This photo, courtesy of Paul Selden, shows the recently found spider fossil. The black line at the bottom is 1 millimeter in length.

A Kansas University researcher has used a remarkably well-preserved 165 million-year-old spider fossil to trace the history of a current species back to the middle Jurassic period.

Paul Selden, distinguished professor of geology and director of KU’s Paleontological Institute, said it’s unusual to find such fossils, as spiders are relatively soft, land-dwelling animals. Found by one of Selden’s colleagues in northern China, this particular fossil came about because the spider was preserved in a fine volcanic ash.

“It’s quite remarkable, really,” Selden said. “If it had been sand, the spider would have been compressed,” rendering it useless.

The spider, a new species called Eoplectreurys gertschi, shows all the features of its modern-day relatives in the plecteurid family, which today inhabits only California, Arizona, Mexico and Cuba.

The body of this once-widespread spider is approximately 3 mm long.

“They’re remarkably similar” to their modern counterparts, Selden said. “They’re obviously very, very closely related.”

While such a find is rare, scientists were able to gather hundreds of examples from the area, from what was a lake bed near Daohugou, China.

Selden said the spider was the oldest of its group found — though some spiders go back 350 million years.

Because the spider belonged to a more primitive family than those found in earlier time periods, scientists had always thought that such spiders existed, but hadn’t been able to locate the fossil evidence to substantiate it.