Daddy long legs are one of the creepiest insects in most homes, but imagine these long-legged arachnids with four eyes. 

Ancient harvestmen, as the insects are more properly known, used to have an extra set of eyes, according to new analysis of an ancient fossil. No other arachnids are known to have evolved fewer eyes over time, making this development unique in the fossil record. 

The 305 million-year-old fossil of (truly) ancient harvestmen was found in eastern France. The ancestor of daddy long legs is called Hastocularis argus. 

"Terrestrial arthropods like harvestmen have a sparse fossil record because their exoskeletons don't preserve well. As a result, some fundamental questions in the evolutionary history of these organisms remain unsolved," Prashant Sharma of the American Museum of Natural History, told Eureka News.

Hastocularis argus was not known until recently, and researchers also discovered vestiges of this extra pair of eyes still exist in the genes of modern harvesters. As harvestmen embryos develop, they briefly form the organs, which disappear before the creatures hatch.  

Surprisingly, Daddy-long-legs are not technically spiders. For an extra dose of creepiness, these long-legged creatures are more closely related to scorpions than they are true spiders. Ancient harvestmen belong to the same group of insects that includes ticks and mites. 

Research into the ancient fossil was led by investigators from the American Museum of Natural History and the University of Manchester. 

"Fossils preserved in three dimensions are quite rare... Our X-ray techniques have allowed us to reveal this fossil in more detail than we would have dreamed possible two decades ago," Russell Garwood of the University of Manchester and a lead author of the study, said.

The remarkable quality of this rare fossil made it possible to examine the structure of the eyes in remarkable detail. 

Arachnids can frequently have two sets of eyes - median, located near the center of the body, and lateral, further away from the middle. Modern daddy long legs lack lateral eyes. 

With this new fossil finding, paleontologists may gain a better understanding of the evolution of arachnids millions of years ago. 

Details of the study into the four-eyed Hastocularis argus were published in the journal Current Biology

After a leg is removed from a modern daddy long legs, the body part can twitch for up to an hour. 

Ancient harvesters are found on every continent on Earth, except Antarctica. There's only one way to get away from the creepy creatures, and you better pack a warm parka.  

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