The “horn” above each eye is not a true horn, and it is not a single scale. It is a raised cluster of several small scales over the eye, standing up in a short, rough point. Like every snake scale, each one is a fold of skin with a hard outer layer of keratin.

Pseudocerastes means “false Cerastes”. It looks like the horned vipers of the genus Cerastes, such as the Arabian Horned Viper, but it is not a close relative. The horns are built differently, one long scale in Cerastes and a cluster of small scales here, and the two groups evolved them separately.

The rough points may break up the outline of the head, so a viper resting among rocks and stones is harder to pick out.

The horns may help shield the eyes from grit and dust. This idea was put forward mainly for desert vipers that bury themselves in sand, so it may matter less for a mountain viper like this one.

They may help vipers recognize their own kind, or play a part in choosing a mate. This is the least certain of the three.