Re: polar sauropods

[John Bois <jbois@umd5.umd.edu>]

On Sun, 6 Dec 1998, Gautam Majumdar wrote:

> John Bois <jbois@umd5.umd.edu> wrote
> >Dwarfism is not the only response to insular environments.  Several
> >species tend to grow bigger, eg., birds, rodents, shrews.  I suppose one
> >should ask: are dinos more analagous to birds or elephants (which do
> >become reduced in size) in this
> >respect. 
> 
> I thought that availability of food would be the primary determinant between
> gigantism and  dwarfism in island environments free from predators. NZ and
> Madagascar are islands but pretty big with lots of resources giving rise to
> gigantism in birds. Dwarfism in elephants occurred only on small islands with
> limited resources. Sri Lankan elephants are not dwarf.

Presumably dinosaurs on NZ would have predators--their dinosaur brethren.
This might have provided an active selective force for large size.

Also, species which are selected for small size by mainland predators may
experience a "release" from this pressure and grow bigger on
islands.  

Elephants, on the other hand, for all we know, may be selected for  big
size for predator immunity.  Landing on some predator-less island they may
then approach a new, small, optimal size.

Then again, forage might be all important.

This is still a very wide-open question.