I have not. Go go gadget Wikipedia.
Huh. So they’re… kinda like great big deep-sea sponges, but actually more closely related to amoebas? And… single-celled? Wow. That’s one heck of a cell. But multiple nuclei, which strikes me as cheating somewhat. I mean that’s essentially just a whole bunch of cells that really don’t have their $#!t together. Like Reuniclus. But yeah, that’s all pretty neat.