Daddy Longlegs are no stranger to today’s world. They are often seen around a typical household, usually found in bathrooms. They are not, however, part of the spider family. Though they have eight legs, they actually belong to a side group of arachnids known as harvestmen, and this is due in part to the one set of eyes they own. However, when a Daddy Longlegs fossil thought to be over 304 million years old was recently analyzed in Eastern France, it was discovered that the arachnids of the past had actually possessed four eyes instead of two.
Researchers hailing from the University of Manchester, located in the United Kingdom, and the American Museum of Natural History, located in New York, conducted a joint study in eastern France on the harvestman fossil.
The fossil had actually been excavated over three decades ago at the excavation site in France but scientists had been unable to analyze it due to the delicate nature of the exoskeleton. Russell Garwood, a paleontologist from the University of Manchester and leader of the study, found a way to analyze tiny fossils by using what is called x-ray computed tomography, more commonly referred to as CT scans.
According to the study, which was published in the April 11 issue of Current Biology, invertebrates, including insects, do not usually preserve well enough to be identified correctly as a fossil due to the environments in which they lived, which caused quick decay of any remains. The result was that although there were traces of fossilized spiders still being discovered today, most were poorly mineralized and possessed very delicate exoskeletons, which proved a challenge to researchers who found the fossils difficult to analyze.
The Daddy Longlegs fossil which the joint team had discovered, happened to die in an environment where a mineral called siderite grew around its body, forming a protective cocoon around the remains of the insect before being compacted into rock. Afterwards, the fossil rotted out and left a three-dimensional void behind. The void in the rock showed the shape of a creature with two different sets of eyes.
“Fossils which are preserved in three dimensions are very rare. Being able to use advanced x-rays to study this fossil has proven to be better than we ever hoped for,” Garwood had said about the fossil.
The discovery by Garwood’s team could help to explain how arachnids’ eyes have developed over the years through evolution, including the difference in placement of the eyes. The fossil had eyes that were placed both median and lateral. Further analysis showed that modern-day Daddy Longlegs possess an unused gene for their eyes, which means that over the years they lost the extra eyes from evolution.
“Groups of different arachnids sometimes lose or modify their eyes with the passage of time,” Garwood said of the findings.
It is unknown as to the reason why modern Daddy Longlegs possess only two eyes instead of four like the fossil has shown, but it is possibly due to the fact they scavenge dying plants and animals on the floor of the forest instead of relying on their sight for hunting prey like spiders do.
By Jessica Cooley