In 1968, a group of researchers, known as the Second Street Expedition, were exploring the Zagros Mountains in Western Iran, looking for new types of reptile and amphibian species. The came upon a snake with a lark corpse in its belly and perhaps the strangest tail of any member of the class Reptilia. It was the first sighting of a spider-tailed horned viper in the 20th century, and its morphology was so bizarre that it wasn’t until 35 years later, in 2003, that the tail, which looks identical to a giant spider, was determined to be a genetic trait rather than a tumor caused by a parasite.

After existence of the species was confirmed in 2006, videos of the spider-tailed horned viper’s hunting habits were finally recorded, revealing one of the most horrific yet incredible examples of aggressive mimicry in nature.

The spider-tailed horned viper’s spider tail in action. 

Following the expedition in ’68, the Second Street researchers handed over their specimens to the Field Museum of Natural History in Chicago, where scientists first thought that the snake was another species from the genus Pseudocerastes that had a solifugid — a type of spider, horrific in its own right — stuck to its tail. After that theory was discarded, scientists believed the growth to either be a genetic trait or due to a tumor. Then a second specimen was discovered in 2003, which gave probable evidence that what researchers had found was indeed a new species.

The solifugid, which scientists thought may have been stuck on the first spider-tailed viper specimen’s tail. Image: Wikimedia / JonRichfield

The species, Pseudocerastes urarachnoides, which is endemic to Iran, has evolved to form a bulb and elongated subcaudal (underside) scales on the end of its tail that combine to look like a spider — common prey for birds in the region. The spider-tailed viper moves the morphed tail in such a way that it does really look like a crawling arachnid, luring in its unsuspecting victim from the sky. Then once the bird touches down, there are instantly fangs in its neck, and then, after a few painful moments of struggle, death.

Pseudocerastes urarachnoides, unlike some other members of its genus, is not venomous, but that bit of good news doesn’t seem that significant when it’s clear this snake can probably scare you to death. Seriously, this creature is a turducken of phobia triggers, and not a single square inch of it looks like anything you’d ever want to touch or see in real life.

Two things seem especially noteworthy here. One: descent with modification and sexual selection led to a snake that could not only perfectly camouflage itself to match the rocks around it, but also dance its spider-tail along its back so flawlessly that it can fool birds into landing on it. Tow: even though Pseudocerastes urarachnoides looks like it crawled right out of Satan’s sandbox, it probably wouldn’t be able to do all that much damage to you in a fight (as opposed to these Tribble-looking caterpillars and even these beautiful flowers, which could inflict enormous pain or death).

All we can say is nature apparently loves to send mixed signals.

A closer glimpse at the spider-shaped tail. Image: Flickr / Omid Mozaffari

What do you think about the spider-tailed horned viper? Is this snake scary enough to set off all your fight-or-flight alarm systems, or can you somehow manage to find a bit of cuteness here? Give us your thoughts in the comments below!

Images: Wikimedia / Omid Mozaffari

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