Reappraisal of archaeal C20-C25 diether lipid (extended archaeol) origin and use as a biomarker of hypersalinity

•Extended archaeol (C20-C25) occurs in different saline aquatic settings.•C20-C25 is not restricted to extreme saline environments.•C20-C25 can be used as a biomarker of hypersalinity down to ca 50 psu (5% NaCl w/v).•Haloarchaea of the order Natrialbales are the main source of C20-C25.•Taxonomy and adaptation to salinity and pH may explain C20-C25 production.