What type are the most primitive multicellular organisms?

The most primitive multicellular organisms are sponges. First of all, this is due to the fact that sponges do not have separate organs, and this role is played by individual cells. It is this simple structure of the body that makes this type of aquatic organisms the most primitive of all. Sponges are found all over the planet Earth and there are approximately 8,000 species. They have a very good function for the rapid restoration of damaged cells, and also reproduce both sexually and asexually.