Beschreibung:
<jats:p>Studies of the fates of clades during mass extinctions at the end of the Cretaceous and near the Cambrian-Ordovician boundary have indicated that geographically widespread groups have a much higher probability of survival than narrowly distributed groups. If biogeographic distribution does play a significant role in influencing the outcome of extinction events, then geographic variability in extinction intensity should be mirrored by patterns of endemism. A comparison of data for the terminal Cambrian extinction indicates that survival of trilobite families in Kazakhstan was significantly greater than in North America. As predicted, the Kazakh sequence was characterized by a significantly larger number of pandemic families. The Baltic Province, which includes Scandinavia, England, and Wales, was composed entirely of pandemic groups and did not suffer any trilobite extinction at the family level. The results are consistent with the suggestion that latitudinal variation in extinction magnitude may be the result of differences in biogeographic structure.</jats:p>