A number of structural isomers of C-33 2,5-dialkylthiophenes (I), C-33, C-37, C-38 2,6-dialkylthianes (II), and 2,5-dialkylthiolanes (III) have been identified in sediment extracts from the Nordlinger Ries, southern Germany. The identifications are based on gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) analysis and confirmed by carbon skeleton determination on desulfurization products using Raney nickel treatment. All the organic sulfur compound classes mentioned exhibit structural distributions dominated by a limited number of all theoretically possible isomers. This provides further evidence for the formation of these compounds by abiogenic incorporation of sulfur into functionalized lipids at the early stages of diagenesis. Absence or low abundance of compounds with the same carbon skeletons in other extract fractions (saturated hydrocarbons, ketones) illustrates the specificity of this early diagenetic process.