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Post by kuni on Feb 17, 2009 6:38:36 GMT
Stoneage,
That's an "argument from incredulity", and isn't particularly useful...
In any case, birds had to go from a "piston-style" breathing method to a diaphragm-less method, regardless of whether they descended from an archosauromorph OR a theropod. In addition, organ structure is generally incredibly difficult to accurate ascertain from fossils, unless it's an organ that has the simple decency to be mostly surrounded by bone, like a brain, etc.
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Post by Dinotoyforum on Feb 17, 2009 21:43:50 GMT
EN Kurochkin Parallel evolution of theropod dinosaurs and birds Journal Entomological Review Issue Volume 86, Supplement 1 / January, 2006 thanks
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Post by Dinotoyforum on Feb 17, 2009 22:06:47 GMT
As a practicing and published cladist I am aware of the pitfalls of the cladistic methodology, yet for all its faults, cladistics is still the most objective method for developing and testing hypotheses of relationships amongst organisms. It is important to note (and it is often overlooked) that a cladogram is not a phylogenetic tree - the phylogenetic tree is a hypothesis derived from the cladogram. A cladogram simply shows relative morphological similarity (in the case of fossils) based on parsimony. My point is that there is nothing intrinsically wrong with cladistics itself, methodologically speaking. The assumption of parsimony is explicit to the method so there is no deceit going on. What is up for discussion is whether cladistics and cladograms are a good basis for constructing phylogenetic trees, but more importantly, if not, then how do we unravel the tree of life - is it a lost cause?
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Post by kuni on Feb 18, 2009 6:36:24 GMT
Yeah, morphological parsimony has already been shown to have issues with modern datasets, which is why most phylogeneticists choose sequence data when they can get it. Fossils are of course a lot trickier -- come to think of it, since most fossils are supposed to hit genus level only, I wonder if someone could take a modern dataset, "degrade" it by removing sequence data and keeping morphology, but still accurately predict genus-level data from it.
Of course, "genus" isn't an inherently meaningful concept outside of paleontology -- heck, a paleontological genus may have no relationship with a genus of living organisms.
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Post by deanm on Feb 18, 2009 20:56:53 GMT
There are at least two different schools of thought on sequence data.
School 1: Sequence data "better than" morphological characters/data.
School 2. Morphological data "better than" Sequence data
School 3. Some of the above and others... (generally put three taxonomists in a room and you will get at least four opinions)
As a friend of mine told me each viewpoint has some merit but ultimately both will need to be considered when suggesting a cladogram. He also uses behaviorial, ecological, geographic distribution, etc as characters in his phylogenetic analyses.
Sequence data can yield alot of phylogenetic characters relative to morphological characters but since it is from a single or very few genes (typically less than 5) there are questions if it represents the organisms phylogeny or just the gene in question phyologeny (the two are not as tied to the hip as most people believe). Several studies have shown that different genes from the same organisms can give different cladograms.
Can you trully seperate phylogentic characters from the same gene and treat them as independant characters relative to each other better than those from one or more morphological structures?
The converse position taken by some taxonomists is that a morphological stucture is formed from the actions of more than one gene so it does represent the organisms evolutionary history better.
So is a lot of phylogenetic information from a single or few genes equal to that of a few morphological characters?
This has been a on-going debate between the various camps.
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Post by stoneage on Feb 19, 2009 2:39:53 GMT
Stoneage, That's an "argument from incredulity", and isn't particularly useful... In any case, birds had to go from a "piston-style" breathing method to a diaphragm-less method, regardless of whether they descended from an archosauromorph OR a theropod. In addition, organ structure is generally incredibly difficult to accurate ascertain from fossils, unless it's an organ that has the simple decency to be mostly surrounded by bone, like a brain, etc. Well the backbone and ribcage surround the internal organs. In dinosaurs the ribcage is compressed laterally while in birds the ribcage is compressed dorsoventrally. What makes the brain so special? Homo neanderthal had a bigger brain then Homo sapien. Does that mean he was smarter. As far as cladistics are concerned bones are mostly all you have to work with. The fossil record is incomplete. There are somewhere near 800 Dinosaur species. Most of them come from incomplete specimens. Many times their is just a tooth, jaw bone, skull, fragments, etc. All this scant evidence is given a name and placed in a cladogram. That is how we came up with Trachodon. Birds and Dinosaurs are related, Did birds come along relatively late from a particular group of Dinosaurs, or did they diverge early and share a common ancestor? I think they diverged early on from a common ancestor. ;D
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Post by tomhet on Feb 19, 2009 7:22:00 GMT
I think they diverged early on from a common ancestor. ;D
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Post by kuni on Feb 19, 2009 21:27:32 GMT
Stoneage, That's an "argument from incredulity", and isn't particularly useful... In any case, birds had to go from a "piston-style" breathing method to a diaphragm-less method, regardless of whether they descended from an archosauromorph OR a theropod. In addition, organ structure is generally incredibly difficult to accurate ascertain from fossils, unless it's an organ that has the simple decency to be mostly surrounded by bone, like a brain, etc. Well the backbone and ribcage surround the internal organs. In dinosaurs the ribcage is compressed laterally while in birds the ribcage is compressed dorsoventrally. What makes the brain so special? Homo neanderthal had a bigger brain then Homo sapien. Does that mean he was smarter. As far as cladistics are concerned bones are mostly all you have to work with. The fossil record is incomplete. There are somewhere near 800 Dinosaur species. Most of them come from incomplete specimens. Many times their is just a tooth, jaw bone, skull, fragments, etc. All this scant evidence is given a name and placed in a cladogram. That is how we came up with Trachodon. Birds and Dinosaurs are related, Did birds come along relatively late from a particular group of Dinosaurs, or did they diverge early and share a common ancestor? I think they diverged early on from a common ancestor. ;D Maybe you think that, but I'm sure not seeing the chain of reasoning here - you jump from ribcages to braincases, incomplete skeletons to cladograms. I'm especially not seeing evidence - in fact, your point about incomplete skeletons leads one to prefer the birds-as-dinosaurs hypothesis, because we have many more complete skeletons explaining the morphological transition than stuff from archosauromorphs.
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Post by stoneage on Feb 20, 2009 3:51:15 GMT
Well the backbone and ribcage surround the internal organs. In dinosaurs the ribcage is compressed laterally while in birds the ribcage is compressed dorsoventrally. What makes the brain so special? Homo neanderthal had a bigger brain then Homo sapien. Does that mean he was smarter. As far as cladistics are concerned bones are mostly all you have to work with. The fossil record is incomplete. There are somewhere near 800 Dinosaur species. Most of them come from incomplete specimens. Many times their is just a tooth, jaw bone, skull, fragments, etc. All this scant evidence is given a name and placed in a cladogram. That is how we came up with Trachodon. Birds and Dinosaurs are related, Did birds come along relatively late from a particular group of Dinosaurs, or did they diverge early and share a common ancestor? I think they diverged early on from a common ancestor. ;D Maybe you think that, but I'm sure not seeing the chain of reasoning here - you jump from ribcages to braincases, incomplete skeletons to cladograms. I'm especially not seeing evidence - in fact, your point about incomplete skeletons leads one to prefer the birds-as-dinosaurs hypothesis, because we have many more complete skeletons explaining the morphological transition than stuff from archosauromorphs. ;D Well so far your evidence is "the majority of Paleontologist think, the majority of evidence favors bird, Nope your incorrect (as usual)", etc. You have given no evidence, just a bunch of meaningless generalizations! You have proved nothing and furthermore you can't ! ;D
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Post by kuni on Feb 20, 2009 4:15:35 GMT
Hey, I've had conversations with a number of dino-bird folks, and the fact is, the Feduccia theory is pretty much going to die out as soon as he does. That's usually what happens when one hypothesis loses out in favor of another one -- it's why people accept things like plate tectonics now, after all. Oh, and that evidence thing: *Fossilized feathered dinosaurs with morphology similar to birds, in fact so similar that the distinction between "bird" and "dinosaur" is tricky at best *Fossil and developmental evidence of digit origin in theropods and birds, turns out they're the same *wing-assisted incline running as a basal pre-flight behavior Now that the Feduccia camp doesn't even have the developmental stuff on their side, they're basically finished. Just admit that the raptors in JP should be fluffy and there's no more need to argue.
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Post by stoneage on Feb 20, 2009 4:41:43 GMT
Hey, I've had conversations with a number of dino-bird folks, and the fact is, the Feduccia theory is pretty much going to die out as soon as he does. That's usually what happens when one hypothesis loses out in favor of another one -- it's why people accept things like plate tectonics now, after all. Oh, and that evidence thing: *Fossilized feathered dinosaurs with morphology similar to birds, in fact so similar that the distinction between "bird" and "dinosaur" is tricky at best *Fossil and developmental evidence of digit origin in theropods and birds, turns out they're the same *wing-assisted incline running as a basal pre-flight behavior Now that the Feduccia camp doesn't even have the developmental stuff on their side, they're basically finished. Just admit that the raptors in JP should be fluffy and there's no more need to argue. ;D Feathered dinosaurs have features that are about 10 to 1 different then birds. Who says that the digits of dinosaurs and birds are the same, show me? Wing assisted incline running is a theory and proves nothing. Velociraptor had feather like structures on its arms but that doesn't mean it evolved into modern day birds. More then likely it was just another dead end. ;D
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Post by kuni on Feb 20, 2009 4:56:49 GMT
I'm not sure what "feathers that are 10 to 1 different" means precisely, but HAVING feathers trumps "common ancestor we haven't found yet" -- there's evidence for one position, and not for the other. You'll have to wait a bit for the digit paper, but there was that SICB talk with a ceratosaur relative that shows the digit pattern matches up (and it was rigorously tested with phylogenetics, not handwaved, too!). WAIR is "just a theory", but it explains a lot. Basically, none of these lines of evidence is perfect, but it's all still pretty good (esp for paleo), and taken together, trumps the nonexistent evidence for an archosauromorph. Heck, even Feduccia thinks raptors were derived birds now, even if he's still holding out on other stuff. I'm afraid that raptors are feathered no matter how this comes out.
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Post by Dinotoyforum on Feb 20, 2009 11:52:27 GMT
;D Feathered dinosaurs have features that are about 10 to 1 different then birds. Yeah, I'm not sure what you mean by this, don't the similarities faaaaaaar outweigh the differences? Did you make the figure up? Of course this depends on your perspective: compare a velociraptor a bird and a fish and your similarities between the former are off the scale. Compare a Velociraptor a bird and a crocodile and the the similarities between the former are reduced (yet still overwhelming). From what perspective are you looking at it? In any case, it's the similarities (shared derived characters) that are important and used for determining relationships in cladistics (to get back on topic) Differences are inevitable and arise through the evolutionary process. If these differences are unique then they are not even put into the cladistic analysis - they do not provide any relationship data (they are used for diagnostic purposes). If you know of a group of organisms which shares more characters with birds than maniraptors share with birds, then we'd have something to discuss. But you don't So nah nah ;D
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Post by sid on Feb 20, 2009 18:18:20 GMT
If you know of a group of organisms which shares more characters with birds than maniraptors share with birds, then we'd have something to discuss. But you don't So nah nah ;D But considering that more than 90% of the species that lived in the Mesozoic didn't fossilized,we can't be sure that something like that (maybe even outside the dinosauria) didnt existed somewhere... ...So,basically,nah nah nah ;D
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Post by Dinotoyforum on Feb 20, 2009 19:06:40 GMT
If you know of a group of organisms which shares more characters with birds than maniraptors share with birds, then we'd have something to discuss. But you don't So nah nah ;D But considering that more than 90% of the species that lived in the Mesozoic didn't fossilized,we can't be sure that something like that (maybe even outside the dinosauria) didnt existed somewhere... ...So,basically,nah nah nah ;D You're using lack of evidence as evidence? how perverse. ;D There are infinite possible alternatives to the dino-bird theory and infinite possible pieces of evidence in support of these alternatives. To believe in any of them requires faith. Possibilities do not counter evidence. Birds might have arrived in a saucer from jupiter - we cant be sure they didn't - their duck saucer may be buried under the ice in the Arctic. But I'm not going to reject the dino-bird theory and all its evidence based on the possibility that there might be a duck-saucer under the ice. Are you?
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Post by sid on Feb 20, 2009 23:29:22 GMT
You're using lack of evidence as evidence? how perverse. ;D There are infinite possible alternatives to the dino-bird theory and infinite possible pieces of evidence in support of these alternatives. To believe in any of them requires faith. Possibilities do not counter evidence. Birds might have arrived in a saucer from jupiter - we cant be sure they didn't - their duck saucer may be buried under the ice in the Arctic. But I'm not going to reject the dino-bird theory and all its evidence based on the possibility that there might be a duck-saucer under the ice. Are you? I got it! Space ducks (Duck Dodger maybe?) came to earth many,many millions of years ago and taught dinosaurs how to fly,then they went away,returning to their far away galaxy...Am i right,am i? ;D ;D ;D
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Post by Dinotoyforum on Feb 21, 2009 0:03:21 GMT
;D you have to come to your own conclusions
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Post by [][][]cordylus[][][] on Feb 21, 2009 0:46:40 GMT
I think the maniraptora and birds both shared a feathered, bird-like-dinosaur ancestor. Some turned into feathered dinosaurs like ceolurosaurs, some turned into birds. How does that sound stoneage? ;D I think most of the anti-feather people/beings ( ;D ) got a little too used to scaly "raptors" and other theropods. ;D
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Post by Tyrannax on Feb 21, 2009 1:05:16 GMT
^ Sounds reasonable to me.
Sid, I wouldn't bet on your Duck Dodgers theory. ;D
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Post by stoneage on Feb 22, 2009 21:03:48 GMT
;D Feathered dinosaurs have features that are about 10 to 1 different then birds. Yeah, I'm not sure what you mean by this, don't the similarities faaaaaaar outweigh the differences? Did you make the figure up? Of course this depends on your perspective: compare a velociraptor a bird and a fish and your similarities between the former are off the scale. Compare a Velociraptor a bird and a crocodile and the the similarities between the former are reduced (yet still overwhelming). From what perspective are you looking at it? In any case, it's the similarities (shared derived characters) that are important and used for determining relationships in cladistics (to get back on topic) Differences are inevitable and arise through the evolutionary process. If these differences are unique then they are not even put into the cladistic analysis - they do not provide any relationship data (they are used for diagnostic purposes). If you know of a group of organisms which shares more characters with birds than maniraptors share with birds, then we'd have something to discuss. But you don't So nah nah ;D First I like to say that "So nah nah" is not an argument for dino-bird evolution. My 10 to 1 quote goes back to when you were telling me that you believed Archaeopteryx was a bird. I read something about Microraptor which listed some of its similaritys and differences with modern birds. However I can't find the article right now. Your statement is very well written and impressive. Are we really sure what the differences and similaritys are? And can we really chart the evolutionary path effectively? Getting back to my discussion with Kuni who claims that differences in anatomy tell us nothing about the inner workings of the internal organs. He claims we can not tell if Dinosaurs had diaphragms. However we do have the remains of Scipionyx samanticus. This Italian Dino-Bird has the well preserved intact skeleton and remnants of the liver, intestines, windpipe and even muscles. Professor John Ruben of Oregon State University, who teachs Dinosaur Biology, Comparative Vertebrate Anatomy, Vertebrate Physiology (respiratory and cardiovascular), and Enviornmental Physiology, examined this specimen with a 70 watt ultraviolet light. The lungs and other structures found in the dinosaur bear little similarity to that of modern birds. The body cavity is seperated into two parts, one containing the lungs and heart, and the other holding the liver and guts. This type of body cavity partitioning is only seen in living animals that use a diaphragm to help ventilate the lungs, such as crocodiles and mammals. The dinosaurs intestines and liver were located toward its tail end. Using and ultraviolet light to illuminate the liver, researchers saw that the organ had a front edge similar to a crocodile's liver and rested against the spot where a diaphragm normally would go. Birds have no diaphragm. Ruben and colleagues found other differences such as the position of the dinosaur's windpipe in comparison to birds' windpipes. Also there was a remnant of a muscle in the right orientation to assist in crocodile-style breathing. Ruben contends that Sciponyx was ectothermic. It had a low metabolic rate while at rest, which is an excellent strategy for conserving energy. But its enhanced lung ventilation capacity gave it the potential for the type of agressive, extended activity of birds and mammals.Theropod dinosaurs were fast , dangerous animals that were not sluggish. They were capable of conserving energy most of the time and when needed go into overdrive. Ruben states this may have evolved from early crocodiles that lived on land and needed extra energy to catch prey. Endothermy is not a prerequistie for achieving a high metabolic rate, given a highly efficient respiratory system and a warm climate. Ruben has also examined Sinosauropteryx which has soft tissue traces and discernable gut contents. The soft tissue impressions in the abdominal chest cavity match the shape and placement of the diaphragm in crocodiles. Birds don't have a abdominal cavity that is seperated from the thoracic cavity. John Ruben, an expert in respiratory physiology, said "a transition from a crocodilian (or theropod) to a bird lung would be impossible, because the transitional animal would have a life-threatening hernia or hole in its diaphragm." According to Ruben this means that if there is a relationship between birds and dinosaurs, "it's not the linear relationship you see in museum displays." Remember the wishbone is found in the basal archosaur Longisquama, and in some theropods not closely related (cladistically) to birds(carnosaurs), and it is absent in some ground birds. So this character is adaptive(meaning convergence is likely), easily lost and sporadically distributed in dinosaurs. This is the nature of science. ;D
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