Subkingdom Eumetazoa

Eumetazoa is a eukaryote clade in Kingdom Animalia containing all major animal groups except sponges, placozoa and several other animals groups about which little is known. The differentiating haracteristics of eumetazoans include true tissues organized into germ layers, and an embryo that goes through a gastrula stage. Most scientists include Ctenophora, Cnidaria, and Bilateria in the subkingdom, but placement within of mesozoans and placozoans is disputes. Phylogenetic research using the molecular clock approach to molecular evolution as well as study of the fossil record suggest suggests eumetazoa evolutionary origins in the Ediacaran Period of the late Proterozoic. Other interpretations exist.