[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: (Paleognath monophyly)
John Pourtless wrote-
a) The presence of such a character state for the dentary would appear to
indicate that it is a symplesiomorphy in birds, or a character reversal.
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.
No, because though Confuciusornis has it (and Gobipteryx and Apsaravis too),
the Catalan enantiornithine nestling, Eocathayornis, Eoenantiornis,
Yanornis, Hesperornis and Ichthyornis lack it. So, given the standard
phylogeny of Pygostylia, you'll note it's more parsimonious as a case of
b) The entire suite of characters we see in paleognaths can be explained in
terms of neoteny, including that most famous paleognath character, the
palatal configuration for which the group was named.
I'm not an expert in neoteny, but I will note that the fact the founding
character of a clade has been disproven as symplesiomorphic means nothing as
long as other characters exist.
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)? What
morphological data would substantiate this? The argument for a
relationship between the Tinamiformes and Galliformes I already mentioned,
but there is more. The vast disparity in the pelves of the ratites
suggests that this grouping of paleognaths, at least, is polyphyletic.
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, and so on and so forth.
Disparity should NEVER be used to advance the idea of para/polyphyly. We
aren't doing phenetics here, we (including Feduccia, Ostrom and others) are
Scope out the new MSN Plus Internet Software ? optimizes dial-up to the max!