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Re: (Paleognath monophyly)






From: "David Marjanovic" <david.marjanovic@gmx.at>
Reply-To: david.marjanovic@gmx.at
To: "DML" <dinosaur@usc.edu>
Subject: Re: (Paleognath monophyly)
Date: Fri, 30 Jan 2004 18:38:18 +0100

----- Original Message -----
From: "John Pourtless" <vindexurvogel@hotmail.com>
Sent: Friday, January 30, 2004 1:49 PM

> I view it is a fundamental dichotomy between the morphological data on one
> hand and the molecular data on the other. Morphological data is
unambiguous
> in its support for the neotenic state of paleognaths, and it remains a
fact
> that time and again alleged synapomorphies of this assemblage are in fact
> symplesiomorphies.


I don't understand why you state all these as facts. For example,
*Hesperornis* is not paleognath, and this has been known for decades. In
addition, Cracraft & Clarke (2001) have identified the following 5 character
states -- none of which is palatal! -- as apomorphies of Palaeognathae (all
unambiguous):


- Posterior portion of dentary strongly forked
- Inflated alaparasphenoid
- Skull with highly pneumatic bone posterior to quadrate articulation
- Loss of caudal maxillary sinus
- Parental care involving primarily males

Sure, Cracraft has supported several suspect hypotheses, such as ostriches
and rheas being sistergroups, or ratites having lost flight only once, or
loons & grebes being sistergroups.  But if you can deconstruct the above 5
characters, then please tell us how.

> Given the significant problems with molecular
> phylogenies of Neornithes (e.g., the placement of Aramidae
> in Sibley & Ahlquist 1990, which contradicts two centuries of
> morphological work including cladistic analysis),

Wait a little. Sibley & Ahlquist 1990 is molecular, but _not_ a phylogeny.
It's DNA-DNA hybridization -- in other words, _phenetics_. Pure phenetics.
For phylogenetic purposes, it can therefore be quite safely ignored.


I accidentally sent my response before it was completed, so disregard the duplicate of this message. At any rate, the characters advanced by Cracraft & Clarke (2001) are as dubious as any others advanced in defense of paleognath holophyly. The posteriorly forked dentary is apparently present in Confuciusornithidae, and the remaining traits are all as explicable within the framework of neoteny as they are within that advanced by Cracraft and Clarke in their study. Furthermore, varying patterns of pneumaticity in the cranial elements have been recorded from throughout Archosauria. The fact that that parental care is not exclusively restricted, at least to my knowledge, to males in paleognaths renders this is a weak synapomorphy, as does its lack of applicability to extinct paleognaths, such as the lithornithids. What remains is scant evidence to contradict a significant amount of work indicating that the paleognaths are polyphyletic, not the least of which is the neotenic derivation of the paleognathous palate itself. Consider also that various members of Paleognathae, e.g., Tinamiformes, 'may" (I emphasize may because of the similarities between Lithornithiformes and Tinamiformes which so impressed Houde) be more closely related to Neognathae (in the tinamou's case, to Galliformes) than they are to other paleognaths. From what I can make of the situation, the case for a holophyletic Paleognathae is extremely tenuous.


JGK

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