4.9" Theropod Middle Metatarsal - Judith River Formation

Theropod Middle Metatarsal - Judith River Formation #145541

This is a 4.9" long, middle metatarsal (toe bone) from a theropod dinosaur. It comes from the Judith River Formation in Hill County, Montana. We don't see any distinguishing characteristics that would allow us to positively assign it to a species or genus. It could be a raptor or juvenile tyrannosaurid. The bone is in fine condition with a little bit erosion at one end. It was left partially embedded in the sandstone it was found in and a coating of sealant has been applied to it to stabilize the specimen.

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 Judith River Formation is one of the world's most prolific sources of Late Cretaceous vertebrate fossils. At least sixteen Orders containing more than forty Genera are known from the formation. These include fish, amphibians, mammals, and insects in addition to reptiles and avian (birds) and non-avian dinosaurs. Among the more interesting specimens is Leonardo, a mummified and fossilized Brachylophosaurus. This is a hadrosaur, a duck-billed dinosaur found with amazing soft-tissue preservation: skin impressions can be found on 90 percent of its body! The pattern in the skin on its feet is even preserved. In addition to Leonardo, the Judith River Formation contains the remains of the theropod Hesperornis, the only known freshwater Hespernorthid, a penguin-like bird.

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