Attempted predation and shell repair in Middle and Upper Ordovician gastropods from Sweden

Abstract

Repaired shell injuries are reported in 11 specimens including six genera and eight species of gastropods from the upper Middle Ordovician (Caradoc) Kullsberg Limestone and the Upper Ordovician (Ashgill) Boda Limestone, Siljan district, Sweden. The specimens are of different sizes and morphologies, including one isostrophic, three low-spired, and six moderately high-spired turbinate forms. Single and repeated episodes of shell damage and subsequent repair are preserved, the breaks ranging from simple arcuate or scalloped fractures to removal of large sections of the apertural margin. Both early and late growth stages show damage, but the injuries are usually restricted to only one whorl. No shell repairs were discovered on the 65 more or less complete specimens of the subulitids, although the smooth shell makes observation difficult. Injuries in the Siljan samples are found in both microgastropods and large specimens, but the sample is too small for meaningful quantification. The shell repair frequency is about 7 percent, based on examination of 404 specimens (54 from Kullsberg Limestone and 350 from Boda Limestone). Most of the repaired injuries are attributed to failed predation, adding significantly to the Lower Paleozoic documentation of predation on gastropods. The gastropod shells are morphologically weak by modern standards, but do show some architectural strengthening features such as narrow apertures, collabral or spiral threads, and other ornamentation. The identity of the predator(s) is unknown.