Here’s a fascinating dinosaur fossil model. It’s the top half of a jaw+skull, scanned by a company named Artec, which manufactures 3D scanners. This model was then sliced into 4 pieces for easier printing (http://www.thingiverse.com/thing:14173). I’ve printed the two pieces of the front half :
Printed with 0.2mm layers. The bottom part took about 4 hours, and the top part about 2 hours. There are 2 more pieces to print, and they’ll take similar times I think.