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Author | Topic: Birds and Reptiles | |||||||||||||||||||||||
arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
tegu writes: In regards to the definition of what a "bird" is, I'm just going to throw this out here. There were some rumblings not too long ago (a few years) about the idea of incorporating all of the birds into the reptile group, or folding the crocodilians and birds together into an archosaur group. Either way "Aves" would effectively cease to be its own MAJOR taxonomic group (more like "Squamata" within the group "Reptilia"). The ornithology professors flipped shits when they first heard of that though. this is more than rumblings; it is now the majority viewpoint among paleontologists, and most biologists. ornithologists didn't particularly like it, at first, but the (vocal) opponents of "birds are dinosaurs" are a small minority in the ornithology community.
I personally support making a separate archosaur group since birds and crocodiles really aren't all that different the issue is not really one of difference or similarity, but of heredity. all the evidence points to aves being a subclade of dinosauria, not a sister clade. you might be able to find some information here or here.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
faith24 writes: Birds cannot move their thigh bone so they must bend their knee while walking or running. Land creatures such as the theropods can move their thigh bone. Also birds required more oxygen than cold blooded animals and so to supply this need, birds have special lungs and supporting musculature. If birds have the same muscle structure as the dinosaurs and could move their thigh, their lungs would collapsed. what a load of sensationalist birds-came-first nonsense! allow me to break this down, point by point. while it might be true that femoral movement must be restricted (note: restricted, not prevented) in some flying birds to prevent collapse of the abdominal air sacs, this wold simply be a trade-off aimed at keeping flight muscles highly oxygenated. if there is really anything particularly to this idea at all, and i'm not convinced that there is. however, i know that when a bird relies more on use of its legs to survive, this condition is simply not found.
quote: rheas move their femora while running. this paper is a comparison between the gait and tracks of the modern rhea and theropod dinosaurs. it turns out that the ratite gait is very much like the dinosaurian one. further, here is a diagram of exactly how much an ostrich's femur rotates while running, from this article on ostrich locomotion. please note that i wrote "air sac" above, and not "lung". while it is common for creationist and birds-came-first-ist literature to group these two together, this would be a fundamental misunderstanding of evolution. it does not work in an all-or-nothing fashion, spontaneous generating whole ("irreducibly complex") systems of organs or organelles. rather, these things come into place piecemeal, and often scaffold. it is quite possible to have a partially avian respiratory system, without abdominal air sacs, or any of the other peculiar skeletal formations tied to the respiratory systems of modern birds. want proof? here's another animal that swings its femora even more widely, and has a lung similar to birds.
quote: get that one? crocodiles, more or less, have the same respiratory system as birds. neither crocodiles nor ratite birds collapse a lung when they run, and crocodiles have a completely different method of locomotion and skeletal arrangement. rather, it seems that avian flight condition evolved around and already developed respiratory system, which then became more reliant on specific adaptions for flight. these have secondarily lost in some flightless birds, such as ratites. in fact, we find that many theropod dinosaurs, specifically the maniraptors, do indeed have partially pneumatized bones, and to about the same degree as modern ratites. this means velociraptor and even t. rex had thoracic and abdominal airs sacs, like flying birds -- just in a reduced capacity. simple enough. something like the crocodilian lung existed in all dinosaurs, and progressed towards the avian lung in theropods. in flying dinosaurs, the air sacs simply greatly expanded, co-evolving with greater and greater flight capability. the earliest flying dinosaurs were not capable of extended powered flight, due in large part to their small sternums. they simply lacked the musculature. as they began to gain this musculature, they made a trade-off: more focus on flight, less on the ground. this trade-off allowed greater expansion of the abdominal air sacs -- but might have limited locomotion on the ground. this is not a problem for the dinosaurian evolution of birds. not in the slightest. Edited by arachnophilia, : No reason given. Edited by arachnophilia, : additional article Edited by arachnophilia, : sorry for the repeated and massive edits, but the more i look at this, the more the whole idea of the necessity of a restricted femur in any avian due to paradoxical collapse of the posterior air sacs.. is just a giant load of bullshit, all put forward by this one particular paper, quick & rubens (2009), with no real basis in anything. please see this blogpost for a strong critique: Page not found | ScienceBlogs
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
faith24 writes: You know, people always thought that birds evolved from dinosaurs. you have misunderstood. and so have perhaps a few members of this forum. birds did not "evolve from" dinosaurs. birds are dinosaurs. in the same way that a lizard is a reptile, or a frog is an amphibian, or you are a mammal. birds are dinosaurs. they are a highly specialized sub-group, but not a separate group.
Some suggest that the Archeopteryx is just a perching bird. picture time! (source) that should settle it, right? not just a bird, much more like a dinosaur.
There are huge differences between birds and dinosaurs that it is impossible for birds to evolved from dinosaurs. no. birds are dinosaurs. birds are highly specialized, yes. most of that specialization is in the form of ossification between bones, such as the digits becoming the carpormetacarpus. but many birds, such as rarites, retain some of the dinosaurian digits, and some, like the hoatzin, are even born with perfect maniraptoran hands, that looks nearly identical to those of a velociraptor.
i'm still confused because there are a lot of misinformation out there you don;t know which one to believe. i suggest reading anything by greg paul.
What do you think about these birds foot print? Geotimes - June 2002 - Bird Fossil Feet i think they're pretty fantastic, don't you?
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
faith24 writes: This article seem to say otherwise about dino-bird evolution. Maybe it was the other way around?http://www.physorg.com/news184959295.html Taq writes: It is speaking of a single species, microraptor. This doesn't mean that the analysis of this single species applies to ALL dino-bird intermediates. it's talking specifically about pretty much all of dromaeosauridae. there's an interesting idea, and goes something like this: all evidence points to archaeopteryx as being not only the earliest bird known to science, but also the earliest dromaeosaurid. the hyperextensible 2nd digit on the foot is a dead give-away. so, some suggest, that the last common ancestor between archaeopteryx and modern birds was also likely the last common ancestor between archaeopteryx and say velociraptor -- and that something like velociraptor secondarily lost flight. this view is apparently not popular among paleontologists. however, this is not what that article is talking about. it's more "birds came first" nonsense, ala feduccia and co. they basically claim that theropods are not dinosaurs, they're birds, and they've magically converged with dinosaurs to nearly 100% homology. and that's just plain stupid.
There is strong evidence that non-avian dinosaurs had the same type of lung: "Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina" this is actually old hat. a paper like this doesn't show that dinosaurs in general had avian air sacs. we know that they did, and have known for a long, long time. rather, it shows that this particular new find has them. even t. rex had air sacs.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Catholic Scientist writes: The emu feet still have scales on them! so, birds have two kinds of scales on their feet: reticulae (on the bottoms, the round reptilian scales) and the scutellae (flat plate-like scales on the top). it turns out that the scutes have a strong relationship to feathers, and lacking a certain protein in development, become feathers. this likely means that birds have one gene that controls feather development all over their bodies, including their feet (such as in microraptor), and another that turns them off in particular places. ie: the dinosaurian scales evolved from feather, not vice-versa.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Catholic Scientist writes: Its not that hard to imagine scales and feathers as being a variation of the same "thing". I always thought that feathers were just elongated scales but I guess I'll have to change that to some scales just being shortened feathers. it's important to note that this is not more birds-came-first nonsense. it just shows that perhaps feathers are further down the dinosaurian family tree than previously thought. this has been confirmed recently, with the discovery of an ornithischian dinosaur with primitive feathers. the strong homology between tianyulong's feathers and theropod feathers indicates that feathers probably go back to before the divergence of saurischia and ornithischia. ie: the very earliest dinosaurs might have been walking around sporting similar proto-feathers, and feathers might even be a defining characteristic for dinosaurs (like hair for mammals). of course, they were probably lost secondarily in larger varieties. in any case, i personally feel that feathers probably go back just slightly further than that, perhaps to basal archosaurs, and go hand-in-hand with the evolution of endotherms. for instance, pterosaurs sometimes have "hair" covering their bodies, and iirc, these "hairs" are strongly related to feathers -- they just didn't evolve into the flight surfaces and were strictly used for warmth. also interesting is the fact that crocodiles have scutes. i'm not sure if these are related to feathers in any way, but wouldn't it be truly strange if the basal psuedosuchians were feathered, and the crocodiles lost their feathers secondarily to adapt better to an aquatic environment? i am not a paleontologist, and at least some of these ideas would be very unpopular among actual paleontologists. i'm sure this is partly because they're generally used to support the aforementioned "birds came first" idea, which states that birds evolved in a separate lineage from basal archosaurs (something very lizard-like, actually), and theropods are not actually dinosaurs. which is so stupid, i can't even describe. see the links i posted above. i am very much not supporting this idea, because it stretches convergent evolution to the point of incredulity.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Bluejay writes: This seems highly unrealistic. Scutes clearly predate feathers in the fossil record. I think they even predate the diapsid-synapsid split, so it seems unlikely that feathers predated that. I'm also highly skeptical because apparently none of the cited work by Alan Brush demonstrating that scutes happen when feather development is suppressed were published or peer-reviewed. Also, I'm not sure that a developmental pathway defaulting to a certain end product is really evidence that that end product is the primitive condition. I'm no geneticist, though, so I could be wrong. well, i knew someone would bring up the potential shortcomings of this idea. thanks for that. yes, i really don't know, but it's an interesting idea.
I could be convinced, however, if they could cause crocodilians to develop feathers instead of scutes using the same techniques. yes, that would pretty cool. the question -- and i'd like to know too -- is whether or not crocodilian scutes are related to avian/dinosaurian scutes. it's entirely possible the avian ones are merely secondary adaptions and not actually related to scutes in other archosaurs at all. it's also possible that this particular gene was in place before the evolution of feathers, the secondary modifications of it is what caused microraptor to grow feathers on its feet. i think it's an interesting area of study, and needs some more examination. in any case, the ornithiscian with proto-feathers certainly pushes feathers further down the family tree. Edited by arachnophilia, : No reason given.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
pisture post!
1. Dinos and most modern reptiles are oviparous, producing eggs that hatch outside of the body. crocodile egg chicken egg most reptiles are oviparous. most dinosaurs are oviparous. all birds are oviparous.
2. Crocodiles have similar abdominal ribs to dinosaurs. crocodile gastralia tyrannosaurus rex gastralia (from sue) note: it's hard to see in the picture, i can't find an especially good depiction of it easily, but theropod gastralia interlock, and are much more diminutive than the giant plates of a crocodile. it should be noted that true gastralia are not typically found in reptiles -- except crocodiles.
3. no fur sinosauropteryx "fur" 4. both reptiles whereas birds are not. dinosaurs are reptiles much in the same way you're an amphibian. you're not cold blooded (i think), you don't go through any metamorposis, and you were born live. you don't need to be around water to keep your skin hydrated. similarly, dinosaurs are endothermic, covered in feathers, stand upright, etc. they don't hug the ground for warmth like a reptile -- they're the reason that "reptile" is not longer a scientifically recognized clade. they make "reptilia" paraphyletic. and your argument is just a little silly anyways, see as how birds are a subgroup of dinosaurs. if B is a subgroup of A, and C is a subgroup of B, C is a subgroup of A.
5. both land dwellers, unlike birds ostriches in israel all birds are ground-based. some live in trees. some on glaciers. none remain in the air constantly. some can't even fly.
6. small similar appearing heads and swishy tails, unlike birds. dromaeosaur zygopophyses while the dromaeosaurid (that includes archie's) tail is still somewhat flexible, it wouldn't have been very "swishy". i know they show the "velociraptors" in jurassic park swishing their tails about, but they would not have been able to do this. above is a photo of what those tails actually looked like: their pre- and postzygoopophyses are extended for several vertebrae, making their tails somewhat stiff, particularly towards the end. compare this to the tip of a crocodile's tail, which must move readily side-to-side to power their travel through water, and to a bird's tail, in which the end is totally fused into a pygostyle. the only similarity to the crocodile's in length, and that gets drastically shorter in cretaceous birds, and not all at once. tail length in dinosaurs/birds as for heads, saltwater crocodile skull
velociraptor skull terror bird skull crocodiles have vertically flattened skulls, which are good for lurking just under the water, while still being able to breathe and see above water. dinosaurs and birds have laterally flattened skulls.
7. Both cohabited whereas birds did not, according to conventional paleontology but not according to the Genesis record. i'm not even sure what that's supposed to mean.
8. Both had teeth and more similar bone structures unlike birds crocodile sketelon archaeopteryx bird and i'll find you a picture of bone cross-sections, if you really like. birds and dinosaurs often have hollow bones; crocodiles do not.
9. Overall appearance of lizards, crocks, iguanas, etc more resemble dinos than birds. "green" iguana american alligator archaeopteryx mockingbird dinosaurs look like what now? now, i know i detailed up above why archaeopteryx is clearly not "just a bird" and is very much a theropod dinosaur. but it's important to note just how much closer dinosaurs are to birds than they are to crocodiles. clearly, they are related to both. Edited by arachnophilia, : No reason given. Edited by arachnophilia, : background color on transparent .png Edited by arachnophilia, : turns out, the "crocodile bird" is a complete myth.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Bluejay writes: Birds are reptiles. And, even if they're not, you can't use the point you're trying to prove as evidence for the point you're trying to prove. i was less than technical with buz. but i'll point here that the word you're looking for is "sauropsid". crocodiles, dinosaurs, birds, and turtles are sauropsids. "reptilia" is a paraphyletic group which specifically excludes birds by definition, and thanks to the re-organization of the cladistic trees, isn't especially appropriate anymore. Also, there are dinosaurs that have beaks! well, ornithischian ones, anyways. i thought about going there, but since their beaks are simply convergent, and they're not especially closely related to the dinosaurs that lead up to birds, i thought it would be a little disingenuous.
Scientific record cites evolution as reason for leg differences and size. indeed. a crocodile's amrs and legs have a very different function from those of a velociraptor.
What? You mean reptiles and dinosaurs lived at the same time and place, whereas birds didn't? If so, you're wrong. if that's what he means, it's quite silly indeed. all three lived in the cretaceous period. Edited by arachnophilia, : background color on transparent .png image
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
ha! very nice. that'll teach me not to track down an original source for an image, and read the page. thanks for that correction, learned something new today.
anyways, in that case, i'll go ahead and take that image down. it was pretty pointless anyways -- i think we all know that birds and crocodiles are both currently alive and share habitats, and that at one time, birds, non-avian dinosaurs, and crocodiles were all alive and shared habitats. i still have no idea what the heck buz's comment was supposed to mean, anyways.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Buzsaw writes: That one dino is considered bird it's really substantially more than one dinosaur, buz. it's every bird that is considered a dinosaur. the same way that every primate is considered a mammal. and, on top of that, there are a whole host of non-avian dinosaurs with feathers. these are actually the ones we don't consider birds, proper. here are the ones we do.
doesn't mean birds are generally considered reptiles. nope. as i posted above, "reptile" is a paraphyletic group, so this point is pretty moot. "reptile" is defined as the class of sauropsids (and basal amniotes) that excludes birds. that's the definition of the colloquial term, versus the cladistic tree. the colloquial definition means nothing, really, in terms of actual evolutionary origin. note that the diagram is missing "dinosauria", as it's really under debate whether or not dinosaurs should be considered reptiles, because they are so dissimilar from every other "reptile".
More objectively, from what I've read, the consensus is that they descended from dinos. no, birds are dinosaurs. they are a highly specialized subgroup of dinosaurs, but they are dinosaurs.
My position that the Biblical record is correct would require many adjustments to the changed physique such as the flattened croc and gater heads, the rear claw in the foot for grasping smaller things, the leg structure, etc. well, you can't argue with "it must have been a miracle" in the face of all the evidence that says exactly the opposite. crocodiles would have had to re-evolve several features, extremely convergently with other modern sauropsids. like, several digits.
Conclusion: there are not more similarities, by and large, of birds/dinos than reptiles/dinos. It's all assumed to accomodate evolution. yeah, let's see that. a. crocodile b. coelophysis c. compsognathus d. archaeopteryx e. velociraptor so let's play, "one of these things is not like the other". keep in mind that one of these is a bird. another is a mostly-ectothermic "reptile". which one is the least similar? oh, and please note that, to be fair, i have included one of the most primitive dinosaurs, the mid-triassic coelophysis, so named for its bird-like hollow bones. Edited by arachnophilia, : typo
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Buzsaw writes: Dinos and modern reptiles whereas birds are not. - Debatable Dinos are reptiles , unlike birds - Debatable Both cohabited whereas birds did not, Both had teeth and more similar bone structures unlike birds - Debatable buz, this is nonsense. i don't mean that your ideas are ridiculous. i mean, nobody knows what the heck you're even talking about. can you rephrase these in ways that make sense? for instance, your first statement lacks a verb. dinos and modern reptiles are what whereas birds are not? and what the heck do you mean by cohabited?
Overall appearance of lizards, crocks, iguanas, etc more resemble dinos than birds. By observation? Yes. Ask anybody on the street to look at lizards, iguanas, gators and crocks whether these by and large look more like dinos, both having swishy tails and similar looking heads than most birds and they will say that they do. most people are idiots. further, most people think dinosaurs look like this: deinonychus antirrhopus, the "velociraptor" (paul 1988) as depicted in "jurassic park" and not this: deinonychus antirrhopus, as it would have really appeared if you show them the far more accurate depiction above, they will invariably say "bird". the fact of the matter is that people thought of dinosaurs as glorified lizards for quite a long time, and frequently depicted them styled after lizards. the fact that when you say "dinosaur" most people think of something very lizard-like does not mean that dinosaurs actually were lizard-like. it just means that people have had inaccurate preconceptions drilled into their heads.
Digits of birds and theropod dinosaurs found to be non-homologous. What has been assumed for the last two decades by prominent paleontologists turns out to be questionable, as is so often the case in the conventional science arena. alan feduccia is not a good person to discuss regarding avian evolution. he's basically the crank of the paleontological world -- him and his cronies larry martin and john ruben. not only are they wrong, but they frequently tout their research as proclaiming things it does not ("birds came first!"). on top of that, none of them are actually arguing for what you would like: they're arguing that birds (and, ahem, theropod dinosaurs) are not actually dinosaurs, but evolved separately and convergently from archosaurs. none of them question evolution, nevermind that birds are theropods. just that they're dinosaurs. which, frankly, is dumb. as for the specific points, here's greg paul on the subject (he's the "paul" i mentioned above, under the jurassic park picture).
quote: just to illustrate how truly dumb this is, let me again post pictures. deinonychus archaeopteryx hoatzin chick (modern bird) hoatzin adult (modern bird) easy to see now? the digits are pretty clearly the same. this different numbering is an arbitrary thing that ornithologists have done because they assumed that birds lost their other digits symmetrically, where as paleontology shows that they did not.
Too often scientists see what they want to see ruben? yeah, i saw a documentary which covered his incredibly ludicrous reconstruction of microraptor gui. i posted it on my blog a while back, and i will now re-post it here.
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Too often scientists see what they want to see so, since you brought up ruben and martin's just plain silly reconstruction of microraptor, i thought i would re-post this entry from my blog, originally posted sept 21. 2008, after viewing a documentary in which martin appeared. please note that this is a blog entry, but it's full of useful links and pictures. please note martin's hilarious reaction to seeing the proper scientific reconstruction of microraptor, and how he very obviously only sees what he wants to.
quote:
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Buzsaw writes: In the Wyoming Rocky Mtn region where I grew up and on the desert I've seen some really fast little miniature somewhat dino looking lizzards which dart around likity split. for very, very short bursts of speed, yes. no "reptile" is an endurance runner. they simply aren't built for it. iirc, the side-to-side running motion actually impairs respiration in reptiles. (perhaps a herpetologist can comment?) but this is definitely not the case in a dinosaur -- their respiration is actually aided by their running. this is the primary advantage that allowed them to become the dominant lifeforms in the mesozoic. the could out-endure any of their prey. look at how a crocodile hunts, vs how an ostrich avoids being eaten. the crocodile is an ambush predator. if it doesn't catch you in the first snap, it simply gives up. they don't give chase. the ostrich will keep running, and running, until it's safe.
Assuming the accuracy of the Biblical record, the dino reptiles pre-flood would have likely been very lively, given the perfect warm climate that is implicated before the flood changed things. so, this is a science forum, buz. we can't just assume things like the accuracy of the bible, or even that genesis is a record of anything. plus, dinosaurs lived in cold climates, too.
Perhaps I missed it but what about the study which I cited about the non-homogeneous digits of dino & bird? it's nonsense, from "birds came first" ornithologists and crackpots. they assume that birds would have lost their digits symmetrically, and thus they cannot be homologous to the theropod hand, which is non-symmetric. this is obviously a bad assumption for a number of reasons:
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arachnophilia Member (Idle past 1365 days) Posts: 9069 From: god's waiting room Joined: |
Bluejay writes: Actually, I was picturing oviraptorids when I wrote that. Now that I think about it, it is kind of a disingenuous comment, given the homology implications. I probably should have avoided that. oh, yes, right. oviraptors. heh, i knew i was forgetting something obvious. oviraptors are closely related to the origin of birds, though the beak is still somewhat convergent, as birds come from the non-beaked theropods. so, that's not nearly as disingenuous as the psittacosaurus picture i almost posted. so, uh, carry on. don't mind me.
I tend to avoid the sciencespeak entirely with Buzsaw. i know what you mean. but it's important to note (and i've pointed it out directly to him as well) as he keeps throwing around this "reptile" term, when "reptile" is really just an a completely arbitrary term that excludes birds and possibly dinosaurs by definition, and has no real relationship to any particular clade.
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