Fossil preserves the soft parts of a 75 million-year-old crab.

PhysOrg has the story of a crab whose gills and other soft tissues were preserved against all odds for 75 million years:

In a paper recently published in Palaeontologia Electronica, Dr. Adiel Klompmaker, University of Alabama Museums’ curator of paleontology, and colleagues reported on a remarkable crab with multiple mineralized soft tissues preserved. This crab lived 75 million years ago during the Cretaceous in the area of present-day South Dakota in an ancient sea known as the Western Interior Seaway.

The crab fossil was collected between 2012–2018, but its importance only became clear when Klompmaker studied the specimen in July 2019.

“I could not believe my eyes when I saw the specimen for the first time,” Klompmaker said. “I grabbed my hand lens to check and, indeed, the crab showed mineralized gills through the broken shell of the crab. I reviewed a paper on fossil gills in a crab a couple of years earlier, so I recognized the gills immediately.”

Prior to the new paper, only four other fossil crab specimens had gills preserved.

The crab jaws—or mandibles—also showed up. The overall shape and location of soft tissues within the crab are not unlike modern crabs. Stomach contents have not been recovered thus far.

“When we searched the literature for preserved soft tissues from any animal living in ancient methane seeps, we found exactly none,” Klompmaker said. “Now that we know soft tissues can preserve in these environments, we would expect to find more fossils with mineralized soft tissues.”


You can read more of Klompmaker’s research here, in Palaeontologia Electronica.