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Re: dino extinction

At 12:31 PM 11/16/96 +1030, Tim Williams wrote:
>You'll get no argument from me on that!  The presence of a condylarth
>(_Tingamurra_) from the early Tertiary of Australia hints that the
>dominance of marsupials on this continent came about not through
>default (i.e. the absence of placentals), but because the marsupials
>were competitively superior to placentals.

        Actually, I think it would be best to assume that other factor were
in effect, considering other instances when placentals beat out the
marsupials.  Perhaps marsupials just had a stronger foothold in Australia?
As with the invasion of South America by placentals, simple "just-so
stories" do not seem to always adequately explain evolutionary phenomena
(although they can be useful, there is a paper in _The Beginnings of Birds_
which covers this topic in some depth, from a more amicable perspective).
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
|           Web Page:  http://faraday.clas.virginia.edu/~jrw6f             |