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 WYO, ZB3, and Zixibacteria). Despite the unclear branching order for most bacterial phyla, several groups of phyla have clear clustering and are referred to as superphyla. The FCB group (now called Sphingobacteria) includes Bacteroidetes, the unplaced genus "Caldithrix", Chlorobi, candidate phylum Cloacimonetes, Fibrobacteres, Gemmatimonadates, candidate phylum Ignavibacteriae, candidate phylum Latescibacteria, candidate phylum Marinimicrobia, and candidate phylum Zixibacteria. The PVC group (now called Planctobacteria) includes Chlamydiae, Lentisphaerae, candidate phylum Omnitrophica, Planctomycetes, candidate phylum Poribacteria, and Verrucomicrobia. The proposed superphylum, Patescibacteria, includes candidate phyla Gracilibacteria, Microgenomates, Parcubacteria, and Saccharibacteria and possibly Dependentiae. These same candidate phyla, along with candidate phyla Berkelbacteria, CPR2,