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Re: monophyletic; polyphyletic; paraphyletic




A paraphyletic group also stems from a most recent common (basal) ancestor, but one or more exgroups have been formally removed (that is why strict cladists dislike them, because they are "incomplete").
Dinosauria is paraphyletic if you formally remove Aves. Amphibia (traditional, sensu lato) is paraphyletic if you formally remove Amniota. Hypsilophodontidae (sensu lato) is paraphyletic if you remove the dryomorphs.
My solution to this dilemma of "incompleteness" is to add {{markers}} for exgroups, so that paraphyletic groups become cladistically complete in informational terms. Family Hypsilophodontidae is paraphyletic, but adding the marker for dryomorphs {{Dryosauridae to Hadrosauridae}} effectively makes it strictly monophyletic (ie. holophyletic).
I call such "marked" groups semi-paraphyletic or semi-holophyletic (both mean the same thing, sort of like half-empty or half-full). By the way, holophyletic is the proper term for cladistically "monophyletic". The pre-cladistic meaning of monophyletic meant holophyletic and/or paraphyletic (i.e. have a common recent ancestor, whether any exgroups have been removed or not). I personally wish the term monophyletic would be abandoned, because holophyletic is more precise (while monophyletic means something different to cladists and non-cladists).
--------Ken Kinman
******************************************
From: "aspidel" <aspidel@infonie.be>
Reply-To: aspidel@infonie.be
To: "The Dinosaur Mailing List" <dinosaur@usc.edu>
Subject: monophyletic; polyphyletic; paraphyletic
Date: Mon, 20 Aug 2001 22:43:07 +0200

Hi dear dino-list members,

First thanks to HP's Ken Kinman and Thomas R. Holtz Jr.'s replies.

Another question:

monophyletic: is it told about a group which is derived from a common basal species?

polyphyletic: is it told about a group which contains species sharing common features but which may derive from different basal species?

And what means paraphyletic?

Many thanks in advance, friendly - LJB.

ps: maybe I'm not clear; and excuse my bad English.


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