Author Topic: Crash Course in Evolution and What It Is  (Read 11603 times)

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Offline Vene

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Re: Crash Course in Evolution and What It Is
« Reply #30 on: January 17, 2012, 11:23:55 pm »
To some extent, it still depends on who you ask, but the only way to make the reptiles monophyletic is to include birds.

Offline Lithp

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Re: Crash Course in Evolution and What It Is
« Reply #31 on: January 17, 2012, 11:36:16 pm »
Wouldn't you also have to include mammals? Monophyletic is "all descendents of a common ancestor," correct? And aren't mammals descended from reptiles?

Offline Vene

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Re: Crash Course in Evolution and What It Is
« Reply #32 on: January 18, 2012, 12:03:38 am »
If we look at the phylogeny we see we don't need to include mammals.
« Last Edit: January 18, 2012, 12:07:17 am by Vene »

Offline Lithp

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Re: Crash Course in Evolution and What It Is
« Reply #33 on: January 18, 2012, 12:14:26 am »
I don't follow. Clearly mammals aren't closely related to birds, dinosaurs, & "modern reptiles," but there are also a number of much older animals, in the Carboniferous & Permian eras, that are classified as reptiles.

Offline Vene

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Re: Crash Course in Evolution and What It Is
« Reply #34 on: January 18, 2012, 12:26:44 am »
Lithp, synapsida is mammals, and anapdsia and diapsida are reptiles. You can easily make mammals monophyletic while keeping them separate from reptiles and have reptiles also be a monophyletic group.

Offline Lithp

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Re: Crash Course in Evolution and What It Is
« Reply #35 on: January 18, 2012, 12:58:00 am »
So, what about this? If the page is to be believed, its ancestors include synapsida & diapsida, & it is still considered a reptile.

Offline Jack Mann

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Re: Crash Course in Evolution and What It Is
« Reply #36 on: January 18, 2012, 01:18:17 am »
For its ancestors to include both synapsida and diapsida, it would require interbreeding between wildly different species.  Rather, it shares a common ancestor with both synapsida and diapsida.

However, it's true that it probably shouldn't be considered a reptile unless mammals are.  Really, what we consider "reptiles" should probably be split into several different groups (testudines, squamates [possibly further split into squamates and sphenodonts], crocodilians, and dinosaurs [including birds]).
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Offline Lithp

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Re: Crash Course in Evolution and What It Is
« Reply #37 on: January 18, 2012, 01:26:49 am »
No, I meant to say that its successors include those groups, sorry, I was rushing around with chemistry, & I'm already something like 3 hours late for bed.

Offline Vene

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Re: Crash Course in Evolution and What It Is
« Reply #38 on: January 18, 2012, 10:34:24 am »
Lithp, here's a phylogeny of that organism:

http://sysbio.oxfordjournals.org/content/54/4/530.full

Paleothyris acadiana is still on a completely different lineage than synapsida.

Offline Lithp

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Re: Crash Course in Evolution and What It Is
« Reply #39 on: January 18, 2012, 10:01:06 pm »
Then I guess this:


Quote
Paleothyris is at the base of a large clade, the Protosynapsida, defined as Paleothyris, Passer, their last common ancestor and all of its decendants. Casineria and the microsaurs are outgroups. The Protosynapsida includes the Synapsida and the Diapsida.

...must be incorrect. All I know is that I keep hearing that mammals evolved from reptiles in the Permian Era. Hence, the conclusion I keep coming to is that either all of those things are wrong, or mammals are descended from animals classed as reptiles.

I wish I had a scanner so I could show you exactly what I'm looking at, but I don't.

Offline Jack Mann

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Re: Crash Course in Evolution and What It Is
« Reply #40 on: January 19, 2012, 08:27:17 pm »
Mammals evolved from a common ancestor to reptiles, one which resembled modern reptiles more than modern mammals.  Because of earlier scientific understanding, they were classified as reptiles, leading to a paraphyletic designation (that is, the descendants of a reptile should likewise be called reptiles).  The common ancestor should be called something other than reptile under monophyletic definitions.  I also think that reptilia should be split up.  Right now, reptiles basically consist of everything in amniota left over after mammals and birds are taken out.  The wastebin of amniotes.
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Offline D Laurier

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Re: Crash Course in Evolution and What It Is
« Reply #41 on: January 26, 2012, 03:04:34 pm »
Tending to agree that "reptiles" is a bogus class. More a "wastebin" than a meaningfull grouping.
Cable (or satelite) TV is like paying someone to projectile poop all over your brain.

Offline Vene

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Re: Crash Course in Evolution and What It Is
« Reply #42 on: January 26, 2012, 05:27:17 pm »
Tending to agree that "reptiles" is a bogus class. More a "wastebin" than a meaningfull grouping.
If you want to see a real wastebin look up protista.

Offline D Laurier

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Re: Crash Course in Evolution and What It Is
« Reply #43 on: January 26, 2012, 07:17:27 pm »
Tending to agree that "reptiles" is a bogus class. More a "wastebin" than a meaningfull grouping.
If you want to see a real wastebin look up protista.
No thankyou. I'm gonna take your word for it.
I'll just pour myself another margarita instead. It's less frustrating.

Cable (or satelite) TV is like paying someone to projectile poop all over your brain.

Offline Lithp

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Re: Crash Course in Evolution and What It Is
« Reply #44 on: January 26, 2012, 08:47:14 pm »
Protists are a fucking mess.