The Marshalltown Formation is a Mesozoic geologic formation. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation. Dinosaurs known from the formation: * Hypsibema crassicauda * Hadrosaurus sp. * Nodosauridae indet. * Dryptosaurus sp. * Tyrannosauroidea indet. * Dromeosauridae indet. * Theropoda indet.