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Date: Sun, 17 Jun 2001 16:34:34 +0200
From: David Marjanovic <david.marjanovic@gmx.at>
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: Crown groups
In (at least vertebrate) paleontology there is an ever-recurring problem -- how to apply classical names like Aves and Mammalia. One idea is to define them as crown groups, i. e. as nodes that include all living members of the traditional groups. This excludes basal members that have traditionally always been considered members: e. g. *Archaeopteryx* and nearly all other Mesozoic birds from Aves = (*Passer* [sparrow] + *Struthio* [ostrich]), *Morganucodon*, *Megazostrodon*, *Sinoconodon* etc. from Mammalia = (placentals + marsupials + monotremes), *Proterosuchus*, *Archosaurus* etc. from Archosauria = (*Crocodylus* + *Passer*). Currently the crown-group definitions of the mentioned taxa have priority; however, many paleontologists simply reject their usage and often the whole crown-group concept. No consensus is in sight. The implementation of the PhyloCode will reset all priority to zero, and these fights will intensify. The current draft of the PhyloCode has no opinion on this, except Recommendation 10A, which is inapplicable -- usage is approximately the same for both methods. Should the PhyloCode have an opinion about this, and if, which one?