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Re: Introducing Mahakala omnogovae, little dromaeosaurid of Mongolia



--- David Marjanovic <david.marjanovic@gmx.at>
schrieb:

> > One can hardly withhold a satisfied grin seeing
> how it
> > all starts to fall into place. This year and the
> next,
> > I think, stand good chances to bring the sort of
> > breakthrough for stem theropod (and possibly stem
> > dino) phylogeny that the last 2 years brought for
> > crown dinos.
> 
> What breakthrough...? Sure, we're a lot closer to
> the picture than we were 2 
> years ago, but... ~:-|

In Neornithes it came to be that all of a sudden,
enough data was available to start building
supertrees. One could not have seen it coming, but at
some point sort of a "critical mass" of data had been
assembled. Senter's new study, the stuff Mickey plays
around with... reminds me of papers like Thomas et al
(2004) http://dx.doi.org/10.1186/1471-2148-4-28 that
were (in retrospect) the first sign of change in
modern bird phylogeny.

I'm not sure, but it *seems* that from a certain point
on (and with a comprehensive character set) adding
taxa does *not* unduly decrease resolution any more.
In Passeriformes, this had actually progressed to a
point where *not* increasing taxon sampling made the
tree shaky (of course, character sampling in molecular
data is only limited by sequencing robot
technology...). Including taxon-poor lineages has
turned out to be the key there.

The molecular complement to Livezey & Zusi is being
prepared presently. It'll be interesting to see where
this gets to.

> > Now (as regards this user), if an associated
> skeleton
> > of that wretched _Gallornis_ would turn up
> *please*...
> > (_Torotix_ wouldn't be too shabby either.
> 
> Are these two even diagnostic? I mean, is really
> every half of a bird 
> coracoid diagnostic beyond "not too far from
> Neornithes"?

Diagnostic as in "different from the other material
that can be directly compared", *arguably* yes (_T._
genuinely so, _G._ just for lack of other contemporary
material).

Diagnostic as in "to assign them to any known taxoin
beyond a (new) genus" (as Hope tried in "Mesozoic
Birds")? Ha! As if ever! And I hope Hope was the last
major atempt to assign Maastrichtian remains of
Neoaves to extant taxa. It looks as if that would not
just be premature, but patently false in almost all
cases.*

And that's where more material would be handy: the
theory that the a particular part of the neoavian
radiation took place shortly before the Big Bang is
robust enough to be tested, and there are these crumbs
of Marsh et al that *could* be the remains of such
birds (basal in or immediately outside a
Procellariformes/Pelecaniformes/Gaviiformes/Spheniscidae/...
clade for example).

Most "Graculavidae" have features that are a very good
match to the mix of plesiomorphies and incipient
apomorphies that would be expected in such a missing
link.

The question is: how can the noninformative taxa be
separated from the more interesing ones? The _Piksi_
paper gave me an idea, but this'll need more time to
mature...


Regards,

Eike


* But that again shows the process that has been made
in the last 5 years. The assumption that a
Maastrichtian neoavian stands even reasonable chances
be assigned to an extant order is withering fast... I
hope.

10 years ago, assigning a Maastrichtian bird bone to
an extant *family* would not have raised too many eyebrows.


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