Ancient Arachnids had Two Sets of Eyes

Modern-day daddy longlegs are certainly terrifying, dwindling on eight willowy gams. Yet a 305-million-year-old fossil shows that their ancestors may have been more eye-catching. In other words, researchers discovered that these arachnids had double vision. 

Researchers from the American Museum of Natural History and the University of Manchester used X-ray imaging techniques to better distinguish certain features of the fossil, named  Hastocularis argus. They discovered that ancestors of this group of arachnids known as harvestmen had two sets of eyes.

"Harvestmen fossils preserved in three dimensions are quite rare and our X-ray techniques have allowed us to reveal this exceptional fossil in more detail than we would have dreamed possible just a couple of decades ago," said Dr. Russell Garwood, a palaeontologist in the University of Manchester's School of Earth, Atmospheric and Environmental Sciences, via a press release.

The fossil showed scientists that these spiders second set of eyes were located near the center of the body, while the lateral set remained on its sides.   

"Although they have eight legs, harvestmen are not spiders; they are more closely related to another arachnid, the scorpion," Dr. Garwood added, via the release. "Arachnids can have both median and lateral eyes, but modern harvestmen only possess a single set of median eyes - and no lateral ones. These findings represent a significant leap in our understanding of the evolution of this group."

More information regarding the findings can be seen via the journal Current Biology.