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Re: Morphological Identifications



What was the name of the show? What is the name of the paper? Do you
know?

Thanks,
Thom Quinn

C. Laibly wrote:
> 
> An interesting article brought to light by those wonderful folks at
> Discovery Channel
>         Two scientists,( names?:( ) completed comprehensive DNA testing on
> the renowned chambered nautilus. According to morphological identification
> and
> speciation-(meaning the number of distinctly identified species) there
> were 9 different species believed to exist, with one exception, the King
> Nautilus. (Believed to be the most primordial and ancient- a true "living
> fossil".) Before the study, it was considered to be either the
> original or pretty near the orginal ancestor of the others. The testing
> proved conclusively that only TWO species existed!, AND, interestingly
> enough, the King turned out to be the more recently developed of the two!
> I found this turn of events to be both fascinating and frustrating and
> wanted to mention it for several reasons...
> 
> 1) I found it intriguing and thought others might also. The show is well
> worth checking out.  :)
> 
> 2) Reading the underlying message from Steve got my gears grinding. I
> would bet my last dollar (being an undergrad, I am sure it is somewhere
> right around here) on the chance of the results being, in no way, an
> isolated incident.
>         It's part of the frustrating same old, same old. Unless we get a
> "window through time", it seems that some assemblages, linneages,trees/bushes
> etc. will be nearly impossible to complete with certainty -> and thus,
> accuracy. Perhaps with this little nautilus scenario, Eoraptor/
> Plateosaurus could be viewed as one or the others ancestor. I am
> speaking from a knowledge base ( my own) that's not quite extensive in
> specific species of dinos, but the point is still clear, I think. Even
> with a cladistic program printing out a tree ( wish I could properly use
> the systematics buzzwords here- parsimony, homogeny, etc.) it seems that
> much information could be just plain old inaccurate in some studies and
> classification systems. Of course, that is no reason to stop research and
> information gathering, but I think the results represent some of the
> pitfalls of modern research, and in cases like species identification from
> fossilized remains, it appears that the pit can be pretty deep. sigh
> Responses welcome!
> 
>  On
> Thu, 23 Jul 1998, Tomporowski, Steve wrote:
> 
> >
> > Well, the bottom line is:  Do we have *any* data that indicates what species
> > concept is correct??  Having concepts of what is happening is fine, but the
> > real advances come when the concept gives of model of reality.  I infer from
> > what you've written that we probably don't have enough data *and* there is a
> > distinct possibility that one concept is not valid all the time.
> >
> > Didymus
> > >
> > >   Why does the fact that _Eoraptor_ appears later or contemporaneously
> > >with _Plateosaurus_ in-and-of-itself disqualify it from being
> > >_Plateosaurus_'s ancestor?
> >
> > It depends on the species concept being used.  The phylogenetic species
> > concept would argue that the ancestral species goes extinct upon
> > speciation, even if one of the daughter lineages is indistinguishable from
> > the ancestral lineage.  (I'm limiting myself to cladogenetic speciation
> > here - anagenesis is another issue altogether.)  As such, ancestors must
> > predate descendents in a perfect fossil record. But, if your species
> > concept accepts post-cladogenetic survival of the ancestor, and you are
> > willing to accept durations for species in the tens of millions of years,
> > then stratigraphy by itself is not a disqualifier.
> >
> >
> >
> > chris
> >
> >  -=--=--=--=--=--=--=--=--=--=
> > Christopher Brochu
> >
> > Postdoctoral Research Scientist
> > Department of Geology
> > Field Museum of Natural History
> > Lake Shore Drive at Roosevelt Road
> > Chicago, IL  60605  USA
> >
> > phone:  312-922-9410, ext. 469
> > fax:  312-922-9566
> >
> > cbrochu@fmppr.fmnh.org
> >
> >