[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: (Paleognath monophyly)
From: "Michael Mortimer" <email@example.com>
Subject: Re: (Paleognath monophyly)
Date: Sat, 31 Jan 2004 21:41:11 +0000
First, I want to compliment John for his continued participation in this
topic, in which everyone seems to be against him. Hopefully it will end
with both parties learning something.
John Pourtless wrote-
The strongly forked dentary, if it is a character reversal, is readily
explicable within a neotenic context, during which see reversal and the
expression of primitive characters.
But it doesn't seem to be a reversal, parsimoniously speaking. Of course,
you argue against the strict application of parsimony, but without it, you
could call pretty much any character that appears outside your ingroup a
reversal. "Toothlessness is not a good synapomorphy of Neornithes because
it could be a neotenic reversal to the primitive state exhibited in
Confuciusornis and Gobipteryx. Sure, given parsimony, these are more
likely to be convergences (as all other enant-grade birds, Jibeinia,
yanornithids, hesperornithines and Ichthyornis are toothed), but we can't
I did not say that parsimony could not be trusted, I said that blind
adherence to it, especially if there are alternative phylogenies which are
just as possible, is not to be trusted. Character weighing is inevitable in
phylogenetic reconstruction, and it will never be turned into a completely
objective discipline. I refer you to Ghiselin's 1984 critique, since he
said it far better than I have.
Cranial pneumaticity caudal to the quadrate and the inflated
alaparasphenoid are the strongest of the characters listed, and the only
two which Cracraft & Clarke produced that I would call "unambiguous,"
however, two such characters do not amount to an overwhelming advantage to
the paleognaths-are-holophyletic concept, and at the very least, it that
seems that multiple possible phylogenies of Paleognathae are equally
Well, we'd need some method of weighing alternative hypotheses. If you
don't like parsimony, what objective method do you suggest?
I feel that the formulation of auxiliary hypotheses, (again see Ghiselin
1984), as Popper defined them. To quote Ghiselin, "There need be nothing ad
hoc in phylogenetics about invoking stratigrapjy, biogeography, genetics,
embryology, or ecology."
> Paleognathae is entirely polyphyletic, and secondarily derived from
>From _where_ within Neognathae?
As mentioned tinamous seem to be more closely related to the gallinaceous
birds than they are to other ratites.
That covers tinamous. Do you propose this topology then?
I would propose the following topology
This places the two in an unresolved dichotomy, which I think is the most
conservative placement. If tinamous are related to Galliformes, I would
argue that tinamous are derived from within Galliformes, and not a
sister-group thereof. Again though I am opting for a conservative approach,
until more data becomes available.
> Some paleognaths may be secondarily derived from neognathous ancestors
> thus closer to Neognathae than to other paleognaths, again indicating
> polyphyly of Paleognathae.
Again, what would the phylogeny look like? Has one been proposed?
Yes, Houde (1988) which I think Mortimer derided as out of date, presented
multiple ppssible phylogenies of the Paleognathae, which Feduccia
concurred with in 1996. Under Houde's hypothesis, some paleognaths are
more closely related to and independently derived from a grade of basal,
paleognathous carinates such as the lithornithids, while others are more
closely related to and perhaps secondarily derived from neognaths (e.g.,
I wouldn't say I derided it. I just pointed out a 1988 paper can't be used
as the backbone for a supposed recent dichotomy of hypotheses, and I
theorized Houde's evidence wouldn't convince me as much as Livezey and
Zusi's. I do intend to read Houde's paper on Monday, so that this debate
can continue with actual data. Feduccia's concurance does nothing to
strengthen my belief in a hypothesis, sorry to say.
Whatever you think of Feduccia's work on the origin of birds, he has done
important and accurate research in his career on various matters pertaining
to the phylogeny of birds. It is one thing to disagree with a man's work in
one area, but disagreeing with him entirely in everything he does (which
some, though not necessarily you, seem to do) because of his work in another
field, is unwarranted. For instance, I think Gauthier's restriction of the
term Aves to a crown-clade is rather useless, but that does not lead me to
dismiss all of Gauthier's work.
more than different locomotory adaptations -- indeed some are cursorial
while others are mediportal --, or perhaps multiple losses of flight
are suggested anyway by geography and a few ontogenetic data)?
It is possible, but what uniquely derived characters are present in the
pelves to unite ratites? To my knowledge there are none. Given this, why
should we presume that the osteology of the pelvic girdle in these forms
is a function of common ancestry, and not reflective of polyphyletic
derivation of these birds?
And what pedal characters are there to support Oviraptorosauria? None I
know of, and they exhibit quite a range of morphologies.
Arctometatarsalian caenagnathids with fused metatarsi, the elongate
subartometatarsalian pes of Caudipteryx, the robust non-arctometatarsalian
pes of oviraptorids, with a lateral digit reduced in Conchoraptor, the
extremely gracile fused arctometatarsalian pes of Avimimus with metatarsal
V fused to it and no digit I. We should presume the pedal morphology of
oviraptorosaurs is a funtion of common ancestry because of the non-pedal
characters that unite them. Similarly, we should presume the pelvic
morphology of ratites is a function of common ancestry because of the
non-pelvic characters that unite them. Disparity has no place in
phylogenetics unless you can show it's also synapomorphy (so if some
ratites shared pelvic characters with some neognaths, you'd have an
argument). Then we'd have to weigh these hypotheses using whichever method
That argument relies on the validity of the alleged cranial synapomorphies,
which is still contested.
Ostriches are paleognaths and are perhaps derived from within the
lithornithithid grade. The closest link between these two taxa is
_Palaeotis weigelti_, but the first _Struthio_ fossils do not appear until
Here, it's very important what type of grade Houde thought lithornithids
were. Paraphyletic to Neornithes, or paraphyletic to Ratites? I suppose
I'll find out come Monday.
Houde argued, IIRC, that they were paraphyletic to ratites.
As for my continued participation, I see no reason why I should not do so,
though I am deeply distressed by the strong assertion (or at least
implication) made in this list that cladistics is essentially the only
scientific way of reconstructing phylogeny and everything else is
pseudoscientic nonsense. Cladistic zealots are as frightening as any other
Scope out the new MSN Plus Internet Software ? optimizes dial-up to the max!