Researchers have debunked the belief that four-eyed daddy longlegs are spiders. After studying a 305 million-year-old harvestman fossil, researchers at the University of Manchester and the American Museum of Natural History found that the species was the member of a separate arachnid group. It was given the quaint name of harvestmen and the creature was blessed with two sets of eyes.

The researchers unearthed the thread-legged fossil about 30 years ago at the Montceau-les-Mines Lagerstatte site in Eastern France. However, scientists were not able to study the strange creature until X-ray computed tomography, commonly known as CT scans, was used by Russell Garwood, the University of Manchester paleontologist who led the study, to analyze it.

Scientists also do not get enough fossil evidence of land-based invertebrates as their fossils decay quickly because of the kind of environment they live in. However, scientists were lucky with this fossil because the species died amid sediments where a mineral called siderite managed to grow around its remains. As a result, a protective concretion was formed before the sediments were compacted into rock. A three-dimensional void was left after the fossil rotted away, said Dr. Garwood.

The void suggested the shape of a creature with two sets of eyes. One set was in the middle of its forehead whereas another pair mounted atop two stink glands on the animal's sides.

The researchers analyzed the whole body of the creature within a matrix of 158 morphological traits. Garwood and his colleagues have got significant insight into how eyes of arachnids were developed.

"Successfully placing fossils in phylogenies [evolutionary histories] is integral to understanding the tree of life. And these particular fossils "are indicative of ancient origins and one of the earliest arthropod terrestrialization events", wrote the authors.

Ganwood added that many enigmatic features in living groups can be known by combining evolutionary developmental biology, fossils and evolutionary biology.