Endoskeleton three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton may function purely for support (as in the case of sponges), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a mollusk exoskeleton evolved into several sorts of internal
Bacterial phyla used for phyla, but generally the name of the phylum is generally the plural of the type genus, with the exception of the "Firmicutes", "Cyanobacteria", and "Proteobacteria", whose names do not stem from a genus name ("Actinobacteria" instead is from "Actinomyces"). The "Acidobacteria" (diderm Gram negative) is most abundant bacterial phylum in many soils, but its members are mostly uncultured. Additionally, they are phenotypically diverse and include not only acidophiles, but also many non-acidophiles. Generally its members divide slowly, exhibit slow metabolic rates under low-nutrient conditions and can tolerate fluctuations in soil hydration. The "Actinobacteria" is a phylum of monoderm