Endoskeleton of a swordfish

An endoskeleton is an internal support structure of an animal. In three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera and Coleoidea. An endoskeleton allows the body to move and gives the body structure and shape. 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; here, a mollusc exoskeleton evolved into several sorts of internal structure, the "cuttlebone" of cuttlefish being the best-known version. Yet they do have cartilaginous tissue in their body, even if it's not mineralized, especially in the head where it forms a primitive cranium. An important advantage of an endoskeleton over an exoskeleton is that the endoskeleton provides more structural support. Image File history File links Swordfish skeleton at the National Museum of Natural History, Washington, DC; digital photo and removal of background by User:Postdlf File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Swordfish skeleton at the National Museum of Natural History, Washington, DC; digital photo and removal of background by User:Postdlf File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Binomial name Xiphias gladius Linnaeus, 1758 Swordfish (Xiphias gladius) are large, highly migratory, predatory fish characterized by a long, flat bill in contrast to the smooth, round bill of the marlins. ... “Animalia” redirects here. ... For the linguistic term, see Phylum (linguistics). ... In object-oriented programming, subclass is a class that is derived from another class or classes. ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Classes Subphylum Homalozoa Gill & Caster, 1960 Class Homostelea Class Homoiostelea Class Stylophora Gill & Caster, 1960 Class Ctenocystoidea Robison & Sprinkle, 1969 Subphylum Crinozoa Class Eocrinoidea Jaekel, 1899 Class Paracrinoidea Regnéll, 1945 Class Cystoidea von Buch, 1846 Class Blastoidea Class Crinoidea Subphylum Asterozoa Class Ophiuroidea Class Asteroidea Subphylum Echinozoa Helicoplacoidea †  ?Arkarua... The sponge, in the phylum Porifera, is a very primitive and specialized animal. ... Orders Aulacocerida (extinct) Hematitida  (extinct) Phragmoteuthida  (extinct) Belemnitida  (extinct) Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Subclass Coleoidea is the grouping of cephalopods containing all the primarily soft-bodied creatures. ... Organs derived from each germ layer. ... This article does not cite any references or sources. ... Spicules Spicules are skeletal structures that occur in most sponges. ... A horny, sulfur-containing protein related to keratin that forms the skeletal structure of certain classes of sponges (American Heritage Dictionary, 2006) Proteinaceous comounds of which the spicules in Demospongiae are composed (Cartage, 2006) ... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... An exoskeleton, in contrast to an endoskeleton, is an external anatomical feature that supports and protects an animals body. ... This article is about evolution in biology. ... This article needs additional references or sources for verification. ...

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