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Author Topic:   Archaeopteryx and Dino-Bird Evolution
arachnophilia
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Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 181 of 200 (347875)
09-09-2006 10:19 PM
Reply to: Message 176 by kuresu
09-09-2006 4:01 PM


Re: the great Archaeopteryx hoax
I think arach was trying to say that velociraptor has long arms compared to the legs. just like birds today--except birds have even longer arms compared to their legs (I think)

flying birds, yes. flightless birds tend to be much shorter, but the evidence is that they evolved from flying birds (though, i believe, there are some crazies that suspect paleognaths came straight from dinos). anyways, longer arms is evidence of avian tendencies.

t-rex would have a very short arm to leg ratio--short arms compared to the legs.

the shortest, actually. except maybe mononykus, but i can never get a straight answer on whether or not that's a chimera.

dromaeosaurs and troodondits have the longest arms, and archaeopteryx holds the record, with arms and legs equal in length. velociraptor has the longest arms of any dinosaurs that's not actually a bird, iirc.


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arachnophilia
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Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 182 of 200 (347876)
09-09-2006 10:21 PM
Reply to: Message 177 by Coragyps
09-09-2006 4:28 PM


Re: Archaeopteryx- most likely fraud, if not, still not transitional
The Solnhofen Limestone is the remnant of that lagoon bottom I mentioned earlier. All seven known Archaeopteryx fossils came from it.

eight if you count the feather.

And it didn't get deposited in a giant forty-day flood, either.

one year flood. :D


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Cthulhu
Member (Idle past 3802 days)
Posts: 273
From: Roe Dyelin
Joined: 09-09-2003


Message 183 of 200 (348191)
09-11-2006 6:55 PM
Reply to: Message 29 by Chiroptera
10-13-2005 4:13 PM


Re: Doh!
Synapsids aren't reptiles, because Reptilia has been redefined to fit into cladistics.

It looks like the following.

-Amniota
|_
|-Synapsida
|-Sauropsida
|-Something or another
|-Reptilia
|-modern reptiles

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Cthulhu
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Posts: 273
From: Roe Dyelin
Joined: 09-09-2003


Message 184 of 200 (348198)
09-11-2006 7:17 PM
Reply to: Message 140 by Dr Jack
09-08-2006 5:35 AM


Re: Archaeopteryx- most likely fraud, if not, still not transitional
The preserved skin portions are on the legs and the underside of the tail, which are not exactly places where feathers need to be. Now, if skin impressions were found on the arms or back, then it would be a reasonable assumption that Juravenator was featherless.
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arachnophilia
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Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 185 of 200 (348256)
09-11-2006 10:35 PM
Reply to: Message 183 by Cthulhu
09-11-2006 6:55 PM


Re: Doh!
Synapsids aren't reptiles, because Reptilia has been redefined to fit into cladistics.

there is no "reptilia." it's sauropsida. sauropsids and reptiles are synonymous, and the term "reptile" was actually discarded in terms of cladistics some time ago, because dinosaurs abd birds (sauropsids) don't fit especially with the connotation of "reptile."


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arachnophilia
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Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 186 of 200 (348258)
09-11-2006 10:37 PM
Reply to: Message 184 by Cthulhu
09-11-2006 7:17 PM


Re: Archaeopteryx- most likely fraud, if not, still not transitional
The preserved skin portions are on the legs and the underside of the tail,

oh, ok, i must have missed that.

we know there was secondary feather loss on the feet, because of genetics.


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Cthulhu
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Posts: 273
From: Roe Dyelin
Joined: 09-09-2003


Message 187 of 200 (348278)
09-12-2006 12:49 AM
Reply to: Message 185 by arachnophilia
09-11-2006 10:35 PM


Re: Doh!
I know Sauropsida is the larger grouping. The last I checked, Reptilia had been redefined as a daughter group of Sauropsida.
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Dr Jack
Member (Idle past 55 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 188 of 200 (348454)
09-12-2006 3:08 PM
Reply to: Message 184 by Cthulhu
09-11-2006 7:17 PM


Re: Archaeopteryx- most likely fraud, if not, still not transitional
The preserved skin portions are on the legs and the underside of the tail, which are not exactly places where feathers need to be. Now, if skin impressions were found on the arms or back, then it would be a reasonable assumption that Juravenator was featherless.

Indeed.

But, Arachnophilia stated all the skin impressions we had showed feathers. This is not so.


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arachnophilia
Member
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 189 of 200 (348608)
09-13-2006 1:01 AM
Reply to: Message 188 by Dr Jack
09-12-2006 3:08 PM


feather-less skin impression
yes, yes, i was unaware of that find. but thanks for pointing it out.

do you think this rules out the dinosaur having feathers? just complicates the matter? any particular take on this? it's rather peculiar that other closely related dinosaurs (both branching lower and higher on the tree, cladistically) did have feathers.


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Dr Jack
Member (Idle past 55 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 190 of 200 (348640)
09-13-2006 4:16 AM
Reply to: Message 189 by arachnophilia
09-13-2006 1:01 AM


Re: feather-less skin impression
I think the most parsimonious explanation is that Juravenator has undergone selective feather loss across some parts of its body and a more complete skin print would reveal this.

But I also think it's important to differentiate between what we can observe and what we can deduce.


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arachnophilia
Member
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 191 of 200 (348642)
09-13-2006 4:27 AM
Reply to: Message 190 by Dr Jack
09-13-2006 4:16 AM


Re: feather-less skin impression
But I also think it's important to differentiate between what we can observe and what we can deduce.

well, the thing is this. we know that at some point dinosaurs/birds lost some feathers. the earliest flying dinosaurs we have are "four-winged," with flight feathers on their feet. genetically, we know that modern bird scutes evolved from feathers.

so the question i'm really asking is, is it safe to say that juravenator probably had feathers, and this secondary feather adaptation? i'm not sure, they note that the skin lacks the follicles for feathers. it might an age/gender thing?

or maybe the simplest deduction is that feathers are convergent. [or reccessive?]

Edited by arachnophilia, : added bracket


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arachnophilia
Member
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 192 of 200 (348643)
09-13-2006 4:35 AM
Reply to: Message 190 by Dr Jack
09-13-2006 4:16 AM


Re: feather-less skin impression
more info:

quote:
Birds have scales and feathers needn't always cover the remainder of the body. The preservation of feathers in Juravenator's nearest relative known to have feathers, Sinosauropteryx is apparently limited to a mindline "mane" of filaments, an may not necessarily have covered the bodies. Whether or not this was the true condition in life could, potentially, be disputed. However, it follows from the enormous diversity of theropod dinosaurs that their feather distributions (both within and among taxa) were considerably more varied than previously though.

Tyrannosaurs are known to have patches of scaly skin, but recent discoveries show that their ancestors probably had feather-like structures. Thus, at some point, feathers must have been either incompletely covering the animal or lost and gained over varying degrees. Moreover, it appears that estimates of feather covering in dromaeosaurs were dramatically underestimated It would appear that our interpretation of feather evolution paints, perhaps too conservatively rather broad coating of feathers on just about anything descended from the common ancestor of all coelurosaurian dinosaurs.

Xing Xu, who has described many of the Chinese feathered dinosaurs, wrote a News and Views piece which raised some interesting cautions about these results: For one, we don't know that Juravenator did not have feathers. All we know is that parts of its body had scales. Fossilization is biased against feather preservation and those few records we have are remarkably rare. The specimen is apparently a juvenile and may, in fact, create a false signal pulling the animal to a particular part of the tree. Normally, this would be the other way around: juvenile characters tend to make you look more 'primitive'. However, Juravenator clumps with a group of small theropod dinosaurs which may share character similarities simply related to the fact that they're small, and not any real common ancestry. It's possible that this animal is more primitive, but unites with these other animals due to bias.

source


hmm.


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Dr Jack
Member (Idle past 55 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 193 of 200 (348646)
09-13-2006 4:41 AM
Reply to: Message 191 by arachnophilia
09-13-2006 4:27 AM


Re: feather-less skin impression
I think the article you quoted answered the question better than I can. :)
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arachnophilia
Member
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 194 of 200 (348834)
09-13-2006 3:55 PM
Reply to: Message 193 by Dr Jack
09-13-2006 4:41 AM


Re: feather-less skin impression
yeah, i got curious, and googled. i still don't quite know what to make of it. very peculiar.
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Archer Opteryx
Member (Idle past 1548 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 195 of 200 (351251)
09-22-2006 8:35 AM
Reply to: Message 147 by Someone who cares
09-08-2006 9:09 PM


Keeping it real
S1WC:

Exactly! That's why I hold to the position that the more distinct specimens with feather imprints are fruad! My point! Reptiles don't have feathers! But engraving them wouldn't be too hard, and it pays well in the museums for a "transitional fossil."

It may interest you to know that the Archaeopteryx fossils are regarded as genuine even by the hard-core creationists at Answers in Genesis. They list your 'hoax' assertion near the top of their Arguments we think creationists should NOT use.


Archer

All species are transitional.


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