Remarkable fossil crickets preservation from Crato Formation (Aptian, Araripe Basin), a Lagerstätten from Brazil

Abstract

The paleoentomofauna recorded in the Crato Formation laminated limestones (Araripe Basin, Aptian) represents one of the most important Konservat-Lagerstätten deposits globally documented. Among the insects, the high morphological fidelity, abundance and diversity of the Grylloidea superfamily allows a more refined study of the external and internal cuticular morpho-anatomical features and preserved soft tissues. Scanning electron microscope analysis with coupled energy dispersion x-ray spectroscopy (SEM/EDS) show that the carcasses of the grylloids are predominantly replaced by three distinct mineral phases with occurrence of features hardly preserved in the fossil record such as the ommatidia's polygonal facets of compound eyes, cuticular layers differentiation (epi and procuticle), internal anatomical microstructures of digestive tract, ovarian fragments, eggs, and visceral and locomotor muscle tissues. The identification of significant microbial evidence associated with the cricket's carcasses allow us to interpret that the main factor responsible for the exceptional cricket's preservation is the influence of microbial mats in the fossilization process.