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| A world without Crocodilia | |
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| Topic Started: Jul 31 2017, 11:51 AM (1,291 Views) | |
| kusanagi | Jul 31 2017, 11:51 AM Post #1 |
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Adolescent
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Future Earth will lilely have no crocodiles so what fills the same niche? Historically it was filled by Palaeozoic tetrapods outside of crown amniotes or batrachians. Bichirs are functionally close enough to the rhipidistians they could become analogs of big, double breathing tetrapods such as embolomers and madtodontosaurs. Exactly how hard is it to get a bichir to become something like Eogyrinus? Something like Mastodontosaurus is maybe harder but some degree of dorsoventral flattening is surely not impossible. Bichir cartilaginous skeletons might become a size constraint for basking or chasing prey onto the land contra Naish's playful reinterpretation of a stegosaur-like cryptid as a bichir. On the other hand, Bawitius reached 3m long in the Cretaceous. Champsosaurs are an example of a non-archosaur reptile filling the same kind of ecological niche as a crocodile or a phytosaur in the Mesozoic. In the absence of archosaurs any ectothermic reptile taking on the role must derive from lepidosaurs. Skinks, Shinisaurus, water monitors, Dracaena and others all demonstrate the ease with which squamates can adapt to aquatic lifestyles with powerful tail strokes. Monitors and tegus also show definite macropredatory trends as did mosasaurs and by chance both living families show species with aquatic tendencies. Then there are the snapping turtles which have a different bauplan but a similar way of life. The multiton protostegid turtles were able to crawl up beaches meaning huge non-pelagic chelonians are also plausible even in the size range of giant fossil crocodilians such as Deinosuchus. Stupendemys is a herbivorous turtle of a relevant mass and warm freshwater habitat. Edited by kusanagi, Jul 31 2017, 11:53 AM.
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| IIGSY | Jul 31 2017, 12:22 PM Post #2 |
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A huntsman spider that wastes time on the internet because it has nothing better to do
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What about snakes and lissamphibians? |
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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 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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| Dragonthunders | Jul 31 2017, 12:23 PM Post #3 |
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The ethereal archosaur in blue
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Yeah, it is likely that in the case of the total extinction of the crocodilian clade, lepidosaurs and chelonians have the best chance of obtaining several of the niches that crocodiles cover, from fish eaters to semi-aquatic ambush predators, at least in a short term period like 10 and 25 million years, probably with a fairly established new groups. I honestly think that with such extinction there would be more room for other varieties of fish to take such niches, as long as there is no greater competition, I would imagine catfishes, pikes and maybe mudminnows as good candidates. |
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Projects "Active" projects The Future is Far Welcome to the next chapters of the evolution of life on earth, travel the across the earth on a journey that goes beyond the limits, a billion years of future history in the making. The SE giants project Wonder what is the big of the big on speculative evolution? no problem, here is the answer Coming one day Age of Mankind Humanity fate and its possible finals. The Long Cosmic Journey The history outside our world. The alternative paths The multiverse, the final frontier... Holocene park: Welcome to the biggest adventure of the last 215 million years, where the age of mammals comes to life again! Cambrian mars: An interesting experiment on an unprecedented scale, the life of a particular and important period in the history of our planet, the cambric life, has been transported to a terraformed and habitable mars in an alternative past. Two different paths, two different worlds, but same life and same weirdness. My deviantart | |
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| kusanagi | Jul 31 2017, 01:03 PM Post #4 |
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Adolescent
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The crown batrachians seem to suffer a size constraint that lungfish-like primitive temnospondyls did not. Cryptobranchids and Beelzebufo seem to be the largest species to have lived, in each clade. Ostensibly batrachians compete well only in cooler climates except as smaller forms but the large size of Aviturus refutes this. Caecilians lack the batrachian respiratory constraints on size because a large, lungless typhlonectid inhabits warm South America but like snakes they do not resemble crocodiles. Sometimes I wonder if retaining internal gill breathing like an amphiuma might be enough for a salamander to reach larger sizes. There were giant amphiumas in the past but nothing anaconda sized.
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? Edited by kusanagi, Jul 31 2017, 01:06 PM.
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| IIGSY | Jul 31 2017, 01:08 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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What size constraint could lissamphibians possibly have? They have an ossified internal skeleton, limbs and lungs. And how does cold water put them at an advantage? |
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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 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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| HangingThief | Jul 31 2017, 01:09 PM Post #6 |
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ghoulish
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Mudminnows are tough little fish that breathe air and can survive buried in damp mud. Oddly specific group to bring up I must say. |
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Hey. | |
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| kusanagi | Jul 31 2017, 01:29 PM Post #7 |
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Adolescent
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Mudminnows are amazing but they don't crawl overland to my knowledge. Pikes certainly do not although they take tetrapod prey. Wels might be more likely than pikes because they not only cross between water bodies and chase prey onto land. Combine a wels with a clarioid and what do you have? Snakeheads, clarioids and bichirs all share similarities in their fusiform bodies, carnivorous diet and ability to breathe atmospheric air with purposefully evolved organs not just through damp skin. The point of difference from tetrapods, dipnoans and sharks is that their crawling is entirely or primarily pectoral whereas that of other bottom walking gnathostomes lends itself to pelvic walking. Clariods famously cannot tear flesh like other catfishes such as ictalurids which disqualifies them (perhaps). Bichirs and snakeheads are still contenders as are anything like mudminnows that could evolve a convergent lifestyle. |
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| Dragonthunders | Jul 31 2017, 01:31 PM Post #8 |
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The ethereal archosaur in blue
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I tend to see that point a little unnecessary, considering that the role of crocodiles tends to be ambush predators, of course in several cases mainly semiaquatic, but it would not necessarily have to go ashore to take those niches.
If I remember correctly, in most cases it is the cutaneous respiration that amphibians depend on, being a little disadvantageous to larger sizes.
Yeah, I like to push the limits of speculation with unusual clades The possibilities that can obtain the same niche to the same level as crocodiles could be odd indeed, although not improbable depending on the possible scenarios. |
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Projects "Active" projects The Future is Far Welcome to the next chapters of the evolution of life on earth, travel the across the earth on a journey that goes beyond the limits, a billion years of future history in the making. The SE giants project Wonder what is the big of the big on speculative evolution? no problem, here is the answer Coming one day Age of Mankind Humanity fate and its possible finals. The Long Cosmic Journey The history outside our world. The alternative paths The multiverse, the final frontier... Holocene park: Welcome to the biggest adventure of the last 215 million years, where the age of mammals comes to life again! Cambrian mars: An interesting experiment on an unprecedented scale, the life of a particular and important period in the history of our planet, the cambric life, has been transported to a terraformed and habitable mars in an alternative past. Two different paths, two different worlds, but same life and same weirdness. My deviantart | |
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| IIGSY | Jul 31 2017, 01:34 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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But they have lungs |
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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 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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| kusanagi | Jul 31 2017, 01:46 PM Post #10 |
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Adolescent
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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. Then a look at the skulls and inferred musculature of champsosaurs suggests they were initially durophages of some kind before evolving into gharial-type forms. Skinks and some other aquatic and non-aquatic lizards are durophagous and the dwarf, durophagous crocodilians such as Bernissartia are now missing, offering a route in for squamates or turtles. (Sadly Dracaena seems too specialised on apple snails.) Edited by kusanagi, Jul 31 2017, 01:51 PM.
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| IIGSY | Jul 31 2017, 01:51 PM Post #11 |
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A huntsman spider that wastes time on the internet because it has nothing better to do
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Please define "fish like", because fish have a very wide rang of physiologies. |
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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 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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| Dragonthunders | Jul 31 2017, 02:02 PM Post #12 |
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The ethereal archosaur in blue
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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. |
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Projects "Active" projects The Future is Far Welcome to the next chapters of the evolution of life on earth, travel the across the earth on a journey that goes beyond the limits, a billion years of future history in the making. The SE giants project Wonder what is the big of the big on speculative evolution? no problem, here is the answer Coming one day Age of Mankind Humanity fate and its possible finals. The Long Cosmic Journey The history outside our world. The alternative paths The multiverse, the final frontier... Holocene park: Welcome to the biggest adventure of the last 215 million years, where the age of mammals comes to life again! Cambrian mars: An interesting experiment on an unprecedented scale, the life of a particular and important period in the history of our planet, the cambric life, has been transported to a terraformed and habitable mars in an alternative past. Two different paths, two different worlds, but same life and same weirdness. My deviantart | |
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| kusanagi | Jul 31 2017, 02:03 PM Post #13 |
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Adolescent
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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. https://www.foss-rec.net/20/105/2017/ The word fish really ought to be abandoned except in fisheries, else restricted to a monophyletic clade such as teleosts or actinopterygians. Linnaeus intended his class Pisces only for teleosts and Pisces is not currently a clade or taxon in zoology. But what I meant more than anything is that crocodile-like and other basal tetrapods were not living amphibians or reptiles but something physiologically plesiomorphic. Edited by kusanagi, Jul 31 2017, 02:24 PM.
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| kusanagi | Jul 31 2017, 02:05 PM Post #14 |
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Adolescent
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Right: did amphiumas break that constraint by possessing fish-like internal gills? Do they have a metabolism like Archegosaurus or like other batrachians? |
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| IIGSY | Jul 31 2017, 02:07 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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You still didn't tell exactly what "fish like" is. In what way are temnospondyls fish like that lissamphibians are not? |
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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 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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