To be truthful, we haven't had the impulse to 3D print a Striped Hyena Skull. At least so far this week. But in case you do, we've found a repository that holds detailed 3D models of numerous biological items, mainly 3D scanned skulls.
Digimorph, part of the National Science Foundation Digital Libraries Initiative, is billed as a "unique biological visualization library". They say:
...develops and serves unique 2D and 3D visualizations of the internal and external structure of living and extinct vertebrates, and a growing number of 'invertebrates.' The Digital Morphology library contains nearly a terabyte of imagery of natural history specimens that are important to education and central to ongoing cutting-edge research efforts.
And they just happen to have a number of 3D models in addition to the images and other material present.
We count 49 STL models freely available for download - and 3D printing. But beware, some of these scans are complex and will involve significant amounts of support material. It turns out that skulls don't always have flat bottoms, who knew?
Yes, we're looking to print the Striped Hyena after all; that's the one pictured above.