Precocious sexual dimorphism and the Lilliput effect in Neo‐Tethyan Ostracoda (Crustacea) through the Permian–Triassic boundary

The E likah R iver section spanning the L opingian ( L ate P ermian) to the G riesbachian ( E arly T riassic) time interval in the C entral A lborz M ountains (north I ran) was sampled for ostracod analysis. We report 79 species distributed among 38 genera. Four new species are described: A cratia ? pervagata F orel sp. nov., M icrocheilinella alborzella F orel sp. nov., B asslerella superarella C rasquin sp. nov. and C avellina nesenensis C rasquin sp. nov. The ontogeny of 13 species is described and sexual dimorphism in the genus M icrocheilinella is here undoubtedly recognized for the first time. Six species show precocious sexual dimorphism of their carapace as early as A ‐5 juvenile. The L illiput effect is for the first time recorded and quantified for two species. Rare long‐time span P alaeocopida species, known throughout the entire P ermian, document relatively long‐term evolution, including the size and growth rate modifications associated with the earlier appearance of carapace sexual dimorphism through time. These patterns might be related to the G uadalupian– L opingian events and/or to climatic modifications occurring during the Permian interval.