"Bulldozing" trails left by a freshwater mussel of the family Unionidae, most probably the Duck Mussel (Anodonta anatina) or the Painter's Mussel (Unio pictorum) on a beach near Kurort. The deep, meandering furrow left in the sand is a classic "ploughing" trace (known as repichnia). These mussels use a large, muscular foot to drag themselves slowly through the upper layer of sediment, leaving behind the U-shaped groove. St.Petersburg, Russia

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