Shiny specks of silver discovered in the fossilized worm poop has baffled the scientists. There is no known explanation how the creatures made it. The ancient dung was produced by tiny worms that lived below the seafloor between 543 million years to 490 million years ago.
The silver specks were found embedded in a lagerstätte. It is a deposit of exceptionally preserved fossils that sometimes includes fossilized soft tissues. It was found in the in the Mackenzie Mountains in Canada. During the time period the region was covered by an ocean.
The largest of the silver specks was around 300 micrometres wide. Human hair is only between 17 and 180 micrometres wide.
The researchers were initially confused as to which animal the coprolites belonged to. But after slicing through the rock samples, they came across fossilized worms still in their burrows, which would have been built below the seafloor.
However, the researchers do not believe the worms were responsible for the silver specks in the poop. The worms would only have been able to obtain the silver from the surrounding seafloor. But after analyzing the surrounding sediment, the researchers found that there were not sufficient concentrations of silver to explain the sizable chunks in the coprolites. Silver was also thought to be toxic to small invertebrates such as worms.
Experts think that the culprit is a “microbial colony that likely extracted it out of the water column. These microbes, most likely bacteria, then deposited the silver inside the worm faeces before it fossilized. This could explain the uniform distribution of the metal throughout the coprolites.