Aww, somebody beat me to it, but that's definitely based on Acanthaster planci, the crown-of-thorns sea star.
1) It has radial morphology (arms, other appendages in a ring), which is a signature of echinoderms.
2) It has spines on the arms. If it weren't for that, I'd say it was an anenome or some other cnidarian.
3) Crown-of-thorns sea stars are infamous for eating corals, sometimes swarming entire reefs and devouring them en masse, hence this comment:
It looks a lot like a crown-of-thorns starfish-esque Pokemon to me.
If that is what its based off of....
... better hide the Corsola.
Hawaii is also famous for their corals, so adding a "troublemaker" that likes to eat them would make sense and help flesh out the regional dex.
3) Sea cucumbers, sea stars, sea lilies, and sea urchins all belong in phylum echinodermata. Since it's not uncommon for pokemon based on animals to evolve into another animal in the same family (Bidoof is a perfect example) or other taxonomic level, I think it's safe to bet that this is either Pyukumuku's evolved form, or the second stage of another unreleased pokemon.
Very cool looking, though. It's a nice blend of realistic and creepy.