Vertebrates /ˈvɜrtɨbrəts/ are animals that are members of the subphylum Vertebrata /-ɑː/ (chordates with backbones and spinal columns). Vertebrates include the overwhelming majority of the phylum chordata, with currently about 64,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm (0.3 inch), to the blue whale, at up to 33 m (110 ft). Vertebrates make up about 4% of all described animal species; the rest are invertebrates, which lack backbones.

The vertebrates traditionally include the hagfishes, which do not have proper vertebrae, though their closest living relatives, the lampreys, do have vertebrae. Hagfishes 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 the hagfishes 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.

Marc W. Kirschner (born February 28, 1945) is an American cell biologist and biochemist and the founding chair of the Department of Systems Biology at Harvard Medical School. His research involves problems in cell and developmental biology, such as the dynamics and function of the cytoskeleton, the regulation of the cell cycle, and the process of signaling in embryos, as well as the evolution of the vertebrate body plan, and applying mathematical approaches to biology.

Kirschner was born in Chicago, Illinois, on February 28, 1945. He graduated from Northwestern University with a B.A. in chemistry in 1966. In 1971, he received his doctorate in biochemistry from the University of California, Berkeley. He held post-doctoral positions at UC Berkeley and at the University of Oxford in England. He became assistant professor at Princeton University in 1972. In 1978 he was made professor at the University of California, San Francisco. In 1993, he moved to Harvard Medical School, where he served as the chair of the new Department of Cell Biology for a decade. He became the founding chair of the HMS Department of Systems Biology in 2003. He was named the John Franklin Enders University Professor in 2009.