Middle-upper Lochkovian (Lower Devonian) conodont succession in the section Segre 4 (Spanish central Pyrenees)

Abstract This study presents a detailed conodont-based biostratigraphic analysis of the Segre 4 section (Pyrenees), spanning the middle to upper Lochkovian. The section yields a continuous and well-preserved conodont succession comprising four globally recognised zones: the trigonicus–kutscheri and kutscheri–pandora β zones (middle Lochkovian), followed by the pandora β– gilberti and gilberti – steinachensis β zones (upper Lochkovian). The conodont assemblages include both cosmopolitan and regionally restricted taxa, allowing robust correlation with key Laurasian and peri-Gondwanan successions. The middle Lochkovian interval is characterised by high diversity and the radiation of the genera Ancyrodelloides , Lanea , and Flajsella , whereas the upper Lochkovian records the diversification of Masaraella and Pedavis . The Segre 4 section provides significant new data on the stratigraphic ranges of several taxa. Notably, Lanea omoalpha and L. eoeleonorae extend into the basal upper Lochkovian, representing the only known occurrences of these species above the middle Lochkovian. Additional relevant findings include the upward extension of Zieglerodina eladioi . The conodont succession also records a marked faunal turnover near the middle–upper Lochkovian boundary, followed by a progressive decline in diversity toward the top of the stage. Low-diversity assemblages dominated by Pedavis , Wurmiella , and Pseudooneotodus , reflecting a pronounced extinction interval, characterise the uppermost beds of the section.