Re: Sex

[Graydon <graydon@dsl.ca>]

On Wed, Feb 28, 2001 at 12:54:43PM -0000, Gavin Rymill scripsit:
> Graydon said:
> > A suggestion I haven't seen is that the tripod stance for high
> > feeding might also have allowed face-to-face breeding.  That would
> > seem to go for sauropods as well; if it can stand up to eat leaves,
> > they could lean on each other for mating.
> 
> Don't you think that if they have reared up, face to face, then they would
> be leaning inwards with their hind quarters quite a considerable distance
> appart. 

This is a question of hip anatomy, but:
    a) stegosaurs and sauropods are often illustrated as being able to
    achieve a nearly vertical stance
    b) they can grasp with the forelimbs to pull closer together
    c) it gets the problem into a single degree of freedom -- height
    -- rather than two (your tail-up sugguestion) or three (any
    conventional 'around the tail' arrangment

Anyone know how vertically a stegosaur _could_ stand?

> I don't feel that their positions would have reached anything like
> the dangerous vertical stance required for the genitalia to meet. It was for
> this reason that in my illustration I put the female with her head down and
> tail raised so that only the male needed to attempt the tripod stance and
> there were no extra sets of forelimbs to get in the way.

That mechanism would work, too, although I wonder about how the tail
_could_ go; there's a very rigid spinal column and an already very low
stance in the forward part of the body; there isn't all that much _to_
lower the head and forelimbs.

-- 
                           graydon@dsl.ca
               To maintain the end is to uphold the means.