Re: Ancestors [was: Re: And while on the theory of phylogenetic reconstruction...]

[Mickey Rowe <rowe@psych.ucsb.edu>]

David Marjanovic (david.marjanovic@gmx.at) wrote:

> Rafael Zardoya & Axel Meyer: The evolutionary position of turtles revised,
> Naturwissenschaften 88, 193 -- 200 (?May 2001)
> 
> "_Fig. 2A -- F_ Alternative hypotheses explaining the phylogenetic position
> of turtles within living amniotes. _A_ Mammals are the most basal living
> amniotes.

For their more recent views, see:

Meyer, A., and Zardoya, R. (2003).  "Recent Advances in the
    (Molecular) Phylogeny of Vertebrates", _Annual Review of Ecology,
    Evolution, and Systematics_, 34:311-338.

They no longer suggest the tree topologies shown in panels B and F of
Fig. 2 in the _Naturwissenschaften_ paper.  There appears to be a
growing consensus that turtles are derived diapsids.  Anyways, in all
of the proposed phylogenies in Meyer and Zardoya 2003 (panels A and
C-E of the earlier paper), mammals are the sister group to the
remaining amniotes.

In Fig. 1 of the 2003 paper is a relatively complete big-picture
dendrogram of the vertebrates.  Areas considered controversial (i.e.,
those to be discussed in the paper) are drawn as polytomies.  Mammals
as sister group to the remaining amniotes is a dichotomy in that
figure.  That's a pretty direct statement that they think the issue is
resolved.

On the other hand, it's certainly not universally accepted yet -- for
instance in:

Grauer, D. and Martin, W. (2004).  "Reading the Entrails of Chickens:
    Molecular Timescales of Evolution and the Illusion of Precision",
    _Trends in Genetics_, 20(2):80-86.

Their Fig. 1 includes the possibility (i.e. the classical view) that
turtles, as primitive anapsids, are the sister group to all other
amniotes.  But it looks to me like that possibility will not be
considered tenable very much longer and most people studying the issue
already think it's not.

-- 
Mickey Rowe     (rowe@psych.ucsb.edu)