Use of term plesiomorphic

"=?iso-8859-1?Q?Dr._Manuel_A._Balc=E1zar_Lara?=" at "=?iso-8859-1?Q?Dr._Manuel_A._Balc=E1zar_Lara?=" at
Thu Apr 29 13:51:57 CDT 2004

Plesiomorphic is used only for pairs of characters in the same
transformation series.
If you have the following TS:

A -> B -> C

"A" is plesiomorphic regarding "B", but "B" is plesiomorphic regarding "C".


Manuel Balcázar

> -----Mensaje original-----
> De: Taxacom Discussion List [mailto:TAXACOM at LISTSERV.NHM.KU.EDU] En nombre
> de Thomas Yancey
> Enviado el: Jueves, 29 de Abril de 2004 02:39 p.m.
> Asunto: [TAXACOM] Use of term plesiomorphic
> I would like some guidance on use of the term plesiomorphic when applied
> to
> a discussion of a lineage of fossil genera with progressively younger
> geologic ranges. In this example, is it appropriate to apply the term
> plesiomorphic to a character that is possessed only by the oldest known
> genus, then is replaced by a derived character in younger genera? I
> suppose
> one could adopt the position that a character of the ancestor is shared by
> all descendents, even if it is lost in most or all descendents, but that
> seems like an inappropriate use of the term.
> However, in practice, is the term used in this manner? Or does it need to
> be applied in a more strict manner? Assuming that there is a range in
> useage of the term, what is considered good practice vs. poor practice? In
> my case, I sense that the term is being used as a substitute for the word
> 'primitive', which does not seem proper. It will be desirable to hear what
> is the current practice in using the term in the area of descriptive
> taxonomic studies.
> Thanks.
> T. Yancey
> Thomas E. Yancey
> Dept. Geology & Geophysics, Texas A&M University
> College Station, Texas 77843-3115
> ph: 979-845-0643
> tyancey at

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