7.8" Fossil Horse (Mesohippus) Skull - South Dakota

This is a skull of the primitive horse Mesohippus sp., collected from the White River Formation in South Dakota. It is Oligocene in age, or approximately 32 million years old. Based on the amount of exposed teeth within the mandible, it's likely that this would have been a juvenile to young-adult.

About 65% of this skull is natural and extremely well preserved, considering the majority of the material collected from this site is typically disarticulated and fragmented. The mandible has undergone the most restoration, with the anterior jaw and teeth bearing a good chunk of restoration. All but two of the premolars in the jaw are natural. The incisors are a mix of heavily restored or composite. Additionally the incisor bone of the upper skull has been restored. The nasal bones and zygomatic arches have undergone restoration which is quite common considering their fragility.

Much of the rock that held this specimen together was removed during prep. These free spaces (between left and right mandible, within orbitals and between premolars and incisors) were later gap filled with false rock to ensure structural integrity of the skull.