The Changhsingian (Late Permian), 4 to 5 m thick Paratirolites Limestone has yielded diverse ammonoid assemblages composed of the genera Neoaganides, Pseudogastrioceras, Dzhulfites, Paratirolites, Julfotirolites, Alibashites, Abichites, Stoyanowites and Arasella. The succession of ammonoid species allows for a subdivision of the rock unit into eight biozones, in ascending order: Dzhulfites zalensis Zone, Paratirolites trapezoidalis Zone, Paratirolites kittli Zone, Stoyanowites dieneri Zone, Alibashites mojsisovicsi Zone, Abichites abichi Zone, Abichites stoyanowi Zone and Arasella minuta Zone. The following 20 new species are described by two of us (DK and AG): Neoaganides ultimus sp. nov., Pseudogastrioceras relicuum sp. nov., Dzhulfites zalensis sp. nov., Dzhulfites hebes sp. nov., Paratirolites coronatus sp. nov., Paratirolites birunii sp. nov., Paratirolites quadratus sp. nov., Paratirolites multiconus sp. nov., Paratirolites serus sp. nov., Julfotirolites kozuri sp. nov., Alibashites ferdowsii sp. nov., Alibashites uncinatus sp. nov., Alibashites stepanovi sp. nov., Abichites subtrapezoidalis sp. nov., Abichites alibashiensis sp. nov., Abichites ariaeii sp. nov., Abichites paucinodus sp. nov., Abichites shahriari sp. nov., Abichites terminalis sp. nov. and Stoyanowites aspinosus sp. nov. After the time-equivalent Chinese occurrences, the material described here is the most diverse assemblage known from the critical interval before the end-Permian mass extinction.

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