Serpentes (Snakes)


Snakes are a diverse group of long‐bodied, limb‐reduced reptiles closely related to lizards; together they are termed squamate reptiles. Primitive snakes with vestigial legs appear in the fossil record of the Cretaceous period (∼90 Mya). Snakes have since been diversified rapidly, and now comprise ∼3500 species that occupy terrestrial, subterranean, aboreal and aquatic niches. All snakes are predators, having highly mobile skulls and jaws that can often swallow prey much larger than their own diameter. Primitive snakes such as boas, pythons and blindsnakes lack venom fangs. Such fangs have evolved repeatedly within more advanced snakes, called the Colubroidea, which make up ∼80% of the diversity of living snakes: front fangs in viperids (e.g. vipers and rattlesnakes), fixed front fangs in elapids (e.g. mambas and cobras) and rear fangs in many lineages of colubrids (e.g. boomslangs and twig snakes).

Key Concepts:

  • Snakes are just one of the many lineages of limb‐reduced lizards – though by far the most successful ones.

  • Snakes have highly flexible (kinetic) skulls and lower jaws, and many forms can engulf prey wider than their heads.

  • Snakes are one of the most rapidly diversifying groups, with more than 3000 living species, mostly belonging to the Colubroidea.

  • Venom‐delivery systems (fangs and glands) have evolved multiple times within the most advanced snake lineage (Colubroidea).

  • The fossil snakes Najash and Pachyrhachis (∼90 My old) retain prominent external hindlimbs, as would be expected given that snakes evolved from lizard‐like reptiles.

Keywords: cranial kinesis; Colubroidea; Serpentes; vertebrates; reptiles; squamates; limblessness; venom

Figure 1.

The four major jaw systems found in snakes. The marginal element on the upper jaw is shown in pink, the elements on the roof of the mouth are shown in yellow and the lower jaw element is shown in blue.

Figure 2.

The internal anatomy of a typical snake in ventral (belly) view. This specimen is a male. After drawing by Kirshner D in Shine .

Figure 3.

The evolutionary relationships of the major groups of living snakes; some minor groups are not shown. ‘Colubridae’ is in quotes because the taxonomy of this hugely diverse lineage is currently in flux (e.g. Pyron et al., ). The numbers on the branches refer to species diversity of each lineage (from http://www.reptile‐, accessed on 2 February 2013); Photo credits (left to right) as follows: (1) Kapustin K, (2) Niemiller M, (3) Djatmiko WA, (4) Vickers T, (5) Jean P, (6) Macdonald S, (7) NBII public domain photograph. Photo 2 © Matthew Niemiller and used with permission, all other photos used are public domain images, courtesy of Wikimedia under their conditions.



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Further Reading

Aldridge RD and Sever DM (2011) Reproductive biology and phylogeny of snakes. New York: Taylor and Francis.

Gower D, Garrett K and Stafford P (2012) Snakes. London: Natural History Museum.

Greene HW (1997) Snakes: The Evolution of Mystery in Nature. Berkeley, CA: University of California Press.

Mullin SJ and Seigel RA (2009) Snakes: Ecology and Conservation. Ithaca: Cornell University Press.

Murphy JC (2010) Secrets of the Snake Charmer: Snakes in the 21st Century. Bloomington:

Pianka ER and Vitt LJ (2003) Lizards: Windows to the Evolution of Diversity. Berkeley, CA: University of California Press.

Shine R (2009) Australian Snakes: A Natural History. Sydney: New Holland Publishers.

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How to Cite close
Lee, Michael SY(Jun 2013) Serpentes (Snakes). In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001543.pub2]