A 360-million-year-old shrimp lies petrified after becoming fossilized in shale. The creature died in an ancient sea over what is now Pontotoc County.

Photo courtesy of Professor Rodney Feldmann, Kent State University

Once, in an ancient sea, a shrimp died, dropped to the ocean floor and settled into dark mud that preserved the creature by cutting off oxygen which would otherwise have led to its decay.

The shrimp lay there near what is today known as Ada and turned to stone. And so it stayed there, untouched for 360 million years until one hot summer day in the mid-1990s when it was found by a paleontologist.

Dr. Royal Mapes, Ph. D., professor emeritus of paleontology at Ohio University, didn’t happen upon the creature by chance; he was searching for fossils along with a group of university students.

“The actual fossils I was specifically hunting were cephalopods that are distantly related to modern squids and octopus,” Mapes said. “The specimen was in a shale quarry lying on the surface just waiting for someone to collect it. I did not know of the special information that this specimen would reveal, but I did note that it was ‘shrimp-like’ and probably important.”

Many years would pass before the world would learn just how important the find really was. Mapes sent the three-inch-long shrimp to an American colleague working in Europe who had previous obligations and wasn’t able to research the fossil quickly.

“Science works slowly,” Mapes said. “We work very thoroughly but we work very slowly. When (the colleague) retired from there, he came back to the United States and brought the specimen with him.”

Believing someone with more expertise in decapods (crustaceans with 10 legs) would be able to research it better, Mapes’ colleague sent the fossil to Rodney Feldmann, professor emeritus of paleontology at Kent State University in Ohio.

Feldmann, along with Carrie Schweitzer, associate professor, from Kent State University’s Department of Geology discovered the astonishing age of the creature — about 360 million years old — which makes it the oldest fossilized shrimp to date in the world.

The importance of the find

The age of the shrimp fossil bested the previous record substantially. Feldman said 360 million is the best estimate but the fossil could be anywhere from 359 to 374 million years old.

“The oldest known shrimp prior to this discovery came from Madagascar,” Feldmann said. “(The one from Madagascar) is way younger, having an age of ... 245 million years.”

Feldmann said the fossil is remarkable not only because of its age, but also due to its remarkable preservation. The muscles that once made up the tail part of the shrimp were preserved, which is extremely rare in fossils.

“When the animal died, it came to rest on the seafloor,” Feldmann said. “The muscles then were preserved by a combination of acidic waters and a low oxygen content as the animal was buried rapidly.”

Approximately 65 million years ago, a wide, gentle raising of land caused the ancient sea to recede.

Feldmann and Schweitzer named the fossil Aciculopoda mapesi, after Dr. Mapes, their colleague and friend.

The discovery makes it one of the two oldest decapods. The other decapod, Palaeopalaemon newberryi, is of similar age and was found in Devonian sediments in Ohio.

“The shrimp from Oklahoma might thus be the oldest decapod on earth,” Feldmann said.

The fossil is an important step in unraveling the evolution of decapods.

“The common ancestor of the two species can probably be found in rocks that once formed the old continent Laurentia,” Schweitzer said. “Nowadays, these rocks can be found primarily in North America and Greenland.”

Feldmann and Schweitzer’s report was made available on Kent State’s Website Nov. 9 and  will be published in the Journal of Crustacean Biology. The fossil shrimp, which Feldmann called priceless, will eventually be taken to the Smithsonian Museum of Natural History in Washington, D.C. and put on display.

Why Ada?

What was a paleontologist from Ohio doing looking for fossils near Ada? Mapes grew up in Muskogee and Oklahoma City and heard about fossils in area abandoned quarries.

“I had been an amateur fossil collector before I turned professional with the university and had collected some material from down in that region,” Mapes said. “I knew that down near Ada there were some very nice collecting localities, and so discovering this place was just an extension of knowing that.”

The place Mapes referred to is the old Ryan Quarry, about four to five miles south of Ada near State Highway 99. The quarries are often on private property and getting permission from land owners is mandatory, Mapes said.

He had made several trips to Pontotoc County before the discovery of the shrimp, and has made many since.

“Usually I stop by every year or two,” Mapes said. “I’ve got kinfolk in Oklahoma City and so forth and I like to fish in Oklahoma. I’m not an infrequent visitor to that part of the world even though I’m all the way over here in Ohio. I guess my heart and my roots are still in Oklahoma.”

Mapes has found many other fossils in Pontotoc County.

“Ada is a very good place for collecting fossils, you just go out and look,” he said. “There’s a number of these black shale quarries in that region.”

His collection zone stretches from Tulsa to north-central Texas with Pontotoc County being right in the middle.

“I’ve made my professional career on those fossils coming out of that area,” Mapes said. “I’ve got a collection here that probably has 300 or 400-thousand specimens coming from that area. There’re lots of good ones there, it just takes time and a lot of work, and a good eye.”

Other finds

Mapes has found many species of fossils in the Ryan Quarry, enough to write papers on them.

“There’s quite a variety of fossils that occur there,” he said. “But almost all of them were swimmers. So apparently this black shale was originally at the bottom of the ocean and it was a black mud that didn’t have any oxygen in it. That meant that everything that was swimming up above that died and went to Heaven fell down into that black mud and all the scavengers couldn’t go in there and eat it up. That’s how the shrimp got preserved.”

Another important find for Mapes was a petrified tree.

“I found a tree trunk laying there that was about nine feet long,” he said. “Trees from that particular age are modestly important. It’s not terribly uncommon, but this was a large one and it was very fresh because it had been excavated out of the quarry.

“I collected part of it and brought it back to Ohio University and a paleobotonist here looked at it and said, ‘Aha! This is a so and so, so and so plant and we can write a paper about this.’ Eventually a graduate student did her Ph. D. dissertation on it. From that one trunk.”

Mapes said it took three trips to collect the tree because it weighed about a thousand pounds. On the trip where the shrimp was found, Mapes and his students made several other interesting discoveries.

“We were doing other collecting while we were there and we found pieces of sharks, bone fragments, cartilage fragments and so forth,” he said. “Other pieces of plants were discovered and then we found a whole host of other creatures.”

Likes the area

Mapes enjoys visiting the area and not just for the fossils.

“People are really pretty friendly down there as long as you treat them with courtesy,” he said. “I even thought about retiring there one time, because you have so many different ages of rock and so many different fossil horizons that are there with very, very well preserved fossils. You’re really sitting right there on a bonanza. Within an hours’ drive, you can be in all kinds of fossil collecting localities.”

He said the only real drawback is the summer heat in the quarries.

“In summertime in July, it’s usually 100-plus degrees, 80-percent humidity and in a black shale quarry, it’s probably 125 degrees. It’s very, very hot.”

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