Animal mesoderm forms by enterocoelic pouching, through invagination of the endoderm. The main deuterostome phyla are the Echinodermata and the Chordata. Echinoderms are exclusively marine and include starfish, sea urchins, and sea cucumbers. The chordates are dominated by the vertebrates (animals with backbones), which consist of fishes, amphibians, reptiles, birds, and mammals. The deuterostomes also include the Hemichordata (acorn worms). The Ecdysozoa are protostomes, named after their shared trait of ecdysis, growth by moulting. They include the largest animal phylum, the Arthropoda, which contains insects, spiders, crabs, and their kin. All of these have a body divided into repeating segments, typically
Bacterial phyla CPR3, Kazan, Perigrinibacteria, SM2F11, WS6, and WWE3 were more recently proposed to belong to the larger CPR Group. To complicate matters, it has been suggested that several of these phyla are themselves actually superphyla (see the section on cryptic superphyla below). The proposed superphylum, Terrabacteria, includes Actinobacteria, Cyanobacteria, Deinococcus–Thermus, Chloroflexi, Firmicutes, and candidate phylum OP10. It has been proposed that several of the classes of the phylum Proteobacteria are phyla in their own right, which would make Proteobacteria a superphylum. It was recently proposed that the class Epsilonproteobacteria be combined with the order Desulfurellales to create the new phylum Epsilonbacteraeota.