{{Speciesbox | name = Eastern fence lizard | image = Eastern Fence Lizard 03-20-08.png | image_caption = Eastern fence lizard (Sceloporus undulatus), Amelia Court House, VA | status = LC | status_system = IUCN3.1 | status_ref = | taxon = Sceloporus undulatus | authority = (Bosc & Daudin, 1801)<ref>Bosc [LAG], Daudin [FM] (1801). In: Sonnini CS, Latreille PA (1801). Histoire Naturelle des Reptiles, avec figures dessinées d'après nature. Tome II [Volume 2]. Première partie. Quadrupèdes et bipèdes ovipares. Paris: Deterville. (Crapelet, printer). 332 pp. (Stellio undulatus, new species, pp. 40-42). (in French).</ref> | synonyms = *Stellio undulatus Bosc & Daudin, 1801 Lacerta undulata — Bosc, 1801 Agama undulata — Daudin, 1802 Tropidolepis undulatus — A.M.C. Duméril & Bibron, 1837 Sceloporus undulatus — Boulenger, 1885 | range_map = Sceloporus undulatus distribution.svg | range_map_caption = The ranges of different S. undulatus subspecies are indicated by color. (note: map is missing distribution in New York State) }}The eastern fence lizard (Sceloporus undulatus) is a medium-sized species of lizard in the family Phrynosomatidae. The species is found along forest edges, rock piles, and rotting logs or stumps in the eastern United States. It is sometimes referred to as the prairie lizard, fence swift, gray lizard, gravid lizard, northern fence lizard or pine lizard. It is also referred to colloquially as the horn-billed lizard. One of its most notable behaviors is that of its escape behavior when encountering fire ants. Taxonomy The generic name, Sceloporus, is derived from the Greek skelos/σκελος, meaning "leg", and the Latin porus, meaning "hole", referring to the enlarged femoral pores found in this genus of lizards. The specific name, undulatus, is Latin for "wave", referring to the transverse dark crossbars on the backs of these lizards. Until 2002, 10 subspecies of S. undulatus were recognized, but re-evaluation showed paraphyly between the subspecies. These were reclassified as four distinct evolutionary species (the three new species being S. consobrinus, S. tristichus, and S. cowlesi). The narrowed redefinition of S. undulatus has been suggested to still contain two subspecies divided by the Appalachian Mountains. None currently hold formal recognition. This variation can be partially attributed to the high nucleotide variation. One study found an average of 38 SNPs per kilobase of DNA. The following cladogram is based on Leaché and Reeder, 2002: Description The eastern fence lizard can grow from 4.0 to 7.5 inches (10 to 19 cm) in total length (including tail).