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Re: Classification Systems



On Wed, 7 Apr 1999, John M. Dollan wrote:

> Okay, on working on this Dinosaur genera list, I have been working with
> a Linnaean system, hoping to be somewhat consistent with modern animal
> classifications.  But it is becoming obvious that a full and accurate
> Linnaean list may not be possible, at least not with out becoming
> hopelessly confusing.  

There are several reasons why a Linnaean system works pretty well for
extant organisms but is hopelessly inadequate for paleontological
purposes:

1)  Living organisms are *far* more completely known than extinct ones,
which provides more characters that can be used in classification.

2)  Extant organisms essentially form a closed set, and new discoveries
are comparatively rare.  On the other hand, previously unknown extinct
organisms are discovered all the time, exposing previously unacknowledged
problems in the taxonomy.

3)  Taxonomies of modern organisms do not have to deal with transitional
species between major groups.  While there are indubitably many species
alive today that will eventually give rise to major radiations in the
future, we don't know about them yet, and so we don't have to accomodate
them in our taxonomies.  Ignorance really can be bliss!


> 1)Using a Linnaean system, but for simplicities sake, using only
> Superorder, Order, Suborder, Infraorder, Family, Genus, Species.  The
> draw back is that it may not be completely comprehensive or accurate.

You're right; it won't.  And, as our friend Dr. Tom pointed out, Using
traditional Linnaean ranks for traditional Linnaean taxa will give you
rather icky situations like a "Class" Aves nested deeply within "Class"
Reptilia, which is itself nested within the "Class" Pisces.


> 2)  Using a cladogram.  The drawback here is that I have run across
> several disparate versions of cladograms in my wanderings over the 'Net
> and the local library.

You'll find the same situation with scientists who use traditional ranks:
witness all the recent controversy over the classification of modern
birds.  The fact is, we simply don't have all the answers yet, and we
don't even know for sure what is the best way to find the answers.  Thus,
people's ideas on how organisms are related to each other are going to
conflict.

-Nick P.