doot.
I don’t see anything impractical about the one that’s just an ordinary ammonite but with spikes.
The Mariella one also looks fairly normal, looks like a number of aquatic snail species
obviously this makes no sense evolutionarily, they must have been created by mermaids to make various instruments out of their shells.
I mean, I suppose they might seem bigger to a predator, and harder to swallow for something that swallows prey whole?
These are some weird regional Omanytes.
It’s crazy to think about how long it took to get more than one-cell life!
Has anyone got some conclusive theories on the functional morphology of this?
This was the “fuck around” era of evolution and being wacky was cool
In my history of life class I was tought it was to do with controlling buoyancy, although all the variation seems odd for that.
Maybe a combination of controlling buoyancy with species identification?
Might be plausible. I’ll have to look it up at one point, maybe there’s some research on this. I think it may be hard to guess why because we don’t have many swimming animals with shells. I don’t know if snails may offer some answers but they are maybe to different in lifestyle.
Probably too different, as snails are benthic, while ammonites where probably nektonic.
Iirc the shells being longer is something about allowing gases in the shell to compress or expand as needed to control bouyancy. I would imagine there is a sac of gas, and the ammonites would siphon water in or out as needed to compress or decompress the gas.
Edit: just looked it up on Wikipedia, it appears the heteromorph ammonites are thought to have maybe been planktonic or benthic.
Definitions for non-nerds:
Benthic means living on or near the sea floor.
Nektonic means free swimming
Planktonic means going with the current as plankton. I should note plankton aren’t all tiny, some are visibile to the naked eye. All it means is unable to propel themselves against current.