A review of the Late Ordovician (Katian) Richmondian Invasion of eastern Laurentia

Abstract

Biotic Immigration Events in which a group of organisms that originated in one geographic region invade and become established in a new geographic region are common during Earth history. Many such events have been documented from the fossil record and have significantly impacted diversification patterns and processes during the history of life. One of the best studied of these events is the Richmondian Invasion, which constituted several waves of biotic invasion from multiple source regions into the Cincinnati Basin of eastern Laurentia during the Katian Stage. The major features of this invasion were first appreciated during the early 1900s and have received significant study since that time. General patterns of the Richmondian Invasion, including the influx of >60 taxa that span ecological roles and taxonomic groups, differential survival of generalist taxa relative to specialist taxa, and significant restructuring of paleocommunities have been well documented and establish this invasion as a “coordinated invasion” within the Invasion Hierarchy of Stigall et al. (2019). Substantial research to further delineate and clarify the details of the Richmondian Invasion has progressed on multiple fronts over the past two decades. These novel analyses into sedimentology, stratigraphy, and geochemistry coupled with detailed paleoecology, evolutionary, and biogeographic studies provide a framework for increased synthesis and understanding of invasion dynamics during this interval. In this contribution, the current state of knowledge of the Richmondian Invasion is reviewed and some of the key implications for understanding both Ordovician diversification and other intervals of Earth history are examined.