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Re: four winged Archaeopteryx



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