[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: [Combined answer: Feathered/scaly theropods: trying to make the point.]





"Jura" writes:


So to rephrase: "All dinosaurs should be considered scaly by default, unless
there is evidence to the contrary."




I think the crux of the trouble here is that the opinions expressed here are very strong and forceful in their presentation. Yet, the opinions are based on little evidence - and based more or less (mostly "more") on Jura's assertions about dinosaurs and the Yixian localitie(s):
(1) all dinosaurs are the same where skin/integument is concerned, so we have no right to picture ANY dinosaurs were feathered unless we can prove they all were.
(2) all feathred dinosaurs are found in one tiny locality, which were susceptibel to some freaky fungal/dendritic phenomonen which look so much like feathers that paleontologists havebeen fooled into thinking they are feathers.
(3) if some specimens shows preserved integument than they ALL should. In other words, Yixian mammals should show hair, Yixian ornithopods should show scutes/scales etc. (But preservation was differential according to the nature of the intgegument - just like Solnhofen and Messel and Santana.)


Assertions 1,2,3 are incorrect. I am not going to accuse "Jura" of being uninformed in this discussion/debate. I would say that the strength of the opinions are not matched by Jura's grasp of the topic. To say that he has not aware of any Yixian birds beside Confuciusornis hints at this. There are at least 20 species of bird so far described, and some have been described in major easy-to-get journals (Science, Nature).

Also:
Check out
posts regarding dino metabolism, or theropod behaviour and see how often
maniraptor gets exapted to all theropods and occasionally, all dinosaurs.

"Exaptation" is an evolutionary term, coined by Gould (I think in the 1980's). It means when an existing structure takes on a new (derived) function - and that new functiuon may replace the old one. I think your usage may not be right. Do you mean "extrapolate?"



Regards, Zoe



_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.