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Re: T-J Extinction event article (more media errors?)

George Olshevsky (Dinogeorge@aol.com) wrote:

<My understanding is that Synapsida presently includes Mammalia
as a subtaxon. What say you?>

  I would think so, in the sense that Synapsida includes
Mammalia by content. Synapsida has, I believe, been defined as
clade = {Mammalia <- Reptilia} so that more taxa can be
included, including paraphyletic pelycosaurs, sinoconodonts,
*Morganucodon*, etc. that are not part of the crown group. And
that even if crown groups are not the best taxa to add names to,
they do exist as much as paraphyletic taxa, and I would argue
that they are also not useful taxa to bear formal names.
Mammalia can be defined, not as a crown group, but as an
explicit statement of the taxa used: *Canis* + *Macropus* +
*Ornithorhynchus,* still have the same content, and even be more
stable. This structure has been the reference taxa, and even if
Multituberculates prove to be closer to Theria than outside of
crown Mammalia, they can be used. Crown clades, as you state,
are quite confuddling and can lead to errors.

Jaime A. Headden

  Where the Wind Comes Sweeping Down the Pampas!!!!

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