[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: (Paleognath monophyly)
> a) The presence of such a character state for the dentary would appear to
> indicate that it is a symplesiomorphy in birds,
Quite certainly not, as Mickey has pointed out.
> or a character reversal.
Then let it be a reversal. :-| Firstly, it's still more parsimonious (all
other characters being equal!) to assume that this reversal happened once
rather than several times. Secondly, a reversal can of course be an
apomorphy. Look at your no longer opposable big toes -- an apomorphy of, uh,
humans or so.
> It may or may not be a synapomorphy of this paleognathous
> assemblage, but its presence in the Confuciusornithidae
> seems to make it a contentious character to use.
Not any more than the presence of fused frontals in carcharodontosaurids
makes the use of this character as an apomorphy of anthropoids, and at the
same time of pachypleurosaurs, contentious. The following phylogenetic tree
is aligned in a monospace font:
|--the diversity of Enantiornithes (paraphyletic?)
`--Ornithurae sensu strictissimo
> b) The entire suite of characters we see in paleognaths can be explained
> terms of neoteny, including that most famous paleognath character, the
> palatal configuration for which the group was named.
Fine -- as I mentioned yesterday, even Cracraft has completely dropped the
palatal configuration. I'd be interested in learning how neoteny can explain
the inflated alaparasphenoid, the highly pneumatic area caudal to the
quadrate articulation, or the strongly forked dentary.
> Paleognathae is entirely polyphyletic, and secondarily derived from within
>From _where_ within Neognathae?
> Some paleognaths may be secondarily derived from neognathous ancestors and
> thus closer to Neognathae than to other paleognaths, again indicating
> polyphyly of Paleognathae.
Again, what would the phylogeny look like? Has one been proposed?
> c) This of course leads one to the timamou/galliform nexus. It is not
> solely on the morphology of the sternum, which you seemingly reject
> its being distinct, but also on that of the coracoid. Trivial characters?
Of course not. But they are _fewer_ than the apomorphies of Palaeognathae
plus the apomorphies of Neognathae. :-) All these would have to be explained
as homoplasies in order to make tinamous and galliforms sistergroups, which
means a higher number of ad hoc assumptions than the alternative.
> d) Or what if that neotenic derivation happened multiple times? Would the
> evidence be found in that some paleognaths are closer to neognaths, while
> others are closer to primitive paleognaths (e.g., Lithornithiformes)?
Yes. Because otherwise we'd never have a reason to think that the neoteny
happened multiple times.
> What morphological data would substantiate this?
Unfortunately, I have to give this question straight back to you.
> The vast disparity in the pelves of the ratites suggests that this
> grouping of paleognaths, at least, is polyphyletic.
No, it doesn't -- evolution happens. Is there reason to think it suggests
more than different locomotory adaptations -- indeed some are cursorial
while others are mediportal --, or perhaps multiple losses of flight (which
are suggested anyway by geography and a few ontogenetic data)?
> Then there is the tremendous diversity in the
> structure of the paleognathous palate itself, which
> alone seems difficult to reconcile with the idea than in its
> derivation we are witnessing one example of neoteny
> in a holophyletic lineage,
Just how tremendous is it? How tremendous does it have to be that you think
it couldn't have evolved from the structure of an exclusive common ancestor?
> and so on and so forth.
:-) I'm interested in the whole list. If you have time, I'd like to ask you
> e) Ligon's work demonstrates that male parental care is the principal, but
> not exclusive condition in ratites. Perhaps it represents an autapomorphy
> of the ratite assemblage, with little if any bearing on the unity of
What is its distribution in Tinamidae, and what does the phylogeny of that
group look like? (Not a rhetorical question -- I have no idea.)
> f) Last I knew, the ergilornithids had not been advanced as the ancestors
> _Struthio_ since 1985, with the general consensus since then being that
> Ergilornithidae represents a textbook case of convergence, in this case
Good. But if ostriches are not paleognaths, and if ergilornithids aren't
their closest relatives either, then what is?