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Great Mondays in (South Dakota) history

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Do you hate Mondays? Like yesterday? It’s alright, you’re in good company. But whatever hate you may have for the start of the work week, keep in mind that many great moments in history occurred on Mondays: Jesse Owens winning the gold medal in Berlin. The publishing of the first Mickey Mouse cartoon. Erno Rubik inventing the Rubik’s Cube puzzle. This new series will try to keep the memory of Great Mondays alive by taking you back through some of the most important Mondays in South Dakota’s own history.

For our first installment, we’re taking a deep dive into the final hours of one of South Dakota’s — or what would become South Dakota’s — earliest murder victims.


Monday May 8, 83,051,312 B.C., 10:38 a.m.

You don’t know that it’s Monday. You’re not even aware of the concept of “mondays.” You’re a Platecarpus, a carnivorous marine reptile, and you’re navigating through the sandy shallow sea that will one day become western South Dakota.

As the sun arcs into the mid-morning sky, small fish swimming nearby suddenly scatter. You see a menacing dark shape loom up out of the corner of your vision, but before you have time to react, it’s already upon you. The world goes blurry as bubbles and blood blot out the sun. The shape has bitten into your front left flipper and is beginning to rip it loose. You feel bones breaking, flesh tearing, and panic begins to set in. But you are flexible, and your jaw is lined with sharp inch-long teeth. Eventually you’re able to bite the shape back and chase it off. You have survived, but not without cost.

Your flipper is a gory mess only loosely connected to your body. Your ability to maneuver in the water has been compromised, and now larger predators have the scent of your blood as it disperses into the sea. To your credit, you manage to survive another few months before succumbing to your wounds. Your remains settle on the seabed that will one day become vast rolling plains, and only the bottom feeders care to notice.

But in strange eons, it is said, even death may die. About 83 million years later your bones are uncovered on a cattle ranch, and pieces of your final story begin to come together.


Our Platecarpus hero was a type of mosasaur, a family of aquatic reptiles related to modern-day monitor lizards. Some mosasaurs were as small as dogs, others grew to the size of school buses. They were common aquatic predators of the Western Interior Seaway, an inland sea that covered much of what is now the Great Plains during the Cretaceous period. This period, running from about 145 million to 65 million years ago, was also the heyday of famous dinosaur families like Tyrannosauroidae and Ceratopsidae, but mosasaurs lived a very different life from those land-lubbing creatures. The story of this particular Platecarpus is revealed — with some minor artistic license — by bones currently held at the South Dakota School of Mines and Technology’s Paleontology lab in Rapid City.

“What’s weird about this specimen, and this gives you a little insight into the life that was being led by these critters... are the shoulder bones of the animal,” SD Mines Paleontology Associate Professor Dr. Darrin Pagnac said. Holding up the fossil, he pointed out how it was swollen — as if the bone had been broken and begun to mend when the creature finally died.

“We’re assuming [healing] is what it was — that it got injured and got this big gnarly callous,” Pagnac said.

Next week, the dinosaurs and mosasaurs have all died out, but the eponymous plains of the Great Plains are still a distant future. Long before bison, there was the brontothere — and their Mondays were awful.


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