[Taxacom] phylogeny (Monotremata)
jgrehan at sciencebuff.org
Tue Aug 9 06:08:08 CDT 2011
It's bad because it fails to specify that the monotremes lack derived features that are shared by marsupials and placentals (and vice versa I presume).
I have a colleague here who has dug up a cretaceous 'cynodont' which has a fully articulated dentary, but still retains the serially replacing teeth, unlike supposed basal mammaliform fossil that have the modern form of tooth replacement, but lack a fully articulating dentary. This could get interesting in due course as this new fossil also appears to have some monotreme characteristics. The author of this find will be working on a publication in the near future, although he did give a presentation on the fossil at a Society of Vertebrate Paleontology meeting a couple of years back.
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Stephen Thorpe
Sent: Monday, August 08, 2011 11:47 PM
Subject: [Taxacom] phylogeny (Monotremata)
increasingly, I get the impression that the basic principles of phylogeny are not well understood
look at the first paragraph here: http://www.ucmp.berkeley.edu/mammal/monotremesy.html
>Monotremes are mammals. Unlike other mammals monotremes lay eggs, as
>did the ancestors of the mammals. For this reason, the Monotremata are
>considered the sister group to all other mammals.<
Surely, this is badly expressed, or even just plain wrong? The reason why Monotremata (or at least the extant lineage thereof) are considered to be the sister group to all other mammals is because they are monophyletic (by virtue of having synapomorphies), in addition to being basal to (outside of) the main mammal clade (by virtue of laying eggs - a plesiomorphy) ...
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