Vertebrate

Vertebrate Temporal range: Cambrian Stage 3–Present, 518 –0 Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N
Diversity: a sturgeon (Actinopterygii), an elephant (Tetrapoda), a shark (Chondrichthyes) and a lamprey (Agnatha).
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Superphylum:	Deuterostomia
Phylum:	Chordata
Clade:	Olfactores
Subphylum:	Vertebrata J-B. Lamarck, 1801[2]
Infraphyla
Agnatha (paraphyletic) Gnathostomata
Synonyms
Ossea Batsch, 1788[2]

Vertebrates (/ˈvɜːrtəbrɪts, -ˌbreɪts/)^[3] are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain.

The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest grouping in the phylum Chordata. The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the cartilaginous fish and the bony fish. Bony fish include the lobe-finned fish, which gave rise to the tetrapods, the animals with four limbs. Vertebrates make up less than five percent of all described animal species.

The first vertebrates appeared in the Cambrian explosion some 518 million years ago. Jawed vertebrates evolved in the Ordovician, followed by bony fishes in the Devonian. The first amphibians appeared on land in the Carboniferous. During the Triassic, mammals and dinosaurs appeared, the latter giving rise to birds in the Jurassic. Extant species are roughly equally divided between fishes of all kinds, and tetrapods. Populations of many species have been in steep decline since 1970 because of land-use change, overexploitation of natural resources, climate change, pollution and the impact of invasive species.