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Re: Heterodontosaurid with protofeathers



----- Original Message ----- From: "evelyn sobielski" <koreke77@yahoo.de>
Sent: Wednesday, March 18, 2009 7:36 PM


But I don't find this all to spectacular. As the article says:

"Only one other ornithischian, an early horned dinosaur called Psittacosaurus, had similar structures but its filaments were sparser, more rigid and only found on its tail."

But, apparently, Heterodontosauridae is the sister-group of all the rest of Ornithischia together (except *Pisanosaurus*).


If the phylogenetic position of birds and mammals in respect to dinosaurs were the other way of what it is, this discovery would be hailed not as "feathers" but as "fur".

Strange fur, as I just mentioned.

We need to come to terms with the fact that there are not just 2 kinds of elongated keratinaceous integumentary structures. The pterosaur researchers have grasped this already, but it gets tiresome to see every wisp of dino "hair" be touted as if it were a veritable rectrix.

We're talking in terms of homologies. It now seems possible that elongated keratinaceous integumentary structures evolved only twice.


The really interesting question here - and it is one that is likely to be swamped by a deluge of faux-feather headlines - is: why? What is the use of such integumentary structures? It is hard to see them as evolutionary neutral, so they are likely to have conferred some benefit. What precisely did it evolve for?

It has been suggested that stage I feathers originally were spines that were used for defense. *Psittacosaurus* and the porcupines have often been compared.


It has also been suggested that (mammaliform) hairs are ectopic whiskers, rather than whiskers being specialized hairs. What has happened to the old story that someone found evidence for whiskers on the snout of *Dimetrodon* many decades ago?