Nonetheless, the determination of the number of species of vertebrates is necessarily imprecise.
The internal skeleton that defines vertebrates consists of cartilage or bone, or in some cases both.
The skeleton of most vertebrates, excluding the most primitive ones, consists of a skull, the vertebral column, and two pairs of limbs.
According to a report by Uetz in 2000, comprehensive compilations of vertebrates reveal a species total of 4,675 mammals, 9,702 birds, 7,870 reptiles, 4,780 amphibians, and 23,250 fishes.
Vertebrates are the best known among the animals, with most species having been identified and described.
The protection of these organs is also thought to have positively influenced the development of the high responsiveness to the environment often found in vertebrates.
Communities pass laws relating to the humane treatment of vertebrates, and they build zoos for their display.
The heart is located either behind the gills, or, in air-breathing vertebrates, between the lungs.
Vertebrates are also considered part of the Craniata, a group of animals that includes all animals with skulls.
Vertebrates are generally divided into two major groups: Agnatha (jawless vertebrates) and Gnathostomata (jawed vertebrates).
The Lampridiformes is comprised of a number of morphologically spectacular marine forms such as the crestfishes, tapertails, ribbon fish, ink-eye, tubefish, and unicorn fish and, of course, the oarfish.
Fish (including lampreys), amphibians, reptiles, birds, and mammals (including humans) are vertebrates.
Meanwhile, the IUCN reports a total of 1,190,200 described, extant species of invertebrates (although this represents an assumably small proportion of actual species of this very incompletely known group).
Vertebrates started to evolve about 530 million years ago during the Cambrian explosion.
Chordata includes two subphyla of invertebrates (Urochordata and Cephalochordata) and the Vertebrates.
Over 50,000 species of vertebrates have been described.
Vertebrates are animals belonging to the subphylum Vertebrata, that is, animals with backbones or spinal columns.
Vertebrates (subphylum Vertebrata) are part of the phylum Chordata, which are animals that had, at some stage in their life, a notochord, a hollow dorsal nerve cord, and pharyngeal slits, among other characteristics.
The five most well known classes of vertebrates (animals with backbones) are mammals, birds, fish, reptiles, amphibians. They are all part of the phylum chordata -- I remember "chordata" by thinking of spinal chord. There are also a lot of animals without backbones.