fossils as roots

[Thomas Schlemmermeyer]

Dear all,

On (    Wed, 3 Mar 1999 07:33:02 -0800), Curtis Clark <jcclark at CSUPOMONA.EDU>
wrote:


>At 07:38 AM 3/3/99 -0700, Hilary Davis wrote:
>>I'd like to hear some opinions on the use of fossils to root a cladogram
>>or tree.  Is this a valid technique given the possibility that a fossil
>>assemblage for a particular extant group may not be complete?
>
>Do you mean use a fossil as an outgroup? It should work as well as any
>extant species: if it weren't extinct (a "living fossil"), and you'd have
>no hesitation in using it then, its extinctness shouldn't be an issue. The
>only question would be whether it has states for all the characters used in
>the analysis of the living species.
>
>
Fossils clearly could work better than extant species if they provided good
characters (amber fossils) and a clear indication about their age (amber
fossils).

Cladogram in its primitive, phylogenetic sense is seen as a tree growing through
time. Fossils could clearly provide information as to the character states
on certain points of time.
                           Cheers,  Thomas