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A world without Crocodilia
Topic Started: Jul 31 2017, 11:51 AM (1,295 Views)
kusanagi
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Jul 31 2017, 02:07 PM
kusanagi
Jul 31 2017, 02:03 PM
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Jul 31 2017, 01:51 PM
kusanagi
Jul 31 2017, 01:46 PM
What started this off was two things: 1) contemplating the similarities of bichirs to rhipidistians, and 2) the plesiomorphic fish-like physiologies of temnospondyls and implicitly embolomers such as 560kg Eogyrinus which are now stemward of crown group tetrapods and possessed a tailfin skeleton. Obviously the giant "amphibians" of the Carboniferous to Cretaceous were fish like in physiology and yet became replaced by aquatic archosaurs, phytosaurs and choristoderes except in the cold south.
Please define "fish like", because fish have a very wide rang of physiologies.
I borrowed the term from Witzman's description of Archegosaurus in contrast to modern batrachians, which are derived and do not represent a primitive stage between bony fishes and reptiles. People like John Hawks make fun of the "all tetrapods are fish" sorts, but Archegosaurus was still a fish though with a developed neck and pentadactyl limbs.
You still didn't tell exactly what "fish like" is. In what way are temnospondyls fish like that lissamphibians are not?
I posted the link. ;)
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IIGSY
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kusanagi
Jul 31 2017, 02:03 PM
The word fish really ought to be abandoned
You know what's even worse than "fish"?

I think you all know what I'm about to say
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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.

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kusanagi
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Jul 31 2017, 02:32 PM
kusanagi
Jul 31 2017, 02:03 PM
The word fish really ought to be abandoned
You know what's even worse than "fish"?

I think you all know what I'm about to say
I would say, amphibian. Modern batrachians and caecilians are not representatives of basal tetrapods any more than amniotes are. Defining Amphibia to include batrachians and caecilians includes a lot of "fish with legs" and no amniote ancestors, though amniotes also derive from a "fish with legs" in the crown Tetrapoda's last common ancestor. Functionally the living Dipnoi are probably closer to the tetrapod and modern temnospondyl LCAs in most respects than are frogs or salamanders.
Edited by kusanagi, Jul 31 2017, 02:59 PM.
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IIGSY
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kusanagi
Jul 31 2017, 02:53 PM
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Jul 31 2017, 02:32 PM
kusanagi
Jul 31 2017, 02:03 PM
The word fish really ought to be abandoned
You know what's even worse than "fish"?

I think you all know what I'm about to say
I would say, amphibian. Modern batrachians and caecilians are not representatives of basal tetrapods any more than amniotes are. Defining Amphibia to include batrachians and caecilians includes a lot of "fish with legs" and no amniote ancestors, though amniotes also derive from a "fish with legs" in the crown Tetrapoda's last common ancestor.
You what's even worse than that? Invertebrate. At least with fish and amphibian, they are vaguely similar in some superficial ways. The same is not true for invertebrates. Even at the most superficial level, there is not a single, even remotely meaningful thing they have common.
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.

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Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


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Dragonthunders
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kusanagi
Jul 31 2017, 02:05 PM
Dragonthunders
Jul 31 2017, 02:02 PM
Quote:
 
But they have lungs

That's great, now you just have to make them not so dependent on cutaneous breathing with a more impermeable skin and you'll probably be close to a suitable model of croc-like lissamphibian.
Right: did amphiumas break that constraint by possessing fish-like internal gills? Do they have a metabolism like Archegosaurus or like other batrachians?
I'm not sure at all, although it is a little fascinating that they maintain that characteristic, it seems to me a little more than normally the neotenic forms of amphibians do not become completely independent of water. I'm not sure about what was the Archegosaurus metabolism, and with batrachians probably, however, I think I would have to investigate a little about it.

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You what's even worse than that? Invertebrate. At least with fish and amphibian, they are vaguely similar in some superficial ways. The same is not true for invertebrates. Even at the most superficial level, there is not a single, even remotely meaningful thing they have common.

That is too subjective to tell the truth.
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Rodlox
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kusanagi
Jul 31 2017, 01:03 PM

To properly fill the role of a croc analog an animal needs to be able to withstand droubt and maybe cross over land. Potentially this means a large fish with an amphibious disposition which is why I said bichirs. Catfish and snakeheads might be able to but pikes and mudminnows?
a croc analogue does not need to be exactly like a croc. bison and kangaroos are analogues, but they each do things the other cannot.
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HangingThief
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Mudminnows aren't an exceptionally likely candidate for crocodilian- like niches, but they do have cylindrical rather than vertically flattened bodies that allow them to slither and crawl on land a little bit rather than just flop like most fish. From personal observation (I have an aquarium with a few mudminnows I caught) they also sometimes use their pectoral and pelvic fins to "walk" along the bottom in a tetrapod- like manner.
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LittleLazyLass
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Future Earth will lilely have no crocodiles so what fills the same niche?

I've only skimmed what we have so far in this thread, but you've got me got on literally the first line here. What logic is there that crocodilians are likely to go extinct? I mean, in some crazy mass extinction, maybe, but they're a resilient group and assuming they're going to go extinct any time soon seems odd.
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IIGSY
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Little
Jul 31 2017, 11:23 PM
Quote:
 
Future Earth will lilely have no crocodiles so what fills the same niche?

I've only skimmed what we have so far in this thread, but you've got me got on literally the first line here. What logic is there that crocodilians are likely to go extinct? I mean, in some crazy mass extinction, maybe, but they're a resilient group and assuming they're going to go extinct any time soon seems odd.
They're very few in number as of now. There is less than 100 species at this point.
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.

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Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


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LittleLazyLass
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Oh goodness, not even a measly hundred species? They're tetrapods, a small group not having more than a hundred species isn't exactly evidence they're doomed.
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I don't even really like this song that much but the title is pretty relatable sometimes, I guess.
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IIGSY
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Little
Jul 31 2017, 11:39 PM
Oh goodness, not even a measly hundred species? They're tetrapods, a small group not having more than a hundred species isn't exactly evidence they're doomed.
Well, it's not just that. But it seems their diversity has been in decline ever since the K-PG extinction.
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


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


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All African countries can fit into Brazil
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HangingThief
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Jul 31 2017, 11:58 PM
Little
Jul 31 2017, 11:39 PM
Oh goodness, not even a measly hundred species? They're tetrapods, a small group not having more than a hundred species isn't exactly evidence they're doomed.
Well, it's not just that. But it seems their diversity has been in decline ever since the K-PG extinction.
Perhaps. But they're still pretty tough animals. All that modern species need is warm shallow water and some sort of prey, and they have a pretty extensive global distribution.
Hey.


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Rodlox
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Little
Jul 31 2017, 11:23 PM
Quote:
 
Future Earth will lilely have no crocodiles so what fills the same niche?

I've only skimmed what we have so far in this thread, but you've got me got on literally the first line here. What logic is there that crocodilians are likely to go extinct? I mean, in some crazy mass extinction, maybe, but they're a resilient group and assuming they're going to go extinct any time soon seems odd.
I figured it was two parts:
a. a thought experiment.
b. humans already nearly did in quite a number of crocodilian species around the world - its not outlandish to think that, by the time we leave the planet, we'd do in the crocs and some other groups.
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kusanagi
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Yes its a thought experiment but all of them are less than LC (least concern) except saltwater croc, spectacled caiman, and American alligator. Humans are likely to create a mass extinction of most species weighing over 20kg which is not only the size range of the few unthreatened crocodilians but of their prey. Of the three spectacled caiman maybe has the best chances of survival. The caimans will found populations in urban areas as they did here in Peru by catching rats, and are smaller than the other two likely survivors, presumably capable of rapid dwarfing if it is neccessary because their average body size already varies by population. There will be no more dwarf crocodilians or long-snouted gavial type crocodilians immediately after the anthropocene and at the very least entire continents will be missing the crocodilians thereby continuing the total decline already in place long before before man.
Edited by kusanagi, Aug 1 2017, 09:18 AM.
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IIGSY
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kusanagi
Aug 1 2017, 07:38 AM
Yes its a thought experiment but all of them are less than LC (least concern) except saltwater croc, spectacled caiman, and American alligator. Humans are likely to create a mass extinction of most species weighing over 20kg which is not only the size range of the few unthreatened crocodilians but of their prey. Of the three spectacled caiman maybe has the best chances of survival. The caimans will found populations in urban areas as they did here in Peru by catching rats, and are smaller than the other two likely survivors, presumably capable of rapid dwarfing if it is neccessary because their average body size already varies by population. There will be no more dwarf crocodilians or long-snouted gavial type crocodilians immediately after the anthropocene and at the very least entire continents will be missing the crocodilians thereby continuing the total decline already in place long before before man. and at the very least entire continents will be missing the crocodilians thereby continuing the total decline already in place long before before man.
Quote:
 
There will be no more dwarf crocodilians or long-snouted gavial type crocodilians immediately after the anthropocene and at the very least entire continents will be missing the crocodilians thereby continuing the total decline already in place long before before man.
Quote:
 
There will be no more dwarf crocodilians or long-snouted gavial type crocodilians immediately after the anthropocene
Quote:
 
Anthropocene
Uh, where still in the holocene.
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


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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