Inside the ‘unique’ tail of Iran’s spider-tailed horned viper

The Iranian spider-tailed horned viper, a rare snake endemic to western Iran, hunts by holding its body completely still while twitching its tail. Its body camouflages among the rocks of its semi-arid Zagros Mountains habitat, but its bulbous tail with accompanying leg-like scales looks remarkably like a large chunky spider. The snake, Pseudocerastes urarachnoides, uses its spider tail to lure unsuspecting mammals and birds to their last meal. Scans of a specimen collected in 1968 and kept in the Field Museum of Natural History in Illinois, United States, now reveal what the lure is made of. “The tip actually consists of enlarged, elongated and modified scales, which are unique among all living reptiles,” lead author Georgios Georgalis, an associate professor at the Polish Academy of Sciences’ Institute of Systematics and Evolution of Animals in Kraków, Poland, told Mongabay by email. The scanned P. urarachnoides specimen. Image © Georgalis et al. (2026). Vipers have attracted the interest of researchers for centuries, Georgalis said, but knowledge of the group’s morphology is still limited. Scientists described P. urarachnoides for science in 2006, but only this year did they publish a high-resolution 3D scan to see the mechanism inside the snake’s tail as part of a scientific study. The tail filaments, the authors said, loosely resemble those found on some ornithodiran archosaurs and other forms from the Triassic and Jurassic periods. This doesn’t mean that they are related, it’s more likely a case of convergent evolution: similar environmental demands pushing the evolutionary development of similar characteristics.…This article was originally published on Mongabay