The team supported their results by examining the expression of an 'eye stalk' gene in living harvestmen and found that in a modern harvestman embryo this gene shows hints of a now-lost lateral eye.
Co-author Prashant Sharma, a postdoctoral researcher at the American Museum of Natural History, said: "Terrestrial arthropods like harvestmen have a sparse fossil record because their exoskeletons don't preserve well. As a result, some fundamental questions in the evolutionary history of these organisms remain unsolved.
"This exceptional fossil has given us a rare and detailed look at the anatomy of harvestmen that lived hundreds of millions of years ago. What we were also able to establish is that developing modern harvestmen embryos retain vestiges of eye-growth structures seen only in the fossil."
Dr Garwood added: "Harvestmen fossils preserved in three dimensions are quite rare and our X-ray techniques have allowed us to reveal this exceptional fossil in more detail than we would have dreamed possible just a couple of decades ago."
This is a video showing the 305-million-year-old harvestman fossil.
(Photo Credit: Paris NHM/Russell Garwood)
This is the 305-million-year-old harvestman fossil.
(Photo Credit: Paris NHM/Russell Garwood)
Source: University of Manchester