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| Sooo, dinosaurs have officially turned into birds | |
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| Tweet Topic Started: Nov 3 2012, 08:13 AM (10,709 Views) | |
| Godzillasaurus | Nov 3 2012, 08:13 AM Post #1 |
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Reptile King
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Not in the evolutionary sense, but in the sarcastic sense. Dinosaurs used to be large, scaly, beasts. Now, everyone thinks they all (yes, including sauropods) had feathers. If there have been countless dinosaur skin-impressions, and only a couple feathered non-ceoulosaur theropods, I guess that just puts feathers on every dinosaur, even when the evidence states otherwise. Anyone else bothered by this?
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| theropod | Oct 15 2013, 09:48 PM Post #46 |
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palaeontology, open source and survival enthusiast
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You have yet to provide evidence against that. Homology in similar structures in related animals should also be assumed by default unless there is counterindication (such as with mammal hair and dinosaur feathers, were we know they evolved independently). |
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| SpinoInWonderland | Oct 15 2013, 10:33 PM Post #47 |
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The madness has come back...
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I have already done so for a long time, do I need to dig them up and post them all again? Why? Can you provide a reason? So we can state that the common ancestor of Dimetrodon and Edaphosaurus should have a sail? Sauropodomorph and Carnotaurus skin impressions, all scaly and no signs of feathers at all |
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| theropod | Oct 16 2013, 01:38 AM Post #48 |
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palaeontology, open source and survival enthusiast
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Since you require me to post my evidence over and over again, why not? See my responses/comments and examples on deviantart and you know-where-else. it's simply phylogenetic bracketing "the same that makes us conclude dinosaurs had eyeballs" Because, as I have told you for soooooo many times, if there were filaments of the kind seen in extant megafauna or on scaly mammals (eg. armadillos, were hair grows between the scales), highly likely as I already demonstrated to you multiple times, it wouldn't be preserved. |
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| SpinoInWonderland | Oct 16 2013, 01:48 AM Post #49 |
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The madness has come back...
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My replies are in orange
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| Jinfengopteryx | Oct 16 2013, 02:12 AM Post #50 |
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Aspiring paleontologist, science enthusiast and armchair speculative fiction/evolution writer
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His point was that the skin impressions don't invalidate the theory. Wether we need hard evidence is another discussion, but it has nothing to do with the skin impressions. Edited by Jinfengopteryx, Oct 16 2013, 02:12 AM.
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| theropod | Oct 16 2013, 05:58 AM Post #51 |
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palaeontology, open source and survival enthusiast
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What do you consider "evidence of homology"? What evidence of homology do you find between the femora of T. rex and Alamosaurus for example? And what the hell does my opinion on Kannemeyria's integument have to do with this? We're talking about Reptiles, not synapsids.
What's because of that? In the lack of concrete evidence, we do the next best thing; Phylogenetic bracketing. In doing so, one must conclude feathers are a plesiomorphy of ornithodira, or even archosauria, because we have no reason to suspect The filaments found among various taxa within these clades are not homologous. That's no monstrous bet, it's the most parsimonous and most probable assumption we can make. It's the same way that we can conclude that an extinct squamate was scaly, and that an extinct mammal was furred (and yes, that IS the exact same thing; we know extant mammals have fur, ergo we know mammals from various clades have fur. in between, there are extinct mammals that we have no direct evidence of fur in. What should be assumed, that they had fur or that they didn't? Or do you think the fur of porcupines isn't homologous with that of other mammals?). |
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| SpinoInWonderland | Oct 16 2013, 11:36 AM Post #52 |
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The madness has come back...
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When the same or very similar structures are found consistently in a clade, like with coelurosaurian feathers. It would show whether you're conservative or liberal with integumentary structures. I already do that. As I already said somewhere else, I think you're being a bit too liberal with those brackets. There is no known evidence for the homology of quills and pycnofibres, just very loose speculation. I don't think even All Yesterdays is that speculative. Wait, what? Phylogenetic bracketing won't get you anywhere near that far! When you suggested this, you should have seen the real point behind that question of a dicynodont's integument that I've asked you. What taxon are you using to bracket feathers, even in the most liberal sensible definition, as the plesiomorphy of Archosauria? There is also no reason to suspect that pterosaur pycnofibres and dinosaur quills/feathers are homologues. Supporting a homology that is only very very loose speculation, and even suggesting a ridiculous phylogenetic spread of feathers(because really, feathers as an archosaurian plesiomorphy is ridiculous, not supported at all, and works on -0 evidence, can you show me a feathered or even quilled pseudosuchian?), is making a very, very, very monstrous bet. The suggestion of feathers as a plesiomorphy of archosaurs already makes an incomprehensible bet larger than the estimated size of the entire universe. The difference there is that we have strong evidence for homology there, in the form of living animals. The same cannot be said for the alleged homology of pycnofibres and quills/feathers, and no need to mention that very ridiculous idea of feathers as archosaur plesiomorphy, well no offense to you intended for calling out on that idea but I think if you ask the scientific community the question "Are feathers a plesiomorphic trait of Archosauria?", I'm pretty sure that they will all say no. |
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| Spinodontosaurus | Oct 16 2013, 01:51 PM Post #53 |
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Herbivore
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Please stop quote mining that study. You are using it to portray a different argument than what it actually presents. It makes you look incompetent when the foundation of your argument disagrees with you. Heres a fun quote for you, from the same study: "Concerning feathers, they may have evolved independently of squamate scales, each originating from the hypothetical roughened beta-keratinized integument of the first sauropsids. The avian overlapping scales, which cover the feet in some bird species, may have developed later in evolution, being secondarily derived from feathers." Edited by Spinodontosaurus, Oct 16 2013, 01:52 PM.
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| theropod | Oct 16 2013, 09:36 PM Post #54 |
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palaeontology, open source and survival enthusiast
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These are also found consistently in all of ornithodira.
OK then. I must admit I have no clue, It has been a long time since my last intensive research on synapsids. For answering your question I´d first have to do a literature survey on the evidence at hand. Well, phylogenetic bracketing tells us non-avian dinosaurs had stage one or higher filaments. Again, is there anything suggestive of them NOT being momologous? No! So what´s so speculative about it? It´s the same reasoning that also makes us concldue coelurosaurs had feathers! Explain that to the scientists! Alligator missisipiensis, a derived member of crurotarsi whose genes contain the information for developing feathers. this makes it likely its a plesiomorphic condition secondarily lost in adult crurotarsi. For all we know they could be, and since that explanation requires only a single evolutionary step as opposed to two, it should be preferred. Sorry if I hurt your feelings that much by suggesting Archosaurs could plesiomorphically have had feathers (again, real definition, not your "pennaceous feather=the only proper feather"). Are you OK now? We also have strong homology in the case of archosaurs, in the form of both living animals and extinct taxa with unambigous evidence for feathers.
I´m pretty sure they won´t. At least I know this study doesn´t: "Beta-keratin localization in developing alligator scales and feathers in relation to the development and evolution of feathers" |
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| Jinfengopteryx | Oct 16 2013, 10:45 PM Post #55 |
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Aspiring paleontologist, science enthusiast and armchair speculative fiction/evolution writer
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Could you show a source for that? Because this is somehow amazing to me. |
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| SpinoInWonderland | Oct 16 2013, 10:57 PM Post #56 |
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The madness has come back...
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I am not talking about those, I am talking about the ancestral non-overlapping archosaurian scales. Can you show me a non-dinosaur dinosauromorph confirmed with such? A more likely explanation is that those genes weren't originally "feather genes". Keep in mind that the same genes that allow the development of hair is also used to develop teeth and fish scales. Well pterosaur pycnofibres are usually compared with mammalian hair and are structured differently from even primitive feathers. Can you please provide me even a single actual case of a feathered/quilled pseudosuchian? Dude, that says that alligator scales are similar in composition and comes from the same genes as feathers, it does not mean that pseudosuchians have actual feathers. |
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| Fist of the North Shrimp | Oct 17 2013, 01:25 AM Post #57 |
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vá á orminum
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@Jingfengopteryx: http://www.ncbi.nlm.nih.gov/pubmed/17784647 |
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| Fist of the North Shrimp | Oct 17 2013, 01:36 AM Post #58 |
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vá á orminum
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Have you read the actual paper, or even the abstract? It means that Alligators most likely evolved from a ancestor that had integument made of feather keratin, most likely something akin to a filament. But the developement is inhibited, which is most likely is a derived state. Just like Crocs might be secondary homoitherm. Hell. Edit: Oh, and concerning the genes that influence the developement of jair and scales, they are not all the same. Of course they share some, but that is because that they are ectodermal structures and develop from the skin. Same for teeth, they are even homolougous with placoid scales. Please, before you refer to those topics again, learn some basic Cytology and Genetics. Edited by Fist of the North Shrimp, Oct 17 2013, 01:58 AM.
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| theropod | Oct 17 2013, 02:56 AM Post #59 |
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palaeontology, open source and survival enthusiast
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See the last line of my last post, that's the paper it's from (it was cited in the wikipedia article about feathers) |
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| theropod | Oct 17 2013, 03:08 AM Post #60 |
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palaeontology, open source and survival enthusiast
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Dude, slowly I'm starting to question whether you comprehended the basic concept of phylogenetic bracketing. The question is, is there even the SLIGHTEST reason to suspect they did NOT have them? You know damn well what they meant. Yes, they would totally have done a study to say "Alligator missisipiensis displays the genes for developing scales!". Furthermore, how do you explain they note these genes were Recapitulated, ie. not developed further during ontogeny? How many scaleless alligators do you see swimming or walking around? Is this sufficient evidence to suggest they were not homologous? Do you even have a source for that, and a proper description? Didn't I already provide you with enough examples of how structure in homologous filaments varies? Because I know scientists who say they are likely homologous, and in fact none who say they weren't. I'm sorry, I can only agree with Mantis shrimp. |
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