Paleoethologic interpretation of complex Thalassinoides in shallow-marine limestones, Lower Ordovician, southern Sweden

Lower Ordovician Thalassinoides (T. bacae isp. nov.) from Öland, Sweden, is characterized by irregularly anastomosing, horizontal tunnel mazes with highly variable branching angles, accompanied by numerous closely spaced, short, vertical shafts that must have provided a large number of burrow openings to the sea floor. These complex trace fossils appear to be agrichnial burrow systems that represent chemosymbiotic feeding behavior by infaunal animals. They occur profusely in thin-bedded fossiliferous, lime mudstone and wackestone that were deposited on a shallow-marine, carbonate platform.