Re: Marsupial forelimbs... or rather hindlimbs

[David Marjanovic <david.marjanovic@gmx.at>]

> > (I'm not certain exactly what Weisbecker et al. mean by "fully
> > aquatic", but full-time aquaticity in the style of sirenians and
> > cetaceans is one placentalian guild that has no marsupial analogs to
> > my knowledge.)
>
> True.

Yes, but then, both the whales and the sea cows evolved more or less as 
early as possible, and immediately spread around the world. The sea cows 
didn't even wait till they had lost functional hindlegs (see *Pezosiren* 
from Jamaica). Then those niches were occupied, and nothing else was able to 
evolve into them anymore.

> Incidentally, it kind of seems that marsupial pouches would be
> *better* for a flying guild than placentalian clinging. And there are
> several lineages of gliding marsupials--it does seem odd that none of
> them have developed flight. (Although, given the rarity of amniote
> flight, especially amniote flight derived from skin-gliding, maybe
> luck has something to do with it.)

The bats, too, apparently evolved around the Paleocene-Eocene boundary in 
the northern continents and immediately reached Australia. There are bat 
teeth in Tingamarra (dated as early Eocene last time I checked). Here, too, 
the marsupials may simply have come too late. Perhaps just a few hundred 
thousand years too late, who knows.