Aves: Dinos or Thecodonts?

[God Fearing Atheist]

I'm just curious as to how many of my fellow evolutionists accept the thecodont origin of aves, as opposed to the standard paleo maniraptor theory.

If any do accept the former, why?

-GFA

[RufusAtticus]

This is a bad poll. Of course birds and dinosaurs share a common ancestor. This is true whether birds are descendents of dinosaurs or not.

Please PM me with better phrasing and I'll modify the poll.

[God Fearing Atheist]

Sorry guys. Sometimes I forget that people have to understand what I mean from what I actually *say*. :(

-GFA

[Coragyps]

Typical atheistic materialistic commie child-molester propaganda - they're the Bird Kind! :D

[Kevbo]

I voted for the first one, because I'm not sure if smaller transitional creatures like Archaeopteryx were ever considered dinosaurs. It's all just semantics, I guess :)

[Oolon Colluphid]

So, with a third of people (atm) wanting to know, who’s going to tell us what a thecodont is? ;)

As far as I’m concerned, birds are dinosaurs. I’ve seen the fossils, up close, and with Per Ahlberg at hand for a short while (DinoBird exhibition at the NHM). I have my own pictures of ‘fuzzy raptor’. You don’t need to be a great anatomist to recognise eg a furcula (once its location in a contortion of bones in a flat chunk of rock has been pointed out ;):o ). ’Fraid I can’t remember what a thecodont is off the top of my head, and can’t be bothered to look it up -- because the dino affinity is perfectly plain to me.

Of course, I could be wrong...

Cheers, Oolon

[mark24]

Shouldn't Therapod be an option?

[Secular Pinoy]

Originally posted by RufusAtticus
This is a bad poll. Of course birds and dinosaurs share a common ancestor. This is true whether birds are descendents of dinosaurs or not.I think it should be phrased as, Do birds have a closer cladistic relationship with thecodont than dinosaurs, or the other way around? This is based on my reading of Henry Gee's book In Search of Deep Time (http://www.amazon.com/exec/obidos/ASIN/0801487137/internetinfidels).

[God Fearing Atheist]

Originally posted by mark24
Shouldn't Therapod be an option?

Thats the second option. Maniraptora is the particular clade of theropod dino that most paleos believe aves are a member of.

-GFA

[mark24]

GFA,

Thanks for the clarification.

Could you cite some Maniraptora species please? Just so I can get a more visual image of what is supposed to be going on.

Thanks,

Mark

[God Fearing Atheist]

Originally posted by mark24
GFA,

Thanks for the clarification.

Could you cite some Maniraptora species please? Just so I can get a more visual image of what is supposed to be going on.

Thanks,

Mark

Sure. Heres a good page. (http://www.geocities.com/dinosauria_pt/Classification-Maniraptora.html) This page (http://www.ucmp.berkeley.edu/diapsids/saurischia/maniraptora.html) discusses some of the groups in more detail.

-GFA

[God Fearing Atheist]

Hello Oolon ;)

"Thecodont" is the name given to the earliest archosaurs, and from which dinos and pterosaurs are decended. Its gone out of fashion with cladistics-types because its a paraphyletic group, but I thought i'd give any potential Feducciaites the benifit of the doubt.

-GFA

[Jesse]

Even if you're not convinced by all the skeletal similarities paleontologists have identified between certain theropod groups (especially the maniraptors) and early birds, all the recent Chinese finds of feathered theropods should settle the issue beyond all reasonable doubt.

Here's a page listing all the major finds:

http://www.geocities.com/earthhistory/fd.htm

For example, there's "NGMC 91":

http://www.geocities.com/earthhistory/fd.htm
http://research.amnh.org/vertpaleo/dinobird.html

http://research.amnh.org/vertpaleo/feather2.jpg
http://www.amnh.org/naturalhistory/0701/images/feather4.jpg
http://research.amnh.org/vertpaleo/feather11.jpg

And "BPM 1 3-13", with very clear impressions of long feathers along its hind leg:

http://www.newscientist.com/hottopics/dinosaurs/fullyformed.jsp
http://www.nature.com/nature/journal/v416/n6876/fig_tab/416036a_F1.html

http://www.nature.com/nature/journal/v416/n6876/images/416036a-f1.2.jpg

And very recently some specimens of "Microraptor" were found with feathers arranged in a way similar to bird's wings (longer outer feathers and shorter inner ones) on both front and hind legs:

http://www.nature.com/nsu/030120/030120-7.html
http://www.newscientist.com/news/news.jsp?id=ns99993298
http://members.aol.com/strigoivv/FeathersOfDinosaursII.html
http://members.aol.com/strigoivv/FeathersOfDinosaursIII.html

http://www.newscientist.com/ns_images/9999/99993298F1.JPG
http://members.aol.com/strigoivv/images/web%20micro%20arm.jpg
http://members.aol.com/strigoivv/images/web%20micro%20leg.jpg
http://members.aol.com/strigoivv/images/web%20micro%20primary.jpg
http://members.aol.com/strigoivv/images/web%20micro%20feather1.jpg

Given that no one, not even Feduccia, disagrees these skeletons really are theropod dinosaurs rather than some other thecodont branch that happened to evolve to look similar to theropods, the only options remaining for the thecodont supporters are to suggest dinosaurs evolved feathers independently by convergent evolution, or that the common ancestor of the thecodont branch leading to birds and the branch leading to dinosaurs already had basically modern-looking feathers and wings. The convergent evolution idea, which I think Feduccia is using as an explanation for these finds, seems totally unbelievable--these feathers seem to have all the main features of bird feathers, including the central shaft, the barbs extending sideways from this shaft which stick together (presumably with the little hooklets found on barbs in modern bird feathers), the same asymmetric shape for the flight feathers, and the same basic arrangement of long/short feathers on the wing. Is it likely that feathers with all these features would evolve twice independently, and on theropods which happen to have so many skeletal similarities with birds as well? As for the "feathers already present on common ancestor" explanation, I don't know if anyone has actually suggested this, but it would suggest that the common ancestor of all dinos descended from creatures which already had basically modern-looking feathers and wings, so that all dinosaurs are essentially flightless birds--if that's true, why haven't any other dinosaur groups been found with feathers? And what about the more "primitive" featherlike structures on other non-dromeaosaur theropods like Sinosauropteryx (http://www.peabody.yale.edu/exhibits/cfd/CFDsino.html)?

[Oolon Colluphid]

Originally posted by Jesse
For example, there's "NGMC 91":

http://research.amnh.org/vertpaleo/feather2.jpg
Wheee! Fuzzy Raptor! (Hmmm, so it’s an NGMC 91, is it? Doesn’t exactly trip off the tongue... ) That thing is just too cool! As I said earlier, I’ve stared at that thing -- well both things actually, both slab and counterslab -- for ages, just inches away from my nose through glass, at the NHM DinoBird exhibition. Got my own pics of it too. It’s a feathery dinosaur!

Thanks for an excellent post Jesse! :notworthy:

And to think that ‘Big Dave’ over at the Faith Forum has said of Archaeopteryx that “We have no idea what kind of skin it had, or if it had feathers.” (The thread is here (http://www.faithforum.org/challenge/topic.asp?TOPIC_ID=2981&whichpage=8), I’ve had a go already, but feel free to bury him further ;).)

Cheers, Oolon

[Urvogel Reverie]

Originally posted by Oolon Colluphid
Wheee! Fuzzy Raptor! (Hmmm, so it’s an NGMC 91, is it? Doesn’t exactly trip off the tongue... ) That thing is just too cool! As I said earlier, I’ve stared at that thing -- well both things actually, both slab and counterslab -- for ages, just inches away from my nose through glass, at the NHM DinoBird exhibition. Got my own pics of it too. It’s a feathery dinosaur!

Thanks for an excellent post Jesse! :notworthy:

And to think that ‘Big Dave’ over at the Faith Forum has said of Archaeopteryx that “We have no idea what kind of skin it had, or if it had feathers.” (The thread is here (http://www.faithforum.org/challenge/topic.asp?TOPIC_ID=2981&whichpage=8), I’ve had a go already, but feel free to bury him further ;).)

Cheers, Oolon


Indeed, an excellent post. I myself am fascinated to no end by the origin and evolution of birds, and their derivation from Maniraptora. As for Dave, well, I have debated him at now three or four different forums for months. He is the most disingenuous creationist I have ever met, and his arguments are specious rot. My lengthy rebuttals I have authored for his faithforum.org posts, have not been posted by the moderates, who it would seem are less than objective. So have at it, Oolon.