Degradation products of the 2,3,6-/3,4,5-trimethyl substituted analog of isorenieratene were characterized in Belarussian petroleums. Devonian oils of low maturity were found to contain high concentrations (e.g., 35 mg/g) of C40 diaryl isoprenoids (2,3,6-/3,4,5-trimethyl substitution) along with an abundance of maturation-related compounds. A maturation scheme for diaryl carotenoid (2,3,6-/3,4,5-trimethyl substitution) precursors was proposed. Diaryl isoprenoids and aryl isoprenoid (2,3,6- and 3,4,5-trimethyl substitutions) contents were found to decrease as a function of maturity. Maturity parameters based on (i) the ratio of two specific C15 aryl isoprenoids and (ii) the ratio of C15 (2,3,6) aryl isoprenoids to C40 diaryl isoprenoids (2,3,6-/3,4,5) were proposed.Degradation products of the 2,3,6-/3,4,5-trimethyl substituted analog of isorenieratene were characterized in Belarussian petroleums. Devonian oils of low maturity were found to contain high concentrations (e.g., 35 mg/g) of C40 diaryl isoprenoids (2,3,6-/3,4,5-trimethyl substitution) along with an abundance of maturation-related compounds. A maturation scheme for diaryl carotenoid (2,3,6-/3,4,5-trimethyl substitution) precursors was proposed. Diaryl isoprenoids and aryl isoprenoid (2,3,6- and 3,4,5-trimethyl substitutions) contents were found to decrease as a function of maturity. Maturity parameters based on (i) the ratio of two specific C15 aryl isoprenoids and (ii) the ratio of C15 (2,3,6) aryl isoprenoids to C40 diaryl isoprenoids (2,3,6-/3,4,5) were proposed.