A taxon erected to contain all metazoa except Porifera: The sponges and wormlike mesozoans are excluded from the taxonomic category of Eumetazoa which comprises all other animals.

"Porifera" is that phylum of the animal kingdom which contains the sponges.

In general they consist of aggregates of cells, mostly choanocytes, which often line canals and chambers usually supported by a skeleton of fibers or spicules.