Anura (Frogs)


The order Anura is a widespread group of over 4000 species of frogs and toads, forming part of the class Amphibia. Adult anurans have a short vertebral column, no tail, stout forelimbs and long, webbed hindlimbs used for swimming and leaping. Most species have an aquatic larval stage, the tadpole.

Keywords: breathing; classification; conservation; development; diet; ecology; enemies; life cycle; habitats; metamorphosis; reproduction; skeletal structure; value

Figure 1.

Life history of an anuran. (A) Adult frogs in amplexus; (B) eggs; (C) egg with gelatinous envelopes and egg proper; (D) first cleavage into two cells; (E) advanced embryonic development with forerunner of spinal cord. (F–I) Developmental history of eggs developing in water: (F) advanced larva with external gills; (G) early hatched tadpole with operculum covering the gills; (H) advanced free‐living tadpole with legs; (I) metamorphosing tadpole with tail partially resorbed. (J) Direct development of land‐laid egg showing froglet in egg capsule; (K) hatched froglet from direct development.

Figure 2.

Skeletal structure of an anuran, seen from the dorsal view; the left suprascapula and scapula have been removed. a, atlas; b, astragalus; c, calcaneum; d, suprascapula; e, exocciptal; f, femur; fp, frontoparietal; g, metacarpals; h, humerus; i, ilium; k, metatarsals; l, carpus; m, maxilla; n, nasal; o, prootic; p, pterygoid; pm, premaxilla; q, quadratojugal; r, radioulna; s, squamosal; se; sphenethmoid; sv, sacral vertebra; t, tibiofibula; u, urostyle. (Slightly modified from Marshall's The Frog: An Introduction to Anatomy, Histology and Embryology.)

Figure 3.

Anuran skull, ventral view. a, parasphenoid; c, columella; e, exoccipital; fp, frontoparietal; m, maxilla; n, vomer; o, prootic; p, pterygoid; pa, palatine; pm, premaxilla; q, quadratojugal; se, sphenethmoid. (Slightly modified from Marshall's The Frog: An Introduction to Anatomy, Histology and Embryology.)

Figure 4.

Anuran skull, view from the right side. A, parasphenoid; AS, angulosplenial; B, anterior cornu of hyoid; C, columella; D, dentary; E, exocciptal; F, nostril; F P, frontoparietal; H, body of hyoid; L, aperture of exit of optic nerve; M, maxilla; MM, mentomecklian; M′, aperture for exit of 5th and 7th cranial nerves; N, nasal; O, prootic; P, pterygoid; PM, premaxilla; Q, quadratojugal; R, aperture for 9th and 10th cranial nerves; S, squamosal, SE, sphenethmoid; T, posterior cornu of hyoid. (Slightly modified from Marshall's The Frog: An Introduction to Anatomy, Histology and Embryology.)


Further Reading

Cogger HG and Zweifel RG (eds) (1998) Encyclopedia of Reptiles and Amphibians. Sydney: University of New South Wales Press.

Duellman WE and Trueb L (1986) Biology of Amphibians. New York: McGraw‐Hill.

Feder ME and Burggren WW (1992) Environmental Physiology of the Amphibians. Chicago: University of Chicago Press.

Halliday T and Adler A (eds) (1986) The Encyclopedia of Amphibians and Reptiles. New York: Facts on File.

Heatwole H (ed) (1994–2000) Amphibian Biology. Vol. 1: The Integument. Vol. 2: Social Behaviour. Vol. 3: Sensory Perception. Vol. 4: Paleontology. Chipping Norton, New South Wales: Surrey Beaty.

McDiarmid RW and Altig R (1999) Tadpoles: The Biology of Anuran Larvae. Chicago: University of Chicago Press.

Stebbins RC and Cohen NW (1995) A Natural History of Amphibians. Princeton, NJ: Princeton University Press.

Taylor DH and Guttman SI (1977) The Reproductive Biology of Amphibians. New York: Plenum Press.

Tyler MJ (1976) Frogs. Sydney: William Collins.

Zug GR, Vitt LJ and Caldwell JP (2001) Herpetology. An Introductory Biology of Amphibians and Reptiles. San Diego: Academic Press.

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Dundee, Harold A(May 2001) Anura (Frogs). In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001537]