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Post by Griffin on Mar 10, 2011 2:14:25 GMT
"Grey seal pups are born with fur, and lose it as they get older.
Baby dolphins have whiskers that they then lose.
A fair step away from a feather-scale switch yes, but certainly seems to be present in animals carrying traits of a species that specialised in a different environment."
Its not the same. I'll even take your points and bring them closer to the conversation at hand for you...
Baby ostriches are born covered in fuzz then lose it later in life.
It doesn't matter though. Heres the difference. They don't ever replace that area with a different type of body covering. Its just bare skin or a different kind of feather. I was pretty clear about that more than one time in the past pages. Nowhere in nature nor the fossil record do we see something being born fuzzy....drops the fuzz then grows scales ( a different kind of structure) in their place. That's all I'm saying.
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Post by gwangi on Mar 10, 2011 3:59:38 GMT
Griffin; cute vid! Okay, just read/skim-read through all of this and I'm not sure when the argument slid to "are dinosaurs (more like) birds" but... Yeah, I'm pretty sure there's some debate in the land of Biology about whether or not reptiles and birds shouldn't be ONE category anyway? We can all speculate on how a crocodile doesn't look like a pigeon but then they're most certainly closer to each other than some fish (which are all in the category "fish" regardless). To be fair, a gallimimus doesn't look much like a crocodile either unless you give it that skin texture! The class Reptilia encompasses numerous unrelated animals lumped together simply because they look alike. Crocodiles are more closely related to birds than other reptiles. Snakes and lizards are more closely related to birds than turtles. The way we classify things is a mess. True, birds don't look like crocodiles but velociraptor doesn't look much like stegosaurus yet we accept them both as dinosaurs without question.
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Post by haretrinity on Mar 10, 2011 4:12:57 GMT
The class Reptilia encompasses numerous unrelated animals lumped together simply because they look alike. Crocodiles are more closely related to birds than other reptiles. Snakes and lizards are more closely related to birds than turtles. The way we classify things is a mess. True, birds don't look like crocodiles but velociraptor doesn't look much like stegosaurus yet we accept them both as dinosaurs without question. ...Exactly? And Griffin; I figured out why the conversation went onto birds, but I was still replying to this part: "...I'm not saying an animal couldn't have had both scales and fuzz on its body. Birds do today. I'm saying that looking at what we know about animal physiology its really not known for any animal to replace one with the other in the same place on the body." My interpretation was that you didn't have many examples of animals switching skin coverings as they got older. If what you meant is that we don't have a feathers-to-scales example then no. Guess we agree, my bad! ...I guess the only question I'd have here then would be what, exactly, is our proof of dinosaurs being scaled? I assume there's a fossil somewhere...? Figure I'll Google it tomorrow though, somehow I've stayed up wayyy too late...!
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Post by Horridus on Mar 10, 2011 17:14:01 GMT
...I guess the only question I'd have here then would be what, exactly, is our proof of dinosaurs being scaled? I assume there's a fossil somewhere...? There are a number of skin impressions indicating scales, just as there are others indicating feathers. However skin impressions from the juveniles of large theropods are unknown, which is the issue here. Actually, with adult tyrannosaurids only very small skin impressions are known (and they haven't even been described) from areas that are also scaley on compsognathids - significant as both tyrannosauroids and compsognathids are considered to be 'primitive' coelurosaurs.
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Post by Griffin on Mar 10, 2011 18:07:27 GMT
...I guess the only question I'd have here then would be what, exactly, is our proof of dinosaurs being scaled? I assume there's a fossil somewhere...? There are a number of skin impressions indicating scales, just as there are others indicating feathers. However skin impressions from the juveniles of large theropods are unknown, which is the issue here. Actually, with adult tyrannosaurids only very small skin impressions are known (and they haven't even been described) from areas that are also scaley on compsognathids - significant as both tyrannosauroids and compsognathids are considered to be 'primitive' coelurosaurs. What he said. So as of now I really don't have anything against a scaly rex or feathered one. Just as long as the adults and babies are uniform.
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Post by eriorguez on Mar 10, 2011 21:24:58 GMT
The only issue I'd have is that scales are unlikely to grow on patches of naked skin.
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Post by Griffin on Mar 11, 2011 1:00:47 GMT
The only issue I'd have is that scales are unlikely to grow on patches of naked skin. I agree. "My interpretation was that you didn't have many examples of animals switching skin coverings as they got older. If what you meant is that we don't have a feathers-to-scales example then no. Guess we agree, my bad!" My dad used to have hair. Now hes bald. Bam another example.
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Post by supersiamo on Mar 11, 2011 5:41:37 GMT
Though there is the possibility of Tyrannosaurus' sporting feathers, fossilized skin impression of Tyrannosaurus were found with no feathery texture.
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Post by eriorguez on Mar 11, 2011 14:41:12 GMT
On places where animals of its phylogenetic position are expected to have scales.
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Post by Griffin on Mar 11, 2011 16:45:28 GMT
And even so it doesn't mean there weren't feathers on that part when the animal was alive.
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Post by dinoguy2 on Mar 11, 2011 20:24:38 GMT
...I guess the only question I'd have here then would be what, exactly, is our proof of dinosaurs being scaled? I assume there's a fossil somewhere...? There are a number of skin impressions indicating scales, just as there are others indicating feathers. However skin impressions from the juveniles of large theropods are unknown, There's a juvi Allosaurus with extensive skin impressions and no trace of feather,s for what it's worth. But also remember that feathers did NOT evolve from scales. This was an untested idea from the 50s that was disproved by Prum and Brush in a number of papers in the late '90s. Feathers evolve from the same type of follicle as scales, but they're no more related to scales than hair is. It's entirely possible for an animal to have been covered head to toe in both scales and feathers. The feathers would simply emerge from the spaces between the scales. There was a really great show I just saw on Science Channel that went into detail on all this with some nice graphics, plus interviews with Prum himself. Can't remember the name...
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Post by Griffin on Mar 12, 2011 21:54:59 GMT
There is also carnotaurus that has skin impressions that are clearly scaly. But neither Allosaurus nor Carnotaurus are that closely related to tyrannosaurus when compared to the feathered theropods.
"It's entirely possible for an animal to have been covered head to toe in both scales and feathers. The feathers would simply emerge from the spaces between the scales."
Yeah just check out an owl's foot.
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jomes
New Member
Posts: 13
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Post by jomes on Mar 13, 2011 3:17:29 GMT
Humans have an extraordinary urge to group everything. Reading these posts, it seems to me that the whole issue is where to draw an arbitrary line. At what point does a mammal like reptile become a reptile like mammal? Hard to say for sure, but we do make a distinction taxonomically.
Lets make it easy and say all vertebrates are fish.
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Post by paleofreak on Mar 13, 2011 8:51:02 GMT
. At what point does a mammal like reptile become a reptile like mammal? Hard to say for sure, but we do make a distinction taxonomically. Well... Taxonomically, there is no such thing as "mammal-like reptiles" or "reptile-like mammals"
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Tyrannosauron
Junior Member
Science cannot move forward without heaps!
Posts: 92
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Post by Tyrannosauron on Mar 16, 2011 4:11:43 GMT
Humans have an extraordinary urge to group everything. Reading these posts, it seems to me that the whole issue is where to draw an arbitrary line. At what point does a mammal like reptile become a reptile like mammal? Hard to say for sure, but we do make a distinction taxonomically. Lets make it easy and say all vertebrates are fish. Even Darwin warned against going that far (to quote: "as if anyone ever denied that [species] have temporary existence" independent of human taxonomy). More recently, it's been pretty well demonstrated that [most] species fall into statistically distinct clusters, both genetically and morphologically. The names we give may be arbitrary, but the divisions in nature aren't.
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Post by lio99 on Apr 9, 2011 2:26:46 GMT
Finally this argument is finished
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