 
Generally most horses cannot (physically?) walk like this at all.

And this also describes simple four legged walking, at least it does 
for horses. The only real difference between walk (Dutch: stap) 
and pace (Dutch: telgang) is that the first is a four stroke 
movement, while the second is a two-stroke movement, with both 
lateral pairs of legs alternating.

> > 3. Putting its left hind leg and its right front leg forward, then
> > its right hind leg and left front leg forward
> 
> this is what most 4-legged animals do during a walk-from lizards to
> horses to platypuses to bears.  Likely this is what Eoplocephalus
> did when moving forwards at a regular, slow pace.

I do not quite agree. This describes the trod (Dutch: draf). Again I 
refer to horses here; since I had to learn the exact walking 
movementes of a horse for my "horse driverslicence" a couple of 
years ago. Trodding is also a two stroke movement, where the two 
diagonal pairs of legs alternate.

I've never heard of a way of moving in which this diagonal way of 
moving the legs is done in a four stroke movement, which is what you 
seem to suggest for slow moving Euplocephalus (and "most 4-legged 
animals [...] from lizards to horses to platypuses to bears"). At 
least, horses don't seem to walk like this at all.

Basically, what I'm trying to say is that there are *much* more 
possibilties for a four legged animal to move than just the three
ones mentioned earlier. This is mainly because that description did 
not mention anything at all about the number the of strokes in the 
movement (and periods in which all legs are off the ground, if there 
are any in).

If I use the abreviations RR=rear right, FR=front right, RL=rear
left, FL=front left, LD=left diagonal (FL+RR simultaneously), 
RD=right diagonal (FR+RL) and Z=period in which none of the legs 
touch the ground (for the Dutch name for this: zweefmoment, 
litterally "floating moment") I come to at least the following 
possibilities, starting all of them from the rear right leg or left 
diagonal:

4. RR FR RL FL         Horse: walk (Dutch: stap)
2. LD Z RD Z           Horse: trod (Dutch: draf)
2. LD RD               ???
2. RR+FR Z RL+FL Z     Horse: pace? (Dutch: telgang), Camel
2. RR+FR RL+FL         ???
3. RR RD FL Z          Horse: canter? (Dutch: galop)
4. RR (RL FR) FL Z     Horse: galop (Dutch: rengalop)
2. RR+RL Z FR+FL Z     Cartoon quadrupeds? ;-)
2. RR+RL FR+FL         ???
1. RR+RL+FR+FL Z       ???  Funny looking, huh? <grin>
(And there must be more, since I did not really try to
fully enumerate all possibilities here, especially all the four 
stroke possibilities...)

The numbers in front are the number of strokes. You can hear them 
when you listen to a moving horse, for example.

So, which one exactly do you (and others on this list?) think 
Euplocephalus (or other quadrupedal dinos for that matter) perhaps 
used? And of course, most quadrupeds can move in more than one way, 
at different speeds. I assume most dinosaurs could too, except 
perhaps the large sauropods, which I really cannot easily image 
doing a galop. ;-)

Jarno Peschier

P.S. I also included the Dutch names just in case; I'm much more 
familiar with those than with the English ones.

  Jarno Peschier, final year computer science student, Utrecht University
mailto:jpeschie@cs.ruu.nl    http://www.students.cs.ruu.nl/people/jpeschie/
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