The main coal forming element in the peat paleoswamp of the Middle Miocene 'Chukurovo' lignite is Taxodiaceae (paleobotanical observation). The great preponderance of diterpenoids in the resinite is a chemical confirmation for the presence of coniferous vegetation in the paleoplant taxa. Subordinate quantities of the sesquiterpenoids cuparene, valencene and cadalene types and longifolane are present. Molecular indicators for angiosperm vegetation are also recognized in the bulk coal. The presence of olean-12-ene, urs-12-ene, 24,25-dinoroleana-1,3,5(10)12-tetraene, and 24,25-dinorursa-1,3,5(10)12-tetraene all indicate flowering trees and provide the possibility to further assess the paleoplant community. The triterpenoid data indicate oxic diagenetic transformation of plant detritus had proceeded by aromatization of ring A-E. (c) 2005 Elsevier Ltd. All rights reserved.