Vertebrate
Channel: 宇宙のすべての知識 プリンシピア
Date: 28/02/2019

Vertebrate, by Wikipedia https://en.wikipedia.org/wiki?curid=36856 / CC BY SA 3.0

#Vertebrates
#Terreneuvian_first_appearances
#Extant_Cambrian_first_appearances
Vertebrate

Vertebrates comprise all species of animals within the subphylum Vertebrata (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,276 species described. Vertebrates include the jawless fishes and the jawed vertebrates, which include the cartilaginous fishes (sharks, rays, and ratfish) and the bony fishes. 

Other vertebrates are the tetrapods, which include a bony fish clade known as the lobe-finned fishes, as well as amphibians, reptiles, birds and mammals. 

Extant vertebrates range in size from the frog species "Paedophryne amauensis", at as little as , to the blue whale, at up to . Vertebrates make up less than five percent of all described animal species; the rest are invertebrates, which lack vertebral columns.

The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, the lampreys, do. Hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as "Craniata" when discussing morphology.

Molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a sister group of vertebrates in the common taxon of craniata.

The word origin of "vertebrate" derives from the Latin word "vertebratus" (Pliny), meaning "joint of the spine." The Proto-Indo-European language origins are still unclear.

"Vertebrate" is derived from the word "vertebra", which refers to any of the bones or segments of the spinal column.

All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal (vertebral column and/or notochord), with a hollow tube of ner...