Harvestmen, familiarly known as daddy longlegs, once had an extra set of eyes, according to an analysis of a 305-million-year-old fossil from France.
Though they share spidersâ€™ eight-legged appearance and penchant for hanging out on bathroom ceilings, harvestmen are more closely related to scorpions, mites, and ticks.Â The arachnids are as ancient as they are ubiquitous, and can be found on every continent except Antarctica.
And unlike spiders, which often have eight eyes or more, harvestmen have only a single pair of eyes.
But when scientists at the American Museum of Natural History in New York City and the University of Manchester in England scanned the fossil using sophisticated x-ray techniques, they found the arachnid had four eyes instead of two.
Finding intact fossils of tiny arthropods like harvestmen is no mean feat, as the creaturesâ€™ delicate exoskeletons rarely stand the test of time.
Before the sediments surrounding the fossil â€œcompacted into rock, an iron carbonate mineral called siderite grew around it to form a nodule, otherwise known as a concretion,â€ said study leader Russell Garwood, a paleontologist at the University of Manchester, via email.
â€œThis stopped it being squashed with the rest of the rock. The fossil then rotted away, leaving a three-dimensional void in the rock.â€