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diversity triggering one of the highest extinction rates in the Late Palaeozoic (Lerosey-Aubril & Feist 2012). This is essentially due to the terminal Frasnian global Kellwasser crises (Feist 1991, McNamara & Feist 2016). The peak of the main level of mass extinction, i.e. the Upper Kellwasser Horizon, coincides with the Frasnian– Famennian boundary as defined in 1993 by IUGS at the base of the Lower triangularis Zone (Klapper et al. 1993). The Famennian starts now much earlier than at the first appearance of the goniatite Cheiloceras (Ziegler 1971) in the Late triangularis Zone which was previously used to define the boundary. Accordingly, and after restriction of both Nephranops and Cryphops to the early Famennian (Crônier & Feist 2000; Feist et al. 2009, p. 16), pha copids lost all remaining three genera recognized to date from the late Frasnian: Chlupacops at the base of the Lower Kellwasser Horizon, and Trimerocephaloides and Acuticryphops at the base of the Upper Kellwasser Horizon (Feist et al. 2009, McNamara & Feist 2016). Thus, and in contrast to previous thinking (Alberti 1970, Feist 1991), phacopids were severely affected by the Kellwasser crises. Elucidation of phylogenetic relationships between taxa prior to and following the terminal Frasnian global biocrises is hindered by the scarcity of recorded trilobite taxa, in particular from shallow near-shore environments. Further difficulties lie in the fact that age attribution of phacopids previously followed ammonoid-based chronology and that modern biostratigraphical assignments of taxa to conodont zones have been achieved only locally (e.g. Ziegler 1962; Lütke 1968; Feist et al. 2009, 2016). For instance, important Uralian taxa close to the Frasnian– Famennian boundary, such as “Phacops (Cryphops)” latilimbatus Maximova, 1955 [assigned herein to the new

Post-Kellwasser event recovery and diversification of phacopid trilobites in the early Famennian (Late Devonian)