Re: Archaeopteryx

["Nick Gardner" <ratites637@hotmail.com>]

Ivan Kwan wrote:
> Throughout the history of discussions on dinosaur-bird relationships, 
> almost every person comes to a foregone conclusion that _Archaeopteryx_ is 
> THE first bird, with all the others (confuciusornithids, enantiornithes, 
> _Iberomesornis_, _Eoalulavis_, _Shenzouraptor_, _Rahonavis_, etc) all 
> falling behind it. It puzzles me that almost every cladogram I can think of 
> relies very heavily on a species that is to date known by just 7 
> 2-dimensional specimens & a single feather (tentatively referred to Archie 
> as well.)

Hey, don't discount those 2-D specimens, they can be pretty useful at times. 
:-)

> I'm very ignorant about all this avian cladistics & stuff, but consider 
> this: what if we've been wrong all along? could it be that _Archaeopteryx_ 
> was NOT the first bird? What if it was actually an 'aberrant' offshoot that 
> evolved from maniraptors before the other birds branched off or was 
> actually more derived than other so-called 'birds'? What if we eventually 
> discover that 'birds' as we know them may be diphyletic or paraphyletic 
> (unlikely, but what if we find out that some of the early birds turn out to 
> be one lineage of dromaeosaurs that evolved more birdlike features?) Does 
> _Archaeopteryx_ still retain its "first bird" status? Or what if others 
> find that once & for all, that dromaeosaurs (or troodonts or 
> oviraptorosaurs) actually evolved after Archaeopteryx split off the 
> maniraptor lineage? Would that put the dinosaur-bird debate in a whole new 
> perspective?

It really wouldn't change anything.  Aves is defined most commonly as 
Archaeopteryx + Neornithes (or some neornithine species), so Aves would just 
expand and take on new taxa.  It wouldn't be all that surprising if 
Rahonavis were found to be perhaps a derived dromaeosaurid or perhaps a 
basal one.

> Somehow every phylogenetic analysis seems to assume that because 
> _Archaeopteryx_ is the oldest bird discovered to date, it is the Ur-bird 
> (_Protoavis_ notwithstanding). I think we need people to scrutinise every 
> feature of _Archaeopteryx_ from every angle, to note every detail, and 
> compare it with EVERY (and i mean every) other Mesozoic bird species & 
> non-avian maniraptor.

When did phylogenetic analyses start incorporating assumptions about time?   
The only time this problem should occur is if the analysis were rooted on 
Archaeopteryx, to which I recall, none are.

> I believe the disagreements on coelurosaur & avialan phylogeny will be 
> around for quite a while, & I do hope that things get resolved as quickly 
> as possible, but I just wish we had more specimens of _Archaeopteryx_ to 
> give more solid proof that it is the "First" bird.

There probably were volant taxa more basal than Archaeopteryx, we just 
haven't found them yet.  However, it is possible that Archaeopteryx truly is 
the first volant maniraptor, but it would be difficult to prove in my honest 
opinion.

Nick Gardner

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