They have massive, segmented jaws armed with rows of spiny teeth, which can make up a third of their body length.
These mouthy creatures are variously called camel spiders, sun spiders, wind scorpions or beard cutters.
Despite these names, they are neither spiders nor scorpions. They belong to a separate order of arachnids, called Solifugae.
They are found in the hotter, drier areas of most continents. However, many people have never heard of them, and science has also tended to ignore them.
That could be about to change, as a new study has examined them in more detail than ever before.
Camel spiders are a diverse lot. Some are up to 20cm long, while others are only a few millimetres.
We know of over 1,000 species, many of them known from only a single specimen. There could be many more.
Camel spiders live life at top speed. "They have very high metabolic rates, they have a short lifespan and are extremely active, running around, eating, mating and dying rapidly," says Lorenzo Prendini of the American Museum of Natural History in New York.
The fastest can scurry at speeds of 10 miles per hour, more than twice the average human walking speed. In Africa they are sometimes called the "Kalahari Ferrari".
If you are alarmed by the notion of a spider-like beast that can outrun you, bear in mind that camel spiders aren't venomous, so the worst they can do is nip you with their jaws.
Those massive jaws are the key to their predatory lifestyle.
They will eat anything they can overpower, mostly insects and other arthropods. Bigger camel spiders will also take on small vertebrates such as lizards, snakes and mice. Given the chance, they will even eat their own kind.
Prendini and his colleagues have surveyed the intricate structures of their jaws in the most comprehensive study yet of these arachnids. Their analysis is published in the Bulletin of the American Museum of Natural History.
To do so, they analysed the jaws of 188 camel spiders, which represented all the Solifugae families. They used collections from museums, as well as specimems collected on expeditions over the last 10 years.
His goal was to standardise the terms used to refer to the various parts of the camel spider. The team has now put forward almost 80 terms to name different bits of their jaws.
This new terminology should make it easier to study camel spiders, and to identify new species.
"The last time there was a major publication of this kind on camel spiders was in 1934, which, considering how conspicuous and ubiquitous they are in some parts of the world, is almost unbelievable," says Prendini.
There are certainly plenty of unanswered questions.
For one, we know barely anything about how camel spiders reproduce. All we know is, it's probably tricky.
Males are smaller and more delicate than the females. So a hopeful male must first convince a female that he is a potential mate rather than prey.
"When they bump into a member of the opposite sex it can be risky," says Prendini. "They first have to identify if it's the same species. If it's a different one then it's a free-for-all. Whoever is bigger will win."
A successful meeting then consists of some sort of intense battle, involving their jaws. Somehow the male then transfers his sperm to the female, but we don't know how.