See more from this Division: Topical Sessions
See more from this Session: After the Last Ammonite and before the First Horse: Patterns of Ecological and Climatic Change during the Paleocene
Abstract:
The zone ranging from southern Wyoming to southern Montana is both the most species rich and the most even, although this region also has the greatest exposure of mid-Paleocene terrestrial sediments and number of To-Ti mammalian localities, many with long collecting histories. A negative relationship between latitude and species diversity is observed for the Torrejonian, while the opposite pattern is observed for the Tiffanian. However, the predictive power of latitude for determining number of species is extremely low in both cases (r2 of 0.018 and 0.0005, respectively). The San Juan Basin saw a decrease in diversity across the To-Ti boundary while diversity increased across the boundary in southern Wyoming. Diversity did not change significantly over this interval north of about 50° latitude. Using generic data, both the Torrejonian and Tiffanian exhibit negative gradients with no significant increase in the r2 values. If estimates of mid-Paleocene species richness are accurate, it suggests a different relationship between richness and latitude compared to the modern pattern in western North America, perhaps reflecting a shallower latitudinal temperature gradient related to a difference in climate.
See more from this Division: Topical Sessions
See more from this Session: After the Last Ammonite and before the First Horse: Patterns of Ecological and Climatic Change during the Paleocene