Vertebrate Evolution: Genes and Development


The most significant differences between the vertebrates and the other chordates lie in the head. These novel features probably emerged as a result of modifications to the developmental program, and they are thought to have aided the vertebrates in assuming a predacious lifestyle. More specifically, the evolution of these characteristics must have involved extensive regionalization of the central nervous system, the evolution of neural crest and ectodermal placodes and alterations to the pharynx.

Keywords: ectodermal placodes; genome evolution; neural crest; pharyngeal segmentation; chordates; vertebrate evolution

Figure 1.

The chordate phylum consists of three subphyla: the vertebrates, the cephalochordates and the urochordates, which are united by their possession of a number of common features at the embryonic stage. These three subphyla do, however, exhibit differing degrees of anatomical complexity, with the vertebrates being the most complex.

Figure 2.

Schematic representation of a cephalochordate, Amphioxus, highlighting the typical shared characteristic chordate features: notochord, dorsal nerve cord, segmented muscle blocks and a segmented pharyngeal region.

Figure 3.

Unique features of the vertebrate head. The vertebrates differ from the other chordates in having a number of features concentrated in the head: they have an elaborate brain, numerous special sense organs, a muscularized pharynx with skeletal support, a backbone and an extensive peripheral nervous system.



Ferrier DE and Holland PW (2001) Ancient origin of the Hox cluster. Nature Reviews of Genetics 2: 33–38.

Gans C and Northcutt RG (1983) Neural crest and the origins of vertebrates: a new head. Science 220: 268–274.

Graham A (2001) The development and evolution of the pharyngeal arches. Journal of Anatomy 199: 133–141.

Graham A and Begbie J (2000) Neurogenic placodes: a common front. Trends in Neurosciences 23: 309–312.

Holland LZ and Holland N (1999) Chordate origins of the vertebrate nervous system. Current Opinion in Neurobiology 9: 596–602.

Le Douarin NM and Kalcheim C (1999). The Neural Crest. New York: Cambridge University Press.

Liem Jr KF, Tremml G, Roelink H and Jessell TM (1995). Dorsal differentiation of neural plate cells induced by BMP‐mediated signals from epidermal ectoderm. Cell 82: 969–979.

Williams NA and Holland P (1998) Molecular evolution of the brain of chordates. Brain Behaviour and Evolution 52: 177–185.

Further Reading

Butler AB (2000) Sensory system evolution at the origin of craniates. Philosophical Transactions of the Royal Society of London B 355: 1309–1313.

Kardong KV (2002) Vertebrates: Comparative Anatomy, Function, Evolution. New York: McGraw‐Hill.

Lacalli TC (2001) New perspectives on the evolution of protochordate sensory and locomotory systems, and the origin of brain and heads. Philosophical Transactions of the Royal Society of London B 356: 1565–1572.

Schaeffer B (1987) Deuterostome monophyly and phylogeny. Evolutionary Biology 21: 179–234.

Web Links

The Tree of Life. A collaborative internet project containing information about phylogeny and biodiversity

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Graham, Anthony(Sep 2006) Vertebrate Evolution: Genes and Development. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0005921]