The mountains of southern Oregon have been hiding monsters. Though Bigfoot still remains undiscovered, scientists have found another creature known for its sizable appendages: a new species of daddy longlegs, reports Livescience.

The species has been dubbed Cryptomaster behemoth, a deservedly intimidating name for such an enormous arachnid. It measures in at a whopping 4 millimeters (0.15 inches) wide. (OK, so maybe that doesn't sound so large, but it's the biggest known species ever discovered in its genus.)

It may seem surprising that such a large arachnid could go unnoticed for so long, but C. behemoth is apparently an elusive creature, preferring to lurk beneath leafy debris and under logs that cover the forest floors where it lives. It is believed to be related to the species C. leviathan, now the second largest member of its genus, which was only just discovered in 1969, also in Oregon but along the coast.

Interestingly, both of these species come in two forms, one significantly larger than the other. The two forms exist for males and females of both species, meaning that there are larger and smaller males and larger and smaller females. Scientists checked, and both forms of each species are not genetically distinct. So it's a mystery as to why these different forms exist.

"The basis for these two forms is unknown — the different forms can be found in both sexes, in both species and from the same localities. Additionally, the two forms are not genetically divergent," the researchers wrote in their paper.

This new species, like all species of daddy longlegs, is not actually a spider, despite the common misconception. Rather, all daddy longlegs are known as harvestmen, and belong to a different order of arachnid entirely from the one that spiders are classified under.

"This research highlights the importance of short-range endemic arachnids for understanding biodiversity, and further reveals mountainous southern Oregon as a hot spot for endemic animal species," write the researchers.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

'Behemoth' new species of daddy longlegs discovered in Oregon mountains
The surprising find shows just how much there is to learn about the biodiversity of southern Oregon's mountainous region.