RE: Sauropod nostrils (was RE: joke........)

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

-----Original Message-----
From: Matthew Bonnan

Perhaps sauropod nasal position has to do with neotony (retaining
juvenile 
characters into adulthood).  Embryonic prosauropods like Mussasaurus
have 
nostrils placed higher on the head and closer to the orbit than adult 
prosauropods which have sniffers in the front.  Maybe sauropods retained
a 
juvenile characteristic in the skull through neotony?  Perhaps also
their 
cartilaginous joints and apparently rapid growth stem from the same
thing?  
Any thoughts?
-------------------------

I find the paedomorphosis (=retention of juvenile characteristics into
adulthood) hypothesis rather unconvincing. I use the term paedomorphosis
rather than neoteny because much of the heterochrony literature uses neoteny
to describe one particular process by which paedomorphosis occurs
(specifically retarding development by slowing its rate). There are other
ways of achieving paedomorphosis, such as cutting short the development time
or delaying the onset of development of a certain feature, and in
palaeontological practice it is just about impossible to to distinguish
which process is responsible for the observed paedomorphosis.
Back to sauropods. The only adequate juvenile sauropodomorph material that I
know are the Mussasaurus specimens. These do not show the extreme narial
retraction of later sauropods so there is nothing to support the idea that
retracted nostrils are a retained juvenile characteristic. Further there
isn't much else about a sauropod skeleton that is paedomorphic, they can
instead be characterised as animals with a lot of "supergrowth" or
peramorphosis, the opposite of paedomorphosis.

cheers

Adam Yates