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Post by gwangi on Jan 28, 2012 4:36:22 GMT
Not really arguing, again, note that I´m ambivalent on this matter and just cited the opinion of someone way more knowledgeable. I´m done with it unless you want to follow in another thread or via pm, but there´s little more I could say. Arguing, debating...whatever you want to call all this. I'm actually backing you up on my last post, don't think you noticed. |
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Post by Horridus on Jan 28, 2012 16:57:33 GMT
What you two seem to be doing is confusing the old taxonomic class Reptilia with a phylogenetic, cladistics-based definition. They aren't the same thing, we're talking about two different systems. That's why 'Sauropsida' is often preferred when talking about cladistics, as it prevents confusion with the old 'class Reptilia'. In Linnaean taxonomy, paraphyletic groupings are allowed, so we can have 'Reptilia' and 'Aves' as separate classes, even though eg. birds are more closely related to crocodiles than crocodiles are to turtles (or even lizards). A group is considered paraphyletic if it includes some of the descendants of a particular common ancestor, but not all of them. In cladistics, paraphyletic clades aren't allowed. So, birds are sauropsids (because they're dinosaurs, which are archosaurs, which are diapsids, which are sauropsids). Check out this Wikipedia article en.wikipedia.org/wiki/Sauropsida. The image below is from the article and shows where the traditional 'Reptilia' and Sauropsida overlap, and where they differ. Note that in 'Reptilia' basal synapsids (on the route leading to Mammalia) are included. Hence their old name of 'mammal-like reptiles'. If we were to make 'Reptilia' monophyletic based on the old definition, mammals would have to be included. Hence the name 'Sauropsida', which moves away from the connotations of the term 'Reptilia'.  I probably haven't explained that particularly well, but please forgive me! |
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Post by Himmapaan on Jan 28, 2012 18:08:20 GMT
I think my head just 'sploded...
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Post by sbell on Jan 28, 2012 18:39:30 GMT
What you two seem to be doing is confusing the old taxonomic class Reptilia with a phylogenetic, cladistics-based definition. They aren't the same thing, we're talking about two different systems. That's why 'Sauropsida' is often preferred when talking about cladistics, as it prevents confusion with the old 'class Reptilia'. In Linnaean taxonomy, paraphyletic groupings are allowed, so we can have 'Reptilia' and 'Aves' as separate classes, even though eg. birds are more closely related to crocodiles than crocodiles are to turtles (or even lizards). A group is considered paraphyletic if it includes some of the descendants of a particular common ancestor, but not all of them. In cladistics, paraphyletic clades aren't allowed. So, birds are sauropsids (because they're dinosaurs, which are archosaurs, which are diapsids, which are sauropsids). Check out this Wikipedia article en.wikipedia.org/wiki/Sauropsida. The image below is from the article and shows where the traditional 'Reptilia' and Sauropsida overlap, and where they differ. Note that in 'Reptilia' basal synapsids (on the route leading to Mammalia) are included. Hence their old name of 'mammal-like reptiles'. If we were to make 'Reptilia' monophyletic based on the old definition, mammals would have to be included. Hence the name 'Sauropsida', which moves away from the connotations of the term 'Reptilia'. I probably haven't explained that particularly well, but please forgive me! But reptilia doesn't have to include the mammals--it can simply include everything from the common ancestor shared between Chelonia and Diapsida. And the group that includes mammals and the reptilia is already called the amniota. |
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Post by Horridus on Jan 28, 2012 18:48:11 GMT
But reptilia doesn't have to include the mammals--it can simply include everything from the common ancestor shared between Chelonia and Diapsida. And the group that includes mammals and the reptilia is already called the amniota. Aye. That's why I mentioned the old definition of Reptilia, which often included the basal synapsids. Under that definition, mammals would have to be included for the group to be monophyletic. 'Mammals evolved from reptiles' is a statement you will find quite commonly in old books (I have a DK nature encyclopedia from the '90s that states exactly that). The definition you mentioned is synonymous with Sauropsida. And yes, these days they are all united as amniotes. |
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Post by arioch on Jan 28, 2012 19:20:53 GMT
Yeah, I think the idea I mentioned was move the whole dinosauria where Aves is in the diagram. But I have to look it out (maybe in the DML... can´t remember where I saw it).
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Post by Griffin on Feb 1, 2012 2:24:48 GMT
Oooh goody just saw this debate.
Um but yeah taking dinosaurs out of reptiles is not really logical. Bottom line is birds ARE reptiles. I know ornithologist who accept this. The doctor who I worked under at the lab back when I was helping with research on fence lizard hormones would always say "its not a bird. Its just a reptile with feathers." The whole warm bloodedness thing is so messy it shouldn't even be included in the "all reptiles must have this in order to be a reptile" thing. Its really the dry scaly skin and production of shelled eggs which counts. (Yes there are things like boas, rattlesnakes and bark lizards who don't actually lay eggs but its not like they have a placenta or anything. The bottom line is they are clearly reptiles just like a platypus is a mammal despite its mode of reproduction).
Most compelling is the fact that crocodillian DNA is closer to bird DNA than it is to any other extant kind of reptile. Crocodillians also have a four chambered heart and have a more upright posture than the splayed of lizards and testudines. Squamate DNA is closer to archosaur DNA than it is to testudine DNA.
Birds are reptiles.
Also how do we know icthyosaurs didn't have scales?
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Post by stoneage on Feb 1, 2012 4:19:08 GMT
Oooh goody just saw this debate. Um but yeah taking dinosaurs out of reptiles is not really logical. Bottom line is birds ARE reptiles. I know ornithologist who accept this. The doctor who I worked under at the lab back when I was helping with research on fence lizard hormones would always say "its not a bird. Its just a reptile with feathers." The whole warm bloodedness thing is so messy it shouldn't even be included in the "all reptiles must have this in order to be a reptile" thing. Its really the dry scaly skin and production of shelled eggs which counts. (Yes there are things like boas, rattlesnakes and bark lizards who don't actually lay eggs but its not like they have a placenta or anything. The bottom line is they are clearly reptiles just like a platypus is a mammal despite its mode of reproduction). Most compelling is the fact that crocodillian DNA is closer to bird DNA than it is to any other extant kind of reptile. Crocodillians also have a four chambered heart and have a more upright posture than the splayed of lizards and testudines. Squamate DNA is closer to archosaur DNA than it is to testudine DNA. Birds are reptiles. Also how do we know icthyosaurs didn't have scales? |
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Post by Griffin on Feb 1, 2012 15:11:18 GMT
Thanks for the link I'll read this later when I get a chance!
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theadmiral
New Member
Fear me...I'll give you a cookie.
Posts: 6
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Post by theadmiral on Feb 8, 2012 5:51:24 GMT
I drew a feathered raptor at school once and a kid leaned over my shoulder and asked what it was. When I replied, he said, "It doesn't look like a raptor".
Teeth, claws, sickle claw, tail; how does it not look like a raptor, even if it does have feathers?
Sigh...
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Post by Horridus on Feb 8, 2012 18:59:08 GMT
I drew a feathered raptor at school once and a kid leaned over my shoulder and asked what it was. When I replied, he said, "It doesn't look like a raptor". Teeth, claws, sickle claw, tail; how does it not look like a raptor, even if it does have feathers? Sigh... It doesn't look like a raptor if it DOESN'T have feathers! More like a noasaur...(although they didn't have sickle claws, on their feet anyway) |
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