Dinámica de la estructura de comunidades del Cenozoico tardío de Norteamérica: Episodios de Recambio Rápido de Fauna (RTE) dentro del concepto de Cronofauna

During the late Cenozoic the highest generic richness tended towards the loss of diversity, although three peaks were recognized with high rates of first records followed a high percentage of extinctions known as Rapid Turnover Fauna Episodes (RTE) (early Hemphillian, late Blancan and late Irvigntonian). However, these events define a pattern that fits the concept of Chronofauna of Olson (1952). The RTE episodes are considered in this structure as transition events between a Chonofauna and another. While the period of relative stability is equivalent to the Chronofauna, in which new ecomorphs are taking a dominant role, persisting around a series of intervals, is not the case in their taxonomic composition, which is altered by small events of low intensity extinctions. Under this pattern, we can deduce that in the last 9 million years, four different Chronofaunas can be recognized: Clarendoniano chronofauna (later section), Blancan chronofauna, Irvingtonian chronofauna and Holocene chronofauna (initial section).