Chapter 5 Devonian stromatoporoid originations, extinctions, and paleobiogeography: how they relate to the Frasnian-Famennian extinction

Abstract

Origination and extinction of stromatoporoid genera show that the rate of origination exceeded that of extinction from the early Early Devonian (Lochkovian) through the early Middle Devonian (Eifelian). For the remainder of the Devonian (Givetian-Famennian), extinction outpaced origination. During the Early and Middle Devonian, tropical to subtropical marine habitats were divided into the Eastern Americas Realm and the Old World Realm—in North America these were separated by the Transcontinental Arch and the Canadian Shield. Eustatic sea level, which had been rising since the Emsian, reached a point late in the Givetian (Taghanic Onlap) where the land barrier was breached, and Old World taxa invaded the Eastern Americas. Sea level continued to rise episodically through most of the Frasnian, followed by an abrupt fall in conjunction with the Frasnian-Famennian extinction. It is concluded that the decrease in stromatoporoid genus diversity, which occurred as Old World and Eastern Americas faunas came into competition, continued with further sea-level rise during the Frasnian. This lowered diversity put the stromatoporoids in a vulnerable position for extinction when climatic disturbances occurred at the end of the Frasnian.