Incredible Fossil Of Ancient Spider Turns Out To Be Crayfish "Someone Had Painted Legs On"

James Felton

James Felton

Senior Staff Writer

clockDec 20 2019, 13:15 UTC

Selden, et al. 2019, Palaeoentomology

Earlier this year, a lot of people got excited when an incredible fossil of an ancient spider was discovered. The specimen appeared to be an amazing find: an exceptionally preserved gigantic spider from the Early Cretaceous previously unknown to science. Unfortunately, it proved to be just a little too incredible for some.

The fossil was reportedly discovered by locals in the Yixian Formation in China, a geological formation that spans 11 million years during the Early Cretaceous, formed some 125-121 million years ago. They sold the fossil to the Dalian Natural History Museum, where researchers described the "new species" in a paper published in Acta Geologica Sinica. The paper describes a "relatively pear-shaped" creature with slim and curved fangs and slender legs covered in fine and smooth short hairs. The team concluded that it was a new member of the Mongolarachne genus, an extinct genus of giant spiders that includes M. jurassica, the largest fossilized spider ever found, and dubbed it Mongolarachne chaoyangensis.


However, when the paper was seen by scientists in Beijing, they noticed a few things that were odd about the specimen, which made them pick up the phone to colleague Dr Paul Seldon, distinguished professor in the Department of Geology at the University of Kansas, who specializes in ancient spider fossils.

Upon seeing the paper, he immediately had his suspicions.

How the fossil appeared in the original paper describing the "new species". Cheng et al, Acta Geologica Sinica, 2019

“I was obviously very skeptical. The paper had very few details, so my colleagues in Beijing borrowed the specimen from the people in Southern University, and I got to look at it. Immediately, I realized there was something wrong with it,” Professor Selden said in a statement.


"It clearly wasn’t a spider."

Selden noted that the creature was missing segments in its legs, and the eyes were too large. It didn't take long for an explanation to emerge.

"I puzzled and puzzled over it until my colleague in Beijing, Chungkun Shih, said, ‘Well, you know, there’s quite a lot of crayfish in this particular locality. Maybe it’s one of those.’ So, I realized what happened was I got a very badly preserved crayfish onto which someone had painted on some legs.”


It appears locals dug up a preserved crayfish and decided to make some money out of it by passing it off as a much more exciting discovery.


Image A shows a mosaic of parts of the specimen as seen under fluorescence microscopy: bright white shows areas of cement used to repair the specimen, bright blue shows the rock matrix, bright yellow marks areas painted with oil-based paint, and dull red is the fossil cuticle. Image B is a map of the specimen showing cracks, cemented areas (grey), and painted parts (brown) Selden, et al. 2019, Palaeoentomology

"They obviously picked up this thing and thought, ‘Well, you know, it looks a bit like a spider.’ And so, they thought they’d paint on some legs – but it’s done rather skillfully. So, at first glance, or from a distance, it looks pretty good. It’s not till you get down to the microscope and look in detail that you realize they’re clearly things wrong with it," Seldon said.


Selden and colleagues, which included lead author of the original paper, Xiaodong Cheng, used fluorescence microscopy to take a closer look at the faux fossil. Under the microscope, they were able to identify areas that were likely oil-based paints used to add legs to the fossil, which shows up in yellow, as well as cracks in the rock that had been fixed with cement. They decided to write their own paper on their discovery of the forgery, publishing it in the journal Palaeoentomolgy.

Selden admitted the forgery was well done and didn't blame researchers at the Dalian Natural History Museum for falling for the fake.

"The people who described it are perfectly good paleontologists – they’re just not experts on spiders,” he said.

An actual crayfish (Cricoidoscelosus aethus) from the Yixian Formation preserved in a similar manner to M. chaoyangensiss but, you know, real. Selden, et al. 2019, Palaeoentomology