The known distribution of conodonts in the Cambrian of Europe, Asia, and North America is not uniform, but no major discrepancies in stratigraphic range of form species has been noted. The oldest reliably dated conodont known is a Hertzina species which is known in upper Middle Cambrian rocks in Nevada and Bornholm (Denmark). Apparently there is a mineralogic evolution from calcium phosphate and considerable organic matter in the oldest specimens to calcium phosphate, with little or no organic material in Upper Cambrian specimens.
The Cambrian conodont faunal distribution may be related to the Cambro-Ordovician trilobite biomeres, at least in North America. The first real diversification of faunas in North America occurs in the Aphelaspis-Elvinia interval which corresponds to the Pterocephaliid trilobite invasion. Even more striking is the fact that the Saukia Trempealeauan = Lower Tremadocian trilobite fauna diversity has its counterpart in the diversity of conodonts which evolved at approximately the same time. Form-species evolution noted in this interval includes the Cordylodus-Oistodus group and a separate but related Oneotodus-Acodus-Acontiodus sequence.