My Favorite Fossil: The Extinct Oyster Gryphaea (AKA Devil’s Toenails)

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I grew up on the outskirts of Grand Junction, Colorado. The photo above was taken only 400 yards from my home. This was my childhood playground. It is here that I was first discovered fossils, and one fossil in particular: a member of an extinct group of oysters called “devil’s toenails” also know by their scientific name Gryphaea. In fact, it would have been difficult to avoid noticing these fossils—the ground was covered with their remains! These fossils were mostly just broken bits, but many times you could find a complete specimen, with both the large upper shell and the small trap door on the backside that opened so the oyster could filter feed from the waters above the fine sandy bottom of a shallow ocean.

The Gryphaea fossil pictured here is one of the many that I collected before I was 10 years old. I’ve collected many other fossils, but these bivalves have always been special to me since they first piqued my interest in science and paleontology in particular. Of course I wanted to find dinosaur bones—especially knowing that new dinosaurs were being uncovered on the other side of town—but Gryphaea had an important lesson to teach me. 

Fossils are usually found in the context of natural communities rather than random bits of ecologically-unconnected organisms. I had billions and billions of fossils in my backyard, including sharks teeth, ammonites and these ubiquitous oysters. Collectively, they inform us that this place had once been a shallow sea from the Upper Jurassic Period about 150 million years ago.  

Forty years after collecting my first fossils, I was able to take my family to to the Great Basin region in Wyoming. While hiking there, we came across layers of eroded rocks that were covered in remains of Gryphaea. It was obvious that we were hiking through Upper Jurassic Period rocks that represented the bottom of that same shallow sea that once covered much of the upper western North America, including my childhood backyard. Here we could see the same community of organisms lying exposed at our feet.

Gryphaea from the Jurassic Period are also found in England, which is where they were first discovered and named. There they are also found with within similar communities of extinct organisms that inhabited shallow oceans. Gryphaea are evidence of the existence of a past world in which these organisms were common on the floors of shallow inland seas.  

I’ve collected many fossils over the years, many of which are far more attractive or unusual, but Gryphaea is a constant reminder to me of the joy of discovery and the sense of wonder at past worlds filled with strange creatures living in shallow sea. It’s amazing to consider that God’s creation includes hundreds of millions and possibly billions of species that existed long before He created us but through fossils like Gryphaea God allows us to glimpse a small portion of his vast handiwork. I like to imagine that in the world to come God’s entire creation will be on display for us to marvel at and we will have all eternity to plumb its depths.


On the side of Sheep Mountain just north of Greybull, Wyoming, there were areas where you cannot walk without stepping on dozens of pieces of fossilized Gryphaea nebrascensis. Here I am looking down at what is just in front of my boot.





Duff, Joel. "My Favorite Fossil: The Extinct Oyster Gryphaea (AKA Devil’s Toenails)" N.p., 19 Nov. 2018. Web. 16 February 2019.


Duff, J. (2018, November 19). My Favorite Fossil: The Extinct Oyster Gryphaea (AKA Devil’s Toenails)
Retrieved February 16, 2019, from /blogs/archive/my-favorite-fossil-the-extinct-oyster-gryphaea-aka-devils-toenails

References & Credits

For more on the fossils of Joel's hike up Sheep Mountain, see Hiking through the Jurassic Period in Wyoming: A Sheep-mountain fossil hunt. Images in this article are used with permission by Joel Duff.     

About the Author

Joel Duff

Joel Duff is a professor of biology at The University of Akron. He earned his B.S. in biology from Calvin College, and a Ph.D. in botany from the University of Tennessee. He research focuses on understanding biological diversity by examining differences in DNA sequences and genome structure. He has worked on numerous plant and animals systems and has authored more than 40 research articles in science journals. He is an active writer and speaker exploring the intersection of science and Christian faith. He is a contributor to the book Grand Canyon: Monument to an Ancient Earth and blogger at Naturalis Historia ( He is an avid nature photographer and enjoys exploring God’s creation with his wife and five children. 

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