The spider-tailed horned viper (Pseudocerastes urarachnoides) is a species of viper, a venomous snake, in the family Viperidae and genus Pseudocerastes. The genus is commonly known as "false-horned vipers".
The species is endemic to western Iran and over the border region with Iraq. The first specimen was found in 1968 by the Second Street Expedition. It was originally described as Pseudocerastes persicus, attributing the tail to either parasite, deformity, or tumors. Another specimen was found in 2003. P. urarachnoides was officially described in 2006. The head looks very similar to that of other Pseudocerastes species in the region, but the spider-tailed horned viper has a unique tail that has a bulb-like end that is bordered by long drooping scales that give it the appearance of a spider. The tail tip is waved around and used to lure insectivorous birds to within striking range.
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