[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: (Paleognath monophyly)

> 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,

So what? Fusion of the frontals is a good synapomorphy of Anthropoidea,
despite also occurring in Carcharodontosauridae and Pachypleurosauria.
        Besides, Cracraft & Clarke write "strongly forked". They don't seem
to quantify this (which is a bad point for them).

> and the remaining traits are all as explicable
> within the framework of neoteny


> Furthermore, varying patterns of pneumaticity in
> the cranial elements have been recorded from throughout Archosauria.

:-) That's precisely the point.

> 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.

Its lack of applicability to, say, *Ichthyornis* does make it somewhat
weaker. But nevertheless, crocodiles and neognaths lack this character, so
it is most parsimoniously optimized as an unambiguous apomorphy of
Palaeognathae (in cladospeak).

> What remains is scant evidence to contradict a significant
> amount of work indicating that the paleognaths are polyphyletic,

What do those hypotheses look like? Even Feduccia doesn't agree with
ostriches being derived from ergilornithid cranes, and I haven't seen any
other explicit hypotheses of paleognath polyphyly.

Sorry for my too short explanation of why ABSRD is meanwhile considered
pseudoscience (in my last post). An important part is that Feduccia et al.
offer no alternative. They never make clear what, if anything, they think is
the closest known relative of birds -- which would give us a testable
hypothesis. They just say ABSRD -- "anything but a small running dinosaur".

> not the least of which is the neotenic derivation
> of the paleognathous palate itself.

What if this neotenic derivation happened only once? Then it would still be
a synapomorphy of Palaeognathae. :-)

> 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
> related to Neognathae (in the tinamou's case, to Galliformes) than they
> to other paleognaths.

Feduccia points out (in his 1996 book) the similarities in sternal shape of
Tinamidae and Galliformes. That's a rather small number of characters,
however -- and not applicable to ratites with their reduced sterna. So
perhaps we're looking at synapomorphies of Neornithes here.

> From what I can make of the situation, the case for a
> holophyletic Paleognathae is extremely tenuous.

If it's less bad than all alternatives, then I'll stick to it, however.