Gnathostomata is the group of vertebrates with jaws. Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms (as opposed to folk taxonomy). ... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... Typical Classes Subphylum Urochordata - Tunicatas 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... Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Orders Antiarchi† Arthrodira† Petalichthyda† Phyllolepida† Ptyctodontida† Rhenanida† The Placodermi are armoured prehistoric fishes known from fossils dating from the late Silurian to the end of the Devonian Period. ... Orders See text. ... Orders Climatiiformes Ischnacanthiformes Acanthodiformes Acanthodii (sometimes called spiny sharks) is a class of extinct fishes, having features of both bony fish ( Osteichthyes) and cartilaginous fish (Chondrichthyes). ... This article is in need of attention. ... Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Human jaw front view Human jaw left view Human jaw top view The jaw is either of the two opposable structures forming, or near the entrance to, the mouth. ...

The group is traditionally a superclass, including the familiar classes of fish, birds, and so forth, and a sister group of the jawless vertebrates Agnatha. However, recent genetic studies are causing a reassessment of Gnathostomata as a grouping. Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Orders See text. ... Orders Many - see section below. ... {{ | name = Agnatha | image = Agnata. ...

It is assumed the jaws evolved from anterior gill support arches that had acquired a new role, being modified to pump water over the gills by opening and closing the mouth more effectively. The mouth could then grow bigger and wider, making it possible to capture small prey. This close and open mechanism would with time become stronger and tougher, being transformed into real jaws. Modified dermal bones on the surface of the skin would migrate into the mouth and become primtive teeth. Placoderms used sharp bony plates as teeth instead. Orders Antiarchi † Arthrodira † Petalichthyda † Phyllolepida † Ptyctodontida † Rhenanida † The Placodermi are fish known from fossils dating to the Devonian period. ...

Other distinguishing characteristics of living gnathostomates are the myelin sheathes of neurons, and an adaptive immune system. In neuroscience, myelin is an electrically insulating phospholipid layer that surrounds the axons of many neurons. ... Drawing by Santiago Ramón y Cajal of cells in the pigeon cerebellum. ... The immune system is the system of specialized cells and organs that protect an organism from outside biological influences. ...

For the phylogenetic tree of Gnathostomata see chordate. The traditional classes of Gnathostomata include: It has been suggested that Evolutionary tree be merged into this article or section. ... Typical Classes Subphylum Urochordata - Tunicatas 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...

• Placodermi - extinct
• Chondrichthyes (cartilagenous fish)
• Acanthodii - extinct
• Osteichthyes (or Teleostomi) (bony fish)
  • subclass Sarcopterygii (lobe-finned fish)
  • subclass Actinopterygii (ray-finned fish)
• Amphibia (amphibians)
• Reptilia (reptiles)
• Aves (birds)
• Mammalia (mammals)

Orders Antiarchi† Arthrodira† Petalichthyda† Phyllolepida† Ptyctodontida† Rhenanida† The Placodermi are armoured prehistoric fishes known from fossils dating from the late Silurian to the end of the Devonian Period. ... Orders See text. ... Orders Climatiiformes Ischnacanthiformes Acanthodiformes Acanthodii (sometimes called spiny sharks) is a class of extinct fishes, having features of both bony fish ( Osteichthyes) and cartilaginous fish (Chondrichthyes). ... This article is in need of attention. ... 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... Subclasses Coelacanthimorpha - Coelacanths Dipnoi - Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. ... Orders See text The Actinopterygii are the ray-finned fish. ... For other uses, see Amphibian (disambiguation). ... For other uses, see Amphibian (disambiguation). ... Orders See text. ... Orders Many - see section below. ... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (includes extinct ancestors)/Placentalia (excludes extinct ancestors) Afrosoricida Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Dinocerata (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla...

External links

• Tree of Life discussion of Gnathostomata
• The Gill Arches: Meckel's Cartilage