Amorphous, gutless, and brainless, simple sponges were the first multicellular animals. That’s what scientists have said for a century. Now a team of biologists suggests demoting sponges and placing comb jellies at the base of a new tree of animal life.
These gelatinous marine predators, including Aulacoctena acuminata pictured here, have more cell types and organs than the sedentary and filter-feeding sponges.