Re: More sauropod sniffers ...

[Adam Yates <A.Yates@zoo.latrobe.edu.au>]

>Well, okay.  My question is, if fast growth and cartilaginous joints
are
>a 
>juvenile characteristic, and if these features were retained into
>adulthood, 
>why would this not be neotony or more precisely paedomorphosis?

The cartilaginous joints of sauropods are certainly a paedomorphic
feature. One thing that seems to be a repeating pattern in heterochrony,
organisms are rarely affected by one process all over (so called "global
heterochrony"). Heterochrony is usually dissasociated so that
hypermorphosis can be operating on one anatomical area of an individual
while neoteny is sculpting another. As for the fast growth thing , this
highlights one problem I have noticed with the classification of
heterochronic characterstics. Should the retention of juvenile growth
rates be called paedomorphosis or is the overgrown morphology they
produce be called peramorphosis? (a classic example of this conundrum is
the human brain) Most heterochrony workers seem to be going with the
latter, see a recent short review by Mike McKinney in Paleobiology 25(2)
pg. 149-153.  

>I brought up this issue to illustrate that there may not be a "reason"
>for 
>having high nostrils: it may have been due to previous historical
>constraint 
>or the vagaries of embryological development.  The skull of Mussasaurus
>is 
>still pretty weird looking to me for a prosauropod.

Point well taken, not everything has to have an immediate adaptive
reason. In this case however I feel that the amount of restructuring
required to produce the retracted nostrils is too great for it not to
have been adaptive, particularly since there is no reason to suppose
that Sauropods evolved from an ancestor whose babies had their nostrils
on top of their heads. Certainly the ancestral saurischian condition was
to have the nostrils near the snout tip at all stages of life (shown by
young theropods eg. Scipionyx,growth series of modern birds, young
hadrosaurs, and growth series of modern crocodilians)  

 
>Again, skulls and
>cervicals 
>take a back seat to limbs and feet: the better to kick you with, my
>dear. =)

Speaking of which, how did you get around the problem of all that
missing cartilage when trying to work out the mobility of sauropod feet?


cheers

Adam Yates