Soft, squishy, ancient spiders are hard to investigate – they do not fossil as easily as bones or exoskeletons. So you can imagine how excited researchers were to find 10 brand new spider fossils in a relatively unexplored area called Jinju Formation.
The Jinju Formation is a geological area of South Korea from the Mesozoic era, between 252 and 66 million years ago. This new spate of fossils, which researchers from the Korean Polar Research Institute and the University of Kansas found in the shale, has increased the number of known spiders in the Jinju Formation from just one to a whopping 11.
But two of these spider
"Because these spiders were preserved in strange slivery flecks on dark rock, what was immediately apparent was their rather large eyes brightly marked with crescentic features, "said Paul Selden, a geologist at the University of Kansas.
" I realized this must have been the tapetum ̵
The researchers believe that this is the first preservation of a spider eye tape in the entire fossil record.
"In spiders, the ones you see with really big eyes are jumping spiders, but their eyes are regular eyes – while wolf spiders at nighttime, you see their eyes reflected in light like cats," explained Selden.
" So, night-hunting predators tend to use this different kind of eye. This was the first time that tapetum was found in fossil. "
" It's nice to have exceptionally well-preserved features of the internal anatomy like eye structure. It's really not often you get something like that preserved in a fossil. " He added:
Most ancient spiders are discovered in amber because it helps to preserve the soft bodies of the arachnids.
However, the researchers think that if these spiders – which have been named Koreamegops samsiki and Jinjumegops dalingwater – were found in amber, the tapetum might have been missed.
"They do not have hard shells, so they are very easy to decay," Selden said. "It's to be a very special situation where they were washed into a body of water. Normally they would flood. But here they they sunk and that kept them away from decaying bacteria.
" These rocks They are also covered in little crustaceans and fish, so there maybe been some catastrophic event like a vinegar bloom that captured them in the gauze mat and sunk them – but that's a conjecture. "
The researchers think that these newly discovered spiders would have been Occupying the same niche as the jumping spider does today.
"But these spiders were doing things differently. Their eye structure is different from jumping spiders, "Selden explained.
Finding 10 new spiders is a huge win for the diversity of spiders from the Cretaceous period – because of the lack of fossils we just do not know what much about these ancient creepy crawlies
But with finds like this, that looks set to change.
The research has been published in the Journal of Systematic Paleontology .