The Collaborative International Dictionary of English v.0.48:

Fossilist \Fos"sil*ist\, n.
   One who is versed in the science of fossils; a
   paleontologist. --Joseph Black.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fossilist
    n 1: a specialist in paleontology [syn: paleontologist,
         palaeontologist, fossilist]