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
Han Chinese subgroups Han Chinese subgroups The sub groups of the Han Chinese people, also known as Sinitic peoples, Chinese dialect groups or just dialect groups, are defined based on linguistic, cultural, genetic, and regional features. The terminology used in Mandarin to describe the groups is: "minxi" ( // "ethnic lineages"), used in Mainland China, or "zuqun" ( //, "ethnic groups"), used in Taiwan. Other than Hui people, which is a classification for Muslims of all backgrounds, no Han subgroup is recognized as one of People's Republic of China's 56 official minority ethnic groups. Mandarin, also known as the Northern dialects, is the