Spider-Tailed Viper....

Pseudocerastes urarachnoides, Spider-tailed Viper - western Iran

I recently learnt about this remarkable snake in Tony Phelp's Old World Vipers (2010 Chimaira, Frankfurt). First discovered back in 1968, this adder was described only a few years back (2006), on the basis of two specimens. Although the original specimen (now the Holotype) was collected in 1968, its taxonomic status remained in limbo, even though the caudal morphology is so different from that of closely related species. One reason was that back then, the Holotype was possibly an aberrant individual (with a deformed or diseased tail).

With a restricted range in the mountainous terrain of western Iran, this poorly known viper has been observed sheltering in rock crevices in the gypsum formations that comprise its hilly, arid habitat.

The capture and observations of a live individual confirmed the hypothesis proposed in the species' description - that the remarkable modifications to the caudal scales are an adaptation for mimicry - of an arachnid. This structure lures prey, very likely birds, for even in the preserved museum specimen the appendage bears an uncanny resemblance to a solifugid (sun spider). It is indeed remarkable to consider the EDB (evodevo) mechanisms that have modified scales into "spiderlegs", and equally underlie the pigmentation patterns!

And observations of this snake's behaviour does indeed been confirm this - see the video clip [Below] from Steve Anderson's website [www.swasiazoology.tripod.com]. The snake has been observed using its caudal lure to attract birds in captivity, and it possibly deceives small mammals (perhaps shrews) too. This adder has a swift strike, and envenomation progresses rapidly.

https://www.sciencealert.com/watch-the-spider-tailed-viper-is-amazingly-good-at-killing