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Triassic Switchout; What if the therapsids made a Jurassic comeback?
Topic Started: Mar 9 2010, 09:44 PM (553 Views)
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Back in the Triassic, the mammal-like reptiles were in decline. The Permian Mass Extinction hit them so hard that save for a few, nocturnal forms, the synapsids ended up dying out completely, allowing the dinosaurs to take charge.

But what if it was the opposite? What if, at some point in the Middle or Late Triassic, circumstances allowed the therapsids a come-back, and the dinosaurs were pushed into the nocturnal insectivore niche? What would develop, and how would it effect what the world looks like now?
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The Dodo
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It should be noted that non-mammalian theraspids did survive into the Cretaceous in the form of Tritylodonts and some Dicynodonts.
I think the herbivorous niches would be probably mostly taken up by Dicynodonts.
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Carlos
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For starters, cynodonts would be the most diverse group; dicynodonts, being initially represented by pig sized forms and later some giants in the Triassic, presumably wouldn't be very diverse in terms of body plans, but there's no doubt that they'd be common.

Are therocephalians meant to survive in this? If so, I suppose their hypercarnivory would mean they'd be dominant predators but eventually they could loose to cynodonts
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The Dodo
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They were on their way out in the mid Triassic weren't they? Depending on when the change occurs I think they could make a come back.
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Margaret Pye
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I always heard it put down to desertification, and diapsids being better at concentrating urine.
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I'd imagine that the switchout would involve the Triassic therapsids surviving into the Jurassic, where the rise in moisture would allow a comeback.
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The Dodo
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How about making it more moist in the Triassic to allow them to take back over?
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But that development might have the synapsids drive all archosaurs to extiction, rather than a mere switching of roles. It could work if it gets humid a little earlier, though (say, very late Triassic).
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Holben
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Moistening all of pangea would spell D.O.O.M for the archosaurs. Desertification let them triumph. But around coastal regions, therapsids have a better chance- lush forests ringed the landmass.
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.

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And perhaps when the forests spread in the Jurassic, the therapsids would travel with them and out-compete the archosaurs.
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Holben
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Myah- the archosaurs reached forms capable of outcompeting the therapsids in the middle triassic. I'm not sure.

I just realised- i wrote DOOM in my last post. Oops.

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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Then again, that didn't seem like the case in the earliest Cenozoic. Back in the Paleocene, mammals were diversifying, but the birds were in domination, including the terror birds at the top. However, as it is known, the mammals ended up ruling the day, despite their staying small for much of the Paleocene.
So perhaps despite appearances, the therapsids could have outcompeted the diapsids.
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