Taxonomic trends in the resolution of detail preserved in fossil phosphatized soft tissues

The preservation style of phosphatized soft tissues from a range of Mesozoic and Tertiary laminated limestones is documented (for the first time in the case of Cerin, Lebanon, and Monte Bolca). Three microfabrics are identified, reflecting the degree of microbial influence on the mineralization process. These are microbial, where the tissues are pseudomorphed by mineralized microbes; substrate, where the site of phosphatization is controlled by the tissue of the fossil organism; and intermediate, where the substrate tissue is mineralized but retains impressions of microbes. These microfabrics tend to characterize particular fossil groups: microbial in arthropods, a combination of microbial and substrate in cephalopods, and substrate in fish. This reflects the relative resistance of the tissues of these taxa to invasion by microbes from the exterior during decay. The source of phosphorus that preserves soft tissues may be external (from the sediment or pore waters), or internal (from the decay of the organism itself). Where an external source is dominant, as at Solnhofen (Jurassic, Tithonian, Germany), most of the taxa present preserve phosphatized soft tissues. Where the source is primarily internal, as at Osteno (Jurassic, Sinemurian, Italy), phosphatized soft tissues are confined to arthropods and some cephalopods. A similar taxonomic control on mineralization has also been documented in experiments. Thus, aspects of the nature of organisms exert an influence on the occurrence and style of soft-tissue preservation, and the level of detail preserved.