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What is a tetrapod?
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Topic Started: Jun 13 2017, 07:27 PM (1,742 Views)
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IIGSY
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Jun 13 2017, 07:27 PM
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A huntsman spider that wastes time on the internet because it has nothing better to do
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On another thread, the subject of the boundaries of "tetrapoda" was brought up.
There is two conflicting views. Anything with recognizable feet is a tetrapod, including the basal ichthyosteglians and other assorted animals.
The second view (and the one wikipedia goes with) is that tetrapoda is only the crown group, with the wider group being "Stegocephalia"
What do you think?
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
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LittleLazyLass
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Jun 13 2017, 07:49 PM
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Proud quilt in a bag
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I've never really heard of the view that stuff like Ichtyostega doesn't count, and it sounds really stupid to me. Crown group definitions always really bothered me.
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totally not British, b-baka!
You like me (Unlike) I don't even really like this song that much but the title is pretty relatable sometimes, I guess.
Me  Forum user Uncanny Gemstar drew what is supposed to be a me. Thanks! Spoiler: click to toggle As they walk in, they're greeted by a small, poorly kept pathway leading to a poorly constructed Japanese-style gate. Behind this, a small field made up of corn, rice, wheat, potatoes, among other plants is contrasted by large piles of books, as well as a few rather out of place looking laptops. Off in the corner, a small woman, with long, striped, and strikingly colorful socks, no shoes, unremarkable denim shorts, a large, fancy black coat, arm warmers, glasses, a tuque, and somewhat unkempt, mid-length blue-and-pink-streaked red hair, is rummaging through a trash bin, located behind a sign saying "employees only". She continues this for a while (walking behind a wall to change her outfit now and then), until one of her visitors coughs. Startled, she looks up, apologizes, and grabs a handful of textbooks and novels before daintily running off to join them. What, you want me to tell you what these mean? Predenterra The (Lost) Lost World The Standing World Read First Clarifications on my sex and genderSorry if I come off as rude, I don't put much thought into word choice sometimes. I'm also super prone to editing my posts, sometimes multiple times, in the minutes following posting. For the love of god, take my posts from my earlier days on the forum with a grain of salt. I was not particularly knowledgeable or mature back then. Some of them are so cringe-worthy I can't even bring myself to look at them. Words Maybe Great Words - Words To Spec By
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Yeah, and even if you don't agree with creationists on that concept, that doesn't mean they can't be decent people. I have friends who are creationist (possibly even young earth) that I get along with fine in general life. I don't think they're right of course, but that doesn't make them intellectual degenerates. ~~The Words of forbidden3
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IIGSY
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Jun 13 2017, 07:52 PM
Post #3
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A huntsman spider that wastes time on the internet because it has nothing better to do
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- Little
- Jun 13 2017, 07:49 PM
I've never really heard of the view that stuff like Ichtyostega doesn't count, and it sounds really stupid to me. Crown group definitions always really bothered me. https://en.wikipedia.org/wiki/Tetrapodomorpha#Relationships
Take a look
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
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Mitosis
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Jun 14 2017, 04:34 PM
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According to the crown group definition, what is a Tetrapod is defined not by morphology, but by ancestry. Only the common ancestor of Lissamphibia+Amniota (or frogs and princes) and all of its descendants are members of the group Tetrapoda, while every other prehistoric four-legged creature (no matter how large degree of a terrestial adaptation it had) is classified as a Tetrapodomorph.
All in all, the phylogeny of non-Lissamphibian, non-Amniote terrestrial vertebrates is a mess, because we don't exactly know where the extant groups came from. Lissamphibia could have come from either Temnospondyls (crocodile-like creatures) or Lepospondyls (salamander or eel-like creatures). Frogs and Salamanders could have come from Temnospondyls, and Caecilians could have come from Lepospondyls, making Lissamphibia polyphyletic. Reptiliomorphs (the ancestors of Amniotes) could have been a sister group of early Tetrapodomorphs, evolving towards a more terrestrial condition in parallel with them, or they could be a sister group to Lepospondyls.
What we know for sure is that lots of lizard, salamander, and crocodile-like creatures were roaming around the Carboniferous, one group eventually spawned modern Lissamphibians, the other modern Tetrapods.
It is interesting to note that modern Tuataras (the most basal living amniotes) have a nervous system more similar to that of modern Lissamphibians, than to other living Tetrapods, which may imply that Lissamphibians and Reptiliomorphs share a close common ancestry, and both developed from a line more closely related to the less successful, more basal, and more aquatic Lepospondyls, rather than the more terrestrial Temnospondyls, which must have evolved a more Amniote-like nervous system convergently to cope with their more terrestrial habitat.
The amniotic egg likely evolved the amniotic membranes gradually, therefore a small, frail creature with small eggs (where gas diffusion could work better while the amnion and chorion were still in a more basal state) is a better candidate for the origin of Amniotes than a large crocodile-like animal, supporting the theory of a close ancestry of Lissamphibians and Reptiliomorphs and a general Lepospondyl affinity for both groups.
Edited by Mitosis, Jun 14 2017, 04:46 PM.
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IIGSY
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Jun 14 2017, 06:02 PM
Post #5
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A huntsman spider that wastes time on the internet because it has nothing better to do
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- Mitosis
- Jun 14 2017, 04:34 PM
The amniotic egg likely evolved the amniotic membranes gradually, therefore a small, frail creature with small eggs (where gas diffusion could work better while the amnion and chorion were still in a more basal state) is a better candidate for the origin of Amniotes than a large crocodile-like animal, supporting the theory of a close ancestry of Lissamphibians and Reptiliomorphs and a general Lepospondyl affinity for both groups. That would place temnospondyls outside tetrapoda, and that would destroy the purpose of even having a "tetrapoda". Trying to figure out what falls in and out of the crown group is a real pain in the ass, so going by this definition is counterproductive as it would pointlessly exclude animals that would otherwise definitely be tetrapods. Tetrapoda should be equivalent to "Stegocephalia", because it includes everything more crownward than Tiktaalik*

*Well, it depends on the author. In some places (Including wikipedia) it does include tiktaalik. I'v even seen include panderichthys one time. But anything beyond that is a no-no. I personally think we should draw the line between tiktaalik and elginerpeton.
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
|
| |
|
Tartarus
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Jun 14 2017, 07:36 PM
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- Mitosis
- Jun 14 2017, 04:34 PM
Frogs and Salamanders could have come from Temnospondyls, and Caecilians could have come from Lepospondyls, making Lissamphibia polyphyletic. What? So it has actually been suggested that Lissamphibia is not a valid clade?
On crown groups I agree somewhat with Little's view on the matter. It does seem somewhat arbitrary to base the definitions of these groups on which creatures survive today. One good example is how things like morganucodonts and docodonts are seen as not being mammals, as they are outside the crown group, yet if they lived today they would almost certainly be seen as mammals.
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IIGSY
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Jun 14 2017, 07:38 PM
Post #7
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A huntsman spider that wastes time on the internet because it has nothing better to do
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- Tartarus
- Jun 14 2017, 07:36 PM
On crown groups I agree somewhat with Little's view on the matter. It does seem somewhat arbitrary to base the definitions of these groups on which creatures survive today. One good example is how things like morganucodonts and docodonts are seen as not being mammals, as they are outside the crown group, yet if they lived today they would almost certainly be seen as mammals. Exactly. Or excluding fuxianhuids and megacheirans from arthropods because they are not in the crown group (well, megacheirans may be closer to chelicerates, but that's a whole nother can of worms)
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
|
| |
|
LittleLazyLass
|
Jun 14 2017, 07:48 PM
Post #8
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Proud quilt in a bag
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Paraphyletic Lissamphibia has been suggested, by my impression is that it's a fairly dead theory at this point. To my knowledge a temnospondyl identity has been favored recently, but it's not my area of expertise.- Quote:
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Reptiliomorphs (the ancestors of Amniotes) could have been a sister group of early Tetrapodomorphs, evolving towards a more terrestrial condition in parallel with them As far as I know this idea never held much water.- Quote:
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Tuataras (the most basal living amniotes) This is flat wrong, they're the sister group to lizards. No more "basal" than any given snake, archosaur, or mammal.- Quote:
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Only the common ancestor of Lissamphibia+Amniota (or frogs and princes) and all of its descendants are members of the group Tetrapoda I swear I never saw this be the consensus before, but wikipedia has indeed switched to this interpretation. Either way, it's a blatantly unhelpful way to classify things: by any reasonable definition something like Cassigyrinus is a tetrapod. Now everyone has to start using "stem-tetrapod" all the time.
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totally not British, b-baka!
You like me (Unlike) I don't even really like this song that much but the title is pretty relatable sometimes, I guess.
Me  Forum user Uncanny Gemstar drew what is supposed to be a me. Thanks! Spoiler: click to toggle As they walk in, they're greeted by a small, poorly kept pathway leading to a poorly constructed Japanese-style gate. Behind this, a small field made up of corn, rice, wheat, potatoes, among other plants is contrasted by large piles of books, as well as a few rather out of place looking laptops. Off in the corner, a small woman, with long, striped, and strikingly colorful socks, no shoes, unremarkable denim shorts, a large, fancy black coat, arm warmers, glasses, a tuque, and somewhat unkempt, mid-length blue-and-pink-streaked red hair, is rummaging through a trash bin, located behind a sign saying "employees only". She continues this for a while (walking behind a wall to change her outfit now and then), until one of her visitors coughs. Startled, she looks up, apologizes, and grabs a handful of textbooks and novels before daintily running off to join them. What, you want me to tell you what these mean? Predenterra The (Lost) Lost World The Standing World Read First Clarifications on my sex and genderSorry if I come off as rude, I don't put much thought into word choice sometimes. I'm also super prone to editing my posts, sometimes multiple times, in the minutes following posting. For the love of god, take my posts from my earlier days on the forum with a grain of salt. I was not particularly knowledgeable or mature back then. Some of them are so cringe-worthy I can't even bring myself to look at them. Words Maybe Great Words - Words To Spec By
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It would have to be something extremely alien, pushing the limits of our imagination. But those are always my favorite kinds of life. ~~The Words of The Xenologist
- Words To Live By
-
Ignorance is never insulting if you're willing to learn, we're all ignorant about most things. ~~The Words of Lamna
- Words I Live By
-
Yeah, and even if you don't agree with creationists on that concept, that doesn't mean they can't be decent people. I have friends who are creationist (possibly even young earth) that I get along with fine in general life. I don't think they're right of course, but that doesn't make them intellectual degenerates. ~~The Words of forbidden3
Member Quotes - jman123
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Ass-breathing fish-lizards? Sounds like a punk rock band
- Sheather
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"Holy fucking shit a toilet paper roll! Our favorite thing!"
- Urufumarukai
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Tyrannosaurus aquastronka
- Kamineigh
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Myo, if you don't stop reading the YouTube comments...
- Lamna
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Are you saying what I think you're saying?
Sheather bathes in cum?
- Cephylus
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And last night I dreamed I was blowing up a Kindergarten with a grenade launcher for no particular reason...
- revin
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Oh, and of course more people get killed by selfies than by sharks. Of course.
- Parasky
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SHEEEEAAAAATTTTTTHHHHHHHHHEEEEEEEEERRRRRRRRR!!!!!!!!
- whachamacalit2
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The smell of rotting flesh really kills my appetite, surprising, but the visual appearance of corpses makes me hungry. Is that weird?
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I mean, let us say I'm a genderfluid blurflux demi-romantic woman who is sexually attracted to men, but only if they are Melanesian and have a voice like that of Nicholas Cage. Okay, so what?
- trex841
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When I first saw that picture, I thought you were dissecting a condom.
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All hail Robo-Stalin.
- Peashyjah
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Seems like everything in this project is now dead.
- Stealth Rock
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Seagulls are pretty much trees, right?
- Watcher
-
We all must finish chapters of our lives to go on to the next. Sometime this means leaving behind versions of ourselves that don't want to die.
- Yiqi15
-
For April fool's, we had to make an orgasm that resembled a human foot.
- Flisch
-
im the black market
- CaledonianWarrior96
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He was a skater birb, she said tweet you later birb
- Most People at Some Point
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Quotes - Some dude called plucas1 from Youtube comments
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Funny, isn't it, that our world needs Clark Kent a lot more than Superman.
- Xenoblade Chronicles
-
Even though he is our creator, that does not afford him the right to take our lives on a whim. But that is the thinking of a homs. He is a god. Such morals cannot apply to gods. So you think we should just shut up and die?! If that is the fate decided by a god. You are mistaken if you think we will simply accept such a fate and wait to die. We'll never stop fighting. Not till the end. To Zanza, the outcome is the same. Thus your logic is flawed.
- Hades - Kid Icarus Uprising
-
When freaky aliens give you lemons, make freaky alien lemonade.
- Kid Icarus Uprising
-
But Souls are delicious. They're like bacon - they taste good on anything. But if you eat them, you completely remove them from existence! They can't move on or... or be reincarnated! Huh. I never really gave it much thought. Besides, what do you mean by reincarnation anyway? You know, being reborn as someone or something else. Which means different body, different memories, different experiences, yes? So isn't being reborn as "something else" the same as being "removed from existence"? I... I... eating souls isn't right! That depends on your definition of "right". All living things survive by eating other living things. So what? You're a god. You should be above all that! Gods are above living things, which doesn't necessarily mean we care about them.
- Some Dude on BBC Two
-
You are being shagged... by a flightless parrot.
Stuff
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IIGSY
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Jun 14 2017, 08:12 PM
Post #9
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A huntsman spider that wastes time on the internet because it has nothing better to do
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- Little
- Jun 14 2017, 07:48 PM
- Quote:
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Only the common ancestor of Lissamphibia+Amniota (or frogs and princes) and all of its descendants are members of the group Tetrapoda
I swear I never saw this be the consensus before, but wikipedia has indeed switched to this interpretation. Either way, it's a blatantly unhelpful way to classify things: by any reasonable definition something like Cassigyrinus is a tetrapod. Now everyone has to start using "stem-tetrapod" all the time. How do you view tiktaalik in this regard?
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
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LittleLazyLass
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Jun 14 2017, 08:22 PM
Post #10
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Proud quilt in a bag
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I always remember that being considered a tetrapodomorph.
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totally not British, b-baka!
You like me (Unlike) I don't even really like this song that much but the title is pretty relatable sometimes, I guess.
Me  Forum user Uncanny Gemstar drew what is supposed to be a me. Thanks! Spoiler: click to toggle As they walk in, they're greeted by a small, poorly kept pathway leading to a poorly constructed Japanese-style gate. Behind this, a small field made up of corn, rice, wheat, potatoes, among other plants is contrasted by large piles of books, as well as a few rather out of place looking laptops. Off in the corner, a small woman, with long, striped, and strikingly colorful socks, no shoes, unremarkable denim shorts, a large, fancy black coat, arm warmers, glasses, a tuque, and somewhat unkempt, mid-length blue-and-pink-streaked red hair, is rummaging through a trash bin, located behind a sign saying "employees only". She continues this for a while (walking behind a wall to change her outfit now and then), until one of her visitors coughs. Startled, she looks up, apologizes, and grabs a handful of textbooks and novels before daintily running off to join them. What, you want me to tell you what these mean? Predenterra The (Lost) Lost World The Standing World Read First Clarifications on my sex and genderSorry if I come off as rude, I don't put much thought into word choice sometimes. I'm also super prone to editing my posts, sometimes multiple times, in the minutes following posting. For the love of god, take my posts from my earlier days on the forum with a grain of salt. I was not particularly knowledgeable or mature back then. Some of them are so cringe-worthy I can't even bring myself to look at them. Words Maybe Great Words - Words To Spec By
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It would have to be something extremely alien, pushing the limits of our imagination. But those are always my favorite kinds of life. ~~The Words of The Xenologist
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Ignorance is never insulting if you're willing to learn, we're all ignorant about most things. ~~The Words of Lamna
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Yeah, and even if you don't agree with creationists on that concept, that doesn't mean they can't be decent people. I have friends who are creationist (possibly even young earth) that I get along with fine in general life. I don't think they're right of course, but that doesn't make them intellectual degenerates. ~~The Words of forbidden3
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Ass-breathing fish-lizards? Sounds like a punk rock band
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Tyrannosaurus aquastronka
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Myo, if you don't stop reading the YouTube comments...
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Are you saying what I think you're saying?
Sheather bathes in cum?
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SHEEEEAAAAATTTTTTHHHHHHHHHEEEEEEEEERRRRRRRRR!!!!!!!!
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The smell of rotting flesh really kills my appetite, surprising, but the visual appearance of corpses makes me hungry. Is that weird?
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I mean, let us say I'm a genderfluid blurflux demi-romantic woman who is sexually attracted to men, but only if they are Melanesian and have a voice like that of Nicholas Cage. Okay, so what?
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When I first saw that picture, I thought you were dissecting a condom.
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All hail Robo-Stalin.
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Seems like everything in this project is now dead.
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Seagulls are pretty much trees, right?
- Watcher
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We all must finish chapters of our lives to go on to the next. Sometime this means leaving behind versions of ourselves that don't want to die.
- Yiqi15
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For April fool's, we had to make an orgasm that resembled a human foot.
- Flisch
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im the black market
- CaledonianWarrior96
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He was a skater birb, she said tweet you later birb
- Most People at Some Point
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Quotes - Some dude called plucas1 from Youtube comments
-
Funny, isn't it, that our world needs Clark Kent a lot more than Superman.
- Xenoblade Chronicles
-
Even though he is our creator, that does not afford him the right to take our lives on a whim. But that is the thinking of a homs. He is a god. Such morals cannot apply to gods. So you think we should just shut up and die?! If that is the fate decided by a god. You are mistaken if you think we will simply accept such a fate and wait to die. We'll never stop fighting. Not till the end. To Zanza, the outcome is the same. Thus your logic is flawed.
- Hades - Kid Icarus Uprising
-
When freaky aliens give you lemons, make freaky alien lemonade.
- Kid Icarus Uprising
-
But Souls are delicious. They're like bacon - they taste good on anything. But if you eat them, you completely remove them from existence! They can't move on or... or be reincarnated! Huh. I never really gave it much thought. Besides, what do you mean by reincarnation anyway? You know, being reborn as someone or something else. Which means different body, different memories, different experiences, yes? So isn't being reborn as "something else" the same as being "removed from existence"? I... I... eating souls isn't right! That depends on your definition of "right". All living things survive by eating other living things. So what? You're a god. You should be above all that! Gods are above living things, which doesn't necessarily mean we care about them.
- Some Dude on BBC Two
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You are being shagged... by a flightless parrot.
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IIGSY
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Jun 14 2017, 08:45 PM
Post #11
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A huntsman spider that wastes time on the internet because it has nothing better to do
- Posts:
- 3,758
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- #1,987
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- Little
- Jun 14 2017, 08:22 PM
I always remember that being considered a tetrapodomorph. Well, I'v heard some people call it a tetrapod. For me, and probably you, recognizable feet=tetrapod
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
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Mitosis
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Jun 15 2017, 10:45 AM
Post #12
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I know Tuataras are not basal in a phylogenetic sense (they are firmly within Diapsids and Lepidosauria), but they are the ones that preserved the largest number of plesiomorphic traits from the common ancestor of all Amniotes.
Mammals and Diapsids all have nervous systems that are more complex than that of Lissamphibians, even lizards, which as you noted, are very close to Tuataras, but the fact that there is little difference between the Tuatara and the Lissamphibian nervous system suggests that all Amniotes evolved a more complex nervous system in parallel with eachother only way after the Synapsid-Sauropsid split.
Another trait that could suggest a close Lissamphibian-Amniote affinity is the presence of the Allantois in both groups. The Allantois is an amniotic membrane that collects nitrogenous waste in the developing embryo. Fish (even Lungfish) don't have this structure, but Lissamphibians have a small Allantois while lacking the other amniotic membranes, which suggests that Lissamphibians split from a line that was already evolving towards the Amniotic condition.
- Quote:
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Well, I'v heard some people call it a tetrapod. For me, and probably you, recognizable feet=tetrapod
Strict crown-group definitions rely completely on ancestry, while disregarding morphology. For example, the first crown-group Amniote is not the first creature that laid an Amniotic egg, but the last common ancestor of Mammals and Birds.
Similarily, the first Tetrapod is not the first Vertebrate that walked around on four legs, but the last common ancestor of Amniotes and Lissamphibians. If Amniotes and Lissamphibians share a close, Lepospondyl affinity, then no matter how terrestrial and crocodile-like Temnospondyls were, they are not Tetrapods.
Edited by Mitosis, Jun 15 2017, 11:16 AM.
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IIGSY
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Jun 15 2017, 12:46 PM
Post #13
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A huntsman spider that wastes time on the internet because it has nothing better to do
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- Mitosis
- Jun 15 2017, 10:45 AM
Similarily, the first Tetrapod is not the first Vertebrate that walked around on four legs, but the last common ancestor of Amniotes and Lissamphibians. If Amniotes and Lissamphibians share a close, Lepospondyl affinity, then no matter how terrestrial and crocodile-like Temnospondyls were, they are not Tetrapods. This is why a crown based definition is extremely counter-productive. So many things that would otherwise be tetrapods are excluded for this dumb reason. Classifying organisms based on which ones are alive today is stupid. Hell, is monotremones where extinct, they wouldn't be classified as mammals.
Plus, how do we know that amniotes are closer to lepospondyls than temnospondyls?
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
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Mitosis
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Jun 15 2017, 01:16 PM
Post #14
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Introducing morphological characteristics to define clades also introduces ambiguity in what constitutes a clade and where do we draw the line between two clades.
For example, imagine that you visit the Carboniferous with a time machine. You start studying a small animal, which is rather similar to a modern lizard, but also different. It has keratinous claws, there is a little differentiation in its teeth, you can clearly see proto-canines and proto-molars, it has a skin that is thicker than that of modern lissamphibians, but somehow also soft and a bit slimy, not at all modern lizard like.
At this point, everything seems to spell out "The First Synapsid" or at least a creature that is definitely an Amniote.
However, ambiguity starts setting in quickly: You put it under an X-ray machine, and see that it has a box-like skull with no fenestra, it gulps down large amounts of water frequently, and it urinates a lot.
Eventually, you get to see how it reproduces: The male mounts the female with a "cloacal kiss".
The female finds a muddy puddle and lays a large amount of small eggs in it.
You put one of the eggs under a microscope and observe its development: The embryo forms, it has an amnion, a chorion, and an allantois, but all three of them are rather underdeveloped and seem more like random mutations that stuck, than true, functioning amniotic membranes.
The mother sometimes returns to the eggs to urinate on them, when the puddle starts drying up.
The embryo forms into a tadpole that seems to be capable of free living, but before it hatches, it transforms from a tadpole into the adult form. The hatchling emerges from the egg, it is air-breathing, has no external gills, and it is ready to start life outside of water.
Now, what kind of animal have you seen? If we go with the morphological definition of an Amniote we are stuck with "It may be an Amniote or may be not", if we go with the crown-group definition, it is definitely not an Amniote.
Since evolution happens gradually and not overnight, morphological characteristics don't help us very much in clearly delimiting clades.
The animals we observed may have been the great-great-great-great-grandparents of Bob the Basal Amniote, but it could be a species belonging to a different clade that died out, maybe a basal clade on the line towards crown-group Amniotes.
- Quote:
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Plus, how do we know that amniotes are closer to lepospondyls than temnospondyls?
I remember reading a study (don't know where sorry) that Lepospondyls and Reptiliomorphs did a lot of experimentation on either becoming pedomorphic (retaining a modified tadpole stage into adult life) or peramorphic (direct development to an adult form while minimizing the time spent as a tadpole) and this could have given rise to a lot of evolutionary flexibility.
Temnospondyls on the other hand pretty much stuck with the tried-and-true method of tadpole young and semi-aquatic crocodilian adults.
Edited by Mitosis, Jun 16 2017, 01:52 AM.
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IIGSY
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Jun 15 2017, 02:54 PM
Post #15
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A huntsman spider that wastes time on the internet because it has nothing better to do
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If I saw such an animal, I'd classify it as a basal amniote. But still an amniote nonetheless.
- Quote:
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Introducing morphological characteristics to define clades also introduces ambiguity in what constitues a clade and where do we draw the line between two clades. People really underestimate the helpfulness of morphological characteristics. Hell, dinosaurs are defined based on morphology. Crown group definitions are not exempt, as you still need characteristics to figure out weather or not they belong in the crown group.
In reality, all classifications are arbitrary and no one is perfect. As you said, a purely morphology based "tetrapoda" can be ambiguous at times, but a crown group definition for tetrapods is even worse. It pointlessly excludes things that would otherwise that would otherwise be tetrapods under any reasonable definition. Same for other groups as well.
As the relative position of chelicerates, mandibulates, and artiopods relative to one another is very uncertain, a strict crown based definition of arthropoda could possibly exclude trilobites, which is extremely pandenic and counterproductive. Plus, trying to figure out weather something falls in or out of the crown group is a real pain in the ass, as is the case with that whole lissamphibia mess.
Edited by IIGSY, Jun 15 2017, 03:07 PM.
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod
ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)
Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents.
Quotes "Arthropod respiratory systems aren't really "inefficient", they're just better suited to their body size. It would be quite inefficient for a tiny creature that can easily get all the oxygen it needs through passive diffusion to have a respiratory system that wastes energy on muscles that pump air into sacs. (Hence why lungless salamanders, uniquely miniscule and hyperabundant tetrapods, have ditched their lungs in favor of breathing with their skin and buccal mucous membranes.) But large, active insects already use muscles to pump air in and out of their spiracles, and I don't see why their tracheae couldn't develop pseudo- lungs if other conditions pressured them to grow larger."-HangingTheif
"Considering the lifespans of modern non- insect arthropods (decade-old old millipedes, 50 year old tarantulas, 100+ year old lobsters) I wouldn't be surprised if Arthropleura had a lifespan exceeding that of a large testudine"-HangingTheif
"Humans have a tribal mindset and it's not alien for tribes to war on each other. I mean, look at the atrocities chimpanzee tribes do to each other. Most of people's groupings and big conflicts in history are directly or obliquely manifestations of this tribal mindset."-Sceynyos-yis
"He's the leader of the bunch You know his Coconut Gun is finally back to fire in spurts. His Coconut Gun Can make you smile If he shoots ya it's firing in spurts. His Coconut Gun Is bigger, faster, stronger too! He's the gun member of the Coconut Crew! HUH!
C.G.! Coconut Gun! C.G.! Co-Coconut Gun! Shoot yourself with a Coconut Gun! HUH!"-Kamineigh
"RIP, rest in Peytoia."-Little
"In Summary: Piss on Lovecraft's racist grave by making lewds of Cthulhu and Nyarlathotep.
Then eat arby's and embrace the void."-Kamineigh
"Dougal Dixon rule 34."-Sayornis
Phylogeny of the arthropods and some related groups
In honor of the greatest clade of all time
More pictures
Other cool things
All African countries can fit into Brazil
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