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K-T to the present.; Do Mammals need cosmic intervention?
Topic Started: Dec 28 2009, 04:49 PM (2,511 Views)
ATEK Azul
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This topic while not a project is for the discussion of a scenario where the Meteor missed and the Dinosaurs survived farther than 65 million years ago.

I know you've heard this scenario a bunch, but heres the twist the point of this topic is to have a world where Mammals realisticly out compete the Dinosaurs by the present day without celestial impacts or sapient species.

Other than the normal restrictions of Mammal evolution like the Amount of vertebrae they can have, there are no restrictions.

Also I'm not posting the things I have thought up until the Topic gets some posts so if you want my ideas, please post comments, questions and contributions.

Also have a nice descussion!
I am dyslexic, please ignore the typo's!
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ATEK Azul
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Alright so it looks like we won't be killing the marine Reptiles. What should we do with them if they are staying and warm blooded, By that I mean what will they evolve into and how Diverse can they get?

Also what happens to the groups that became aquatic Mammals? Do they stay as land forms or are they driven to extinction?

Also do you think terror Bird equivilents might replace some Dinosaurs?

And will the same Bird groups that went extinct in our timeline go extinct here?
I am dyslexic, please ignore the typo's!
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Carlos
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I think marine reptiles could co-exist with mammals. For instance, sea mammals could take herbivore/mollusc eating niches with marine reptiles taking dolphin and seal niches
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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Venatosaurus
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What about marine birds rather than marine mammals, if you remember primitive penguins and Hesperornids were already around in the Late Cretaceous, so in a world without the KT, they would continue to occupy such niches and continue to adapt and change. So I think it'd be more likely to see Gannetwhale-like birds rather than seal-like mammals, though otter-like mammals are very likely, or not, it's really up to the owner of this project ;)



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ATEK Azul
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I think Otters are acceptable. As for sea Reptiles co-existing with other creatures I think it's possible if they find their own niches as JohnFaa pointed out.
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Carlos
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Though with birds around things get less easy for the marine reptiles. Both penguins and hesperornithes could eventually take over fast fish hunter niches, reducing marine reptiles to slower forms like elasmosaurs and conservative mosasaurs. With mammals on the scene things would get tougher for those reptiles
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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Holben
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I think it would take a very long time for marine reptiles to evolve warm-bloodedness, YDG. And i think the niches would be taken before evolution was complete.

Birds taking fast fisher niches? Definitely possible, Pinguinis did that very well. But all the fast fisher birds we have (our only example) live in cold climes... i think. I'll have to check.

I'd like to see mosasaurs surviving, and taking killer-whale or dolphin (that includes killer whale, technically) niches. But they'd need some substantial prey to support anything more than about 4m long.
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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Ddraig Goch
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Hesperornis lived in relatively warm waters, didn't it?
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Holben
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Substantially, Not typical though.
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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The Dodo
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I think mosasaurs could produce some fast hunters since some where becoming ichthyosaur like around the end of the Cretaceous.
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Vultur-10


Mammals might be able to become serious competitors in the small and mid sized niches given time. Repenomamus was heading in that direction... I don't think they'd force dinosaurs out, but they could fill niches that dinosaurs didn't -- arboreal squirrel and monkey type niches, freshwater small semiaquatic types (otters, beaver, nutria, muskrat...). Also there were few burrowing dinosaurs; something like Repenomamus could found a radiation of badger-types and burrowing weasel-types.

I can even see mammals doing fairly well as mid sized carnivores eventually; modern cats etc. seem to be significantly faster than even the quickest dinosaurs.

I could see mosasaurs entering the niche of sperm whales today - huge deep-diving squid-hunters. The immense Cachalot Mosasaur, 60+ feet long and 15+ tons, would have a very deep tail and a massive head; its teeth would be longer and less serrated, evolving from "cutting" to "piercing" teeth. Its lungs would be very efficient at extracting oxygen. The lungs might also be very large, though this would require unusually dense bone to help diving. Depending on how long it had been adapting to deep diving, it might develop other oxygen-storing or -conserving adaptations.

---

Actually, though, without K-T, I think the giant hadrosaur herds would dominate the world more and more, and whole ecosystems would develop around them (quick-flowering plants, short-lived insects that eat those plants, etc. that feed off the hadrosaur dung left behind by the passing of a herd, for example). The whole world would be shaped by the colossal herds, and the climate changes that happened in our world might conceivably not happen, depending on how much this different ecosystem affected CO2 levels. If the hadrosaur herds eventually wiped out all the forests, replacing them with grasslands and such - only plants that were really tough and spiky or grew and set seed incredibly fast would survive - a lot less CO2 would be locked up, and so the world would stay warmer.

I played around with this idea once and came up with all sorts of weird stuff ... soil-scooping (to get the roots that made up a big part of the plant's biomass) hadrosaurs with shovel jaws, aggressive scavenging omnivorous sauropods in the foothills of the mountains, an Antarctic microbiothere marsupial which evolved humanlike intelligence, etc.
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Carlos
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I doubt it. I mean, I think once the Eocene thermal maximum came around vegetation would change radically and while forests wouldn't be as dense as they were in our world due to the presence of large herbivores I think it would be a dramatic change for the herbivores. That, alongside a general trend for the decline of ornithopods in the late Cretaceous (sans Hadrosauria only a few other genera remained), could mean marginocephalians (which, aside from large ceratopsids, also included many small, adaptable ceratopsians as well as the pachycephalosaurs) as well as notosuchians and herbivorous mammals (not to mention several herbivorous theropods) could rise in dominance.

Still, its obvious hadrosaurs would survive to the modern days, albeit mostly as tropical giants
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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Holben
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If they grew too big, surely the spread of rainforests would stop them?
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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Ddraig Goch
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Megatherium dwelled in forests sometimes, though, didn't it? If something that size could live in a forest, the it would surely be easy for a hadrosaur.
Save the Blibbering Humdinger from extinction!
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Vultur-10


I think the hadrosaurs would limit the rainforests, rather than vice-versa...

AFAIK the hadrosaur herds were more ecologically dominant than any modern analogue ... well, the bison herds before market hunting, *maybe*, but only in part of their range, and only in the brief time between the end Pleistocene extinction event and major human activity there ... and even then I'm not sure they were *that* dominant. (And the analogy isn't very good anyway, as nothing before humans ate primarily bison, or many adult bison at all -- no equivalent of tyrannosaurs). And it seems that bison were a big part of what kept many American prairies from turning into shrublands or woodlands; I think hadrosaurs could do the same only far more so.

Edited by Vultur-10, Jan 6 2010, 12:02 AM.
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Holben
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Ddraig Goch
Jan 5 2010, 04:08 PM
Megatherium dwelled in forests sometimes, though, didn't it? If something that size could live in a forest, the it would surely be easy for a hadrosaur.
You chose the wrong example.

Megatherium was around just as grass came into its own, in the first prairies and fields. Forests became sparser, and the trees had thin trunks and stayed far apart to conserve water.
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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