Thalassinoides

Thalassinoides is an ichnogenus of trace fossil used to refer to 'dichotomously or T-branched boxworks, mazes and shafts, unlined and unornamented'.:179 Facies of Thalassinoides increased suddenly in abundance at the beginning of the Mesozoic.:251 Such burrows are made by a number of organisms, including the sea anemone Cerianthus, Balanoglossus and fishes, but are most closely associated with decapod crustaceans of the (former) infraorder Thalassinidea.