Let's talk about: Amphibious civs

I remember the hallmark of amphibians evolving into amniotic animals is that reproduction and larval growth no longer rely on water.
One problem is that the limbs of vertebrates that can use tools are not suitable for amphibious life, but we can consider Metamorphosis like frog.But this is just like terrestrial organisms that rely heavily on water for survival.

One important aspect is how a species has evolved limbs that can use tools, such as primate’s hands. One could be the octopus’s tentacles.

A civilization that relies on water for egg laying and reproduction? (I keep an eye on frogs.)
A civilization that possesses the ability to live in water and directly enters the water to develop underw ater resources? (Beaver? I’ve played Timberborn recently.)

Perhaps taking a look at the fantasy creatures in DND,like Bullywug, Sahuagin, Locathah, Triton.

This creature has multiple limbs for locomotion (as well as the upper membranes, which play a small role). The upper limbs are a pair of human-like arms, and a pair of tentacles. I don’t think there’s any reason why the arms wouldn’t be useful underwater. They can be used for grabbing and clawing at prey, as well as simple tool use, while the upper tentacles can be used for grabbing or locomotion.

It’s evolved for floating at the surface, or hunting in shallows. It occasionally goes on land, but prefers staying in the water.

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The species I mentioned earlier is that aquatic vertebrates only have four limbs.
Considering arthropods with more limbs, may crustaceans have the potential to evolve their hands?
In your imagination, is it a vertebrate or an animal with an exoskeleton?

It’s a vertebrate, with an area of shell over its back.

And there’s no reason that vertebrates couldn’t have more limbs.

Existing vertebrate organisms only have four limbs, as their ancestors only evolved four limbs, which were sufficient for land travel.
I am thinking about the possible evolutionary pathways of this organism.
Assuming that the divergence between this organism and the existing evolutionary path on Earth is a fish. Should it have evolved to specialize a pair of long front fins into claws that can grab food?
One question is what kind of environment prompted it to evolve step by step into this shape.

edit: The divergence between vertebrates with more limbs and the Earth’s evolutionary line extends to the number of paired fins in earlier fish species.
Speaking of the prototype of this thing, I feel like Triops spp

It evolved from this:
It has 18 limbs, plus the tail. It mainly hunts on the sea floor. I’m still working on the intervening stages. I had intended to have something similar to this, with some longer legs, a pair or grasping claws, and a ballast organ to help it rise higher. This would then develop to go to the surface, and evolve to breathe air. The claws would become better at manipulation, and the longer legs become more complex, while some of the other limbs become more tentacle-like. Also, I had the tail splitting into tentacles.

Exactly what the possibility of these things evolving naturally is, I’m not sure. But, I designed this with a view to creating this line of creatures in thrive eventually. I’m open to criticism in terms of realism, though.

Extraterrestrial lifeforms don’t have the same evolutionary history of Earth lifeforms

Aquatic benthic vertebrates? I think of a possibility that it evolved from a mollusk that evolved a structure similar to a notochord, and later evolved into an inner skeleton and spine. Its ancestors may have been a bilaterally symmetrical single back armored creature.
You can take a look at Monoplacophora.

One question is what advantages the evolved notochord has brought to it.Perhaps it has evolved into segmented back armor.

We cannot imagine it without foundation, we can only learn from known evolutionary history. There is a phenomenon of convergent evolution in nature, where there may be an optimal solution.
Just like the multi legged vertebrates mentioned earlier. There are only four limbs in existing vertebrates, as meat finned fish have evolved only two pairs of lateral fin. And the Climatiformes that evolved three pairs of lateral fin did indeed exist and was quickly eliminated

Yes, but from generalizing it, by taking the specifics of it you will end up saying “since humans are the only species that was capable of becoming spacefaring, all spacefaring species must look like humans”, and you are saying an equivalent of that by claiming that all vertebrates analogoes must have four limbs.

Yes, but you can only assume that an alien species might have convergent traits when those traits either are required for survival or evolved multiple times on Earth, but tetrapods only evolved once. And while yes, you could say “this species that evolved six limbs went existinct” it means little since the number of fins isn’t the only factor to dictate if they are successfull; how do you know that they didn’t go extinct simply because their competition reproduced faster than them and had a more efficent stomach?

So this is just my speculation, we are assuming a situation that has not occurred in nature.

A known fact is that multiple paired lateral fin are relatively common among the Climatiformes, but only two or even one pair of paired lateral fin were preserved when developing bony fish. And terrestrial life even only requires a pair of legs.

I don’t deny the possibility of being born by chance, but limb degeneration is clearly more likely to evolve than multi limb transformation, just like whales returning to the ocean with degraded hind limbs. Intraspecific competition will promote this specialization

If by ‘tetrapod’, you mean quadruped, I’m not sure that’s really true, considering that dinosaurs are now considered to have evolved from two-legged ancestors. Some of them (such as Spinosaurus and Iguanodon) then developed a tendency to walk on four limbs, while others (such as Stegosaurus and Diplodocus) had four legs.

That could be a good alternative evolution for it. I had conceived of a creature with pseudopods running along its body evolving a spine, which allowed it to get more of a range of movement, and the pseudopods evolving into legs. The legs were then adapted or degraded.

I have no idea about that. I found little information on the function or evolution of this.

Tetrapods are the branch of life all land-dwelling vertebrates belong to

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Yeahhh, i wasn’t so sure what term to use to designate a civilization that is built in land and water, and “amphibian” could be confused with the clade “amphibia”, but i didn’t find any term that would fit, and “semiaquatic” give us a lot of variation, from aquatic rats to seals.
Maybe we can use the “amphibian civ” term to denominated civs that are located in both enviroments.

It still uses the amphibian term here. And now that we actually got to the crux of the issue, I think you need to be an actual amphibian (having adaptations to survive at least a little bit on land) to have an amphibian civ. Any other interpretation is just a rehash of the underwater civ argument of “bro, they can just hold their breath and constantly jump in and out of the water”.

The tentacled creature I came up with was intended to be about the furthest one could get in terms of intelligence with a species evolving entirely underwater. It can go onto land, and can breathe air, but isn’t adapted to surviving there. It would be possible to develop simple tool use underwater, and presumably also construction of tools, rather than merely using individual stones, etc. I don’t think such a creature would have any chance of developing an understanding of fire when it spends little time on land, and would probably have to stay constantly moist.

But, what should be the minimum requirements in Thrive for an amphibious civ. to develop? Would the species need to spend a lot of time interacting with fire to master it? In other words, would they need to make fire many times before the species was able to use it in general? This would probably require being able to survive for a long time on land, although the player could perhaps use brief trips onto land to start a fire before immediately returning to the water. Would they be able to develop construction of primitive hand axes, for instance, underwater?

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This is indeed a problem, and some empirical effects of fire seem to have no effect on them. They may rely on water to establish early Primitive Society without fire. Perhaps it is the pursuit of delicious cooked food, perhaps it is simply a religious preservation of fire, or perhaps it is the discovery of pottery fragments from natural fires and their use as tool materials?

This is basically the crutch of the issue I have with people saying that water species can just “hold their breath” to do stuff on land.

True. I guess most of the specifics couldn’t really be decided until the aware stage is in development. But however it’s done, there will always be players trying to find exploits to do something the game isn’t designed for.

like space porpoises?