| Discoaster, Gephyrocapsa, Coccolithus, Gephyrocapsa oceanica|
Ceratolithus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the later part of the Arenig stage of the Ordovician Period, approximately 478 to 471 million years ago.
Ceratolithus has been found in the Lower Ordovician of China (Arenig, Meitan Formation, Central Szechwan).
The haptophyte genus Ceratolithus.