Unravelling the distribution of decapod crustaceans in the Lower Eocene coral reef mounds of NE Spain (Tremp-Graus Basin, southern Pyrenees)

Modern reefs are considered important hot spots of biodiversity, but the analysis distribution invertebrate fauna across different reefal domains in ancient ecosystems can be challenging, because fossil record is usually affected by strong taphonomic biases. The lower Eocene coral reef well-exposed outcrops Ramals (Tremp-Graus Basin, southern Pyrenees, northeast Spain), preserve a high diversity groups, including decapod crustaceans. In facies belt formed 100–200 m width E–W trending belt, set closely spaced mounds up to five meters high, surrounded skeletal-rich (packstones, rudstones) inter-reef facies. These also allow fossil-association present inner and outer fore-reef facies, which dominated skeletal packstones with molluscs, foraminifera, corals, bryozoans, crustaceans, echinoderms vertebrate fragments (fishes crocodiles). framework consists framestones bioclastic wackestone packstone matrix, abundant colonial as well crustose red algae, encrusting foraminifera (Solenomeris), solitary corals bryozoans. developed within mesophotic zone, disturbed episodic activity storm-induced waves. crustaceans was subjected extensive paleontological statistical analyses. 911 specimens include 41 species belonging 21 families. Most were concentrated periphery mound suggest that core hosted highest abundance Carpilioids most group Ctenocheles sp. areas, Litoricola macrodactylus pyrenaicus showed preferences for environments. Decapod associated faunas lived close association disappeared from area after demise due increase depositional depth fine terrigenous sedimentary input, illustrating how changes at local scale extrinsic factors.