4" Fossil Ornithomimid (Struthiomimus?) Middle Metatarsal - Montana

Fossil Ornithomimid (Struthiomimus?) Middle Metatarsal - Montana #353317

This is a 4" long, fossil metatarsal (toe bone) of a small ornithomimid dinosaur, with Struthiomimus sedens being a likely candidate. It was collected from the Hell Creek Formation in Custer County, Montana. The shape of this metatarsal is common in small to large theropods. Organisms that had this middle metatarsal shape are categorized into the "Arctometatarsal" group. The reason for the shape of the bone is still debated, however a plausible hypothesis for the shape is to reduce compressive stress on the foot while running.

The bone is overall in excellent condition with repaired cracks that continue up through the thinnest portion of the metatarsal.

Struthiomimus were long-legged, bipedal, ostrich-like dinosaurs with toothless beaks. They reached estimated sizes of approximately 13 feet in length. It is thought that due to their abundance, they must have been herbivores or omnivores.

Struthiomimus sedens skeleton in the Oxford University Museum of Natural History

The Hell Creek Formation

Renowned for both its age and rich sedimentary layers, the Hell Creek Formation is one of the most intensively studied fossil-bearing regions on Earth. To date, scientists have documented 158 genera of animals and 64 genera of plants from its rocks, with new finds emerging regularly. Beyond iconic dinosaurs such as tyrannosaurs, ceratopsians, and hadrosaurs, the formation has produced an extraordinary array of life, including amphibians, reptiles, lizards, snakes, turtles, fish, sharks, birds, and early mammals. Together, these fossils provide the most complete picture of the ecosystems that thrived just before the Cretaceous–Paleogene extinction event.

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