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Re: "Ichabodcraniosaurus" and NGMC 91



Mickey Mortimer (Mickey_Mortimer11@email.msn.com) wrote:

<This is confusing to me.  Assuming a taxon is diagnostic, aren't we
expected to name it?>

  Why? A specimen attribution serves the same function. For ease of
communication, you _can_ attribute another term to accompany it, but there
are a number of things that go along with it, including assumption of
specific variation through specimens, and ignorance of individual
variation. Even a host of variations doesn't make a species a species in
some circles, and one enters this game with certain preconceptions,
including how species are defined, hopw speciation occurs, and how much a
specimen can be identified beyond individual variation before it suddenly
becomes a it's own species. As Norell said, there are dozens of rather
poorly preserved or scrappy material specimens that he _could_ name, but
chooses not to (read Makovicky and Norell, 1997, for why they chose not to
refer several postcranial skeletons to a new taxon, but later (Makovicky
and Norell, 1999) referred to *Velociraptor*, emphasizing patience) that
only exemplifies this.

<As long as there isn't a good possibility of it being diagnosable due to
ontogenetic/pathological/individual variation, I don't see the problem. 
Even if it's poorly preserved, naming and describing diagnostic organisms
is one of the main goals of biology, is it not?>

  But that's just the problem ... in this case, individual variation is
not being accounted for ... both diagnosed taxa are based on much more
partial material than is NGMC 91, and according to those who've had the
opportunity to examine the specimen with a microscope, dentist's pick, and
have had their eyes mere millimeters from the surface of the specimen,
there is not enough similarity to warrent referral. Now perhaps
photographs may not indicate this, but the specimen has not been fully
described, and neither for *Sinornithosaurus* or *Microraptor* (though
this is being ammended), so comparison is hardly finite for anyone even
reasonably unless they've _seen_ the material.

<For instance, I think there's a good possibility Microraptor is more
closely related to neornithines than to Dromaeosaurus, and may even be an
avian.  Thus, I would dispute calling it a dromaeosaurid. I don't see how
such issues are naive.>

  I see this as an assumption of the polarity of many basal features in
the matrix. It is suggestible (indeed, has been for over 15 years) that
*Archaeopteryx* may be basal within the tree, even though birds derived
from that branch. For some reason, many people have been operating on the
assumption that the opposite was true. But the fossil records appears to
supply an earlier diversity of birds before the development of non-volant,
terrestrial even, theropods who became ever increasingly larger in the
latest Jurassic and earliest Cretaceous and radiated into what we call the
Troodontidae and the Dromaeosauridae. Other ... more orthodox ... views
have tempered our theories and prevent us from operating more freely it
what was supposed to be a _guiding_ framework, rather than a restrictive,
rigid one: cladisitic analysis.


=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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