WI: An Different Permian Extinction

Now Im sure most of us have heard of the catastrophic Permian Extiction...It killed I think 50% or more of Life's Organisms. What If the Permian Extinction was less drastic, and the Mammal-Like Reptiles that dominated that Era lived, while the Proto-Dinosaurs died off. Would there be no Birds? Would We elvolve from the Mammal Like Reptiles and still slightly resemble ourselves? Was there an Mammal-Like Reptile that had the capacity of Devolping Sentience? What would be the consequences of an Species similar to us appearing around the time of OTL Cretacous Extinction
 
Actually, most estimates for species extinction for the end-Permian range between 90 and 95%. The 50% is more like the end-Cretaceous.

If the mammal-like reptiles (therapsids) survived and the proto-dinosaurs (early archosaurs) didn't, I would expect that the therapsids would still evolve into mammals. There were serveral lineages that were headed in that direction, so there was probably one or more evolutionary advantages to becoming a mammal.

Assuming that the birds evolved from dinosaurs (which I agree with), by killing off the early archosaurs birds would never evolve. However, that may allow bats to expand even ore than they did. Perhaps some insects would evolve into the small bird niches, but I wouldn't expect many large insects (they were decreasing or gone by the Permian).

It's hard to tell if/when a sentient creature would have evolved. Simon Conway Morris thinks one would have, but Stephen J Gould probably wouldn't have. Some of the early mammal evolution could have similar to OTL if the larger therapsids replaced the dinosaurs.
 
What I was thinking was that the Therapsids would evolve into forms similar to the MegaFauna of the Eocene to the Piloecence. One of the smaller Therepasids could adapt an Aboreal Lifestyle...and establish a lineage of creatures not so unlike ourselves.
 
With recent activity on Alternative Zoology on these boards, I think this is a good idea as any to ressurect this thread...Annyone have any ideas?
 
When life never really died

Now Im sure most of us have heard of the catastrophic Permian Extiction...It killed I think 50% or more of Life's Organisms. What If the Permian Extinction was less drastic, and the Mammal-Like Reptiles that dominated that Era lived, while the Proto-Dinosaurs died off. Would there be no Birds? Would We elvolve from the Mammal Like Reptiles and still slightly resemble ourselves? Was there an Mammal-Like Reptile that had the capacity of Devolping Sentience? What would be the consequences of an Species similar to us appearing around the time of OTL Cretacous Extinction

The Permian extinction killed around 95% of life but the mammal like reptiles largely survived excluding the Pelycosaurs. However there was a lesser exctinction at the end of the Triassic wiping out the beast reptiles and pseudo crocodiles estimated to have wiped out 20% of life forms. Assuming it had had a different effect maybe there would have been a beast reptile man and furry birds. In H.G Wells's Into the Abyss there are theriodonts in the abyssal depths
 
About the therapsids, I'd think we'd see them taking a rather different approach than the dinosaurs. First off, they'd be considerably smaller, with the largest ones not much longer than 4 meters. The reason dinosaurs got so big is due to a number of physiological quirks after all, which the mammals didn't have.

Btw, before this thread gets moved again to ASB (like the thread recently about dinosaurs surviving), I'm all for sticking it here in before 1900, since the POD is in 250,000,000 YBP, which is obviously before 1900. :D
 

mojojojo

Gone Fishin'
Would all the niches occupied by birds OTL be occupied by bats in this TL? What forms could they take?
 
I think there wouldn't be any bats in this timeline, but there would be something that would look convergently like bats, but instead have evolved from some Mesozoic mammal branches, like docodonts or triconodonts.
 

Keenir

Banned
I think there wouldn't be any bats in this timeline, but there would be something that would look convergently like bats, but instead have evolved from some Mesozoic mammal branches, like docodonts or triconodonts.

or from the branch which led in OTL to Volacotherium
 
or from the branch which led in OTL to Volacotherium

I'd have mentioned Volaticotherium, but I didn't remember the name off the top of my head. Also, you bring up something curious there, Volacotherium's position inside the early mammals is rather obscure. Generally, we have to assume that there was at least one (more probable is two) radiations of the mammals inside the Jurassic and the Cretaceous, which we begin to uncover only now.
 
About the evolution of flying therapsids/mammals ITTL; I'd say that there's a reasonable chance that some kind of flying animal would evolve from a branch of pre-mammalian therapsids, rather than from true mammals like TTL's (equivallent of) symmetrodonts or triconodonts.

Remember that there won't be any competition from pterosaurs, or indeed any archosaurs ITTL, so it's entirely possible that some branch of arboreal therapsids evolves a gliding membrane and eventually true flight rather early on - possibly even around the same time as the OTL pterosaurs evolved.

However, these flying therapsids would propably be very different from bats, primairily because they would lack echolocation and the well-developed sense of hearing of true mammals.

And unlike OTL bats, these flying therapsids would not need to adapt to a nocturnal lifestyle, as there are no other flying vertebrates to compete with, so their sense of vision would be their primary sense, and they would almost certainly develop large eyes and colour vision.

And the design of their wings could also be very different from that of bats; instead of four fingers supporting the flight skin, we could see a design in which only an elongated and overdeveloped fifth finger supports the flight skin, just like in the OTL pterosaurs. And it's also possible that, instead of being supported by the fifth finger, the flight membrane is supported by an overdeveloped bony "spike" protruding from the wrist. Certain OTL flying squirrels have such "spikes" in order to enlarge the surface of their flight membrane, so such an adaptation wouldn't be unprecedented in evolution.

So in all, these hypothetical flying therapsids might look more like the OTL pterosaurs than the OTL bats.

..
However; there is no reason why only one branch of therapsids/mammals would evolve true flight ITTL.

And regarding the fact that it is very likely that mammals or a very close analogue to them are still going to evolve ITTL, there's still is a good chance that some small nocturnal gliding mammal with a well-developed sense of hearing and possibly even a primitive sense of echolocation (there are, after all, also a few species of shrew that use a primitive form of echolocation) eventually evolves, and subsequently evolves into a nocturnal flying species that is very similar to the OTL bats.

Competition with diurnal flying therapsids could very well have a similar effect on the evolution of flying mammals as competition from diurnal birds had in OTL.
 
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