Two samples of a vertebra and a jawbone from two specimens of the Upper Jurassic Pliosaurus funkei from Spitsbergen have been described with respect to findings of fluorescing inclusions of liquid petroleum hosted in mineral precipitates representing a former primary skeletal porosity. Analyses were undertaken to elucidate potential animal and/or petroleum derivation(s) of the fluid(s) and possibly the timing of infilling with respect to the burial history of the hosting Pliosaurus. The fluid inclusion temperatures of homogenisation range from 47 to 117 °C. The earliest trapped fluids are primary aqueous inclusions occurring in calcite and barite close to the boundary to the skeletal matrix, followed by (or penecontemporaneously with) isolated, bluish-fluorescing, primary petroleum inclusions in vicinity of the aqueous fluid inclusions in barite. These inclusions homogenise at the highest measured temperatures.
Subsequently trapped hydrocarbons homogenise at lower temperatures as their density increases. Such observations of decreasing API (increasing density) with decreasing temperature may be related to secondary changes in migrated petroleum during earlier documented uplift at Spitsbergen. Biomarkers reflect a depositional condition for the Upper Jurassic shales, i.e., the source rock expelling petroleum was potentially the rock occurring just below the Pliosaurus-bearing strata. In addition to inclusions validating a petroleum origin, a few low-viscosity, reddish- brown colored inclusions, not likely to represent a bituminous liquid, are observed, potentially of an animal origin.