Fossilized Mosasaur from Local South Dakota Ranch Traveled to National Conference

Christy Hammond, Contributing Writer

Part of a fossilized Plioplatecarpus tympaniticus mosasaur was discovered in a layer of rock from the Niobrara Formation in 1996 on a South Dakota ranch.

The fossilized specimen was finally brought into the lab in 2016 to remove it from the rock. Kelsie Abrams and Kenny Brown uncovered a significant paleontological find in the mosasaur’s remains.

Abrams, preparator and lab manager at the James E. Martin Paleontology Research Laboratory, located on the South Dakota School of Mines and Technology campus in Rapid City, explained their mosasaur is unique, because of the site of its healed injury.

Mosasaur skeletons had two shoulders bones, a scapula and a coracoid, which attached to the humerus bone. This specimen showed one perfect set of shoulder bones and the other side showed where the mosasaur had been injured in the shoulder area, causing the scapula and coracoid to fuse together as one bone and part of the humerus to curl up. Healed bone growth in these areas confirmed that the mosasaur lived for some time after his injury.

Abrams explained that paleontologists find plenty of mosasaurs with healed injuries to their vertebrates, skull, and tail, but finding a specimen with healed injuries to its shoulder area is “a rare and unique find.”

Mosasaurs were not dinosaurs. They were swimming marine reptiles that breathe air and were closely related to modern day snakes and monitor lizards. There were many different species of this common creature that lived in the Cretaceous period, around 82-87 million years ago, and went extinct along with the dinosaurs.

Brown, a lab volunteer, removed the mosasaur from the hard rock it was encased in and Abrams performed the detail work.

Abrams said, “We called him “Nemoa�� because of his bum flipper. Knowing the traumatic event he went through and survived – you realize how tough they were. It gives him more life than just being a skeleton.”

Abrams presented “Nemo” to the paleontology world in October at the Society of Vertebrate Paleontology conference in Salt Lake City.