RE: Neogondwana and Epitheria

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

>Folks, I don't understand something. Modern small mammals and birds have
>big dispersive abilities and quite easily colonise other continents
>especially if empty ecological niches are present. 

I don't think this holds as a general rule.  Sure, rats (Rattus_) and mice
(_Mus_), for example, have proven to have excellent dispersive abilities,
but this is due more to their generalized dietary habits (and very resilient
constitutions!) than their small size per se.  North America has yet to be
invaded by hordes of marsupial moles (_Notorytes_) or tree shrews
(_Tupaia_).  (I wish!)

As for birds, as Darren Naish pointed out in a recent post, many bird
species that are good fliers simply refuse to fly over bodies of water.

http://www.cmnh.org/fun/dinosaur-archive/2001Dec/msg00625.html



Tim