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Author | Topic: Plausible Evolutionary Chains for Educational Use | |||||||||||||||||||||||
RAZD Member (Idle past 1436 days) Posts: 20714 From: the other end of the sidewalk Joined: |
trilobitomorpha and chelicerata (spiders and horseshoe crabs) are separate subphyla of arthropoda. Trilobites to spiders would be even better, as this would be another transition from aquatic to terrestrial. compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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arachnophilia Member (Idle past 1375 days) Posts: 9069 From: god's waiting room Joined: |
spiders and trilobites share a common ancestor -- something like a neotonous trilobite. looks like the larval form. you won't see a transition from trilobites to spiders and more than you will see one from dogs to cats.
i'm not actually very clear on arthropod evolution. i can point lith in this way, he'll explain to you why the initial request is silly.
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RAZD Member (Idle past 1436 days) Posts: 20714 From: the other end of the sidewalk Joined: |
i can point lith in this way I was thinking of calling him in to discuss other transitions from water to land, the evolution of bugs with legs, etc. Probably have some difficulty finding fossil evidence (we are talking pretty small stuff). compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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Lithodid-Man Member (Idle past 2961 days) Posts: 504 From: Juneau, Alaska, USA Joined: |
Like arach mentioned, trilobites and chelicerates (horse shoe crabs, spiders, etc) are very distantly related.
Traditionally four subphyla of arthropods, Crustacea, Chelicerata, Trillobitomorpha, and Unirama (although the latter is almost certainly polyphylectic) were recognized. The relationship between the four is unknown, and it is possible that at least one of those represents an independantly derived arthropod bauplan. Where the trilobites differ in a signicant manner from chelicerates is in the presence of antennae in front of the mouth. Chelicerates lack preoral appendages. This may not seem like a big difference, but is really significant. More recent analyses are strongly suggesting that the 'uniramians' (insects, millipedes, centipedes) are close to the crustaceans (united as the Mandibulata) and are a sister taxon to the Trilobitomorpha - Chelicerata clade (called the Arachnomorpha). A good summary of this and other suggested phylogenies can be found at: Palaeos: Page not found About the evolution of terrestrial arthropods... Well not much is known. In all liklihood the arachnids (spiders and their kin) derived from forms similar to the extinct sea scorpions, the Euryptida. Modern scorpions are the least derived of the arachnids (mites and ticks, the Acarii, being the most derived). There is a possible centipede-like marine arthropod from the Cambrian, and clear terrestrial primitive myriopods from the Silurian. My invert zoo papers are at school in my office. Somewhere here at home in all of my reprints I have an excellent article by Ed Bousfield on arthropod mouthpart morphology that I think has subsequently (more or less) been in agreement with more recent genetic work and cladistic analyses. Doctor Bashir: "Of all the stories you told me, which were true and which weren't?" Elim Garak: "My dear Doctor, they're all true" Doctor Bashir: "Even the lies?" Elim Garak: "Especially the lies"
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Equinox Member (Idle past 5173 days) Posts: 329 From: Michigan Joined: |
RAZD wrote:
quote:This is a pretty tall order if sufficient detail is included for each step along the way. While this may be the ultimate goal, it would be better broken down into discussable sub-sets. It certainly is a tall order if each step is to be supported by a complete fossil (or even an incomplete one). However fossil proof is not needed for a plausible chain. Since I’m only talking about plausible chains, they are NOT a tall order. It’s just a matter of an artist taking a few minutes to do it in consultation with an appropriately specialized biologist (like many people here - maybe lithoid man for the spider chain?). In fact, just this morning I watched, on the Cosmos series (Carl Sagan), the following plausible chains, with literally hundreds of steps in each one: Molecules to camelsMolecules to turtles Molecules to sponges Molecules to monkeys Molecules to dinosaurs Molecules to birds Molecules to starfish Molecules to humans They are on episode #2 (“one voice in the cosmic fugue”), and start around 25 minutes in. I’m looking for things like that which are more accessible to everyone, like say on a webpage or in a JPEG format, or such. Plus, more detail beyond the line drawings in Cosmos would be nice too. (If anyone doesn’t have the cosmos series, I highly recommend it - it single-handedly inspired thousands of people to enter the sciences). It’s at: Cosmos: Carl Sagan (1980) (just read the reviews if you are unsure - my 5 year old loves it already, it’s our special daddy-son “movie”). I hope I’m being clear that these are plausible (as in “not contradicted by the fossil record, nor by other evidence, such as genetic evidence”), chains. I’m not asking for cases where we have every leg bone of every creature at every step (or even a fossil of every step), or any such level of proof. Edited by AdminPD, : Fixed Link -Equinox _ _ _ ___ _ _ _You know, it's probably already answered at An Index to Creationist Claims... (Equinox is a Naturalistic Pagan - Naturalistic Paganism Home)
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RAZD Member (Idle past 1436 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Could you (or an admin) shorten your url to:
Cosmos: Carl Sagan (1980) using [url=(your url)]Cosmos: Carl Sagan (1980)[/url] It's so long it forces the page width too wide. Thanks.
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Equinox Member (Idle past 5173 days) Posts: 329 From: Michigan Joined: |
Thanks for telling me how to do it. Now I know.
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Equinox Member (Idle past 5173 days) Posts: 329 From: Michigan Joined: |
you know, I could even imagine a very plausible chain going back from a spider to the common ancestor, and then forward to the trilobite. As long as the common ancestor were noted, then this would work too.
I wonder if Lith knows of drawing or such of those transitions - not actual fossils, but plausible, scientifically consistent estimates? Thanks- -Equinox _ _ _ ___ _ _ _You know, it's probably already answered at An Index to Creationist Claims... (Equinox is a Naturalistic Pagan - Naturalistic Paganism Home)
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RAZD Member (Idle past 1436 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Anyone that knows of a chain of evolution from (X) to (Y) feel free to post it here. This thread is for accumulating various evidence(s) of long term evolution (macroevolution) for use in the debates.
Enjoy.
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RAZD Member (Idle past 1436 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Synapsida to Therapsida to Cynodontia to Mammaliforms to Morganucodontidae to ...
From reference (1) below
quote: The article then goes on to list a number of examples and their features, however it concentrates on the later fossils and the ones that are in transition (two jaw joints), and doesn't provide much information on the ones preceding them.. I would like to flesh this out with a list of the fossils involved from the first reptilian example to the final mammalian example, however my access to resources is limited at the moment, so help would be apprecieated. Names in the article: Therapsid (or Therapsida)tritylodont cynodonts Probainognathus (genus under cynodont) ictidosaurians Diarthrognathus Morganucodonts On tritylodont it quotes
quote: On Probainognathus it quotes
quote: On Diarthrognathus it says
quote: On Morganucodonts it quotes
quote: and then it says
quote: and it also talks about modern snakes having double jaw joints
quote: Other facts on the transition given are
quote: From reference (2) below:
quote: There is a wealth of information on that and following (linked) pages. It seems to me that this can be organized by fossil with a description of the initial reptilian example followed by the changes with each subsequent fossil, demonstrating the small level of change at each stage. The intent would be to show that at the start there was a reptile head, jaw, teeth and ear structure and that at the end there was a mammal head, jaw, teeth and ear structure, thus the creationist "cannot change one kind into another" would be refuted -- unless "kind" included all reptiles and all mammals (including humans) in one "kind" -- through "microevolution" steps and stages. Resources I have found include (1) http://www.geocities.com/...naveral/Hangar/2437/therapsd.htm(2) Palaeos: Page not found Enjoy. compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share. |
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