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Primate-like or big-bodied multituberculates?; What prevented multis from attaining these forms?
Topic Started: Mar 21 2010, 04:52 AM (950 Views)
Dean
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The multituberculates were the most successful group of mammals, they survived for 100 million years. We don't know whether they were the first offbranch from the main mammalian line, or did they evolve independently from a very mammal-like cynodont, but we know that:

-They evolved viviparity independently, after they split from the main mammal line, which was still oviparous.
-They gave birth to tiny helpless young, but had no pouch, similar to the reproduction of non-marsupial metatherians.
-They were in the same niche as rodents, and even had a similar bodyplan and tooth-configuration.


Now, if they were so successful, so long-lived, and evolved so many therian-like traits much earlier than real therians, why did they only evolve rodent-like forms?

The rodent-like form is basically the most basal mammalian form. From that they could easily evolve a primate-like one, which is very similar to the rodent-like body, or even carnivoran, ungulate or elephant-like forms.

If they lived for so much time, and were so successful, why did they conserve the basal body, and not radiate into more diverse forms like therians, or even monotremes?

Can you imagine scenarios, which would've allowed them to radiate?
Edited by Dean, Mar 21 2010, 04:53 AM.
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Carlos
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Quote:
 
The multituberculates were the most successful group of mammals, they survived for 100 million years. We don't know whether they were the first offbranch from the main mammalian line, or did they evolve independently from a very mammal-like cynodont, but we know that:

-They evolved viviparity independently, after they split from the main mammal line, which was still oviparous.
-They gave birth to tiny helpless young, but had no pouch, similar to the reproduction of non-marsupial metatherians.
-They were in the same niche as rodents, and even had a similar bodyplan and tooth-configuration.


Whereas multies gave birth or layed eggs is unknown and speculation at best, though its obvious their young were underdeveloped like in monotremates and metatherians; also considering how soft tissues were never found they might as well have had pouches.


The limitations on the body plan can indeed perhaps be resulted due to lack of opportunity, though its worth to note that their body plan was perfect for many niches. Worth to note is the fact that, being relatively basal mammals, its possible multies could see in UV, and so they could be potentially more colourfull than the usual mammalian colouring pattern.
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

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The Dodo
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They were quite diverse in the Paleocene weren't they? Maybe if there was less competition around at that time they could of expanded a bit more.
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Dean
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The Dodo
Mar 21 2010, 05:52 AM
They were quite diverse in the Paleocene weren't they? Maybe if there was less competition around at that time they could of expanded a bit more.
They were quite diverse, but only in rodent like forms. Why didn't a multituberculate cow or wolf develop?
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Carlos
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Mostly because of competition and, well, they still had the crawling leg gait
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

My Patreon:

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Dean
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JohnFaa
Mar 21 2010, 07:40 AM
Mostly because of competition and, well, they still had the crawling leg gait
Yeah, I forgot that most non-therians still had the therapsid gait.


Well, in that case, it might stimulate the development of monkey-like arboreal climbers, and maybe large-bodied herbivores who walk like dicynodonts.
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Holben
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Since a lot of the time they were around the dinosaurs 'ruled', they couldn't take any large niches there. In the early Cenozoic, most mammal lines were set down, and rodents and multis came into competition. After a while, i reckon it was that that forced them to extinction.
Time flows like a river. Which is to say, downhill. We can tell this because everything is going downhill rapidly. It would seem prudent to be somewhere else when we reach the sea.

"It is the old wound my king. It has never healed."
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Dean
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Holbenilord
Mar 21 2010, 12:06 PM
Since a lot of the time they were around the dinosaurs 'ruled', they couldn't take any large niches there. In the early Cenozoic, most mammal lines were set down, and rodents and multis came into competition. After a while, i reckon it was that that forced them to extinction.
So in an Eutherian-less Cenozoic, multis playing the role of "the other rodents" may have produced primate-like forms.


Hmm, maybe the whole extinction of the multis happened because of their metabolic rate. If Cenozoic rodents already led a fast-paced life like modern rodents, then maybe the multis looked like rodents but lived a slower life, like primates. Eventually eutherian rodents may have outcompeted them, because they were darting around, eating anything in sight and reproducing like mad, and by the time multis reached the food source there was nothing left for them.
Edited by Dean, Mar 21 2010, 04:12 PM.
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Carlos
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Not to mention that only gondwanatheres (which may be basal multies appearently) and maybe a certain cymolodontian multie clade I forgot developed teeth apropriate for grazing, something rodents already had. And the sprawling gait was also a disadvantage, as unlike glires multies didn't managed to produce cursorial forms
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

My Patreon:

https://www.patreon.com/Carliro

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The Dodo
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So to keep them the most obvious thing to do would be to stop rodents evolving.
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Holben
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Or inhibit reproduction. Rodents spawn at a mighty rate, halving this would still let them thrive. But reduce them to one- or two- a litter and they may stand worse off than the multis.
Time flows like a river. Which is to say, downhill. We can tell this because everything is going downhill rapidly. It would seem prudent to be somewhere else when we reach the sea.

"It is the old wound my king. It has never healed."
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Dean
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Or, a dog-sized multi, whose specialization is preying on rodents.
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Margaret Pye
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Climbing might be their best bet for survival - sprawling gaits are much less of a disadvantage up a tree. (Or they could independently evolve upright posture, of course :-) )
My speculative dinosaur project. With lots of fluff, parental care and mammalian-level intelligence, and the odd sophont.
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seascorpion
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[Or, a dog-sized multi, whose specialization is preying on rodents]

im pretty sure multituberculates went extinct because rodents replaced them, maybe one would have hunted smaller multies
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The Dodo
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Yes, but one could make a niche by preying on the small rodents replacing the others. Their main competition then would probably be groups like Carnivora.
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