Opossum was the first animal that came to mind when I saw the shape of this skull.
This is only about half the size of a typical Opossum skull.
Using the pattern of dentition, the range of possible animals can be narrowed considerably. Step one is to determine the total number of teeth. Here we have a total of 20 teeth in the upper jaw.
That tells us to suspect mammals with 40 total teeth.
The jaw clearly contains five incisors on each side. Raccoons only have three incisors per side, so this is clearly not a Raccoon. Browsing through the dental formulae reveals only one mammal with five incisors to a side and that is the Opossum. So, why the small size and only 40 teeth?
A close examination of the lower jaw reveals undeveloped teeth that have not yet emerged. Many mammals do not get their full complement of teeth until maturity. Had this little fellow survived a few more months, it would have acquired all 50 teeth characteristic of the species. Proper identification of most living things requires consideration of many details. Don’t be eager to make an identification based on just a single point.