About 75 million years ago a shallow sea covered the Great Plains region. In today’s Badlands the bottom of that sea appears as a grayish-black sedimentary rock called Pierre (peer) shale. This layer is a rich source of fossils. A variety of fossilized animals have been found in the Park from these sea creatures that sank to the bottom of the sea when they died including the cephalopod (squid-like creature), clams, crabs, snails, ancient fish, mosasaurs (giant marine lizards), pterosaurs (flying reptiles), Archelon (giant sea turtles) and Hesperonis (diving bird similar to a modern loon).
Eventually the continental plates shifted, causing the land under the sea to rise and the water to retreat. During this time the Badlands looked nothing like it does today. The climate was warm and humid with abundant rainfall. The Badlands were a subtropical forest, which flourished for millions of years. Ultimately, the climate cooled and dried and the Badlands became grasslands similar to the current landscape. Today, the colorful banding of the Badlands buttes is caused by fossilized soils. These soils tell researchers a great deal about the climatic history of the Badlands. The loose, crumbling rocks formed from these ancient solids hold one of the greatest collections of fossil mammals on Earth. Some fossilized mammals that have been found in the Badlands include the Leptomeryx (deer-like mammal), Oreodonts (sheep-like mammal), Archaeotherium (distant relative of modern pigs), Mesohippus (three-toed ancestor of the modern horse), Hoplophoneus (saber tooth cat), Subhyracodon (an agile rhinoceros), Ischromys (squirrel-like rodent), Metamynodon (massive rhinoceros) and Paleolagus (ancestral rabbit).
From 1993 to 2008, the National Park Service, along with South Dakota School of Mines and Technology (SDSMT), have spent 15 field summer sessions at the Pig Wallow Site (The Big Pig Dig). From early June through late August, student paleontologists worked this excavation site. Excavation started in June 1993 when two visitors from Iowa discovered a large backbone protruding from the ground near the Conata Picnic Area. Originally thought to be a four-day excavation, this site became a 15-year project. The site’s name, the Pig Dig, comes from that first exposed fossil, originally thought to be the remains of an ancient pig-like mammal called Archaeotherium. It was later identified as a Subhyracodon, a hornless rhinoceros, but the name “Big Pig Dig” stuck. Along with Archaeotherium, 17 other animal species have been found at the site. Discoveries include ancient three-toed horses, tiny deer-like creatures, turtles and a bobcat-sized saber-toothed cat. Over 13,000 bones have been excavated from the site for research purposes. In 2012, the National Park Service is considering a new fossil excavation.
Please help protect paleontological resources in the Badlands and anywhere you travel by leaving fossils where you find them. When a fossil is removed from its environment, much of the information critical to scientists is destroyed. It is important to researchers that fossils remain where they are found geologically and in the same position they are found. If you find a fossil in the Badlands, please don’t be tempted to pick it up. You may observe, photograph and admire everything you see. If something you find seems unusual, contact park staff