Trichoplax is probably the simplest multi-cellular animal in the world. It resides in seawater and looks like a tiny pancake made up of many cells. It moves over rocks, digesting any algae that it finds on them. A trichoplax is more complicated than a protozoan, however, it does not have specialized organs. This simple animal was discovered in an aquarium in 1883 in Austria and was originally thought to be an animal larva.