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Possibility of fully armless bipedal Mammals?
Topic Started: Aug 3 2017, 09:59 AM (1,702 Views)
Dazzle Aug 3 2017, 09:59 AM Post #1
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In Dougal Dixon's After Man book, one concept I'm surprised never got as popular(er, became a trope like Flightless Bats, Whale Birds, ect) is the Wakka
http://vignette2.wikia.nocookie.net/speculativeevolution/images/9/9c/Wakka.png/revision/latest?cb=20130327230925

The book implies that South America once again became an isolated continent 25 million years from now. Given how strange island fauna can get, could something like the Wakka ever evolve? A fully bipedal therapod-like mammal with no arms.

It just seems too strange, well, most things in After Man are too strange to be true. At least in the way they are presented.
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TAXESbutNano Aug 5 2017, 01:59 PM Post #16
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Little
Aug 5 2017, 01:49 PM
Ignoring the armless clause for a second, kusanagi pointed out in a general spec thread that one of the causes of bipedalism in mammals comes from heavy, large clawed forelimbs used to dig into insect mounds (such as in pangolins and giant armadillos). I wonder, could something like this evolve in a predatory animal - i.e. freeing up overdeveloped forelimbs to be the primary method of taking down prey, rather than the jaws?
A lot of microcarnivorous mammals (e.g marsupial mice, grasshopper mice, etc) use their forelimbs for manipulating prey, so it seems possible. It's a shame that those flesh-eating rat-kangaroos don't have postcranial remains known...
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IIGSY Aug 5 2017, 02:09 PM Post #17
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From what I know, the sauropsid spine is generally more conductive towards bipedalism. Isn't it?
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Punga: A terraformed world with no vertebrates
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ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

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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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TAXESbutNano Aug 5 2017, 02:14 PM Post #18
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Maybe it's the fact they can actually use their tail for stuff. I mean, the synapsid design has great buttcheeks as long as it's Homo... well, Homo sapiens sp., but it isn't really well-adapted to conserving a tail big enough to balance your torso with.
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IIGSY Aug 5 2017, 02:15 PM Post #19
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Nanotyranus
Aug 5 2017, 02:14 PM
Maybe it's the fact they can actually use their tail for stuff. I mean, the synapsid design has great buttcheeks as long as it's Homo... well, Homo sapiens sp., but it isn't really well-adapted to conserving a tail big enough to balance your torso with.
Some mammals (and other synapsids) have pretty robust tails
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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TAXESbutNano Aug 5 2017, 02:22 PM Post #20
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Insect Illuminati Get Shrekt
Aug 5 2017, 02:15 PM
Some mammals (and other synapsids) have pretty robust tails
Mmh, but it's generally pretty rare. Synapsid tails are generally weak AF.
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IIGSY Aug 5 2017, 02:29 PM Post #21
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Nanotyranus
Aug 5 2017, 02:22 PM
Insect Illuminati Get Shrekt
Aug 5 2017, 02:15 PM
Some mammals (and other synapsids) have pretty robust tails
Mmh, but it's generally pretty rare. Synapsid tails are generally weak AF.
Why though? The first synapsids and the first sauropsids looked practically identical, yet here we are now. What could have led to the disparity in tail strength between synapsids and sauropsids?
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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Nyarlathotep Aug 5 2017, 02:56 PM Post #22
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Megaraptor could be an example of theropods doing that. Other Megaraptorans weren't as extreme, but they still had more impressive claws than other large theropods, even Spinosaurs. I guess they're the closest you get to Mesozoic deathclaws.
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Rodlox Aug 5 2017, 03:35 PM Post #23
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Little
Aug 5 2017, 01:49 PM
Ignoring the armless clause for a second, kusanagi pointed out in a general spec thread that one of the causes of bipedalism in mammals comes from heavy, large clawed forelimbs used to dig into insect mounds (such as in pangolins and giant armadillos). I wonder, could something like this evolve in a predatory animal - i.e. freeing up overdeveloped forelimbs to be the primary method of taking down prey, rather than the jaws?
like Utahraptor? that was the theory, yes, that it had switched from the kill-with-feet method of their smaller kin, to kill-with-hands method.
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TAXESbutNano Aug 6 2017, 06:18 AM Post #24
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Insect Illuminati Get Shrekt
Aug 5 2017, 02:29 PM
Why though? The first synapsids and the first sauropsids looked practically identical, yet here we are now. What could have led to the disparity in tail strength between synapsids and sauropsids?
No caudofemoralis muscle. You see the same pattern in birds- no caudofemoralis, no big tail.
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kusanagi Aug 6 2017, 10:16 AM Post #25
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Little
Aug 5 2017, 01:49 PM
Ignoring the armless clause for a second, kusanagi pointed out in a general spec thread that one of the causes of bipedalism in mammals comes from heavy, large clawed forelimbs used to dig into insect mounds (such as in pangolins and giant armadillos). I wonder, could something like this evolve in a predatory animal - i.e. freeing up overdeveloped forelimbs to be the primary method of taking down prey, rather than the jaws?
Mammals are walking bipeds in one of three cases: 1) descent from leaping mammals (transition full in sthenurines but partial in leptictids and jerboas; for a parallel see also dinosaurs as descendants of lagerpetonids and Scleromochlus) 2) heavy forearms (pangolins and giant armadillos as an alternative to knuckle walking) and 3) hominins and Paradolichopithecus (partial in gibbons and some atelids). Because 3 have long arms and were primitively evolved to be arboreal leapers they actually fit 1 and 2. Only 1 and 3 have a tendency to orthograde posture.
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ÐK Aug 6 2017, 10:25 AM Post #26
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Nanotyranus
Aug 6 2017, 06:18 AM
No caudofemoralis muscle. You see the same pattern in birds- no caudofemoralis, no big tail.
Not to say that they never had a caudofemoralis of course, they just lost it. Pelycosaurs do appear to have had a caudofemoralis that was the primary retractor muscle for the femur, which later switched to a more mammal-esque arrangement in therapsids. Just to clarify that, IIGS.
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IIGSY Aug 6 2017, 12:34 PM Post #27
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ÐK
Aug 6 2017, 10:25 AM
Nanotyranus
Aug 6 2017, 06:18 AM
No caudofemoralis muscle. You see the same pattern in birds- no caudofemoralis, no big tail.
Not to say that they never had a caudofemoralis of course, they just lost it. Pelycosaurs do appear to have had a caudofemoralis that was the primary retractor muscle for the femur, which later switched to a more mammal-esque arrangement in therapsids. Just to clarify that, IIGS.
So why did birds and mammals loose it?
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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Archeoraptor Aug 6 2017, 12:52 PM Post #28
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birds-long tail bad for flying as you see msot bird,except mesozoic groups had short tails
mammals-maybe was the ereact gait and not need for them in valance,somo basal mammals were burrowers so maybe long tails weren´t useful for that
Astarte an alt eocene world,now on long hiatus but you never know
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IIGSY Aug 6 2017, 12:53 PM Post #29
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Archeoraptor
Aug 6 2017, 12:52 PM
birds-long tail bad for flying as you see msot bird,except mesozoic groups had short tails
mammals-maybe was the ereact gait and not need for them in valance,somo basal mammals were burrowers so maybe long tails weren´t useful for that
1. Many pterosaurs had long tails and they flew

2. Basal mammals actually still had sprawling gaits. Plus, dinosaurs have erect gaits and they have large muscular tails
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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LittleLazyLass Aug 6 2017, 01:20 PM Post #30
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 Mammals are generally quadrupedal; dinosaurs as a[n overly] general rule were bipedal. Something like a theropod, ornithopod, or the ancestral dinosaur needs a long tail, because it provides balance when moving bipedally. Without it their horizonal biped stance wouldn't work at all. Something quadrupedal like a ceratopsid or a brachiosaur (which, unlike diplodocids, couldn't rear)? They have noticeably quite short tails. It's not worth the energy investment for a quadruped. This can also apply to a more upright stance, because the center of balance shifts.

On flying animals, a long tail is indeed rather inefficient, it's gonna create drag. That's why only short-tailed pterodactyloid pterosaurs got very large. Perhaps it's why the birds with their pygostyle outcompeted things like microraptorians.
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