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 thermophilic sulphate-reducers. Thermomicrobia The "Thermotogae" is a phylum of whose members possess an unusual outer envelope called the toga and are mostly hyperthermophilic obligate anaerobic fermenters. "Verrucomicrobia" is a phylum of the PVC superphylum. Like the "Planctomycetes" species, its members possess a compartmentalised cell plan with a condensed nucleoid and the ribosomes pirellulosome (enclosed by the intracytoplasmic membrane) and paryphoplasm compartment between the intracytoplasmic membrane and cytoplasmic membrane. The branching order of the phyla of bacteria is unclear. Different studies arrive at different results due to different datasets and methods. For example, in studies using 16S and few other sequences