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RE: Gallinuloides and Galliformes



--- Roberto Takata <rmtakata@gmail.com> schrieb:

> Dear e-pals,
> 
> What is the current phylogenetic status of
> Gallinuloides amidst other
> Galliformes? Is it considered a basal taxon to all
> other Galliformes
> (as Mayr & Weidig 2004) or is it a basal Phasianoid
> (as Dyke 2003)?

[to be taken with a severely unhealthy dose of NaCl;
see last paragraph as for why:]

Biogeography does not suggest Mayr/Weiding (+Mayr
2006) are correct; other data more equivocal.
Transoceanic dispersal capability in galliforms
generally rather weak and always seems to have been
(migration near non-existent in extant spp FWIW);
megapodids + cracids *possibly* of Gondwanan
(?Mesozoic? not supported by fossil record though)
radiation relics, whereas phasianoids seem fairly
certainly Laurasian radiation. Trans-N Atlantic
distribution of Gallinuloididae is indicated by
material, but des not fit well with "basal to all
other Galliformes" hypothesis. If so, almost certainly
conserved plesiomorphies due to age of lineage, but
this means caveat emptor their position in regard to
other stem lineages; apomorphies in Galliforms -
ecologically conservative, morphologically homogenous,
ancient - are subtle as compared eg to Anseriformes.
"Basal to all galliforms" is misleading - "late
survivors of stem-group divergence" would be better
way to put it; if stem lineage, has been evolving on
its own for long time (as per Figure 7 in Mayr &
Welding).

Phasianoid radiation s.l. (including guineafowl, NW
quails) took place probably 35-25 mya,
post-Gallinuloididae, though may have started earlier;
many questionable "galliforms" known from Paleogene
deposits. Quercymegapodids puzzling but in need of
thorough revision - biogeography of Ameripodius is
laughable (IIRC *only* non-marine avian taxon with W
Gondwanan + W Palearctic fossil record, ha!)
Phasianoid radiation probably generally Asian, though
guineafowl indicate role of Indian Ocean needs
investigation; odontophorids trans-Beringia dispersal?

How do Gallornis, Argilipes, Percolinus (candidates
for Gallinuloididae-lineage members, latter two are
unfortunately Harrison & Walker taxa methinks),
Tristraguloolithus (Cretaceous egg from canada
w/"cracid" shell morphology) tie into picture? I find
Mayr/Weidig's attempt to argue away biogeography
rather lukewarm; basically, Galloanseres paraphyly
would support their hypothesis better than the present
state of hypotheses... that Kurochkin did not
seriously dump a lot of his isolated fragments into
the Galliformes is, well, interesting...

Major problem in Galliformes in general is 30-ma lack
of unequivocal fossil record, which happens to be
where the true stem group fossils (as opposed to
hypothetical late stem-divergence survivors like
Gallinuloides) are to be found: Cretaceous origin for
group well-supported, but no good fossil record until
early Eocene; fossil record of extant early
divergences (cracids, megapodes) so incomplete it is
actually shocking. *Something* can be assumed to have
happened during the Paleogene, but what?

Eike

PS: phylogenetic status of Gallinuloididae comparable
to Presbyornis in Anseriformes, which shows a mix of
largely obscured plesimorphies and bizarre
apomorphies. Not to be expected to such degree in
galliforms though for reasons given at end of paragrah 1.




        
                
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