A novel C-30 vanadyl alkylporphyrins, 13,15-ethano-3ethyl-2,7,12,18-tetramethylporphyrin (i.e., 8-nor-deoxophylloerythroetioporphyrin; 8-nor-DPEP) has been isolated from a Middle Miocene siliceous shale. The structure of intact vanadyl porphyrins was determined by X-ray crystallography. The structure suggests it to be originated from specific chloropigments such as chlorophylls a(2), b(2), c(2), and c(3) or bacteriochlorophyll a, hence potentially being a biomarker of specific photoautotrophs.