Thalassinoids are ichnofossils with shapes such as galleries and tunnels primarily in marine sedimentary environments, often made by Thalassinidea decapod crustaceans. Other creators include true shrimps, prawns, lobsters, mud shrimps, polychaete worms known for branching burrows, insect larvae like beetles in coastal areas, and fish such as rays and pleuronectiforms (e.g., plaice) that exhibit similar behaviors.