The arachnids known today as daddy longlegs previously had two pairs of eyes.
Researchers say a 305-million-year-old harvestman fossil discovered in France says a lot about the evolutionary history of the critters, which presently only have one set of clustered eyes on top of their heads. (Via National Geographic)
High-resolution X-ray images of the fossil reveal ancestors of the spider-like daddy longlegs had another set of eyes closer to the sides of their heads, called lateral eyes. (Via LiveScience)
The researchers then looked at modern harvestmen embryos and found they still retain the gene for the lost set of eyes; though they only form one set when they hatch. (Via American Museum of Natural History)
So why did modern daddy longlegs lose those extra eyes? one of the study's authors speculates the species might have adapted to darker areas and no longer needed them, according to Wired.
The researchers say the bodies of these species have changed very little as they've evolved, but the discovery is a rare, detailed look into the differences between ancient and modern arachnids.
As the study's lead researcher notes, "Terrestrial arthropods like harvestmen have a sparse fossil record because their exoskeletons don't preserve well." (Via American Museum of Natural History)
Harvestmen have exoskeletons like spiders, but it's important to note, although they might look like spiders, they're really not.
As the International Business Times reports, they're more closely related to scorpions, which also have exoskeletons. And unlike spiders, daddy longlegs' bodies look like single, oval-shaped structures.
Real spiders have even more eyes than their look-alikes, actually—usually about six or more. (Via Slate)
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