Dinosaurs in Iowa

Did dinosaurs once live in Iowa?

The simple and unqualified answer is “Yes, without a doubt!” But the actual evidence for dinosaurs in Iowa is limited to only a few fossils.

Dinosaur fossils have been found in several states adjoining Iowa (Nebraska, Minnesota, Missouri, South Dakota), and wandering dinosaurs would have been unimpeded by these artificial boundaries.

Fortuitous circumstances are needed to preserve dinosaur remains in ancient sedimentary environments. Following the death of an animal, the bones need to be buried within the sediments and protected from chemical and mechanical destruction. Many great dinosaur discoveries are associated with sediments of ancient river systems, where dinosaur bones may be preserved within floodplain and river channel deposits. The discovery of fossil bones is aided by a careful understanding of a region’s geology (where to look), considerable patience (keep looking), and a significant measure of good fortune.

Dinosaur-bearing Cretaceous strata in Iowa and adjoining states.

Sedimentary deposits from the Age of Dinosaurs cover extensive portions of Iowa and have real potential to yield dinosaur fossils. The Jurassic Fort Dodge Formation was deposited at the same time as strata in the American West that have produced remarkable dinosaur fossils, but no Jurassic dinosaur fossils have yet been found in Iowa. The Cretaceous formations are more widespread in Iowa, and these same formations have produced dinosaur fossils at scattered localities in the central United States.

The microscopic structure of a petrified dinosaur bone fragment from Guthrie County, Iowa, shows a once-porous network of vascular canals for blood vessels. (Enlarged 3-mm-wide view.)

The microscopic structure of a petrified dinosaur bone fragment from Guthrie County, Iowa, shows a once-porous network of vascular canals for blood vessels.
(Enlarged 3-mm-wide view.) Photo By Brian Witzke

In Iowa, a fragment of fossil bone was found by the author in 1982 in ancient river gravels of the Dakota Formation in Guthrie County. The microscopic structure of this fragment (shown above) revealed densely vascularized bone, indistinguishable from that seen in typical dinosaur bone. Although not terribly impressive by itself, the Guthrie County discovery confirms that dinosaur fossils indeed occur in the Dakota Formation of Iowa.

Fossil dinosaur vertebrae 3 and 4 inches longhave been found in Dickinson (left) and Plymouth counties, Iowa, respectively. These specimens likely came from hadrosaurs.

Iowa’s First: Charlie Gillette of Dickinson County picked up a dark-colored, 3-inch fossil bone from a load of landscaping gravel that came from a nearby gravel pit. When his uncle Jack Neuzil, a retired educator and dinosaur enthusiast, saw the bone he suspected that it could be a dinosaur vertebra. His suspicions were confirmed by a leading dinosaur paleontologist, and the discovery of Iowa’s first identifiable dinosaur bone was soon reported in the Des Moines Register (9/7/2000). The fossil is a tail vertebra from an unknown dinosaur, possibly a hadrosaur.

An earlier first:  Following this discovery, a second dinosaur vertebra from Iowa has come to light thanks to Doris Michaelson of Bellevue. Her father, John Holdefer, had a keen eye and was fascinated by the rocks and fossils that he saw as a Materials Inspector for the Iowa Highway Commission. Sometime in the mid-1930s he picked up a fossil bone from a conveyer in a gravel pit near Akron in Plymouth County, and the bone was kept on a shelf and occasionally used as a doorstop in the family’s home. In response to a recent newspaper article about dinosaurs in Iowa, Mrs. Michaelson contacted the Iowa Geological Survey and brought the bone in for identification. It is a partially weathered 4-inch dinosaur vertebra, likely from an hadrosaur.

Locations of dinosaur fossils in IowaIt’s only a matter of time before some lucky searcher examining Iowa’s Cretaceous formations or Ice-Age gravels finds the next dinosaur fossil from Iowa. So keep looking!