This is a .81" Tyrannosaur premaxillary tooth from the Judith River Formation of Montana. This formation is approximately 70 million years old, or about 5 million years old than the Hell Creek Formation which produces T-Rex.
These oddly shaped teeth with two ridges located on the lingual side where originally described as Aublysodon more than a century ago based off of isolated teeth and jaw fragments. More recent discoveries of more complete Tyrannosaur skeletons from this formation has lead to the discovery that these teeth are actually the premaxillary teeth from juveniles of other Tyrannosaur species.
Comes in an acrylic display case.
The Judith River Formation is one of the 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 the reptiles, avian and non-avian dinosaurs (birds). Among the more interesting specimens is Leonardo, a mummified and fossilized Brachylophosaurus. This is a Hadrosaur, a duck-billed dinosaur with amazing preservation of the soft tissues of the body. The pattern in the skin of the feet is even preserved. In addition to Leonardo, the Judith River Formation contained the remains of the theropod Hesperornis, the only known freshwater Hespernorthid, a penguin like bird.