Raikos sheetus
Thanks to the absence of A. redensis, R. electra was allowed to grow more densely among eachother, feeding off of nutrients from the hydrothermal vents. Eventually, this lead to a situation where a division went wrong and 2 ended up stuck together. They kept multiplying and those specimens eventually became Raikos sheetus.
They form sheets(obviously) over hydrothermal vents to maximize their surface area, and constantly multiply but this quickly levels off due to their metabolism lowering as they get bigger, as an attempt to conserve resources . Thanks to having the combined force of many cells rather than one, they can generate and store enough electricity to scare away any members of the Tetraplacus genus that may try to eat them, though any that can’t produce sufficient electricity may still be susceptible to predation. New sheets can form via fragmentation.