Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."

[Tim Williams <twilliams_alpha@hotmail.com>]

Mickey Mortimer wrote:

> Er... I simply meant that all the non-Wellnhoferia specimens lack 
> sufficient
> evidence to differentiate them taxonomically from each other.

How strong is the case that _Wellnhoferia grandis_ is a distinct species?

>  If you want to argue similarity in plumage between
> Archaeopteryx specimens is due to similar ontogenetic stages of differently
> sized taxa instead of ontogenetically independent plumage (as Tim was
> hypothesizing), you'll need to first show Senter and Robins were wrong in 
> their failure to differentiate more than one non-Wellnhoferia taxon.

To continue this thread, the fact that all _Archaeopteryx_ (or 
archaeopterygid) specimens show plumage irrespective of their size is 
unsurprising, since even young ones were probably also able to fly.

But _Beipiaosaurus_ is a different case: it could not fly.   It has the 
osteological apparatus (the pygostyle) to support a fan of tail feathers, 
but in the sole specimen of _Beipiaosaurus_ no fan is preserved.  Instead, 
the tail feathers are of the non-pennaceous variety.  If the feathers were 
used for a non-locomotory purpose (such as display) then the pennaceous 
morphology may only have appeared late in ontogeny, with the onset of sexual 
maturity.  In this respect, pennaceous plumage would be functionally 
analogous to the cranial ornamentation of neoceratopsians and hadrosaurs.

Of course, "display" is the functional hypothesis that is raised when all 
other options are exhausted; it's like the default hypothesis to account for 
any structure that has no other obvious purpose (offensive/defensive; 
locomotion; thermoregulation, etc).

Jaime Headden wrote:

> 2) the smallest specimens have been given their own species at some point 
> in history, from the Haarlem to the Eichstätt specimens,

The large Berlin specimen was also given its own genus and species at one 
point: _Archaeornis siemensi_.  One could write a whole book about the 
historical taxonomy of _Archaeopteryx_ over the past century-and-a-half.




Tim

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