The Madrean alligator lizard (Elgaria kingii), also known commonly as King's alligator lizard and el lagarto de montaña in Mexican Spanish, is a species of lizard in the family Anguidae. The species is native to the southwestern United States and adjacent northwestern Mexico.

The specific name, kingii, is in honor of Phillip Parker King, an Australian-born Royal Navy officer who surveyed the coast of South America.^[3]

E. kingii is found from southeastern Arizona and southwestern New Mexico, United States, southward to Jalisco, Colima, Nayarit, southeastern Zacatecas, and southwestern Aguascalientes, Mexico.

E. kingii is found in a variety of habitats including desert, grassland, shrubland, and forest.^[1]

E. kingii is oviparous.^[2]

Three subspecies are recognized as being valid, including the nominotypical subspecies.^[2]

• Elgaria kingii ferruginea (Webb, 1962)
• Elgaria kingii kingii Gray, 1838
• Elgaria kingii nobilis Baird & Girard, 1852

Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Elgaria.

• Baird SF, Girard C (1852). "Characteristics of some New Reptiles in the Museum of the Smithsonian Institution". Proceedings of the Academy of Natural Sciences of Philadelphia 6: 125–129. (Elgaria nobilis, new species, p. 129).
• Boulenger GA (1885). Catalogue of the Lizards in the British Museum (Natural History). Second Edition. Volume II. ... Anguidæ .... London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiii + 497 pp. + Plates I–XXIV. (Gerrhonotus kingii, pp. 274–275).
• Gray JE (1838). Catalogue of the Slender-tongued Saurians, with Descriptions of many new Genera and Species. Annals and Magazine of Natural History, First Series 1: 274–283, 388–394. (Elgaria kingii, new species, pp. 390–391).
• Smith HM, Brodie ED Jr (1982). Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. ISBN 0-307-13666-3. ("Elgaria kingi [sic]", pp. 86–87).
• Stebbins RC (2003). A Field Guide to Western Reptiles and Amphibians, Third Edition. The Peterson Field Guide Series ®. Boston and New York: Houghton Mifflin. xiii + 533 pp. ISBN 978-0-395-98272-3. (Elgaria kingii, pp. 334–335 + Plate 41 + Map 124).
• Webb RG (1962). "A New Alligator Lizard (Genus Gerrhonotus) from Western México". Herpetologica 18 (2): 73–79. (Gerrhonotus kingi [sic] ferrugineus, new subspecies).

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