An Early Triassic small shelly fossil-style assemblage from the Virgin Limestone Member, Moenkopi Formation, western United States

Small shelly fossils (SSFs) are minute moulded or replaced by apatite, and less commonly, other minerals like glauconite iron oxides. This taphonomic mode is best known from Cambrian deposits, though some occurrences occur across geological time. Instances of small shelly-style preservation were found in insoluble residues the Lower Triassic Virgin Limestone Member exposed southern Nevada, western United States, a second such occurrence this unit. Fossil steinkerns tiny brachiopods, echinoid spines ophiuroids fluorapatite, with scarce phosphatic internal moulds bivalves two ostracods. In contrast, crinoid ossicles, almost all which >1000 µm, preserved as stereomic silica dolomite. Though style similar to another fossils-style assemblage, assemblage preserves greater diversity, likely reflecting variation palaeocommunities shelf. The size selectivity phosphatization clear, majority <1000 µm phosphatized. Importantly, original skeletal material does not exert strongest control on preservation: ossicles whilst ophiuroid fragments It that underlying mechanisms related particle skeletons elements coupled local pore water environment. Early equatorial seas characterized warm temperatures lower oxygen levels fostered fossil-style shelf during