A recently published paper by a UA paleontologist shows a rare soft tissue discovered in a crab fossil. The crab lived 75 million years ago in the area of present-day South Dakota. Most animals and plants never fossilize with the exception of hard parts such as shells and bones and soft tissues such as muscles and gills.
Dr. Adiel Klompmaker is the curator of paleontology at the Alabama Museum of Natural History. The crab was collected between 2012-2018 but as Klompmaker studied it in 2019, he noticed something different.
With the naked eye and hand lens, the crab had mineralized gills through its broken shell. Afterward, the crab was placed into a microCT scanner, with the expectation of seeing the gills in higher resolution for more details. However, that’s not what Klompmaker and his team saw.
“We didn’t see additional gills, what we did see is additional soft tissues preserved,” Klompmaker said.
This is only the fifth of its type of fossil crab specimens discovered with gills preserved.
Klompmaker said the key finding is about what scientists can learn for the future.
“What is also important is that other researchers can build upon our research by looking at other soft tissues and perhaps preserve other animals from those types of ecosystems. And one of the key implications of our research is that…foster tissues can preserve in these types of environments,” Klompmaker said.
Part of the digestive tract of the crab was still preserved, which is extremely rare with fossils of this age.
“So, we found a food pipe, we found a stomach, we found a mandibles of crab jaw. So we had part of the digestive tract still even preserved,” Klompmaker said.
The crab was discovered in limestones which represents an ancient methane cold seep. Typically, these areas host a diverse ecosystem.
“These are specialized environments that are still around today and very different parts of the ocean where methane is coming up from the subsurface into the water column, and supports a very diverse ecosystem locally. Right as methane is bubbling into the ocean,” Klompmaker said.
In previous discoveries, animals living in methane seeps had no preserved soft tissues. This discovery leads Klompmaker to believe more fossils with soft tissues will be discovered. The team couldn’t identify the species of crab because certain features of the shell weren’t preserved, such as the spine.
The crab specimen with its soft tissue preserved is in the Alabama Museum of Natural History.
