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An object lesson

In case anybody needed an object lesson on the importance of of sampling an
adequate range of taxa in doing your phylogenetic analysis, the paper by C-L
Gao, G.P. Wilson, Z-X Luo, A. Murat Maga, Q Meng and X Wang,
    "A new mammal skull from the lower Cretaceous of China with
    implications for the evolution  of obtuse-angled molars and
    'amphilestid' eutriconodonts," (Proceedings of the Royal
    Society B, apparently only on-line so far, doi:10.1098/
    rspb.2009.1014 )
that Jerry Harris mentioned a few days ago provides one.  The paper has, not
ONE, but TWO phylogenetic analyses.

One looks at the new critter, Juchilestes, and otherwise mainly at
Triconodonts, along with a few early Mammaliaforms (Sinoconodon,
Morganucodon: the usual suspects) and a few sample "Trechnotheres."
("Trechnotheria," in case you have trouble keeping the utterly unmemorable
and nondescriptive names recent paleomammal students have given to the
clades they postulate, is the clade of definite Therians: Symmetrodonts and
us. (Where, in case you haven't kept up with the literature since 1979,
Kuehneotherium is NO LONGER considered to be a Symmetrodont.))
This analysis finds Eutriconodonta  to be
with respect to Trechnotheria: some "Amphilestids" more closely related to
us than they are to other "Amphilestids".

But the other analysis (briefly reported in the paper, details in the Online
Supplementary Information), based on the work of Luo, Kielan-Jaworowska and
Cifelli (Acta Palaeontologica Polonica vol 47 (2004) and THE BIG BOOK)
surveys a wider range of taxa, and seems to recover a MONOPHYLETIC
Eutriconodonta (though still splitting "Amphilestids" into two groups widely
separated in the Eutriconodont tree), with Multituberculates closer to us
than the Eutriconodonts are.(*)

Moral: As the authors of the paper say "the issue of monophyly or paraphyly
of the 'Eutriconodonta' is in part dependent on sampling in a broader
taxonomic context."  One suspects that similar problems arise elsewhere!

(*) (I'm a bit puzzled on one point here: as I recall it, Luo,
Kielan-Jaworwska and Cifelli's FAVORED tree did not connect
Multituberculates with Haramiyids: constraining them to unite in a
monophyletic Allotheria resulted in a tree that wasn't much worse, they
said, but ruled out such a close link between Multituberculates and
Trechnotherians.  The tree in the Online Supplementary Information, however,
seems to have Haramiyids and Multis together in a position closer to
Trechnotheria than Eutriconodonta!)


Allen Hazen
Freelance philosopher (formerly: University of Melbourne)