The devastating end-Permian mass extinction (252 my ago) is regarded as the most severe biotic crisis of the last 500 million years. Profound and rapid greenhouse gas release by Siberian magmatism led to a tropical seawater temperature increase of eight to ten degrees led to a complete reworking of the biosphere (e.g. Joa-chimski et al. 2012; Schobben et al. 2014). Heating, loss of oxygen in seawater, and ocean acidification are thought to have caused the extinction of ca. 90% of ma-rine animal species in a protracted time interval of per-haps less than 1,000 years. We challenge the view of a single extinction pulse, based on the latest Permian am-monoid record in Iran. Contrary to other parts of the world, this critical time interval is completely repre-sented in the Julfa and Abadeh areas of Iran. Statistical analyses of stratigraphic confidence intervals led us to identify extinction pulses before the traditionally identi-fied extinction horizon. In addition, the body size of am-monoids declined by orders of magnitude over the last 0.7 my years of the Permian period. Similar pre-mass extinction declines and disturbances of the carbon cycle have sometimes been reported from other regions, sug-gesting a widespread, but often overlooked environ-mental deterioration at a global scale, well before the traditional main extinction event (Kiessling et al. 2018). Ammonoids may thus help in the detection of environ-mental stresses that eventually led to the collapse of the marine palaeocommunities.

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