May 2025: Wing-shaped snail

Toarctocera subpunctata (Goldfuss, 1844)

Middle Jurassic (Aalenian, c. 178 million years)

Opalinuston Formation, Boll, Baden-Württemberg

Size of the snail: c. 3 cm

Wing-shaped snails (family Aporrhaidae) are widespread and species-rich in the Mesozoic. These marine snails are characterised by a conical spindle and have conspicuous spines at the aperture. Some species still occur today. The best known is the pelican’s foot (Aporrhais pespelecani), which is widespread from Norway and Iceland to the Mediterranean Sea. The name was given because of its apertural spines, which give the shell the shape of this bird’s foot. The fossil of the month, Toarctocera subpunctata, comes from the early middle Jurassic (Aalenian) of Boll in Baden-Württemberg, from the Opalinuston Formation (approx. 178 million years old). The species also occurs in the somewhat older Jurensismergel Formation (upper Lower Jurassic, Toarcian).

This makes it one of the earliest confirmed representatives of the family Aporrhaidae and the superfamily Stromboidea. Toarctocera subpunctata occurs in the foreland of the Swabian Alb and Franconian Jura (Baden-Württemberg and Bavaria) and has also been recorded from Switzerland and France. It has been found in dark clayey rocks, which indicate that the seabed was muddy and very soft. The long spines of Toarctocera subpunctata are interpreted as extentions that prevented it from sinking into the soft seabed. This is called a snowshoe strategy, as snowshoes also serve to prevent sinking. The spines are very long and fragile. In the vast majority of specimens they are completely broken off, but occasionally fossils with well-preserved spines are also found. Toarctocera subpunctata is one of the most common species in the Opalinuston and Jurensismergel Formations. For example, it is very common in the Mistelgau clay pit near Bayreuth. The species was therefore an important component of the communities at that time.

Alexander Nützel

Reconstruction of the wing-shaped snail Toarctocera subpunctata with complete apertural spines. In most specimens, the spines are completely or partially broken off. The spines prevented them from sinking into the muddy seabed. Christian Schulbert, from Gründel et al. (2009).