The Eifelian is named after the Eifel Mountains of Western Germany, which exposed the GSSP section at the Wetteldorf Richtschnitt outcrop.
[8] The end of the Eifelian was marked by a biological crisis known as the Kačák Event, a two-part interval of extinction which led to ecological turnover among ammonoids, conodonts, and other free-swimming animals.
[11][12][13] Warming and sea level rise through the Eifelian and beyond would have had major effects on diversity, likely leading to the downfall of several marine biogeographic realms.
The cool-water Malvinoxhosan Realm (MXR), on the northwest edge of Gondwana, was decimated as rising temperatures eliminated suitably temperate habitat.
[14] Fauna of the Eastern Americas Realm (EAR), which was restricted to a shallow basin in southwest Laurussia, were gradually replaced by aggressive cosmopolitan species of the Old World Realm (OWR), which invaded through a seaway cutting along a flooded continental arch on the western edge of Laurussia.