Theirs less than 10,000 known sponge species and only 3 known placazoa species, all remaining animal species have some form of nervous system. based on known species, the vast majority of those are arthropods, which have central nervous systems.
Theirs less than 10,000 known sponge species and only 3 known placazoa species, all remaining animal species have some form of nervous system. based on known species, the vast majority of those are arthropods, which have central nervous systems.