Thalassinoides is a trace fossil tunnel system most likely made by a decapod crustacean, such as a shrimp, while feeding. The tunnels range from between 2 and 6 cm/3/4 and 2 1/3in in diameter and are usually found in rocks that were deposited in calm waters, below the turbulent waves and currents of the tidal zone. Because wave and current action were not dominant here (unlike the settings for Ophiomorpha, see below), animals tended to feed closer to the substrate.