Paleontology in Iowa facts for kids
Paleontology in Iowa is all about studying ancient life in the state of Iowa. Scientists look for fossils here to learn about Earth's past. Iowa has a rich fossil history, especially from the Paleozoic Era. This era includes the Cambrian to Mississippian periods.
Millions of years ago, Iowa was covered by a shallow sea. This sea was home to many creatures. These included brachiopods (shellfish), bryozoans (tiny colonial animals), cephalopods (like squids), corals, fishes, and trilobites (ancient sea bugs). Later, this sea dried up. But a new sea covered Iowa during the early Mesozoic Era.
As this second sea disappeared, Iowa became a warm, subtropical coastal plain. Duck-billed dinosaurs roamed this land. Later, the Western Interior Seaway covered the state. This deep sea was home to large swimming reptiles called plesiosaurs. The early Cenozoic Era doesn't have many fossils in Iowa. But during the Ice Age, glaciers moved into the state. Giant animals like mammoths and mastodons lived here then.
Ancient Life in Iowa
Iowa has no fossils from the Precambrian Era. So, its fossil story begins in the Paleozoic Era. During the early Paleozoic, a large, shallow sea covered most of Iowa. The bottom of this sea was full of life.
Sea Creatures of the Paleozoic Era
Many different creatures lived in Iowa's ancient sea. These included brachiopods, bryozoans, cephalopods, corals, molluscs, and trilobites. In the Mississippian Period, Iowa's sea life changed. It included blastoids, brachiopods, corals, crinoids (sea lilies), and starfish.
Blastoids from this time are found in southeastern Iowa. Brachiopods like Atrypa and Spirifer are found in Benton County. Corals like the colonial Hexagonaria also lived there. Crinoids are found near Le Grand and in southeastern Iowa. Some starfish from Le Grand are very rare. Fish teeth from this period have also been found. As the Paleozoic Era ended, Iowa's seas dried up. For a long time, no new sediments were laid down. Instead, old rocks wore away.
Dinosaurs and Sea Monsters of the Mesozoic Era
During the early Mesozoic Era, a new sea covered Iowa. This brought back sediment deposition. As this sea slowly disappeared, Iowa became a warm, subtropical coastal plain. Rivers flowed through the land. Later, dinosaurs lived here. However, their fossils are rare in Iowa. Dinosaur fossils are more common in nearby states like Minnesota and South Dakota. But dinosaurs could easily walk across these areas.
No Jurassic dinosaur fossils have been found in Iowa. However, the Fort Dodge Formation in Iowa is from the same time. This formation has dinosaur fossils in western states.
Cretaceous rocks cover more of Iowa than Jurassic ones. About 95 to 100 million years ago, rivers flowed west across Iowa. They created floodplains and coastal lowlands. These rivers deposited the sediments of the Dakota Formation. This is Iowa's oldest Cretaceous rock. The climate was warm, and Iowa had lush, subtropical plants. Unlike Jurassic rocks, these Cretaceous rocks hold dinosaur fossils. At least one type of primitive hadrosaur (duck-billed dinosaur) lived here. It was over 30 feet long!
Over time, the rivers of the Dakota Formation were covered by the Western Interior Seaway. This huge sea expanded northward. It left behind shale and chalk. Large swimming reptiles called plesiosaurs lived in this sea. Their fossils are found in several parts of Iowa. Long-necked elasmosaurs (a type of plesiosaur) might have eaten rocks from northwestern Iowa's quartzite. These rocks could have been used as gastroliths (stomach stones). In other places, the same deposits have fossils of mosasaurs (giant marine lizards) and pterosaurs (flying reptiles).
The Manson Impact and the Ice Age
About 75 million years ago, a large asteroid hit Earth. It was about 1.5 miles wide. The impact site is near the modern town of Manson. This event created the Manson crater, which is about 22 miles wide. The impact caused huge damage to life on land and in the sea. It sent rock debris far away, even to South Dakota. It also caused giant tsunamis. Life slowly recovered from this impact. But then, the Cretaceous-Paleogene extinction event happened. This was likely caused by another asteroid impact in Mexico.
The early Cenozoic Era has few fossils in Iowa. This is because sediments were wearing away, not building up. But later in the Cenozoic, glaciers moved into Iowa. As they melted, they left new sediments. During the Ice Age, Iowa was home to mammoths and mastodons. Their remains are found in many places across the state. The glaciers also picked up and moved older fossils. These included plesiosaur bones, shark teeth, and even two dinosaur bones. These dinosaur bones, moved by glaciers, are the best dinosaur fossils found in Iowa.
History of Fossil Discoveries
Scientists have been finding fossils in Iowa for a long time. These discoveries help us understand the state's ancient past.
Early Discoveries
In 1804, Meriwether Lewis of the Lewis and Clark Expedition found a fossil fish jawbone. He found it along the Missouri River in Harrison County. This was the first fish fossil found in the Niobrara chalk. It is also the only fossil from the Lewis and Clark Expedition that still exists. Today, it is kept in a museum in Philadelphia.
In 1824, Dr. Richard T. Harlan named the species Saurocephalus lanciformis. But he thought it was from a marine reptile. Later, in 1830, Isaac Hays described a similar fossil fish. This helped correct Harlan's mistake. In 1856, Joseph Leidy confirmed it was a fish and dated it to the Cretaceous Period.
In 1858, W. James Hall made an important discovery. He found crinoid fossils near Le Grand. The limestone there preserved these fossils in amazing detail. Later, in the 1890s, an amateur collector named B. H. Bean became an expert on Iowa's Mississippian life.
Dinosaur and Starfish Finds
In 1928, a femur (thigh bone) was found near Decatur, Nebraska. It was from an ornithopod dinosaur, about 32 feet long. This was the first dinosaur bone found in the Dakota Formation. In 1930, B. H. Bean found a limestone block with 183 individual starfish fossils. Starfish fossils are very rare, so this was a huge find!
Later in the 1930s, John Holdefer found a fossil bone in a Plymouth County gravel pit. He took it home and used it as a doorstop! Its scientific value was not known for many years.
In 1982, Brian J. Witzke found a fossil bone in Guthrie County. It was in a river gravel deposit from the Dakota Formation. Under a microscope, scientists saw many blood vessels. This showed it was a dinosaur bone. This was the first confirmed dinosaur fossil found in Iowa.
After this, Doris Michaelson, John Holdefer's daughter, read about Iowa's dinosaur fossils. She wondered if her father's "doorstop" bone was important. She took it to the Geological Survey Bureau. They confirmed it was a dinosaur vertebra (backbone), likely from a hadrosaur.
On September 7, 2000, the first identifiable dinosaur fossil was reported. Charlie Gillette found it in Dickinson County. It was a dark, three-inch-long fossil from landscaping gravel. His uncle, Jack Neuzil, a retired teacher, thought it might be a dinosaur vertebra. A paleontologist later confirmed it.
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Pentecopterus is a Eurypterid that patrolled the early Ordovician waters of what is now Decorah.
In 2015, scientists found the remains of a giant Megalograptid eurypterid (sea scorpion). It was found near Decorah in the Winneshiek Shale. This creature was named Pentecopterus decorahensis. It was one of the largest arthropods ever, reaching almost 5 feet, 7 inches long! The shale also has fossils of giant conodonts, Astraspis (an ancient fish), giant algae, and other rare creatures.
Places to Explore Fossils
Iowa has some special places for fossils and natural history.
Protected Areas
- Rockford Iowa Fossil and Prairie Park
Natural History Museums
- Iowa Museum of Natural History, University of Iowa
- Putnam Museum, Davenport
- University Museum, University of Northern Iowa, Cedar Falls
Clubs and Associations
- The Mid-America Paleontological Association
