Ammonite

as a former PhD in Geology and Palaeontology, this picture grabbed me immediately . I think it is a bit too blur but I like the crop a lot (here the photohrapher in me speaks, as from a scientific point of view, it is not a good idea to crop like this).
You might also want to try a special fossil photography technique - therefore you need a thion wire of Titan which you light with a match or candle and then you hold the fossil in the white smoke. The Titanoxyd will cover the fossil with a white coating so that you only see the structure without any distraction from the material that forms the fossil. Such pictures can have an amzing 3d effect - a bit like you know it from pictures taken in an SEM. You can easily remove the coating under floating water.
I have some samples online - if you want to check: http://www.fotocommunity.de/pc/pc/mypics/715683/display/20410254
BW
Axel

Cool pictures nice effect, but I think I'll leave that to the professionals