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Re: Fossil species
Well Steve, this has been a problem for a very, very long time.
However, there could someday be computer algorithms (utilizing optimality
criteria of information content) which could help eliminate much of the
Not sure how well they would work for fossils, but they have been
tested on a family of extant fishes (Caesonidae). It contains 20 species,
and this family's optimal classification was mathematically determined to be
4 genera (two distinctive species were placed in monotypic genera, one genus
with 8 species, and another with 10 species). With the added stratigraphic
data of fossils, I would guess the computer algorithms might be a little
Anyway, if you are interested in quantitative methods and optimality
criteria, you might find it interesting:
Carpenter, K.E., 1993. "Optimal Cladistic and Quantitative Evolutionary
Classifications as Illustrated by Fusilier Fishes".
Syst. Biol. 42(2):142-154.
Steve Brusatte wrote:
On Mon, 4 Feb 2002 20:40:10
>In a message dated 2/4/02 7:09:11 PM, firstname.lastname@example.org writes:
><< >Too bad there is no real scientific method for determining what
belongs to a genus.
>Certainly. Every Linnaean rank above species, as mentioned in a previous
>post, is completely arbitrary and based on the observer. >>
>I don't really see *fossil* species as being much, if any, less arbitrary
Unfortunately, when dealing with fossils, what you allude to is correct.
But, the enigmatic concept of a genus applies to everything living and
extinct. However, it certainly seems easier to differentiate between say,
_Psittacosaurus mongoliensis_ and _P. sinensis_, than to divide the
_Psittacosaurus_ species into distinct genera. This was discussed onlist a
few months or so ago, with no one able to come up with a distinct set of
characters to divide _Psittacosaurus_ into two genera (of course, some may
have missed the post...in which case I would be interested in hearing
I don't see cladistics as an end to all means, but the idea of a clade is
certainly much more stable than something like a "genus."
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