April 10, 2014
Scientists Find Four Eyes In 305M-Year-Old Daddy Longlegs Fossil
[ Watch the Video: Ancient Harvestman Arachnid Images Reveal Secrets ]
Lawrence LeBlond for redOrbit.com - Your Universe Online
While living harvestmen have a single pair of eyes, a newly-described harvestmen fossil from France shows that this creature’s early ancestors actually had two pairs of oglers to help it get around. The fossil, named Hastocularis argus, was found in eastern France and has been dated to about 305 million years old.
H. argus not only had median eyes – those found near the center of the body – but lateral eyes on the side of the body as well. The research on this ancient arachnid has been published in the journal Current Biology by researchers from the American Museum of Natural History and University of Manchester. The new finding adds a significant amount of detail to the evolutionary history of this diverse and highly successful group of arthropods.
Using X-ray imaging techniques, the team was able to distinguish features of the unusually well-preserved fossil like never before.
"Although they have eight legs, harvestmen are not spiders; they are more closely related to another arachnid, the scorpion," Dr Russell Garwood, a palaeontologist in the University of Manchester's School of Earth, Atmospheric and Environmental Sciences, said in a statement.
"Arachnids can have both median and lateral eyes, but modern harvestmen only possess a single set of median eyes - and no lateral ones. These findings represent a significant leap in our understanding of the evolution of this group,” added Garwood.
“Terrestrial arthropods like harvestmen have a sparse fossil record because their exoskeletons don’t preserve well,” said Prashant Sharma, a postdoctoral researcher in the Museum’s Division of Invertebrate Zoology and one of the lead authors on the new study. “As a result, some fundamental questions in the evolutionary history of these organisms remain unresolved. This exceptional fossil has given us a rare and detailed look at the anatomy of harvestmen that lived hundreds of millions of years ago.”
Surprisingly, when the team looked deeper into the genes of living harvestmen, they discovered hints of the now-lost lateral eye in modern harvestmen embryos. But by the time they hatch, these arachnids do not form the lateral eyes, only median ones.
“Fossils preserved in three dimensions are quite rare,” said Garwood. “This is especially true of harvestmen. Our x-ray techniques have allowed us to reveal this fossil in more detail than we would have dreamed possible two decades ago.”
The research team also included researchers from Humboldt University Berlin and Harvard University. The work was supported by the National Science Foundation.