On Diamond, you can only get Cranidos.
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Pokemon white
In the main fossils are tirtouga and archen but after you got the national dex, you can go to the dream world and get fossils of ominite etc.
helix fossil=omanyteroot fossil=lileepclaw fossil=anorithdome fossil=kabutoarmor fossil=sheildonskull fossil=cranidosomanyte into omastar-level 40lileep into cradlily-level 40anorith into...