Response of the Silurian jawed polychaete fauna to environmental changes during the Mid-Ludfordian Glaciation in the Prague Basin (Czech Republic)

Numerous recent studies have revealed that the Ludfordian was an unstable part of the Silurian Period, linked with global climatic changes and glaciation, changes in ocean chemistry, and a distinct perturbation of the carbon cycle expressed by the largest carbon isotope excursion throughout the whole Phanerozoic, the Mid-Ludfordian carbon isotope excursion (MLCIE). These dramatic environmental changes were associated with faunal crises in conodont (Lau conodont Bioevent) and graptolite (Kozlowskii graptolite Bioevent) faunas. The response of other faunal groups to global environmental changes during the mid-Ludfordian has been less thoroughly documented. Here, we present an analysis of the taxonomic composition and stratigraphical distribution of jaw-bearing polychaete worms from the Ludfordian strata of the Prague Basin. Based on more than 5,000 diagnostic posterior maxillae, more than thirty species were recorded from the studied interval. The family Rhytiprionidae was recorded from the peri-Gondwanan region for the first time. During the MLCIE and the Mid-Ludfordian Glaciation interval, the jawed polychaete fauna was disturbed and reorganised but recovered relatively quickly, sooner than, e.g. lingulate brachiopods. The most distinct change was documented at the end of the Polygnathoides siluricus Zone marking the beginning of the glaciation. Approximately half of the species showed a continuous range through the event interval, twenty percent of species represented Lazarus taxa, six percent disappeared and 24 percent appeared during or after the event interval in the Kosov section.