Category: vertebrates...

in some forms, as snakes and whales, the limbs have been lost or greatly modified over time
vertebrates are also characterized by a muscular system consisting primarily of bilaterally paired masses and a nervous system partly enclosed within the backbone
Brave men are all vertebrates; they have their softness on the surface and their toughness in the middle. (G.K. Chesterton)
Vertebrates originated about 500 million years ago during the Cambrian period.
vertebrate is derived from Latin vertebratus "jointed, articulated"
Although the vertebral column is perhaps the most obvious vertebrate feature, it was not present in the first vertebrates, which probably had only a notochord. The vertebrate has a distinct head, with a differentiated tubular brain and three pairs of sense organs (nasal, optic, and otic).
With the exception of certain rodents, no other vertebrate [except Homo sapiens] habitually destroys members of his own species. (Antony Storr)