subkingdom parazoa
The Parazoa are an ancestral subkingdom of animals, literally translated as "beside the animals". They are not microscopic and have differentiated cells. However, they are an outgroup of the animal phylogenetic tree being that they do not have tissues or organs. The only surviving Parazoans are the sponges, which belong to the phylum Porifera. Their simplicity has been adaptive, and sponges have remained important in benthic marine habitats since their origin.