Abstract
World-wide distribution patterns of conodont species during the Cambrian, Ordovician, and Silurian are assessed quantitatively using a Coefficient of Similarity (CS) formula. The validity of the idea is examined that there is a correlation between CS values and the geographic distance between the sample points, and that changes in CS values may, at least in part, reflect plate motions. To minimize effects of local palaeoecological control and the varying degree of exploration of the faunas, well known faunas are used from comparable depositional environments on the several continental plates.