The discovery was revealed in a newly-found fossil. UK and American scientists used X-ray technologogy to discover that fact in images of a 305-million-year-old harvestman fossil.
The fascinating find is revealing that the ancient arachnids the species Hastocularis argus have a set of eyes located close to the center of the head and another set on the sides of the insect’s head.
The researchers said that the ancient arachnids were related to spiders but not actually spiders.
"Although they have eight legs, harvestmen are not spiders. They are more closely related to another arachnid, the scorpion," wrote study author Russell Garwood, a paleontologist at the University of Manchester in the UK.
“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," the scientist added.
Today, arachnids include a group of animals that includes harvestmen and also spiders and scorpions, which can also have two sets of eyes, Garwood said. But the scientist added that modern harvestmen only have one set of eyes.
“Terrestrial arthropods like harvestmen have a sparse fossil record because their exoskeletons don’t preserve well,” stated Prashant Sharma, a postdoctoral researcher in the American Museum of Natural History, Division of Invertebrate Zoology and one of the lead authors on the new study.
“As a result, some fundamental questions in the evolutionary history of these organisms remain unresolved," the scientist added. "This exceptional fossil has given us a rare and detailed look at the anatomy of harvestmen that lived hundreds of millions of years ago.”
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