A Rare Snake with a Spider-Like Tail.. What is the Secret Behind This Strange Formation?

- In the dry and harsh climate of the Zagros Mountains in western Iran, life has found an amazing way to survive. Then, what initially appeared to be a plump spider climbing the rocks caught the eye.

But when the aerial predator pounced on it, it became prey, after something that looked like a rock initially attacked it. However, that rough rocky surface is nothing but the rugged back of a snake with horn-like protrusions on its head, while the "spider" is the tip of its tail moving in an enticing manner.

When scientists collected a sample of the spider-tailed snake with horns in Iran in 1968, the spider-like tip of its tail did not attract their attention. Sara Rowan, an assistant curator in the Department of Reptiles and Amphibians and the director of core laboratories at the Negaunee Integrative Research Center at the Field Museum in Chicago, said, "Anyone looking at the tail thinks it has a tumor or some kind of growth or parasite, and that this is just an abnormal case.

No one believed that this shape could be normal for the species until another sample was collected in 2003." The 1968 sample remains preserved in the collections of the Field Museum as the type specimen, meaning the specimen to which scientists refer to determine the morphological characteristics of the species, according to Rowan.

Researchers used this type specimen in 2006 to describe the snake as a newly discovered species, naming it Pseudocerastes urarachnoides. Now, Rowan and her colleagues have used X-ray imaging to take a detailed internal look at the vertebrae at the tip of the tail.

The results were published in the scientific journal "The Anatomical Record" on Thursday. The lead author of the study, Dr. Georgios Georgalis, an assistant professor at the Institute of Animal Methodology and Evolution at the Polish Academy of Sciences in Krakow, said: "Some other snakes, such as sand vipers and rubber snakes, have vertebrae at the tip of their tails that take on very strange shapes, making them look like they are from another world.

We wanted to find out if the tail of the horned snake and the spider-tailed snake is strange to the same extent from the inside." However, the researchers discovered something unexpected, highlighting that skeletal structures do not always reveal the full story of animals, whether they are alive or have been extinct for a long time.

A snake living on the edge during her PhD studies, Rawan first saw a "stunning" video of a horned snake with a spider-like tail moving its unusual tail to lure birds in 2008. It is known that other snakes also move their tails, especially young vipers whose tail tips are bright green or vivid yellow, which may make them look like a worm moving in front of unsuspecting frogs.

Rawan said: "But the mechanism at the tip of the spider-tailed snake's tail is completely different and on another level." This snake is difficult to spot, as it uses its muscles to live on steep rocky slopes.

Its harsh habitat also makes studying or collecting samples from it in the wild difficult. Rawan recounted that "some of the videos I watched of these snakes while they were moving show that they are inside very small crevices, where you wouldn't think any animal could cling well, let alone a snake that has no limbs.

When you actually hold a bird, the snake sometimes launches from the rock surface with the bird. The entire lifestyle of the snake is very strange.

When Rawan met Georgalis at a conference in 2023, he expressed interest in studying the type specimen of this snake. Georgalis, as a paleontologist, studies modern snakes to understand the scattered fossil remains of ancient extinct snakes.

Rawan recalled that the timing was very appropriate, as the Field Museum was preparing to acquire a new lab for X-ray computed tomography, or XCT. This technology allows scanning objects to produce thousands of X-ray images and create three-dimensional images that provide a look inside structures without damaging the samples, such as the interior of the snake's tail.

Dr. Kurt Schwenk, an emeritus professor in the Department of Ecology and Evolutionary Biology at the University of Connecticut at Storrs, who is not involved in the study, stated that the skeletal structures of snakes contain hundreds of vertebrae, meaning that the spinal columns of snakes have not been adequately studied in the past. The type specimen was the first to be scanned after the lab began operations in late 2024.

The scans revealed that the vertebrae inside the tail are normal and resemble those found in most snakes, according to Georgalis. He stated that the fleshy appendage instead consists of elongated and modified scales, with no bony component present.

Georgealis explained to Afaq News: "If these remains were available to us today only as fossils, we would not have been able to reconstruct the shape of its spider-like tail or even imagine it." As a specialist in reptile morphology, Schwenk did not expect that the part used to lure prey would consist of soft tissues only.

He clarified that "modifying scales to become different structures, such as spines, horns, and protrusions, is quite common among lizards and snakes. Unlike the head, these modifications rarely involve the underlying skeleton, if that happens at all." Typically, snake vertebrae are shorter in the tail, but Schwenk noticed that the tail vertebrae appear unusually small in the horned snake with the spider-like tail.

Schwenk said: "The short vertebrae in the tail make it flexible specifically. This would enhance the tail's ability to create the tight, winding curves necessary to give a realistic character to the movements of the part used to lure prey, which resemble the movements of a spider."

An "amazing" adaptation, and there are still questions about the horned snake and the spider-like tail, including how this intriguing feature, known as the tail lure, evolved at the end of its tail. Rawan spoke about the Persian horned snake and the field horned snake, the two closest species to the spider-tailed snake: "If you look at these two species, you will find that their tails are strange."

She addressed the hard, dry outer covering of the tail: "It looks smaller than it should be, and it is covered with a thick layer of keratin," adding: "At least in the samples I have seen, its color also differs. The snake is somewhat sandy brown or gray, while the tail is black."

It stated that many snakes move their tails, either to scare off predators or to lure prey, but the horned snake with a spider-like tail may be an extreme example, similar to rattlesnakes, of how certain traits can develop over time due to specific behaviors. Rawan added that future research may focus on the genetic mechanisms that may have been activated or deactivated for the appearance of the spider-like appendage.

Schwenk said he believes this behavior was likely present in the ancestors of snakes. He concluded that "the spider-tailed snake took this inherited behavior from its ancestors and modified it into something truly amazing."

The spider-like structure, along with the undulating movements of the tail, gives the impression of a spider moving so realistically that when I first watched a video of this behavior, I was completely deceived.