most ecologically-severe mass extinction, and the Givetian crisis was ranked as the eighth. Even in areas with oxygenated seabeds, such as parts of Morocco, the ecospace of Hangenberg event communities was restricted to only a few ecological groups, particularly slow-moving pelagic predators (i.e. ammonoids and acanthodians) and epifaunal sessile filter feeders (i.e. bivalves and bryozoans). Impact on life Reef builders Reef ecosystems disappeared from the fossil record during the Hangenberg Event, not returning until the late Tournaisian. Metazoan (coral and sponge) reefs had already been devastated by the Frasnian-Famennian event, and were still recovering during the Famennian. The end of the Famennian not only eliminated the metazoan reef community, but also many calcimicrobial reefs which were previously unscathed. Nevertheless, in the absence of pressures from metazoan communities, there was a brief resurgence of microbial carbonate in the early Tournaisian, a similar pattern to other mass extinctions. The last true stromatoporoid sponges, a major group of Devonian reef builders, completely died out in the Hangenberg Event. Conversely, tabulate corals were apparently not strongly impacted. Rugose corals, which were already fairly rare, experienced a large extinction and ecological turnover before rediversifying in the Tournaisian. Bryozoans maintained high rates of both speciation and extinction during the late Famennian, with only a small drop in overall richness. The Hangenberg event effectively "refreshed" bryozoan diversity, eliminating old clades and allowing new forms to radiate and eventually reach a diversity peak in the Visean stage. Other invertebrates Ammonoids were nearly wiped out by the Hangenberg Event, a fact noted very early in the study of the extinction. One major Famennian group, the clymeniids, were already suffering smaller extinctions just prior to the event. Although clymeniids survived the extinction event itself, they became a dead clade walking and died out shortly after it. Ammonoid extinction rates were highest near the base of the Postclymenia evoluta zone, in the early part of the crisis. 75% of remaining families, 86% of genera, and 87% of species died out at this time. A few cymaclymeniids (including Postclymenia) briefly expanded into a cosmopolitan ‘survivor’ fauna, but ultimately died out at the end of the crisis. Only one ammonoid family, the Prionoceratidae, survived the full extinction interval and went on to rediversify into later goniatite groups. Extinction in non-ammonoid nautiloids and gastropods is poorly studied, but appears to have been significant as well. Bivalves were barely affected, even in anoxic deep-water environments.