Yep, I'm dragging this topic out and shaking the dirt off of it.
Ommie, your main objection to Archaeopteryx's being a 'missing link' between birds and saurians was that there didn't seem to be a furcula present.
Well, I hafe to tell you that it's not a good reason anymore. talk.origins sez..
quote:It used to be thought that the possession of a furcula distinguished birds from dinosaurs. Indeed, up until recently even clavicles were few and far between in even theropod dinosaurs (the suggested closest group to the birds and from which the birds evolved - see Ostrom 1976). However, it has been found that theropod dinosaurs did indeed have clavicles (e.g. Bryant &Russell 1993) and they have been found in several species, e.g., Segisaurus, Velociraptor, Euparkeria, Ornithosuchus, Saltoposuchus, Ticinosuchus. Also, Chure & Madson (1996) reported furculae in a non-maniraptoran, allosaurid dinosaur.
It has been found that the clavicles are often small and poorly ossified. This is no surprise, since they are of little evolutionary advantage to your average theropod dinosaur. However, birds too show this variation in ossification, especially amongst the carniates and some parrots, clavicles are reduced or even missing. Therefore the apparent absence of clavicles in some theropod dinosaurs may well be due to poor ossification rather than true absence. However, furculas have been found in some theropod dinosaurs, namely the Oviraptorosauria (Barsbold et al. 1990, Bryant & Russell 1993), for example Oviraptor and Ingenia. Thus furculas do not appear to be diagnostic to birds and certain members of the suggested closest group to the birds now appear to possess furculas so it is a neutral character.
A commonly cited criticism of this is that most of the theropod dinosaurs listed here post-date Archae. However, none of these is claimed as the ancestor anyway, and Eupakeria is a Triassic form. The presence of clavicles shows that this character is a feature of theropod dinosaurs and thus was probably present in early theropods.
Posted by Da_bang80 (Member # 528) on :
I'm not so sure that I believe in birds desending from dinosaurs either. Just because there are some dinosaurs with feathers, or look like birds deosn't mean they descended from them. Some dinosaurs had fur, and looked a bit like warthogs. But no-one ever said that warthogs descended from dinosaurs. It was just a trait characteristic of the species, like the platypus or bat. It's a funny thing, the past. We're just working of bits and pieces, like trying to put together a hundred page essay, after it was thrown out the window. We may never learn or explain some of the things that have happened.
Posted by First of Two (Member # 16) on :
Yes, but Archaeopteryx is just a major link in the collection of links that would lead most people capable of high-level deductive reasoning to conclude that there's a chain somewhere.
It's a lot more than 'looking a bit like.' It's 'showing a physiology which indicates a distinct, consistent biological trend towards becoming.'
Posted by Omega (Member # 91) on :
So you're saying that because there's a good excuse for there being no evidence of it, I should accept that Archyopterix is some sort of reptile-bird hybrid. Illogical.
And it still doesn't explain the BACKWARDS furcula in one of the six specimines. Nor does it explain the rubber cement that the feather impressions are in.
Posted by First of Two (Member # 16) on :
Lots of things can happen to move bones when something dies, Omega. Especially after the thing has been deceased for a while. Ever seen a deer carcass that's been ravaged by scavengers?
I keep looking, but that 'plastic cement' thing seems to be a Creationist Urban Legend (like the Paluxy river tracks and Darwin's supposed recantation), as there is no backing for it anywhere.
Posted by Da_bang80 (Member # 528) on :
quote:Originally posted by First of Two: Lots of things can happen to move bones when something dies, Omega. Especially after the thing has been deceased for a while. Ever seen a deer carcass that's been ravaged by scavengers?
I keep looking, but that 'plastic cement' thing seems to be a Creationist Urban Legend (like the Paluxy river tracks and Darwin's supposed recantation), as there is no backing for it anywhere.
Who knows, maybe some of the fossil skeletons are really just big fuck-ups. and the dinosaurs didn't really exist. It's a long shot, but hey, it's nice to entertain am unfeasable idea once in a while, sometimes you get lucky. BTW did you ever see a skunk after it's been dead in the middle of the highway for a week? don't look much like a skunk no-more...
Posted by First of Two (Member # 16) on :
What the article points out, Omega, is that since clavicles don't always fossilize, and when they do, often fossilize badly, then insisting upon their presence as the sole criteria for judgement is intellectually dishonest.
It would lead one to the erroneous conclusion that parrots cannot be birds, either.
Posted by First of Two (Member # 16) on :
I take back what I said about the rubber cement being an Urban Legend. The accusation WAS made...
[ March 07, 2002, 08:14: Message edited by: Grokca ]
Posted by Malnurtured Snay (Member # 411) on :
::Looks around for Omega::
Posted by Omega (Member # 91) on :
Hmm... I must have missed this thread's "new posts" indicator back when it was new. Sorry.
OK, then, the feathers are probably real. Still no evidence for evolution, any more than a platypus is. And you never explained the reversed furcula. Posted by First of Two (Member # 16) on :
No such animal, as far as I can find. Nowhere on the net, at least, ever says that any Archaeopteryx had a reversed furcula.
You may be thinking of the hallux, which is SUPPOSED to be reversed in birds but not in reptiles, and is reversed, but not to the extent of a bird, in Archaeopteryx.
Posted by G.K Nimrod (Member # 205) on :
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