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Author | Topic: Theropods and Birds showing a change in kinds | |||||||||||||||||||||||||||
Dr Adequate Member (Idle past 285 days) Posts: 16113 Joined: |
Wasn't pointing out a problem with your point, just being pedantic with the terminology. To continue a little bit further in that vein, Compsognathus isn't a maniraptoran. Here's the modern understanding of coelurosaur phylogeny (based on Senter (2007), from the wiki page on Coelurosauria: Thanks. Now I'm all confused ... I used to know this once ... Apologies to everyone if I've messed up my taxonomy. I'll edit my posts to put it right for posterity ... later. Edited to add: I've just been looking at Wikipedia, and now I'm really confused. Because, apparently, so is everyone else.
The position of the Compsognathidae within the Coelurosaur group is uncertain; some hold the family as the basalmost of the coelurosaurs, while others as part of the Maniraptora. Right. So what are the deinonychosauria and the dromaeosauridae? Put it this way, what's the smallest clade containing both Deinonychus and Compsognathus? Edited by Dr Adequate, : No reason given.
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DC85 Member (Idle past 380 days) Posts: 876 From: Richmond, Virginia USA Joined: |
it keeps changing and they're debated. The more they find the more diverse they seem to be. The line is sketchy just as the line between birds are. This is a wonderful example of diversity and evolution
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Dr Adequate Member (Idle past 285 days) Posts: 16113 Joined: |
It keeps changing and they're debated. The more they find the more diverse they seem to be. The line is sketchy just as the line between birds are. This is a wonderful example of diversity and evolution. well then **** evolution and double **** the scientific method. What I want is complete certainty about everything forever. So, there, you did it, I'm going to become a creationist and from now on I'm going to give one sure and simple answer to every question, as follows: "The reason that it's that way is that God wanted it to be that way. And the cause that it's that way is that God did it by magic". Screw reality, I'm going home. Edited by Dr Adequate, : No reason given.
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caffeine Member (Idle past 1025 days) Posts: 1800 From: Prague, Czech Republic Joined: |
Well it seems like I was speaking as if things are a lot more resolved than they reall are. From UCMP's page on Coelurosauria:
quote:
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caffeine Member (Idle past 1025 days) Posts: 1800 From: Prague, Czech Republic Joined: |
The point is that at one point along the lineage the dinosaurs had only down feathers. Assuming that they evolved in a low-humidity environment is cool, but there isn't a lot of those isn't it. Care to give an example of such an environment ? Because it sounds to me the only place this would fit would be the desert. There were more deserts in the Late Triassic and Early Jurassic than there are now, as a result of the big supercontinent leaving many regions a long way from the sea. These areas would also be subject to great temperature swings, and a trapped layer of air helps the body to not heat up too quickly in the day as well as not cool down too fast at night. A little bit of reading about down insulation on the web seems to suggest that you're right about it being pretty useless when wet. The consensus also seems to be that it's pretty much the supreme insulator when dry, however.
I can't access the link, but it's important not to mix up down feathers and 'dinofuzz'. Sorry about the link - this one should work. And don't worry, I'm not getting feathers confused with simpler filaments. From the abstract:
quote: This only mentions pennaceous feathers, contour feathers like flight feathers; not the plumulaceous downy ones, but the body of the article seems to talk about these as well. This dinosaur is hardly unique though. Here's the discussion of Caudipteryx and Protoarchaeopteryx from an open-access journal that we can all read:
Two feathered dinosaurs from northeastern China quote: Isn't beta-keratin a pretty common thing ? (My bio classes are far right now lol) Reptiles scales contain beta-keratins too, but they're also constructed partly from alpha-keratins. In modern animals, bird feathers are unique in being composed almost entirely of beta-keratin, and this is something they seem to share with the filaments of Shuvuuia. Edited by caffeine, : tags and typos
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xongsmith Member Posts: 2578 From: massachusetts US Joined: Member Rating: 6.8 |
Caffeine writes:
A little bit of reading about down insulation on the web seems to suggest that you're right about it being pretty useless when wet. The consensus also seems to be that it's pretty much the supreme insulator when dry, however. And, remember - who said any of these sorts of features had to be optimal? They only had to be good enough. Edited by xongsmith, : change period to question mark. - xongsmith, 5.7d
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Taq Member Posts: 9973 Joined: Member Rating: 5.7 |
If birds are just dinosaur, how can anything be transitional between dinosaurs and birds ? Obviously, we are talking about a transition between non-avian dinosaurs and avian dinosaurs.
Obviously, there are features that distinguish birds from their dinosaur ancestors. These are the ones that have to be shown transitional. And that is exactly what we have in these transitionals. Archaeopteryx has teeth and a long tail which are non-avian dinosaur traits. Non-avian dinosaur traits in Archaeopteryx:1. Premaxilla and maxilla are not horn-covered (i.e. no beak). 2. Trunk region vertebra are free. In birds they are fused. 3. Cerebral hemispheres elongate, slender and cerebellum is situated behind the mid-brain and doesn't overlap it from behind or press down on it. In birds the cerebral hemispheres are stout, cerebellum is so much enlarged that it spreads forwards over the mid-brain and compresses it downwards. 4. Neck attaches to skull from the rear as in dinosaurs not from below as in modern birds. 5. Center of cervical vertebrae have simple concave articular facets. In birds the vertebrae are different, they have a saddle-shaped surface. 6. Long bony tail with many free vertebrae up to tip (no pygostyle). 7. Premaxilla and maxilla bones bear teeth. 8. Ribs slender, without joints or uncinate processes and do not articulate with the sternum. Birds have stout ribs with uncinate processes (braces between them) and articulate with the sternum. 9. Pelvic girdle and femur joint is archosaurian rather than avian (except for the backward pointing pubis as mentioned above). 10. The Sacrum (the vertebrae developed for the attachment of pelvic girdle) occupies 6 vertebra. The bird sacrum covers between 11-23 vertebrae. 11. Metacarpals (hand) free (except 3rd metacarpal), wrist hand joint flexible. In birds the metacarpals are fused together with the distal carpals in the carpo-metacarpus, wrist /hand fused. 12. Nasal opening far forward, separated from the eye by a large preorbital fenestra (hole). Where a fenestra is present in birds, it is always greatly reduced, and is involved in prokinesis (movement of the beak). 13. Deltoid ridge of the humerus faces anteriorly as do the radial and ulnar condyles. Typical of reptiles but not found in birds. 14. Claws on 3 unfused digits. 15. The fibula is equal in length to the tibia in the leg. This again is a typical character of reptiles. In birds the fibula is shortened and reduced. 16. Metatarsals (foot bones) free. In birds these are fused to form the tarsometatarsus. 17. Gastralia present. Gastralia are "ventral ribs," elements of dermal bone in the ventral wall of the abdomen. Typical of reptiles, they are absent in birds. cribbed from here Hmf, that's a lot of non-avian features in a bird. But then there are also avian features: 1. Feathers.2. Opposable hallux (big toe). 3. Furcula (wishbone) formed of two clavicles fused together in the midline. 4. Pubis elongate and directed backward. So Archaeopteryx has a mixture of avian and non-avian features, just as one would expect if modern birds are descended from non-avian dinosaurs.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7 |
I should have better expressed myself. What I mean is that if the fakes are well made enough to fool the paleontologists who examine it into thinking they are real and go up to the publishing. Which paleontologists were fooled? In which scientific peer reviewed journal was this fossil presented as a real fossil? From what I have read National Geographic (not a peer reviewed scientific journal) presented this fossil without first checking with knowledgable paleontologists. In fact, Storrs L. Olson strongly criticized Nat Geo for publishing the article without it first going through peer review:
quote: The only solution is that the publishers require CT scans on every fossil coming from china before publishing it. The solution appears to be letting real paleontologists take a look at the fossil before letting art directors write stories about it.
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New Cat's Eye Inactive Member
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In Message 35, arachnophilia provided this information:
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arachnophilia Member (Idle past 1344 days) Posts: 9069 From: god's waiting room Joined: |
taq writes: cribbed from [talk origins] oof, somebody needs to update t.o!
1. Feathers. as noted in the other thread, this doesn't seem especially unique anymore. primitive feathers have even been found in ornithiscian dinosaurs, meaning that's almost certainly a non-avian dinosaur trait.
2. Opposable hallux (big toe). as mentioned in the other thread, archaeopteryx does not have an opposed hallux. on most of the 7 specimens, the feet are a bit obscured, or twisted, and it was hard to tell. however, recent examination points out that the hallux is in precisely the same position and orientation as on other dromaeosaurid dinosaurs.
3. Furcula (wishbone) formed of two clavicles fused together in the midline. furculae are about the first bones to disappear from dinosaur skeletons. but even coelophysis had one.
4. Pubis elongate and directed backward. as in all dromaeosaurs. none of this stuff is particularly special. here are the avian characteristic of archaeopteryx from jacques gauthier's 1986 paper where he classifies avialae (his grouping of aves as not been generally well received) and comments by thomas holtz.
quote: as you can see, it's pretty relative and arbitrary. and the more we learn about non-avian dinosaurs, the more similarities we have been finding -- which crosses a good number of these classification off the list. Edited by arachnophilia, : No reason given.
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Ronken  Suspended Junior Member (Idle past 4591 days) Posts: 5 From: China Joined: |
nice post ! thanks for sharing!!!
{The following message was spam and was deleted - Adminnemooseus} Edited by Adminnemooseus, : Spam links deleted. Edited by Adminnemooseus, : No reason given.
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xongsmith Member Posts: 2578 From: massachusetts US Joined: Member Rating: 6.8 |
Is this article I found on Facebook relevant to this thread?
Why the world has to ignore ReptileEvolution.com - Scientific American Blog Network- xongsmith, 5.7d
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arachnophilia Member (Idle past 1344 days) Posts: 9069 From: god's waiting room Joined: |
not unless you believe this crackpot who makes david peters look positively academic.
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pandion Member (Idle past 3001 days) Posts: 166 From: Houston Joined: |
Sounds like a lizard, doesn't it?
Also sounds like a cat. I'm just saying that a hiss isn't evidence of anything.
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