Evolution of Crustaceans at the edge of the end-Permian crisis: Ichnonetwork analysis of the fluvial succession of Nurra (Permian–Triassic, Sardinia, Italy)

Decapod crustaceans are among the most efficient ecosystem engineers of the Phanerozoic, but the path that led to their engineering success is poorly known. The Permian–Triassic continental succession of Nurra (early Cisuralian–early Middle Triassic; Sardinia, Italy) sheds light on this obscure subject, because it preserves the oldest (Roadian) fluvial Ophiomorpha and Camborygma, ascribed to ghost shrimps (Decapoda: Axiidea, Gebiidea) and crayfishes (Decapoda: Astacidea, Parastacidea), respectively. These crustacean trace fossils are part of a well-preserved ichnofauna including Arenicolites, Diplocraterion, Helminthoidichnites, Palaeophycus, Planolites, rhizoliths, Skolithos, Spongeliomorpha, Taenidium, Treptichnus, alongside an undetermined tetrapod footprint, helical burrows and Sinusichnus-like traces.