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Isn't Australosphenida the same as
Prototheria? --
Philo
17:31, 15 December 2006 (UTC)
Hello Ucucha,
I do know that living eutherians are outnumbered by extinct eutherians, but that's a very different case since living eutherians are still numerous and not reduced to a handful of species. The problem I see here is that you are claiming present diversity of species as a reason for saying the group has not almost disappeared. If there were only 5 living species of vertebrates (say, a lamprey, a bird and 3 mammals), the subphylum would be highly diversified. It would also have "nearly entirely died out". This is exactly parallel to the case here. Diverse, yes; numerous, no. Most species in the group are extinct. That is precisely what is meant by "nearly entirely died out", irrespective of present diversity.
I think it's rather simple. Today we have 5 species belonging to just 2 monotreme families (out of the 4 that are known to have existed), and all of these belonging to the same order (out of the 2 that are known to have existed). Most of the present diversity is within just one family and most of that is within just one genus. Maybe there are more species known to be alive at the present time than at any one point in prehistory, but they are restricted to fewer taxa. By any reckoning this must count as a reduction in overall diversity. The remaining Australosphenida are less diversified than they would have been if kollikodontids, steropodontids and/or ausktibosphenidans had survived. But even if they were more diversified today (say, one species from each of the five groups), as long as there were only a handful of them it wouldn't change the fact that they have "nearly entirely died out".
If you dispute this, can I invite you to say how you would express the fact that there are currently but few species, from fewer lineages than ever before? Gnostrat ( talk) 05:48, 21 September 2008 (UTC)
![]() | This article is rated Start-class on Wikipedia's
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![]() | This article links to one or more target anchors that no longer exist.
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Reporting errors |
Isn't Australosphenida the same as
Prototheria? --
Philo
17:31, 15 December 2006 (UTC)
Hello Ucucha,
I do know that living eutherians are outnumbered by extinct eutherians, but that's a very different case since living eutherians are still numerous and not reduced to a handful of species. The problem I see here is that you are claiming present diversity of species as a reason for saying the group has not almost disappeared. If there were only 5 living species of vertebrates (say, a lamprey, a bird and 3 mammals), the subphylum would be highly diversified. It would also have "nearly entirely died out". This is exactly parallel to the case here. Diverse, yes; numerous, no. Most species in the group are extinct. That is precisely what is meant by "nearly entirely died out", irrespective of present diversity.
I think it's rather simple. Today we have 5 species belonging to just 2 monotreme families (out of the 4 that are known to have existed), and all of these belonging to the same order (out of the 2 that are known to have existed). Most of the present diversity is within just one family and most of that is within just one genus. Maybe there are more species known to be alive at the present time than at any one point in prehistory, but they are restricted to fewer taxa. By any reckoning this must count as a reduction in overall diversity. The remaining Australosphenida are less diversified than they would have been if kollikodontids, steropodontids and/or ausktibosphenidans had survived. But even if they were more diversified today (say, one species from each of the five groups), as long as there were only a handful of them it wouldn't change the fact that they have "nearly entirely died out".
If you dispute this, can I invite you to say how you would express the fact that there are currently but few species, from fewer lineages than ever before? Gnostrat ( talk) 05:48, 21 September 2008 (UTC)