Birds are Theropod Dinosaurs

Rebutting the claims that they are not.

Geology, Geophysics, Oceanography, Meteorology etc.

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Birds are Theropod Dinosaurs

#1  Postby theropod » Sep 08, 2011 12:48 pm

Greetings,

Here is a link to my self imposed suspension from posting with full disclosure. Since that week has now passed and I have had time to reflect I offer the entire forum my apology. I will strive to remain more detached from the subject at hand, and not succumb so easily to the dark side.

As many of you are aware there is a thread over in Creationism/ID about Gary S. Gaulin's flavor of ID wherein CharlieM attempted to rebut my claim that birds are indeed theropod dinosaurs HERE.

Props to Rumraket for his post HERE. Well done indeed! I note that the cladogram was not really addressed.

HERE is a link CharlieM provided which made note of the fact that some researchers hold an opinion that has no support in physical evidence. I'd call that reference an own goal. Let's look at those words again;

Some researchers today do not agree that dinosaurs gave rise to birds, and are working to falsify this theory, but so far the evidence for the *ETA (current theropod/bird link) theory has swamped their efforts. If they were to conclusively establish that birds are more likely descended from another group (Crocodylomorpha, the group containing crocodiles, has been suggested), that would be a major upheaval in our knowledge of phylogeny. One single well-preserved fossil bird unequivocably of Triassic age might shed some doubt on the theory of the maniraptoran affinities of birds. That would be a major find. Some bird-like fossils have been presented as Triassic birds, but so far have not held up under peer review. Such is the dynamic nature of science.


I'll get to crocodiles later

So this link doesn't support the current thinking is wrong. It just says there are some that are working to establish this possibility and no supporting evidence exists. The fact that they are welcome to keep looking is just fine by me. Should they turn up convincing evidence that counters our collective, and expanding, understanding of the current theropod to bird link I will listen/read/learn from what they offer.

CharlieM wrote:If they have "morphology identical to modern birds" why is Ricardo Melchor calling them an "unknown group of theropod dinosaurs"? Surely he is making an assumption because of his prior belief.


As for what Ricardo might or might be assuming I can't know. The features they share is what links the two groups. Since birds are theropods I still can't see what one could call an assumption. He is probably expressing the fact that the ever growing body of empirical data, which displays a great deal of consilience, tells us that no valid exceptions to this relationship withstand close examination. Those trace fossil don't. For all anyone knows the trace maker could have been a little tooth jawed theropod with an odd foot, maybe specialized to hunt for bugs in a mud flat.

I'll note again this reference is to a trace fossil. Trace fossils are problematic in that they are not organic in nature. Not that trace fossils do not provide us great information. They do! However we cannot know if this was an evolutionary dead end that arose in a distinct branch of Theropoda and left no skeletal remains in the geologic column. The reduced hallux in most theropods is not evidence that was the case in all theropods. While the trace fossil tries to push back the date for expression of this trait it does not make a disconnect from the theropod group because these hallux are present in reduced form in many well studied examples. Also the trace cannot reveal anything beyond the basic foot morphology, speed, direction of travel and approximate weight. Critical skeletal features aside from the load bearing foot cannot be studied, and then only the layout of the phalanges, not which actual bones were retained/moved/gained to generate the trace. It is true that in the foot morphology of a great many maniraptoran theropods developed a distorted and deadly second toe, so adaptability in the foot morphology of theropods was evident and is documented. This is partly why trace fossils are assigned different classification than other types of fossils. What these fossils tell us is that something came by here and its foot was shaped like this. From that substrate up we are projecting towards likely possibilities.

In the posting of which I am making note there was a picture of an eagle looking at you with both eyes. Big deal! Here's a nice big theropod with the same features. Note the reduced nasals and orbital fenestra situated on the outside of the cranium which combine for forward looking vision. Handy feature to have when you kill with your mouth and need to know where that is in relation to your prey. Also note the reduced hallux easily seen on the left foot. It's that little bone sticking out backward from the rest of the foot.

Image
SOURCE

If I'm not mistaken there are theropod footprints which show where the hallux contacted the substrate. Why yes there are such things!

Image
SOURCE

See the smaller tread/toe contact point to the aft of the forward pointing three toes? Theropod hallux impression.

I think it best to reference some previous thoughts I have posted on this matter. HERE I present a little examination of the rise of dinosaurs. The earliest skeletal remains we have of dinosaurs have morphological features which define them. These are not birds. No bird from this era has been found. *There's a nice illustration of this key skeletal morphology further along in this post.

If there are some vague objections implying that paleontology is an assumption based science I suggest one read THIS post I constructed just to put those assertions to rest. There's much more to the study of paleontology than I cite in my generalization, and it's a growing and dynamic field. Nobody can keep up with all the finds of late coming to publication. None of that flood of knowledge is contributing to anything other than what paleontologists have been proposing for years. Objections? Sure. Evidence? None.

HERE is a post where I show that annual varves allow us to apply yet another method to the array of methods available to accurately date natural history. This is important stuff, but I don't expect it's completely obvious. Has something to do with all those feathered dinosaurs they keep digging up in China, but in a 'round about' way.

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Abstract


Letters to Nature:
Nature 387, 390 - 392 (22 May 1997); doi:10.1038/387390a0

"New evidence concerning avian origins from the Late Cretaceous of Patagonia"

Fernando E. Novas & Pablo F. Puertat

The spate of recent discoveries of Mesozoic birds has substantially improved our understanding of the early evolution of birds and flight, but has failed to close the morphological gap between the Upper Jurassic Archaeopteryx lithographica, the earliest known bird, and the Dromaeosauridae, the group of non-avian theropod dinosaurs regarded as most closely related to birds. Here we describe a theropod dinosaur from Patagonia, Unenlagia comahuensis gen. et sp. nov., which partially fills this gap. Despite the relatively late appearance of this dinosaur in the fossil record (Upper Cretaceous), several features of Unenlagia are more bird-like than in any other non-avian theropod so far discovered.Unenlagia resembles Archaeopteryx in the morphology of the scapula, pelvis and hindlimb. But several shared, primitive features of the pubis, ischium and hindlimb proportions suggest that Unenlagia may represent the sister taxon of the Avialae (=Aves). The structure of the forelimb[/i] suggests that the avian mode of [b]forelimb folding, and the extensive forelimb elevation necessary for powered, flapping flight, was already present in cursorial, non-flying theropod dinosaurs.


Just more hard evidence, based on direct observations, in support of the theropod/bird position. It keeps getting better, read on.
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Nature Vol 436|14 July 2005 doi:10.1038/nature03716

"Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs:"

Patrick M. O’Connor & Leon P. A. M. Claessens
...
Postcranial skeletal pneumaticity has also been reported in numerous extinct archosaurs including non-avian theropod dinosaurs and Archaeopteryx. However, the relationship between osseous pneumaticity and the evolution of the avian respiratory apparatus has long remained ambiguous. Here we report, on the basis of a comparative analysis of region~specific pneumaticity with extant birds, evidence for cervical and abdominal air-sac systems in non-avian theropods, along with thoracic skeletal prerequisites of an avian-style aspiration pump. The early acquisition of this system among theropods is demonstrated by examination of an exceptional new specimen of Majungatholus atopus, documenting these features in a taxon only distantly related to birds. Taken together, these specializations imply the existence of the basic avian pulmonary Bauplan in basal neo-theropods, indicating that flow-through ventilation of the lung is not restricted to birds but is probably a general theropod characteristic.



Theropods and birds shared skeletal AND respiratory attributes which adds more support to the connection that birds and theropods share, and indeed places both within the same clade.
_____________

Journal of Vertebrate Paleontology
Vol. 9, No. 2 (Jun. 30, 1989), pp. 125-136 (article consists of 12 pages)

Abstract
FULL PDF

Journal of Vertebrate Paleontology
Vol. 9, No. 2 (Jun. 30, 1989), pp. 125-136 (article consists of 12 pages)

"A New Species of the Theropod Dinosaur Syntarsus from the Early Jurassic Kayenta Formation of Arizona"

Timothy Rowe

Abstract:
Until now, Syntarsus was based on a single species, S. rhodesiensis, known only from southern Africa. The discovery of Syntarsus in North America adds significantly to the increasingly detailed resemblance of African and North American Early Jurassic terrestrial vertebrate faunas. The new species, Syntarsus kayentakatae, is based on a complete skull and partial skeleton, and more fragmentary remains of at least 16 additional individuals, all from a narrow stratigraphic interval in the Kayenta Formation. Syntarsus kayentakatae is diagnosed by parasagittal cranial crests and fusion of the fibula to the calcaneum in adults. Syntarsus is the most derived member of the newly diagnosed theropod taxon Ceratosauria, possessing 22 apomorphies that arose subsequent to the divergence of ceratosaurs from other theropods. Syntarsus shares 20 of these with Coelophysis bauri, one of the earliest well-known theropods. By their first appearance, probably late Carnian, ceratosaurs already possessed a history involving considerable morphological transformation. A number of these characters arose convergently much later in time in ornithurine birds.


So there's a whole group of anatomical/skeletal features already present in the earliest of theropods, which display a wide presentation of diversity, and these features didn't convergently arise within the linage that gave rise to birds until, "...much later in time." The theropods proceed the emergence of birds because they give rise to them, and indeed all that follow in this line are therefore theropods.
_________

Abstract
FULL PDF


Journal of Vertebrate Paleontology Vol. 5, No. 2 (Jun., 1985), pp. 133-138

"A New Family of Bird-Like Dinosaurs Linking Laurasia and Gondwanaland"

M. K. Brett-Surman and Gregory S. Paul

Abstract
A new family of theropod dinosaurs is described based on metatarsi from North America and Argentina. Because birds are theropod descendants, there are often problems in assigning isolated metatarsi to the proper group. Differences between the metatarsi of ground birds and theropods are detailed. In particular, it is shown that the length/width ratio of articulated metatarsi cannot be used to distinguish higher taxa. This new family represents the first occurrence of the same genus of theropod dinosaur from both Laurasia and Gondwanaland at the end of the Cretaceous, a time when the two supercontinents were supposedly still separate.


This paper is dealing with the question of geographic distribution of small bird-like theropods, not that birds are anything other than descendants of theropod dinosaurs, and that these groups are so similar that it is hard to make a distinction between any two taxa let alone species, based on a single skeletal morphology, and more. The distinction(s) is/are supported in the full paper with lots of other goodies.
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Image

Image

IMAGES SOURCE

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"WHY ORNITHOLOGISTS SHOULD CARE ABOUT THE THEROPOD ORIGIN OF BIRDS"
The Auk 119(1):1-17. 2002 | doi: 10.1642/0004-8038(2002)119[0001:WOSCAT]2.0.CO;2
Richard O. Prum

The HTML view is just the reading list, and 4 illustrations, to really get to where one can get to know the subject well enough to challenge the theropod to bird link. It even includes the views of those proposing to challenge the bird/theropod link. If one can digest that reading list in less than a month I'll be impressed. If one digests every reference there and comes away thinking there is any way that birds arose from any other pathway than via theropod dinosaurs they are fooling themselves.

Think about it. There is evidence from just about every angle we apply that shows that theropod dinosaurs gave rise to birds. There are some out there studying anything and everything to overturn this mass of cross supporting evidence. Those researchers have not done that. I can't help but accept what that mass of evidence tells us.
_________

Abstract
FULL PDF


Naturwissenschaften
Volume 91, Number 10, 455-471, DOI: 10.1007/s00114-004-0570-4
455-471, DOI: 10.1007/s00114-004-0570-4

"The origin and early evolution of birds: discoveries, disputes, and perspectives from fossil evidence"

Zhonghe Zhou


Abstract
The study of the origin and early evolution of birds has never produced as much excitement and public attention as in the past decade. Well preserved and abundant new fossils of birds and dinosaurs have provided unprecedented new evidence on the dinosaurian origin of birds, the arboreal origin of avian flight, and the origin of feathers prior to flapping flight. The Mesozoic avian assemblage mainly comprises two major lineages: the prevalent extinct group Enantiornithes, and the Ornithurae, which gave rise to all modern birds, as well as several more basal taxa. Cretaceous birds radiated into various paleoecological niches that included fish- and seed-eating. Significant size and morphological differences and variation in flight capabilities, ranging from gliding to powerful flight among early birds, highlight the diversification of birds in the Early Cretaceous. There is little evidence, however, to support a Mesozoic origin of modern avian groups. Controversy and debate, nevertheless, surround many of these findings, and more details are needed to give a better appreciation of the significance of these new discoveries.


The birds we have with us today are not the same as birds that arose from those theropod roots. Evolution has selected them to have filtered out into the birds species extant today. Still, those roots remain in all modern birds and that makes them theropods. The mammals we have with us today, including us, were nothing like the mammals extant in the late Cretaceous. Why should we expect birds to be any more similar to their ancestors?

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NATURE |VOL 412 |26 JULY 2001

"Dinosaurian growth rates and bird origins"
Kevin Padian, Armand J. de RicqleÁs & John R. Horner

Dinosaurs, like other tetrapods, grew more quickly just after hatching than later in life. However, they did not grow like most other non-avian reptiles, which grow slowly and gradually through life. Rather, microscopic analyses of the long-bone tissues show that dinosaurs grew to their adult size relatively quickly, much as large birds and mammals do today. The first birds reduced their adult body size by shortening the phase of rapid growth common to their larger theropod dinosaur relatives. These changes in timing were primarily related not to physiological differences but to differences in growth strategy.
...
Dinosaurian versus reptilian growth rates:
Comparing these two histological lines of evidence, our own investigations of extant and extinct archosaurs (including birds), as well as a survey of the published literature on bone histology, reveal a dichotomy between those archosaurs related to crocodiles and those related to birds and dinosaurs. This distinction can be traced back to the division of the two lineages at least by the Middle Triassic, over 230 million years ago. ...


In this study the bone itself was examined, in great detail, in a diverse manner, which shows that bird bone and theropod dinosaur bone share a histology that does not include the characteristics of the always growing crocodile ancestry.

The evidence has lead me to accept that theropods diversified as the environment would allow, and among those many branches of diversity is a limb that leads to modern birds. Take away the limb nearest the trunk and the rest falls. The fossil evidence alone tells us that theropods emerged first, and birds arose later directly from those theropod progenitors.

Thanks,

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Re: Birds are Theropod Dinosaurs

#2  Postby trubble76 » Sep 08, 2011 1:08 pm

Great stuff! A fascinating read, thank you. :cheers:
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Re: Birds are Theropod Dinosaurs

#3  Postby Rumraket » Sep 08, 2011 1:26 pm

Excellent post, Theropod. Very informative.
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Re: Birds are Theropod Dinosaurs

#4  Postby chairman bill » Sep 08, 2011 1:44 pm

Yeah, but where's the fossils of birds with horns like triceratops? Eh? Eh? And did T. Rex have a beak? Eh? And why are there still dinosaurs if we've now got blue tits? Er ... (Fundie mode CB is 96 years old, incontinent & just slightly deranged. Ed.)
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Re: Birds are Theropod Dinosaurs

#5  Postby CharlieM » Sep 09, 2011 8:43 pm

theropod wrote:Greetings,

(Snipped)

As many of you are aware there is a thread over in Creationism/ID about Gary S. Gaulin's flavor of ID wherein CharlieM attempted to rebut my claim that birds are indeed theropod dinosaurs HERE.


I wasn't trying to rebut your claim that birds are indeed theropod dinosaurs. I know that there is compelling evidence for the claim and I can see that you've shown us a great deal of that evidence in your post. I was pointing out that. no matter how much evidence you see as supporting your views its not a good idea to take anything as fact, especially when it involves the study of past events that cannot be repeated. As I said to Rumraket, "For all I know birds may have descended from theropod dinosaurs."

I see nothing wrong in examining, as objectively as is possible, all the evidence. If, say, all marsupials had gone extinct several million years ago and all we had to go on was fossilized bone, where would we place Tasmanian wolves in relation to placental wolves, tigers and dolphins? How do you tell which are derived traits and which are the result of convergent evolution?

Consider marsupial moles and their relationship to Cape golden moles:

http://www.sciencedaily.com/releases/2010/11/101103081920.htm
Although related to kangaroos, koalas and other marsupials, living marsupial moles far more closely resemble Cape golden moles, which burrow through the desert sands of Africa. The two golden-furred animals not only look indistinguishable when seen side by side but share many other similarities in their teeth and skeletons that reflect their subterranean lifestyles.
Yet the Cape golden mole is a placental mammal -- the group that includes rats, bats, elephants and humans -- and these two very different branches of the mammal family evolved from a common ancestor at least 125 million years ago, says Professor Archer. Having diverged in ancestry, however, their similar lifestyles have meant that they have converged in anatomy.
"This fossil discovery came as a real shock," he says. "Until now, we had always assumed that marsupial moles must have evolved in an unknown ancient Australian desert because, like Cape golden moles, the living marsupial moles survive only in deserts.
"Yet this ancestral Australian mole, which is not as specialised as the living form, has been discovered in ancient rainforest deposits -- not deserts. The fossils suggest that they became mole-like while burrowing through the mossy floors of those ancient forests."
This missing link has solved a second mystery about how the highly specialised V-shaped teeth of the living marsupial mole evolved. Although they are almost identical to the teeth of their African counterparts, it is now clear that they went down a completely different evolutionary pathway to get there, says co-author Dr Robin Beck of the American Museum of Natural History.
"This ancient link makes it clear that marsupials followed a completely different path from placentals but ended up with almost identical-looking teeth."
Co-author UNSW Associate Professor Suzanne Hand said: "It goes to the heart of global debates about relationship versus convergence -- whether animals are similar because they are closely related or similar because they have had to adapt to related challenges. It's also exciting because it so beautifully demonstrates just how adaptive Australian marsupials can be when given the right evolutionary challenges and enough time to meet them."


Opposing viewpoints should not be ignored or swept under the carpet.

Common descent is allowed for in ID so it makes little difference whether birds are or are not descended from theropod dinosaurs, but it is an interesting area to look into so thank you for providing your evidence. It justifies more than a quick scan so I will study it more fully when I get the time.
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Re: Birds are Theropod Dinosaurs

#6  Postby Weaver » Sep 09, 2011 8:59 pm

CharlieM wrote:
Common descent is allowed for in ID so it makes little difference whether birds are or are not descended from theropod dinosaurs, but it is an interesting area to look into so thank you for providing your evidence.

Of course it is - when one makes up the rules of one's "science" as one goes along, trying to encompass most of what's known while leaving things open for future REAL scientific discoveries, one's "science" will be full of such allowances.

REAL science, however, doesn't allow or dis-allow anything - it simply observes what IS and what IS NOT, and doesn't postulate the un-observable or illogical (in this case, an "intelligent designer" AKA god).
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Re: Birds are Theropod Dinosaurs

#7  Postby Animavore » Sep 09, 2011 9:05 pm

I posted these on the Inside Nature's Giants thread but they fit here, too. These are the bones of a modern day bird, a ratite called a cassowary (smaller ones), and a theropod dinosaur called a banjosaurus.

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Ribs.

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Toes.

What's called "incontrovertible evidence" I believe.
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Re: Birds are Theropod Dinosaurs

#8  Postby Calilasseia » Sep 09, 2011 9:16 pm

CharlieM wrote:Opposing viewpoints should not be ignored or swept under the carpet.


However, creationists and their speciation variants, the IDists, want to sweep vast swathes of hard scientific evidence under the carpet when that evidence doesn't support their presuppositions. But then it's not as if we're lacking in evidence for ideologically motivated duplicity on the part of creationists etc. Dover Trial, anyone?

CharlieM wrote:Common descent is allowed for in ID


Really? So why have IDists spent so much time trying to reject it?

CharlieM wrote:so it makes little difference whether birds are or are not descended from theropod dinosaurs


The evidence that they are, and that appropriate anatomical modifications appeared over time in different parts of the lineage in a manner entirely consistent with the current scientific paradigm, renders fabricated magic entities superfluous to requirements and irrelevant.

CharlieM wrote:but it is an interesting area to look into so thank you for providing your evidence. It justifies more than a quick scan


It also justifies something more than the erection of yet more fabricated apologetics, of the sort we've seen from the likes of Luskin, Sarfati et al.

CharlieM wrote:so I will study it more fully when I get the time.


That little lot should keep you occupied for about a month at least.
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Re: Birds are Theropod Dinosaurs

#9  Postby theropod » Sep 09, 2011 10:47 pm

theropod wrote:Greetings,

(Snipped)

As many of you are aware there is a thread over in Creationism/ID about Gary S. Gaulin's flavor of ID wherein CharlieM attempted to rebut my claim that birds are indeed theropod dinosaurs HERE.


CharlieM wrote:I wasn't trying to rebut your claim that birds are indeed theropod dinosaurs. I know that there is compelling evidence for the claim and I can see that you've shown us a great deal of that evidence in your post. I was pointing out that. no matter how much evidence you see as supporting your views its not a good idea to take anything as fact, especially when it involves the study of past events that cannot be repeated. As I said to Rumraket, "For all I know birds may have descended from theropod dinosaurs."

I see nothing wrong in examining, as objectively as is possible, all the evidence. If, say, all marsupials had gone extinct several million years ago and all we had to go on was fossilized bone, where would we place Tasmanian wolves in relation to placental wolves, tigers and dolphins? How do you tell which are derived traits and which are the result of convergent evolution?


Hey CahrlieM,

I hope you don't mind that I fixed the quote boxes so that my written text can be distinguished from yours.

From your words above I can see that you feel it is best to remain skeptical of taking anything as fact no matter how much evidence is presented. I can appreciate the thought, but there comes a point where skeptical thinking is self defeating. The thing is that these past events need not be repeated since we have extant representatives that retain traits which are definitive of theropods. Beyond the pelvic elements on which I focused the spectrum of traits that birds retain is staggering. The pictures that Animavore posted is an example of this. (Nice pictures BTW).

CharlieM wrote:Consider marsupial moles and their relationship to Cape golden moles:

Link to news release (text snipped).


Nice example of convergent evolution, but this is not the same type of possibility as the emergence of birds from theropods. We know this because the fossil record documents the emergence of birds and how they evolved. In order for birds to have arose by the same means as the two types of mammals cited here there would have to have been a period of time wherein the birds were nothing like theropod dinosaurs. This isn't what we find. Go back and read my references. The first birds are so hard, but not impossible, to distinguish from theropods because birds are theropods. Theropods are found in older strata than the first birds.

CharlieM wrote:Opposing viewpoints should not be ignored or swept under the carpet.


The very fact that I generated this thread, and cited the peer reviewed material I did, is clearly not ignoring the issue. Note that most of those references are fully accessible. Had I wanted to sweep anything under the rug I would not have bothered to spend the better part of 3 days constructing my post in the manner I did.

CharlieM wrote:Common descent is allowed for in ID so it makes little difference whether birds are or are not descended from theropod dinosaurs, but it is an interesting area to look into so thank you for providing your evidence. It justifies more than a quick scan so I will study it more fully when I get the time.


This is the very first time I have read the words I made bold above. If you actually hold this view you feel the first replicators on this planet held all the instructions needed to lead to the bio-diversity we see both in the fossil record and in extant organisms. That's what you are claiming? Or are you asserting that common descent, with modification, was all a part of the designers plan? Have you got any evidence at all to support this view? If one holds that view then the designer must continually tweak the DNA of every single life form that has ever lived or ever will. How can I say that? Every single organism is subject to mutation. There is no known way to stop this.

I hope that my post does inspire you to study the citations provided. Note that one of those citations alone has a reading list which would require more than a month of full time study to cover.

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Re: Birds are Theropod Dinosaurs

#10  Postby theropod » Sep 09, 2011 10:49 pm

Animavore,

Very nice photos!

Thanks for posting them.

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Re: Birds are Theropod Dinosaurs

#11  Postby Animavore » Sep 09, 2011 11:00 pm

theropod wrote:Animavore,

Very nice photos!

Thanks for posting them.

RS

They're not photos they're screen grabs from Inside Nature's Giant. You can watch here in UK and Ireland http://www.channel4.com/programmes/insi ... res-giants (episode called Dinosaur Bird). Or if not there are means.
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Re: Birds are Theropod Dinosaurs

#12  Postby Animavore » Sep 09, 2011 11:06 pm

I should mention in that episode they list a few anatomical similarities between therapies and birds. Worth a watch. Dawning makes an appearance too.
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Re: Birds are Theropod Dinosaurs

#13  Postby theropod » Sep 09, 2011 11:12 pm

Animavore wrote:
theropod wrote:Animavore,

Very nice photos!

Thanks for posting them.

RS

They're not photos they're screen grabs from Inside Nature's Giant. You can watch here in UK and Ireland http://www.channel4.com/programmes/insi ... res-giants (episode called Dinosaur Bird). Or if not there are means.


Fuck! I tried your link and they tell me that because I'm one of the great unwashed Yanks I can't watch the feed.

Still, the screen captures illustrate the point very well.

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Re: Birds are Theropod Dinosaurs

#14  Postby Animavore » Sep 09, 2011 11:18 pm

Torrents are handy I've heard. :whistle:
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Re: Birds are Theropod Dinosaurs

#15  Postby Onyx8 » Sep 10, 2011 2:40 am

theropod wrote:
Animavore wrote:
theropod wrote:Animavore,

Very nice photos!

Thanks for posting them.

RS

They're not photos they're screen grabs from Inside Nature's Giant. You can watch here in UK and Ireland http://www.channel4.com/programmes/insi ... res-giants (episode called Dinosaur Bird). Or if not there are means.


Fuck! I tried your link and they tell me that because I'm one of the great unwashed Yanks I can't watch the feed.

Still, the screen captures illustrate the point very well.

RS



Try bathing.

Sorry just bookmarking, I always like listening to you.
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Re: Birds are Theropod Dinosaurs

#16  Postby CharlieM » Sep 14, 2011 3:18 pm

I've been shown some convincing evidence that birds evolved from theropod dinosaurs. But I wasn't arguing that the evidence isn't there. Not everyone takes it as beyond question. So I would say I'm still entitled to ask, should it be taken as an unquestionable fact?

This part of the discussion all started because I made a statement which I did not qualify but was obviously from my point of view and I was criticized for doing so. Other posters who are on the majority side of the debate make unqualified statements from their point of view which are not necessarily facts, so what is the difference? With regard to scientists who think that the bird from theropod explanation need not necessarily be true, the reference below is another example. I've included a couple of quotes:
[url]
http://bio.fsu.edu/James/Ornithological ... 202009.pdf[/url]

Evaluation of Alternative Hypotheses:
Although we think that the BMT (birds are maniraptoran theropod dinosaurs) hypothesis has not been tested and is not as overwhelmingly supported as has been claimed, it is not, for those reasons, necessarily incorrect. Analysis of our new matrix, however, which allows for evaluation within a comparative framework of the BMT hypothesis and four alternative hypotheses for the origin of birds (Fig. 3), and review of the literature, indicate (1) that several predictions derivable from the BMT hypothesis are not supported; (2) that some maniraptorans may belong within Aves, which potentially supports the three alternatives to the BMT hypothesis that incorporate this topology (the neoflightless-theropod hypothesis, the early-archosaur hypothesis, and the crocodylomorph hypothesis); (3) that avian status for even some maniraptorans weakens support for both the BMT hypothesis and the neoflightless-theropod hypothesis; and (4) that, of the alternatives to the BMT hypothesis, the early-archosaur and crocodylomorph hypotheses are equally compatible with currently available evidence. We expand on these points below.


Conclusion:
We have pursued two goals: evaluation of whether the BMT hypothesis is as well supported as has been claimed, and evaluation of alternative hypotheses for the origin of birds within a comparative phylogenetic framework. We conclude that, because of circularity in the construction of matrices, inadequate taxon sampling, insufficiently rigorous application of cladistic methods, and a verificationist approach, the BMT hypothesis has not been subjected to sufficiently rigorous attempts at refutation, and the literature does not provide the claimed overwhelming support.Our analyses and independent data indicate that two of the alternatives to the BMT hypothesis are as probable as the BMT and are potentially supported by specific osteological data. These alternatives are the early-archosaur hypothesis, positing a sister-group relationship between Longisquama and Aves, and a variant of the crocodylomorph hypothesis. Both hypotheses include the proposition that some maniraptorans are actually birds more derived than Archaeopteryx.

Ostrom (1975, 1976a, b) and subsequent researchers like Gauthier (1986) were correct in noting the extensive similarities between maniraptorans and birds, a conclusion only strengthened by more recent discoveries, but evidence suggests that at least some maniraptorans belong within Aves. If Aves (inclusive of some maniraptorans) does not belong within Theropoda, at least some maniraptorans should be classified as birds rather than dinosaurs, and Aves should not be considered a lineage of living dinosaurs. On the basis of our results, the next two major challenges are to evaluate further the possibility that some maniraptorans in fact belong within Aves, rather than the reverse, and to further explore whether birds may have been derived from theropods, “early archosaurs,” or crocodylomorphs, the three most likely candidates given current evidence. At present, the origin of birds is an open question.
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Re: Birds are Theropod Dinosaurs

#17  Postby CharlieM » Sep 14, 2011 3:33 pm

theropod wrote:

CharlieM wrote:Consider marsupial moles and their relationship to Cape golden moles:

Link to news release (text snipped).


Nice example of convergent evolution, but this is not the same type of possibility as the emergence of birds from theropods. We know this because the fossil record documents the emergence of birds and how they evolved. In order for birds to have arose by the same means as the two types of mammals cited here there would have to have been a period of time wherein the birds were nothing like theropod dinosaurs. This isn't what we find.

RS


You are using theory to justify the facts. The moles look similar due to convergent evolution. Birds and theropods look similar due to the line of descent. You cannot use these statements which are dependent on the theory as evidence to confirm the theory.
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Re: Birds are Theropod Dinosaurs

#18  Postby Strontium Dog » Sep 14, 2011 4:09 pm

CharlieM wrote:You are using theory to justify the facts.


No he isn't. He's using the fact that there is a clear line of descent from theropods to birds and the fact that true moles and marsupial moles follow entirely separate lines of descent.
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Re: Birds are Theropod Dinosaurs

#19  Postby CharlieM » Sep 14, 2011 5:05 pm

One to watch for UK residents, "Planet Dinosaur" one of six on BBC1 at 8:30pm tonight.
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Re: Birds are Theropod Dinosaurs

#20  Postby mark1961 » Sep 14, 2011 5:13 pm

I think they're dinosaurs because they're tough bastards. I mean Emperor penguins-Antarctica...Winter!!!!

Well 'ard :dopey:
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