Intermediate forms (Was Re: Taxonomy)

[Chartier Michel <chartiem@MAGELLAN.UMontreal.CA>]

On 2 Jun 1999, Norton, Patrick wrote:

> 
> Speaking of taxonomy, a recent issue of Skeptic magazine (Vol. 6 No. 4   
> 1998) has an interview with Jack Horner in which he briefly discusses   
> what he sees as a problem historical and current classification systems   
> have dealing with transitional forms.  Many on this list have probably   
> spoken with JH about this and have far more insight into his thinking   
> than I, but the article suggests that he's proposing to account for   
> transitional forms by showing hypothesized ancestor-descendent   
> relationships as "versions" of a taxon (Tyrannosaurus 1.0, Tyrannosaurus   
> 1.5, 1.6, etc.) in a cladogram.  An example he offers of transition (his   
> words) begins with Styracosaurs from the Judith River Formation in   
> Alberta (75 Ma), through 3 transitional forms found in the Two Medicine   
> formation of Montana, to Pachyrhynosaurus of the Horseshoe Canyon   
> Formation in Alberta (68 Ma).  Versions 1.0 through 1.5 of Styracosaurus?
> 
I haven't seen this article, but the problem of intermediate "species" or
forms in the fossil record and how to classify them has been tackled by
several paleomammalogists already. See articles on early Eocene primates
by Drs. Ken Rose and Tom Bown and papers on Eocene artiodactyls by Drs.
Leonard Krishtalka and Richard Stucky (mid-80s). Also papers by these
authors in a 1993 book entitled _Species, species concepts and primate
evolution_. Do a search of the Bibliography of Vertebrate Paleontology
on-line for these sources.

Michel Chartier