Re: Armadillos at the K/T?

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

----- Original Message -----
From: "Ken Kinman" <kinman@hotmail.com>

>      Actually I would say that the emergence of xenarthrans probably
> occurred even earlier than 76 million years ago, but there is no evidence
I
> know of which indicates they ever existed outside of the Americas and
> Antarctica.  Perhaps they were barred from the Old World by competitive
> exclusion.

Based on both morphological and molecular evidence, the xenarthrans are
quite an old group, but I would not be surprised if they split off in the
late Maastrichtian or even only at the beginning of the Paleocene. There is
not a single Cretaceous eutherian known from South America at present.
Earlier accounts of Cretaceous xenarthrans in SA are based on the idea that
the gondwanatheres (hypsodont teeth) might have been xenarthrans; this seems
to be totally out of favor. Current evidence is that boreosphenidans didn't
reach "outer Gondwana" (SA, Antarctica, Madagascar, India, Australia) before
quite late in the Cretaceous; the only Cretaceous boreosphenidans from there
are the new metatherian tooth from Madagascar and the eutherian astragalus
*Deccanolestes* from India, both Maastrichtian.

David W. Krause: Fossil molar from a Madagascan marsupial, Nature 412, 497f.
(2 August 2001)
(by "marsupial" he means "non-deltatheroidan metatherian", so it's not
necessarily in the crown group)
        When I first read about this onlist, I thought it might be yet
another australosphenidan... the author addresses this possibility and
falsifies it. :-]

To infer the existence of armadillos that looked and behaved like the modern
ones is speculation. I can't say it's wrong, of course, having only negative
evidence, but I wouldn't base a hypothesis on the K-T mass extinction on a
speculation.