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Old 01-18-2019, 10:00 PM
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What is--and isn't--a dinosaur?


In another recent thread, somebody asked about the possibility of the Loch Ness Monster being a Plesiosaur. The general consensus was "no." But one person weighed in with the statement that the Plesiosaur was not a dinosaur. I have heard the same about Dimetrodons and Pteradactyls. Also, that chickens are dinosaurs. "Dinosaur" is rapidly becoming a non-term that doesn't usefully describe much.

Is there a definitive list of creatures that are generally considered by the public to be dinosaurs, but fail to meet some specific scientific definition of the term? Most of my knowledge of dinosaurs came from that ubiquitous set of plastic toys every boy had in the 1960s, and of course some of those sets included woolly mammoths and sabertooth tigers, so as learning tools, those were suspect.
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Old 01-18-2019, 10:33 PM
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From the wiki:


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Under phylogenetic nomenclature, dinosaurs are usually defined as the group consisting of the most recent common ancestor (MRCA) of Triceratops and Neornithes, and all its descendants. It has also been suggested that Dinosauria be defined with respect to the MRCA of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia", encompassing ankylosaurians (armored herbivorous quadrupeds), stegosaurians (plated herbivorous quadrupeds), ceratopsians (herbivorous quadrupeds with horns and frills), ornithopods (bipedal or quadrupedal herbivores including "duck-bills"), theropods (mostly bipedal carnivores and birds), and sauropodomorphs (mostly large herbivorous quadrupeds with long necks and tails).
Pterosaurs are not dinosaurs, nor are icthyosaurs, plesiosaurs, or mosasaurs.


ETA here is a pretty good primer.

Last edited by Darren Garrison; 01-18-2019 at 10:35 PM.
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Old 01-18-2019, 11:45 PM
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Originally Posted by Horatio Hellpop View Post
"Dinosaur" is rapidly becoming a non-term that doesn't usefully describe much.
This is a rather ignorant thing to say. "Dinosaur" has a perfectly well-understood meaning which, while it doesn't square with the prior superstition of "Them Big Bad Dead Things What Were Dumb And Big", is extremely useful to paleontologists and biologists in general.

We're learning more and more about how animals are related, and, due to that, are learning how to group like animals together, as opposed to previous classifications which boiled down to "Things What Got Wings" and "Things What Swim Real Good" and "Things You Can Eat On Friday" and so on, which hurt understanding more than they helped it. In terms of useful descriptions, going by families and lineage is more useful than going by what kinda happened to look similar to a barely-trained Natural Philosopher back in the era before microscopes or toilet paper.
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Old 01-19-2019, 09:30 AM
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Yeah "rapid" is not the term for stuff that dinosaur-obsessed 80s Kindergartners were on top of.

Last edited by Ruken; 01-19-2019 at 09:30 AM.
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Old 01-19-2019, 11:35 AM
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In layman's terms -- during the early Triassic, a few groups of reptiles split off from another group of reptiles. The original group (which is already only a subset of reptiles) was called the Archosaurs. They went down a few lineages. Pteradactyla (flying reptiles from the same era as the dinosaurs) are in this group. So are the true dinosaurs. So are modern crocodiles.

Plesiosaurs and mosasaurs are entirely distinct lineages from the Archosaurs. Mosasaurs are actually monitor lizards that took to the sea and became adapted to an aquatic lifestyle. They aren't dinosaurs -- they are lizards. A lizard can't evolve into a dinosaur -- it can develop similar traits, and it can become so distinct from its ancestors that it is no longer truly a lizard (although generally mosasaurs are considered true lizards) but it can't become a dinosaur.

Plesiosaurs are a lot murkier. The current theory is that they split off from an earlier ancestor of the Archosaurs -- so a group of reptiles split off into what would become the plesiosaurs and what would become the Archosaurs, and the Archosaur lineage split off again, into dinosaurs and crocodiles.

Dimetrodon went extinct millions of years before the dinosaurs first evolved. Not only are they not dinosaurs -- they are actually more closely related to mammals. That's right -- Dimetrodon is our very distant cousin. One group of reptiles became what are known as Stem Mammals -- aka the first Synapsids. Synapsids are all mammals, and all proto-mammals that are more closely related to mammals than to any group of reptiles, and Dimetrodon is in that group. To paleontologists who know what they're looking for, a Dimetrodon skull looks far more mammalian than reptilian.

So to sum it up -- pteranodons are about as closely related to dinosaurs as crocodiles are. Unless you're going to call a modern crocodile a dinosaur, you shouldn't call a pteranodon one either. Plesiosaurs are a little bit more distant, but still in the same group. Mosasaurs are about as far removed from dinosaurs as you can get while still being a reptile, and Dimetrodon are more closely related to us than they are to any dinosaur.

All birds are theoropods dinosaurs -- members of the same group as Velociraptor and Tyrannosaurus. The only way you can define a bird as not being a dinosaur is if you arbitrarily define dinosaurs as being extinct members of their group, and then you run into trouble. There were birds earlier than 65 million years ago, who coexisted with more traditional dinosaurs. Where do you draw the line?
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Old 01-19-2019, 12:03 PM
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All birds are theoropods dinosaurs -- members of the same group as Velociraptor and Tyrannosaurus. The only way you can define a bird as not being a dinosaur is if you arbitrarily define dinosaurs as being extinct members of their group, and then you run into trouble. There were birds earlier than 65 million years ago, who coexisted with more traditional dinosaurs. Where do you draw the line?
Despite your excellent explanation, you end with this. If there were "birds" earlier than 65 million that were different from "traditional dinosaurs", then in fact you must be saying there are specific differences between birds and traditional dinosaurs other than extinction. So why don't those things provide a way to say this group is dinosaurs and that group is not without relying on extinction.
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Old 01-19-2019, 12:09 PM
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Despite your excellent explanation, you end with this. If there were "birds" earlier than 65 million that were different from "traditional dinosaurs", then in fact you must be saying there are specific differences between birds and traditional dinosaurs other than extinction. So why don't those things provide a way to say this group is dinosaurs and that group is not without relying on extinction.
That's like saying that sauropods aren't dinosaurs. There were sauropods earlier than 65 million years ago, and yet we can characterize dinosaurs into "sauropods" and "non-sauropods". That doesn't make the sauropods not dinosaurs -- they are a specific type of dinosaur.

Same goes for birds. They are a type of maniraptoran theoropods dinosaur. There's no physiological differences so grand between a bird and archaropteryx that suddenly makes a bird no longer fit the definition of "dinosaur".

A chicken is much, MUCH more similar in every way that counts -- and separated by less time, too -- to a microraptor or even a tyrannosaurus, than either of those animals are to a stegosaurus.
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Old 01-19-2019, 12:15 PM
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As with many such terms, there are the scientific uses, and there are the public uses. It's like the issue with "fruits" and "vegetables", a dispute that results in confusion over things like tomatoes (biological fruits, culinary vegetables). cf. "Berry"

It's not shocking that the public image of what a "dinosaur" is was formed by an inaccurate understanding of what the term was being used to describe many decades ago. The unscientific public tends to be very indiscriminate in mis-using technical terms. It's not helped any by the fact that scientific usage tends to sharpen with time, as more information is known. Most people on the street still think there are nine "planets" in the Solar System, because that's what we learned as kids, and the fact that the term "planet" had to undergo some more rigorous definition to be useful to the scientific community doesn't phase them.

When I learned about "dinosaurs" back as a child in the 60s, there was very little distinction made in the juvenile books I was reading between different types of reptilian creatures of the Mesozoic Era. So we cheerfully called pteranodons, pterodactyls, plesiosaurs, etc. "dinosaurs", because that's how they were presented (it's quite possible that there were distinctions being made in the books I read, but a seven-year-old often doesn't bother with such things). And, of course, the whole idea that modern birds are just "dinosaurs" that survived extinction wasn't really being discussed at the time. They may well be "dinosaurs" in a biological classification sense, but you'll never convince the public that they are "dinosaurs" in an every-day usage sense.
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Old 01-19-2019, 02:43 PM
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I dunno; you just have to have the right incentives in place for people to believe it. When the food cart outside of the best dinosaur museum in the world is selling "dino nuggets", and the most famous dinosaur paleontologist in the world (who's also at that museum) is assuring you that, yes, those nuggets are in fact genuinely made from dinosaur meat, the kid who's eating his lunch at the museum is going to believe that, yes, he is eating dinosaurs, because that's just so cool!!!.
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Old 01-19-2019, 09:24 PM
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I dunno; you just have to have the right incentives in place for people to believe it. When the food cart outside of the best dinosaur museum in the world is selling "dino nuggets", and the most famous dinosaur paleontologist in the world (who's also at that museum) is assuring you that, yes, those nuggets are in fact genuinely made from dinosaur meat, the kid who's eating his lunch at the museum is going to believe that, yes, he is eating dinosaurs, because that's just so cool!!!.
Sorry, they already have those.
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Old 01-20-2019, 06:37 AM
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Is there a definitive list of creatures that are generally considered by the public to be dinosaurs, but fail to meet some specific scientific definition of the term?
I don't think a definitive list exists, all I find are pop-culture listicles like this one, and it's not very good, I doubt anyone is really calling Dunkleosteus a dinosaur.

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doesn't phase them.
Faze, not phase.
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Old 01-20-2019, 07:15 AM
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DSYoungEsq, I know they exist. The scenario in my post wasn't hypothetical: They really do serve dino nuggets at the Museum of the Rockies, home of Jack Horner, champion of calling birds dinosaurs.
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Old 01-20-2019, 10:56 AM
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Dinosaurs aren't. Dinosaurs were.
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Old 01-20-2019, 11:16 AM
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Dinosaurs aren't. Dinosaurs were.
We've been over this, there are about 10,000 species of dinosaur alive today!
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Old 01-20-2019, 12:32 PM
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DSYoungEsq, I know they exist. The scenario in my post wasn't hypothetical: They really do serve dino nuggets at the Museum of the Rockies, home of Jack Horner, champion of calling birds dinosaurs.

Do you think Jack Horner is more famous than Robert Bakker? Because those are the top two names I was speculating about from your earlier post.
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Old 01-20-2019, 01:54 PM
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Well, Dr. Grant from Jurassic Park was (at least loosely) based on Horner, a point that's sometimes mentioned in articles about the book or movie, which probably gives him more widespread exposure than Bakker. Mind you, I have no idea which one of them is more deserving of fame.
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Old 01-20-2019, 05:25 PM
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Ok, back in 1841 paleontologist Sir Richard Owen, used "Dinosaur" or "Dinosauria" to refer to the "distinct tribe or sub-order of Saurian Reptiles" . He lumped in Theropoda (which include modern birds) and Ornithischia (which oddly means "bird hipped" but are not that closely related to birds). Owen had no idea that Theropoda were related to birds, he was sure they were reptiles. He also didn't know that Ornithischia were quite separate from Theropoda. Thus, he made a error in lumping the two together, ad thinking they were reptiles.


The Ornithischia are completely extinct.

Not every scientist agrees that Aves should be part of Theropoda, and thus, technically "dinosaurs" It's a cladistic definition and not all accept it.

However, since many scientist do, you have the awkward term "Non-avian dinosaur" and if you dont include "non-avian" some pedantic smart ass will be sure to correct you. "No- dinosaurs are not extinct, i saw some in my backyard this morning, and I will have fried dino today for dinner!".

While somewhat correct, and sometimes humorous, they can also be called wrong.

Why wrong? Because the non-scientific term "dinosaur" is different than that actually correct term Dinosauria. Yes, I know.

So, yes, Dinosauria includes modern birds and does NOT include pterosaurs, mosasaurs, ichthyosaurs, plesiosaurs, and Dimetrodon, etc.

But "Dinosaur" as a layman's term means "big extinct reptile like creature" and can certainly include pterosaurs, mosasaurs, ichthyosaurs, plesiosaurs, and Dimetrodon, but does not include Birds.

Yes, it's not scientific, but everyone knows what they are talking about.

So, do be kind when correcting usage and make sure that you're not hijacking or getting off track. If someone posts "Humans never lived along dinosaurs, that movie is wrong" he is obviously using the layman's term.
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Old 01-20-2019, 06:21 PM
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Do you think Jack Horner is more famous than Robert Bakker? Because those are the top two names I was speculating about from your earlier post.
Well, I recall that years and years ago (10+ years, IIRC) I was Pitted for citing Bakker in some dinosaur thread that I don't even remember what it was all about at the moment. Apparently he wasn't considered a "real" paleontologist by other scientists, so maybe Horner is the more famous of the two.

Back on topic, I was pleased when we got some dinosaur-themed breakfast cereal recently that proclaimed it had "8 dinosaur shapes" on the box, and my 8-year-old son said that it was wrong because pterodactyls and dimetrodons weren't dinosaurs.
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Old 01-20-2019, 06:52 PM
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Ok, back in 1841 paleontologist Sir Richard Owen, used "Dinosaur" or "Dinosauria" to refer to the "distinct tribe or sub-order of Saurian Reptiles" . He lumped in Theropoda (which include modern birds) and Ornithischia (which oddly means "bird hipped" but are not that closely related to birds). Owen had no idea that Theropoda were related to birds, he was sure they were reptiles. He also didn't know that Ornithischia were quite separate from Theropoda. Thus, he made a error in lumping the two together, ad thinking they were reptiles.


No. No "error" was made--he correctly grouped them together because all three groups shared the derived characteristic (the term modern, not his) of five fused vertebrae in the sacrum. See this, this, and for an illustration this.



Also, no credible paleontoligist denies the dinosaur origin of birds--that is nutbag flat-earther territory.
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Old 01-20-2019, 07:12 PM
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Well, I recall that years and years ago (10+ years, IIRC) I was Pitted for citing Bakker in some dinosaur thread that I don't even remember what it was all about at the moment.


Found it. And this is what the guy said to you here in GQ.

Last edited by Darren Garrison; 01-20-2019 at 07:15 PM.
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Old 01-20-2019, 07:29 PM
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No. No "error" was made--he correctly grouped them together because all three groups shared the derived characteristic (the term modern, not his) of five fused vertebrae in the sacrum. See this, this, and for an illustration this.



Also, no credible paleontoligist denies the dinosaur origin of birds--that is nutbag flat-earther territory.
Yes, but Dinosauria are not reptiles and Owen had no idea that Birds were Dinosauria.

No, it's not nutbag stuff. Honestly there are reputable scientist who argue that altho Aves and Dinosauria have a common ancestor, they split off before.

https://en.wikipedia.org/wiki/Longisquama



Background
Main articles: feathered dinosaurs and origin of bird flight


A minority of scientists prefer the hypothesis that birds evolved from small, arboreal archosaurs like Longisquama. They see these as ectothermic animals that adapted to gliding by developing elongated scales and then pennaceous feathers. This hypothesis, however, is not supported by cladistic analysis.


https://answers.yahoo.com/question/i...5120521AAVvzTQ

There is no consensus. Most paleontologists are cladists, and practically all cladists believe that birds evolved from a dinosaur. There are also many biologists who have not kept up with the latest research on bird origins, and they were taught as undergraduates that birds evolved from a dinosaur similar to Deinonychus if they received their university education since the late 1960s. These 2 groups add up to over 50% of scientists. Starting in the mid-1990s, however, more and more scientists now doubt that birds evolved from a dinosaur. It started with developmental evidence by scientists such as Richard Hinchliffe, who found that birds most likely had fingers 2-3-4 but fossil evidence strongly suggests that theropod dinosaurs have fingers 1-2-3. Then scientists like John Ruben, Alan Feduccia, and Larry Martin did research that show that the taxonomic characters uniting theropod dinosaurs and birds are extremely unlikely to be homologous, suggesting instead that they are only superficially similar. Then, in 2000, a paper based on the re-examination of the fossil Longisquama, which was part of the group of fossils being brought to the USA from Russia, shows that it has feathers that were likely homologous with those of birds. Since Longisquama is not a dinosaur by any stretch of the definition or the imagination, it dealt a severe blow to the view that birds evolved from a dinosaur.

Knowing that Longisquama feathers would deal their cladistic religion and their careers a severe blow, because they would have to admit that cladistic analysis failed time after time to come up with the correct answer about the real ancestor of birds, some paleontologists tried to bury the facts. .... That is not all, the cladists are spending time courting the popular press and ignorant journalists to continue propping up the theory that birds evolved from a dinosaur.

The facts simply do not support the dinosaurian origin of birds, because there is no known fossil that has the features of Deinonychus and that lived in a period of time before the oldest known birds. ...Of course, cladists once again deny this piece of evidence, as they had done to all other pieces of evidence that contradict the dinosaurian origin of birds.

So, in short, if a paleontologist's career or career opportunity is dependent on adhering to the largely refuted dinosaurian origin of birds, then he/she probably has little choice but to keep on pretending that birds evolved from a dinosaur and bury both the facts and his/her own integrity. OTOH, scientists who are interested solely in a better understanding of nature are joining the small but growing number of real scientists who have abandoned the dinosaurian origin of birds.



https://today.oregonstate.edu/archiv...her-way-around
CORVALLIS, Ore. - A new study just published in the Proceedings of the National Academy of Sciences provides yet more evidence that birds did not descend from ground-dwelling theropod dinosaurs, experts say, and continues to challenge decades of accepted theories about the evolution of flight.

A new analysis was done of an unusual fossil specimen discovered in 2003 called "microraptor," in which three-dimensional models were used to study its possible flight potential, and it concluded this small, feathered species must have been a "glider" that came down from trees. The research is well done and consistent with a string of studies in recent years that pose increasing challenge to the birds-from-dinosaurs theory, said John Ruben, a professor of zoology at Oregon State University who authored a commentary in PNAS on the new research.

The weight of the evidence is now suggesting that not only did birds not descend from dinosaurs, Ruben said, but that some species now believed to be dinosaurs may have descended from birds.



https://academic.oup.com/icb/article/40/4/504/101454

https://onlinelibrary.wiley.com/doi/...002/jmor.10382

http://archive.news.ku.edu/2000/00N/...ne23/dino.html

Those guys are not, in "nutbag flat-earther territory". They are experts- which you are not.
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Old 01-20-2019, 07:31 PM
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And in one of those odd coincidences, I see that the latest post at SV-POW! (which I linked earlier) readdresses the sacral brain thing.
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Old 01-20-2019, 07:47 PM
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This article does a great job debunking the "Birds Are Not Dinosaurs" movement.

https://blogs.scientificamerican.com...aurs-movement/
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Old 01-20-2019, 07:51 PM
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Also, from your first link:

"A minority of scientists prefer the hypothesis that birds evolved from small, arboreal archosaurs like Longisquama. They see these as ectothermic animals that adapted to gliding by developing elongated scales and then pennaceous feathers. This hypothesis, however, is not supported by cladistic analysis."

Not supported by evidence...

Your second link goes to Yahoo Answers so forgive me if I don't take it seriously.
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Old 01-20-2019, 07:56 PM
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This article does a great job debunking the "Birds Are Not Dinosaurs" movement.

https://blogs.scientificamerican.com...aurs-movement/
Yes. Absolutely the mainstream argument hinges entirely upon cladistics and by their arguments Aves are part of Dinosauria. They have solid arguments.

However, since this is science and not name calling on a playground, the contrary is not considered "nutbag flat-earthers". Real scientists can post conflicting papers and argue these things out. However, since the fossil evidence is extremely thin, the mainstream may be proven wrong by a discovery being dug up as we speak. That's how science works. Or the dissenters may be proven wrong, also.

But I cheerfully concede that currently the mainstream is that Aves are part of Dinosauria.
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Old 01-20-2019, 07:59 PM
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Also, from your first link:

"A minority of scientists prefer the hypothesis that birds evolved from small, arboreal archosaurs like Longisquama. They see these as ectothermic animals that adapted to gliding by developing elongated scales and then pennaceous feathers. This hypothesis, however, is not supported by cladistic analysis."

Not supported by evidence...

Your second link goes to Yahoo Answers so forgive me if I don't take it seriously.

It's "not supported by cladistic analysis." Cladistics is not the end all be all of science. And again that is being argued as we speak.

That simply shows the arguments going on, so your ad hominem is not needed. However, I posted several peer reviewed articles.
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Old 01-20-2019, 08:20 PM
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Found it. And this is what the guy said to you here in GQ.
Wow, it's been 17 years already! Man, I'm getting old. Anyway, it looks like that poster wasn't a fan of either Horner nor Bakker, so I don't know what to tell everybody (he/she hasn't logged on since 2003, so there's probably no way to ever know). It's been a long time, but I think I brought up the sacral brain thing in that thread because I had read Bakker's "The Dinosaur Heresies" not too long before, and I didn't realize that it was considered outdated.
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Old 01-20-2019, 11:56 PM
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It's "not supported by cladistic analysis." Cladistics is not the end all be all of science. And again that is being argued as we speak.

That simply shows the arguments going on, so your ad hominem is not needed. However, I posted several peer reviewed articles.
It's totally fine to study the question of whether dinosaurs are the ancestors of birds. It's also fine to dispute the scientific consensus and test a new hypothesis. Almost everyone who has done so has concluded that birds are descended from dinosaurs, aside from a few fringe dissidents. Just because they are fringe doesn't make them wrong, but in this case the evidence seems to be strongly against them. Not just cladistic evidence either-- we have transitioned forms between ground dwelling theoropods and birds.

The researchers who buy into BAND seem to have a preset idea of what the ancestor of birds should look like, and since ground dwelling theoropods don't fit the bill (no pun intended) they look to small arboreal lizard-like creatures that lived millions of years before birds did (while avian dinosaurs lived alongside more modern birds, and the fossil record is full of transitionary forms so close that scientists constantly argue over whether a given dinosaur is a true bird or only a bird-like theoropod).
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Old 01-21-2019, 04:48 AM
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I gleaned the following clading diagram from Wikipedia. Is it more-or-less correct? Obviously it's highly simplified and omits several extinct orders.

Phylum Chordata
|
|\___ Tunicates & Lancelets
|
|\___ Hagfishes
|
|\___ Lampreys
|
|\___ Sharks & Rays etc.
|
|\___ Spiny Sharks (extinct)
|
|\___ Ray-finned fishes
|
|\___ Coelacanths
|
|\___ Lungfishes
|
|\___ Frogs & Salamanders
|
|\___ Mammals
|
|\___ Turtles
|
|\___ Snakes & Lizards
|
|\___ Crocodiles
|
|\___ Pterosaurs
|
|\___ Stegosaurs, etc.
|
|\___ Brontosaurs, etc.
|
|\___ Ceratosaurs, etc.
|
|\___ Allosaurs, etc.
|
\___ Tyrannosaurs & Birds, etc.
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Old 01-21-2019, 06:01 AM
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I gleaned the following clading diagram from Wikipedia. Is it more-or-less correct?
[...]
|
|\___ Mammals
|
|\___ Turtles
|
|\___ Snakes & Lizards
|
|\___ Crocodiles
Not quite - the snake-lizard/other reptiles split happens before the turtles/archosars split, AFAIK the current position to be.

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Old 01-21-2019, 09:12 AM
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Not quite - the snake-lizard/other reptiles split happens before the turtles/archosars split, AFAIK the current position to be.
Thank you very much! (It looks like this is a relatively recent correction; my old diagram might have been compatible with the Wiki pages of several years ago.)
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Old 01-21-2019, 10:02 AM
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It's still not a settled thing, as the articles make clear, but I'd bet on the genetics vs pure fossils
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Old 01-21-2019, 10:20 AM
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Hey MrDribble, interestingly enough the only criticisms of Cladistics I can find out there are from the DANB crowd. I find that very interesting...

I'm not sure why you're against Cladistics. What issue with that discipline do you have? Cladistics is the idea that we should group living things based on their ancestry rather than their characteristics. You are against This?

Note that using genetic evidence to place an animal within a group based on ancestry is a form of Cladistics. Cladistics is not only based on fossils, and it's not only applicable to extinct species.
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Old 01-21-2019, 12:22 PM
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Ermm, firstly, get my name right

Secondly - what on Shub-Niggurath's Hundredth Left Tit gives you the idea I'm against cladistics?
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Old 01-21-2019, 12:57 PM
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Doh! I think I've been mixing up you and DrDeth and that's where the extra R came from... sorry about that.

I was trying and failing to respond to this post:

Quote:
It's "not supported by cladistic analysis." Cladistics is not the end all be all of science. And again that is being argued as we speak.

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Old 01-28-2019, 07:51 PM
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The latest in dinosaur feather analysis.
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Old 01-28-2019, 08:39 PM
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Interesting. Science marches on.
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Old 01-29-2019, 05:27 AM
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Cool link, thanks.
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Old 01-29-2019, 09:19 AM
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When I learned about "dinosaurs" back as a child in the 60s, there was very little distinction made in the juvenile books I was reading between different types of reptilian creatures of the Mesozoic Era. So we cheerfully called pteranodons, pterodactyls, plesiosaurs, etc. "dinosaurs", because that's how they were presented (it's quite possible that there were distinctions being made in the books I read, but a seven-year-old often doesn't bother with such things). And, of course, the whole idea that modern birds are just "dinosaurs" that survived extinction wasn't really being discussed at the time. They may well be "dinosaurs" in a biological classification sense, but you'll never convince the public that they are "dinosaurs" in an every-day usage sense.
Well, there you go, Gramps. You're going off of what was published in kid books 50 some-odd years ago, which was probably 20 or more years out of date versus the state of the paleontological art of the time. They probably didn't mention feathered dinosaurs, warm blood or any of the other critical things we now know about them.

Even the kid books draw those distinctions these days- they point out that certain lineages of dinosaurs developed as early as the Jurassic (prior to Archaeopatryx), and eventually evolved into something similar to today's birds by the Cretaceous- they go so far as to show a Tyrannosaurus skeleton and a chicken skeleton together and note how absolutely similar they are.

The other creatures- the aquatic icthyosaurs and mosasaurs are contemporaries of dinosaurs, but strictly speaking aren't dinosaurs. It's like considering whales or dolphins fish, because they live in the ocean.

It sounds like a lot of people think "reptilian creatures that lived during the Jurassic, Triassic or Cretaceous periods = dinosaur", even though we can easily point at alligators and crocodiles which evolved during those periods, and point out that they are not dinosaurs.
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Old 01-29-2019, 09:47 AM
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The other creatures- the aquatic icthyosaurs and mosasaurs are contemporaries of dinosaurs, but strictly speaking aren't dinosaurs. It's like considering whales or dolphins fish, because they live in the ocean.
Of course, ironically, whales and dolphins (and icthyosaurs and pleiseosaurs and T. rexes and humans) are fish, after all.
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Old 01-29-2019, 10:05 AM
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Of course, ironically, whales and dolphins (and icthyosaurs and pleiseosaurs and T. rexes and humans) are fish, after all.
That's because "fish" isn't a useful term. You are lumping together bony fishes, jawless fishes, and cartilaginous fishes. Those groups split off from each other millions of years before life reached land. Yes, you and a dolphin and a plesiosaurs and a trex are all more closely related to bony fishes like a carp or salmon than such a fish is to a shark or ray or lamprey.
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Old 01-29-2019, 10:14 AM
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To get more specific -- long, long ago, fish first evolved. One group became the jawless fish, one the bony fish, and one the cartilaginous fish. You also had the armored fish like dunkleosteos and the spiny sharks, but those two flares are totally extinct.

Among the bony fish, you've got ray finned and and lobe finned fish, and the lobe finned fish are the ones who would eventually become amphibians. Most lobe finned fish are extinct, with coelacanth being one exception. And yes -- a coelacanth is more closely related to you, than it is to a ray finned fish, and WE are more closely related to that ray finned fish than it is to a shark.

Cladistics is about classifying things by their relationship to one another. If you want to use common traits instead -- "they both have fins" or "they both fly" -- you're welcome to, but that's not a scientific approach, any more than "a beaver is a fish because Catholics eat it on friday" is.

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Old 01-29-2019, 10:38 AM
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In other words -- can YOU give us a useful definition of the word "fish" that includes all bony, jawless, and cartilage fish, but not any other animal?
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Old 01-29-2019, 11:26 AM
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Correction: Most aquatic lobe-finned fish are extinct. But some lobe-finned fish are currently sitting at computer keyboards typing to each other about the oddities of cladistics.

In exactly the same sense that it's correct to say that a chicken is a dinosaur, it's also correct to say that a whale is a lobe-finned fish. If "non-avian dinosaur" is not a useful category because it's not a clade, then neither is "non-terrestrial lobe-finned fish".
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Old 01-29-2019, 11:32 AM
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In other words -- can YOU give us a useful definition of the word "fish" that includes all bony, jawless, and cartilage fish, but not any other animal?
Useful? Of course. Something like (as Wikipedia put it): "Fish are gill-bearing aquatic craniate animals that lack limbs with digits." A real evolutionary biologist could even define the group

Cladistically, this is a not monophyletic group, but so what? A group definition doesn't have to be monophyletic to be useful. "Domesticated animals" and "edible plants" aren't monophyletic groups either, but they're darned useful classifications.
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Old 01-29-2019, 11:35 AM
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Those are useful categories from the point of view of trying to figure out, "can I keep this animal in an aquarium?" Or "am I likely to enjoy eating this animal?" Or "my nephew says he likes dinosaurs, what kind of you should I buy for him?".

They are not useful when we are trying to figure out where on the tree of life a creature belongs.
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Old 01-29-2019, 11:45 AM
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Also, I think that non avian dinosaur IS a useful term. We all know what it describes -- dinosaurs who lack avian properties. However, many animals that went extinct 65 million years ago, had teeth, and to you or I would look like a dinosaur, are NOT non-avian, because that line is very blurry. And while we don't share many traits with the coelacanth, birds very much share many traits with dinosaurs, while dinosaurs (such as Stegosaurus) share very few traits with other dinosaurs (such as velociraptor). So you could make the argument that while cladistically humans are lobe finned fish, their traits separate them sufficiently from fish that calling a human a fish in everyday usage is ridiculous. After all, there are traits that all mammals share that fish lack.

What trait do all birds share that non avian dinosaurs universally lack?
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Old 01-29-2019, 12:10 PM
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In exactly the same sense that it's correct to say that a chicken is a dinosaur, it's also correct to say that a whale is a lobe-finned fish. If "non-avian dinosaur" is not a useful category because it's not a clade, then neither is "non-terrestrial lobe-finned fish".
"lobe-finned fish" is a clade, though (one that includes us tetrapods), and "fish" is not. So you can correctly say we're lobe-finned fishes, but we're not fish. Silly as that sounds.

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Old 01-29-2019, 12:12 PM
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"lobe-finned fish" is a clade, though (one that includes us tetrapods), and "fish" is not. So you can correctly say we're lobe-finned fishes, but we're not fish. Silly as that sounds.
I don't see why that's "silly".
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Old 01-29-2019, 12:16 PM
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Not a Dinosaur

Godzilla

Anguirus

Rodan

Rhedosaurus (the thing from Beast from 20,000 Fathoms)

Whatever the hell that thing Ringo Starr was riding in Caveman)

Everything in the movie When Dinosaurs Ruled the Earth, ironically

Everything except the T. Rex in the Land Unknown (although the head later showed up as "Spot" on The Munsters)

The Dimetrodons in journey to the Center of the Earth (1960)

The creatures in Jules Verne's original novel A Journey to the Center of the Earth (1864)

The creatures in Edgar Rice Burroughs' Pellucidar series (although burroughs does get credit for dinosaurs in his Pal-ul-don and Caspak series)

"Dinosaurs" on alien planets. I don't care how much they may look like them, they have a different ancestry.


Dragons

Sirrush (probably)

Mkele-Mbembe, whatever they are, more than likely. I don't care what Disney says.


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