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Re: attack on dinosaur--horrific video
True, marsupials seem to have been shouldered aside by the placentals in
every continent except Australia
I still disagree. In the Cenozoic, the northern continents only ever had
ecologically opossum-like metatherians; they managed to enter Africa in the
Eocene, and then they died out on all four continents in the late Miocene
for unknown reasons (in the cases of North America and Europe, we could
blame the climate -- loss of tropical rainforests and all --, but obviously
not in the cases of Africa and Asia, and of course today's North American
opossum can deal with all temperate climates). In South America there was
that impact and mass extinction right before the Great American Interchange,
except that for rainforest taxa the interchange may have started much
earlier (there was an SVP meeting abstract a few years ago about a 9 Ma old
tapir from South America), and even before that, there were only the
surviving didelphid, microbiotheriid, and caenolestid marsupials (of which
the caenolestids survive in spite of the recent immigration of shrews), the
mysterious argyrolagids, and the carnivorous borhyaenoids. Antarctica is a
moot question (and in the Eocene, there were South American "ungulates" as
well as marsupials and the last gondwanathere on the Antarctic peninsula).
That only leaves Australia.
And then of course, kangaroos have broken loose in Europe several times and
survived the winters and all, before they were (in each case) all shot by
hunters. I'm told they have better digestion than sheep...
And Australia has had rodents since the Miocene. Considering the
morphological diversity that rodents have managed to evolve in South
America, they could replace several clades of Australian marsupials. Yet
they haven't. They didn't even evolve a rabbit analogue the way they did in
SA (the mara).
(where the opposite may be true, based on the 'condylarth' _Tingamarra_).
Which, like *Kharmerungulatum*, is "the tooth, the whole tooth, and..."