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How could an octopus like creature evolve to live/survive on land? Would it want to live on land?

For my world I am having 2 intelligent species on the planet. One lives on land, one lives both in and out of the water. I have finished the land creature, and I need help for the water/land creature.

The water/land creature has 8 tentacle-like things on its body. It has weak bones in its tentacles and a skull in its head. How could it evolve to live on land, and why would it even want to live on land?

Notes about planet: The temperature is 59.6°c. The mass is 3.98x earth. Surface gravity is 1.5546875x earth. The atmospheric pressure is 12.98 atmospheres. The atmosphere is 31% Sulfur dioxide, 4.6% CO2 6% hydrogen sulfide, 58% nitrogen and 0.4% methane.

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    $\begingroup$ Why is it so damn hot on your planet and how does anything live on land with such temperatures? What purpose are the highly detailed atmosphere conditions? And how is a weak boned creature going to survive 4x earth gravity if strong boned creatures wouldnt be able to reach human sizes unless build like a miniature elephant? $\endgroup$
    – Demigan
    Nov 9, 2021 at 12:01

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Snail style

Let us think of body plans. The main issue with living on land is not drying out. Did any relatives of the octopi manage that?

mollusc family tree

https://kaiserscience.wordpress.com/2018/05/01/mollusk-family-tree/

snails

Depicted: snail, nautilus (both from Wikipedia)

Snails are second cousins to the cephalopods. They have a mollusc body plan and protect themselves against harsh circumstances on land with their shell. The shell allows water conservation and also protection from heat. Snails can survive even in deserts.

So too your land-going octopoids. They have robust shells to protect them. They make slime to get around. There are existing cephalopods with shells - the nautili. They are cool beasts. Use them as your model.

I was thinking your land would be brutal for land-dwellers but realized I was thinking of the ocean as our own cool pH neutral ocean. Of course in such a hot planet the ocean will be hot, and an atmosphere with so much SO2 will mean the ocean is sulfuric acid. All good!


As to why they would go on land, why does any immigrant emigrate? Escaping bad circumstances at place of origin, or taking advantage of good opportunities in new place. Your ancient pioneers could leave the water and find food on the shore. It was safe from aquatic predators on the shore and such predators as there were on land were not able to prey on your octopi. Evolution over time selected for individuals who could spend more time out of the water and on the beach and points inland. That is how it worked in our world, several times.

Thinking about this does make me curious about the evolution of snails (and slugs!) as compared to other terrestrial lineages. I will need to read up.

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It wouldn't want to live on land.

Not because Octopuses couldn't evolve to live on land. They totally could.

But, because your surface temperature is as high as the maximum average temperature ever on earth. and your gravity is enough to crush people.

They'll be much happier in the oceans, where they don't need to support their bodies, and they're out line of sight of direct sunlight.

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