An enigmatic species of Schistidium (Grimmiaceae, Bryophyta) from the Sayan Mountains, Asian Russia

During a field trip to Tunkinskie Goltsy Range, East Sayan Mountains, Republic of Buryatia a peculiar specimen of Schistidium with strongly concave, cucullate leaves was collected from rocks in a temporarily dry stream bed.It was identified as Schistidium chenii (Lin) Cao, Gao & Zhao.This species was previously known from two high mountain localities in China (Tibet and Xinjiang Uygur Autonomous Region).A molecular phylogenetic analysis of the Sayan specimen found its closest relative to be S. occidentale, a widespread western North American species, but recently discovered in Spain.The description based on specimen from Russia is provided; a comparison with S. occidentale and species similar to S. chenii in morphology is given.