[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: BIRD CHARACTERISITICS
I was just sifting through some old email and I stumbled onto this
one from an old thread ( one of the most interesting) and I realized
that I had not answered it. So in the spirit of Christmas I want to
resurrect an old scientific debate.
> 26 Oct 1997 12:42:49 CDT
>From: "Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>
>Subject: Re: BIRD CHARACTERISITICS
>Matthew Troutman wrote:
>> Do you mean when you talk about the tarsometarsus the one seen in
>>ornithuraes? The kind of metatarsus seen in Archaeopteryx and is the
>>same one as the one in enantiornthines.
> Here's a question for the bird workers out there. Hou, Martin,
>and Feduccia make a big deal about similarities (that sound like
>symplesiomorphies) between the metatarsus of _Archaeopteryx_ and
>Enantiornithes. Now, let's ignore for a second that they managed to
>their characters in such a way that this conformation was treated as >a
>seperate evolutionary novelty unrelated to the neornithine
>Let's also ignore polarity for the time being:
> Is the metatarsus of _Archaeopteryx_ more similar to that of
>Enantiornithes? Wellnhoffer (_Illustrated Encyclopedia of Pterosaurs_)
>that archie's metatarsus was unfused, has this been refuted? Is there
>something I'm not seeing here?
Fedducia and Martin both claim that the Maxberg specimen ( sadly it
was stolen a few years ago) had its metatarsals fused in a
proximo-distal pattern like enantiornithines ( or their "Sauriurae" )
and in contrast to the disto-proximal pattern seen in Ornithurae birds.
I do not know that this claim can be proven.
> Now, add polarity back in. If archie's metatarsus is more
>to that of the Enantiornithes, how does it compare to that of a
>outgroup (e.g. Troodontidae, Dromaeosauridae, etc.). Bear in mind that
>et al.'s outgroup choice (_Petrolacosaurus_) is undoubtedly unsuitable
>proper phylogenetic analysis.
Honestly I cannot make an imformed opinion on this subject other
than the metatarsus of dromaeosaurids is quite similiar to than of
Archaeopteryx and that I think Tom said somewhere that the metatarsus of
Hulsanpes is fused. What pattern; proximal- distal or disto-proximal, is
not stated. ( Have any insights Tom?)
Hou et al's paper for the most part was good and interesting. But
their views on the ancestry of birds clouds their thinking on many
issues ( Sauriurae, for example.) The speculation that Archaeopteryx is
somewhat off the main line of avian evolution is interesting and may be
the most parsimonous if the Ornithothoraces is artificial ( I for
example, believe that the strut-like coracoid, pygostyle etc. may have
evolved in parallel, which is a distinct possibility.) Hou et al also
state that the ossification of the bony sternum, carina, and triosseal
canal probably evolved in parallel. The sternum of Eoalulavis supports
that early birds ( "sickle-claw", Archaeopteryx) had a widely unossified
sternum and that the carina may have arisen early in enantiornithine
evolution and possibly in parallel to that of ornithurae birds. The
triosseal canal of ornithurae birds is formed mainly by the coracoid and
incipently by the scapula and furcula. The triosseal canal of
enantiornithine birds is formed mainly by the scapula and incipently by
the coracoid and furcula.
I am not supporting Feduccia or Martin totally but I do believe
they make some vald points that are all together dismissed and ignored.
While we are on the subject , Iberomesornis, what is it?
Enatiornithine, ornithothoracine, something else? More study must be
done, particulary on the triosseal canal to tell conclusively what it
Now again, I am not completely supporting Feduccia or Martin, the
points made by Chiappe and Sanz are probably more parsimonous, but I
have some reservations. The features Feduccia and Martin and Hou and
Zhou site for Sauriurae: anterodorsal ishchial crest, dorsal knob on the
femur, proximo-distal fusion of the metatarsus can be plesiomorphic for
Aves, and they probably are.
So if anybody has any thoughts feel free to reply.
Get Your Private, Free Email at http://www.hotmail.com