2. 4. Break a leg (was re gliders to fliers?)

["Martin Barnett" <martin.barnett3@virgin.net>]

----- Original Message -----
From: Matthew Bonnan <mbonnan@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Sunday, September 26, 1999 3:41 PM
Subject: Re: Gliders to Fliers? (Was Re: Ruben Strikes Back)


> Dinogeorge says:
> >Breaking a leg isn't fun for any animal, quadruped or biped. But at least
a
> >quadruped has three other usable legs while the broken limb heals; a
biped
> >has only one. I consider bipedality to be a hindrance that must be
overcome
> >by compensating adaptations in the forelimbs and other parts of the body.
>
> Again, here I disagree.  Breaking a leg is a bad deal for most animals,
and
> because it tends to hinder their food collecting abilities and makes them
> more susceptable to predators, I don't see what the difference is

Perhaps (and I know this word has been marginally villified surrounding
these threads, but what the heck) it has to do with support after the injury
if said animal survives breakage.  When a biped breaks it's leg and manages
however it does to survive on one, the weight of it's body is focused
largely on the one healthy leg - twisting the hip slightly from it's natural
position to sustain load and also distributing mass onto a smaller surface
area (ie, one foot).  When a quadruped has the same injury it is
distributing it's mass across three quarters of it's usual surface area,
not half as in bipeds.  The resultant damage to the hips MAY in theory be
greater on the biped than the quadruped.  Plus if the biped hip is not
centred in it's natural position while the quadruped's is, there are serious
potential ramifications on the spine as well - a delicate skeletal feature
no matter who you are and an injury incurred forceably hopping on one leg
would probably be a permanent one as anyone (including myself) with a dodgy
back will tell you.  No animal especially a predator wants a dodgy back for
the rest of their lives, but odds are n favour of a biped getting one over a
quadruped it seems.
Hope that helps,
                          Samuel Barnett