[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Stratigraphy, biogeography & cladograms



In a message dated 1/19/99 12:28:23 PM EST, BartlemaL@emh10.bliss.army.mil
writes:

<< I believe you're trying to ask if birds are monophyletic or
 paraphyletic.  Its something I have often wondered about myself,
 especially lately with the recent Chinese finds.  To anyone:  Has this
 issue been explored?  Perhaps by Feduccia? >>

Any group of organisms can be legislated into being monophyletic simply by
declaring it to be the taxon whose composition is the last common ancestor of
the included organisms plus all of its descendants. The question is, What
other organisms are in the taxon besides the ones you've legislated into it?
For example, the taxon formed by the last common ancestor of birds and mammals
is monophyletic and includes birds and mammals by definition. It also happens
to include practically all the other amniotes.

Likewise, we can call "birds" any member of the taxon formed by the last
common ancestor of modern birds and enantiornithans. This is a monophyletic
taxon. What other animals are in it besides modern birds and enantiornithans?
Dromaeosaurids? _Archaeopteryx_? _Protoavis_? _Mononykus_ and _Parvicursor_?
These would be the questions requiring research.