Anomuran and brachyuran trackways and resting trace from the Pliocene of Valduggia (Piedmont, NW Italy): environmental, behavioural, and taphonomic implications

We report a rich ichnofacies including trackways and a resting trace made by indeterminate anomuran and brachyuran crabs, and other organic sedimentary structures produced by invertebrates. This is the first fossil record of crab trackways and resting trace in a shoreface intertidal environment from the Pliocene sediments of Valduggia area (Vercelli, Piedmont, NW Italy). Behavioural and palaeoenvironmental data allow reconstruction of the possible scenario of the upper shoreface surface in this area of the northern paleo-Adriatic Gulf during the Pliocene. The resting trace is tentatively compared to the rehydrating and respiration behaviour of a semiterrestrial (?Ocypodidae) crab, documented for the first time in the fossil record. A single trackway is tentatively assigned to the locomotion of a land hermit crab, the first such fossil record from the paleo-Mediterranean area. Moreover, among other invertebrate burrows, hypichnal Halopoa cf. H. imbricata is reported in shallow marine deposits for the first time. Palaeontological, petrological, sedimentological, taphonomic, and ethological implications are discussed and compared with neoichnological data. This notable discovery enlarges our scant knowledge on the palaeo-ichnology of decapod crustaceans.