First record of agglutinated worm tubes from the uppermost Cambrian of Estonia

A new species of agglutinated tube, Cryptosiphon oboloides sp. nov., is described from the Furongian of Estonia. The agglutinated tubes are composed of pieces of lingulate shells that are placed to form an overall pattern. The studied agglutinated tube strongly resembles cases of modern caddisfly larvae, though we do not suggest any phylogenetic affinity to caddisflies. The tubes originally contained an organic inner lining with a sticky external surface that enabled worms to glue on shell fragments and sand grains. The relatively well-arranged grains in the tube wall suggest that the animal actively assisted in gluing the shell fragments, orienting, and finding the right place for them. It is possible that worms capable of building agglutinated tubes from shell material originated in Baltica and later dispersed to the Armorican Terrane Assemblage and other regions in the Early to Middle Ordovician.