I found a model of a rhino that wasn't solid or printable so I used the free program MeshMixer to edit it (http://www.meshmixer.com).
I filled holes, smoothed the mesh, edited some parts with a brush and made all details at least 1 mm thick. I also uploaded the color model in a zip file.
The original file is here: http://archive3d.net/?a=download&id=6f77cd41