* Dinosaurs did not have feathers
http://news.nationalgeographic.com/news/2006/03/0315_060315_dinosaur.html
The fossil of a small, predatory dinosaur discovered in Germany has experts rethinking how feathers developed among the dinosaurs that likely gave rise to birds.
The authors say the new species undermines the notion that a covering of simple, hairlike feathers was characteristic of such early theropods as was previously believed.
Given its position in the dinosaur family tree, Juravenator "should bear filamentous feathers," Xing Xu said in an interview. But Chiappe says the new fossil didn't seem to bear any physical evidence of feathers, missing or not. "You could expect to see follicle [in the skin], small pits that contain feather buds. We don't see them in Juravenator," Chiappe said.
http://en.wikipedia.org/wiki/Juravenator
Juravenator is a genus of small (70 cm long) coelurosaurian [Compsognathidae] dinosaur, which lived in the area which would someday become the Jura mountains of Germany, about 151 or 152 million years ago.
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ReplyDeleteThis is an old and incomplete preliminary study - Chiappe and others did a follow up with more detailed analysis of the fossil remains including using ultraviolet light (the same method that was used to expose details of pterosaur soft tissue) and was able to find better evidence of filamentous integumentary structures and also clear evidence that they were not internal collagen fibres (as Feduccia had suggested) but were external and therefore some sort of integument
ReplyDeletehttp://www.ingentaconnect.com/content/schweiz/njbgeol/2010/00000258/00000003/art00001?token=00571ab98449d81929383a4b3b25703a7b6c5f387b6f2c7446732a726e2d58464340592f3f3b57523c747f3
here are more detailed photos as the other is just an abstract and imprecise
http://dinogoss.blogspot.com/2010/12/borsti-lives-up-to-its-name.html
Ford Fairlane posted:
ReplyDelete"and was able to find better evidence of filamentous integumentary structures and also clear evidence that they were not internal collagen fibres (as Feduccia had suggested) but were external and therefore some sort of integument"
They found some sort of "integumentary structure".
Here is a quote from the other link you gave:
http://dinogoss.blogspot.com/2010/12/borsti-lives-up-to-its-name.html
"As the authors note, it's possible that at this early stage of evolution, feathers and scales co-existed across the body of dinosaurs like Juravenator, and possibly even Sinosauropteryx and Dilong, where no scales are preserved but feathers are still found only in certain parts of the body. So far, this kind of co-existence of widespread scaly skin with fringes of feathers has only been known in the ornithischian Psittacosaurus but, they point out, it's not inconsistent with theoretical models of feather development and evolution."
The ornithischian Psittacosaurus is not considered to be on the line leading to birds (obviously).
Consequently we can conclude that the "integumentary structure" is some kind of decayed skin or other structure.
Unless you want to change everything and begin claiming that birds evolved from Ornithischians. Do you want to do that?
For those following this (if any) ths is also worth quoting:
ReplyDeletehttp://www.ingentaconnect.com/content/schweiz/njbgeol/2010/00000258/00000003/art00001?token=00571ab98449d81929383a4b3b25703a7b6c5f387b6f2c7446732a726e2d58464340592f3f3b57523c747f3
"Portions of the epidermis preserved mainly along the tail provide the only glimpse of the morphology of the skin of basal coelurosaurs, and structures newly revealed under UV light hint at the possibility of filamentous integumentary structures - akin to those interpreted as proto-feathers in other basal coelurosaurs - also covering the body of this dinosaur."
Note the wording:
"hint at the possibility of filamentous integumentary structures"
I wish I could get away with that sort of argument. I could just "hint at the possibility" of anything I wish.
"The ornithischian Psittacosaurus is not considered to be on the line leading to birds (obviously).
ReplyDeleteConsequently we can conclude that the "integumentary structure" is some kind of decayed skin or other structure.
Unless you want to change everything and begin claiming that birds evolved from Ornithischians. Do you want to do that?"
This argument is not logical. Psittacosaurus not being on the line to birds is irrelevant as obviously it is not the only example of such structures in dinosaurs and most are theropods and maniraptors. And either way it does not follow that this must be decayed skin - the most logical and parsimonious explanation for such filaments in an ornithiscian (as well as the other groups) would be that they have a history that predates the split between the two major dinosaur groups or even, given that pterosaurs also have pycnofibres, originates in earlier archosaurs. The argument that it must be decayed skin is a wild guess that doesn't fit the evidence.
I do not agree.
ReplyDeleteYou might check out the ideas and work done by Alan Feduccia and Theagarten Lingham-Soliar. I do not want to use up time arguing about this.