Re: four winged Archaeopteryx

[Tim Williams <twilliams_alpha@hotmail.com>]

Kris (mariusromanus@aol.com) wrote:

> Tim, don't get your feathers ruffled... No need to get defensive. I  mean 
> no harm.

I wasn't aware I was being defensive.  But thanks for the reassurance.

> I think you are making 2 very bad assumptions. One is that if any 
> integument is preserved, then all aspects of the integument for the animal 
> are thereby represented.

No, I wasn't making this assumption at all.  I was very careful to avoid 
making this assumption.

> And second, if a region is feathered on one, and naked or scaled on 
> another, this region is reflective of the whole of the animal...

Isn't this the same assumption as the first one?

> I can't remember, are the tubercular epidermal impressions located 
> everywhere on the _Juravenator_? [snip] Anyway, hopefully you aren't saying 
> that there is no possible way _Juravenator_ could have had feathers.

Here's what Gohlich and Chiappe (2006) have to say...

"Thus, the absence of feathers in _Juravenator_, a taxon otherwise nested 
within feathered coelurosaurs, is noteworthy (Fig. 4). The extent to which 
feathers covered the body of these
non-avian dinosaurs is not well known for some taxa ... The fact that 
_Juravenator_ lacks any evidence of feathers in portions of integument 
otherwise feathered in these coelurosaurs indicates that these animals may 
have differed greatly in the extension of their feathery covering.  However, 
the role of ontogeny and seasonality in the development of the plumage of 
these dinosaurs remains uncertain, and the possibility cannot be ruled out 
that feathers evolved more than once or became lost in taxa such as 
_Juravenator_..."

That sums it up for me.

> And your comment about birds not being found in Solnhofen has absolutely 
> NOTHING to do with
> what I was saying... That was waaaaay off the mark.

I don't think it's at all off the mark.  Neornithean birds, as far as it is 
known, show no evidence of losing their feathery body covering through 
natural selection.  But things may have been different for their non-avian 
cousins, back in the Mesozoic.  It is impossible to frame an evolutionary 
scenario that explains the distribution of feathers in non-avian Theropoda 
without invoking either multiple losses or multiple gains of feathers for at 
least part of the body.

Also, don't forget that _Juravenator_ may have been very close to the origin 
of feathers - and it might even lay outside the feathered theropod clade (if 
Compsognathidae is paraphyletic).  Thus, it could be primitively 
featherless.

> If logic follows, what you are saying about compsagnathids and pterosaurs 
> living in tropical >Germany (that being, they didn't have feathers or hair 
> because of the weather)

Well, it was only a suggestion...

> Also, most desert mammals and all desert birds, have the need for hair and 
> feathers (besides flying)... and the HOT climate is one of the major 
> reasons.

I thought it was the cold desert nights.

> And one more thing, it looks like this discussion of the presence of 
> integument on a fossil has to do a lot with taphonomy...

That's hard to disagree with.

Cheers

Tim