This Oreodont skull was found in the Badlands of South Dakota. Oreodonts were Artiodactyls (even toed ungulates) that lived during the last half of the Eocene up until the end of the Miocene (40 million to 5 million years ago). There are many types of artiodactuls alive today including animals such as pigs, sheep, hippos, and deer, just to name a few.

After collection in the field, former curators coated the skull in a shellack, a common practice in the past that was meant to stabilize and further preserve fossils. Unfortunately, the shellack often darkened and cracked, obscuring the details of the specimen. 

The current curator of the Dunn-Seiler Museum is slowly removing the shellack from this skull to reveal the fossil beneath. Here you can see the progress! Which do you prefer; the side with the shellack, or the side that has been cleaned?