Giant Worm Shell

Thylacodes arenarius

Thylacodes arenarius is a sea snail characterized by its irregularly shaped shell, which can grow to lengths of 100 to 200 millimetres. The shell features a round opening with a diameter of 11 to 15 millimetres, and its inner surface is smooth and shiny. This species is cemented onto hard surfaces, resembling the calcareous tubes of certain marine worms. The visible part of the body exhibits a red color with cream markings, while the foot is atrophied, losing its ability to move. This species is found in the Eastern Basin of the Mediterranean Sea and in European waters of the North Atlantic Ocean. It typically inhabits depths shallower than 40 metres, with most occurrences recorded at depths less than 80 metres. Divers may encounter these snails on rocky substrates or other hard surfaces in their natural habitats. Thylacodes arenarius does not have a typical movement pattern due to its atrophied foot. Instead, it remains fixed to its substrate, making encounters with divers more about observing its unique shell structure and coloration.