Classes of Vertebrata

Members of Subphylum Vertebrata make up most of Phylum Chordata. They share all of the characteristics of that phylum (including a notochord, dorsal hollow nerve cord, pharyngeal slits, and a postanal tail), but have their own distinct characteristics that seperate them from the other two subphyla, Cephalochordata and Urochordata. They have a neural crest that forms during embryonic development, near the neural tube--this is also associated with pronounced cephalization (the concentration of sensory and neural equipment in the head). Vertebrata receive their name from the vertebral column they all share--a spinal cord made up of seperate bones or pieces of cartilage. It is also important that Vertebrates have a closed circulatory system.

Vertebrates are divided into two superclasses. Superclass Agnatha contains all jawless vertebrates--it is divided into Class Myxini (hagfishes) and Class Cephalaspidomorphi (lampreys). Superclass Gnathostomata contains most animals normally associated with vertebrates--all of them have hinged jaws. It itself is divided into Class Chondrichthyes (cartilaginous fishes, e.g. sharks and rays), Class Osteichthyes (bony fishes, e.g. bass and tuna), Class Amphibia (amphibians, e.g. salamanders and frogs), Class Reptilia (reptiles, e.g. snakes and lizards), Class Aves (birds, e.g. owls and eagles), and Class Mammalia (mammals, e.g. koalas, platypuses, bats, and humans).

Ver`te*bra"ta (?), n. pl. [NL.] Zool.

One of the grand divisions of the animal kingdom, comprising all animals that have a backbone composed of bony or cartilaginous vertebrae, together with Amphioxus in which the backbone is represented by a simple undivided notochord. The Vertebrata always have a dorsal, or neural, cavity above the notochord or backbone, and a ventral, or visceral, cavity below it. The subdivisions or classes of Vertebrata are Mammalia, Aves, Reptilia, Amphibia, Pisces, Marsipobranchia, and Leptocardia.


© Webster 1913.

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