The earliest known Trypanites borings in the shells of articulate brachiopods from the Arenig (Ordovician) of Baltica

Several specimens of the Arenig (Volkhov Stage) brachiopod Antigonambonites from Northwest Russia and North Estonia bear the earliest known Trypanites borings in articulate brachiopod shells. Two basic types of borings are recorded: rare large rounded borings that penetrate the shell of the brachiopod, and abundant borings that follow the shell, almost never intersecting it. Rare shell repair marks are associated with some Trypanites borings. Presumably some shell-boring worms inhabited also the living Antigonambonites brachiopods, suggesting that diverse shell boring strategies had evidently evolved by the Arenig.