A series of novel tetracyclic triterpanes based on the lanostane skeleton, ranging in cars-bon number from C_(30) to C_(32), were identified for the first time in Eocene lacustrine depo-its of Biyang Depression, China. These compounds have been identified by GC, GC- MS, andcoinjection with authentic standard, as 8β(H), 9α(H)- lanostane (C_(30)), 24-methyl- lanostane(C_(31)) and 24- ethyl- lanostane (C_(32)). Mechanisms are proposed for the origin and geologicalfate of these compounds. To the best of our knowledge, this is the first confirmed occur-rence of lanostanes in the sedimentary record. A series of novel tetracyclic triterpanes based on the lanostane skeleton, ranging in cars-bon number from C_ (30) to C_ (32), were identified for the first time in Eocene lacustrine depo-its of Biyang Depression, China. These compounds have was identified by GC, GC-MS, and coinjection with authentic standard, as 8β (H), 9α (H) - lanostane (C 30), 24-methyl- lanostane (C_ (32)). Mechanisms are proposed for the origin and geologicalfate of these compounds. To the best of our knowledge, this is the first sure occur-rence of lanostanes in the sedimentary record.