Re: Reduced Consensus (Was: Afrotheria revisited)

[Allen Hazen <allenph@unimelb.edu.au>]

    Thanks Mike Taylor for your reply!

    "Reduced consensus" sounds about like what I figured had 
happened.  I looked briefly at the additional information,  but have 
to look at it more carefully to see if it tells me anything. 
Arsinoitherium doesn't seem to have a particularly high proportion of 
missing data in their matrix, so it's not quite like your 
hypothetical "Eodino".  On the other hand, I can think of reasons why 
it might be a problem.  It was the largest (body mass) of the taxa 
they considered, and has famously unusual teeth (long row of 
bilophodont postcanines, premolars pretty well molarized, as I 
recall, though I haven't looked recently and am not a trained 
observer of dental characteristics).  So I guessed it would have lots 
of special autapomorphies, making it into a LONG BRANCH.  And we all 
know THEY can be a worry!

    I'm still not 100% convinced it isn't cheating: I'm genuinely not 
sure.  I think there can be legitimate and principled reasons for 
excluding taxa, but throwing away data always makes me nervous.  Yes 
the data matrix gives a well-resolved tree for 22 taxa, but is that 
because of "gerrymandering"?  Would it be possible to get a DIFFERENT 
well-resolved tree by excluding one of the other taxa (this is 
something that time and computer power could check!)?  I saw no 
comment in the paper or supplementary information indicating how 
Arsinoitherium was excluded (from tree or from matrix, to raise the 
issue David Marjanovic raises) or what the rationale was: some 
discussion would have been reassuring.

    Micky Mortimer crowed on the DML forum recently about a published 
criticism of a paper that had achieved a well-resolved tree by 
excluding taxa from consideration: crowed because he had made a 
similar criticism some months ago on the forum.  I'm hoping he will 
comment: does he think Tabuce et al. are doing something good, or bad 
like the people he crowed over.
    (Does saying "crowed" enough times count as dinosaur relevance?)

    I'm rather hoping that Tabuce et al. are in the clear, since 
their conclusions appeal to me.  Christine Janis and a co-author have 
recently (last year?) published a paper in "Journal of Mammalian 
Evolution" (called "Spiny Norman and the Garden of Eden") arguing 
that a holarctic origin for placentalia is the more parsimonious 
hypothesis in terms of the number of vicariance and migration 
episodes it postulates, and Zack, Penkrot et al. (last reference in 
Tabuce &c's paper) find close Eocene relatives for the Macroscelidea 
in North America!
...
    Leading to another mild discomfort I feel about Tabuce &c.  They 
say they have found the apheliscines to be a sister-taxon of the 
Macroscelidea, but their trees actually show Apheliscus as a sister 
of Macroscelidea+Paenungulata.  I assume this is what their dental 
and tarsal characters show: Zack and Pencrot have an above-the-tarsus 
character (co-ossification of the distal tibia and fibula) which 
would unite Apheliscus with crown Macroscelidea.  (I think: I've got 
to re-read their paper more carefully.)

    Anyway... I'm a non-paleontologist (I'm a philosopher, 
specializing in logic) and never confident that I'm saying anything 
that REAL paleos will even think deserves COMMENT!  I found the 
Tabuce &co paper very interesting, I am by no means confident that I 
have spotted any real flaws in their work... and I will read with 
interest whatever the pros have to say about it!

Allen Hazen
Philosophy Department
University of Melbourne