MORPHOLOGICAL VARIATIONS IN MIDDLE DEVONIAN GASTROPODS FROM THE STRINGOCEPHALUS LIMESTONE, GERMANY

The Middle Devonian sees a rise in durophagous organisms and predation-resistant features amongst gastropods, dubbed the mid-Paleozoic precursor to the Mesozoic Marine Revolution, setting the stage for the widespread restructuring of shallow benthic ecosystems that occurred during the Mesozoic. There is little quantitative evidence of how gastropod morphology responds to durophagous predation and what factors are most beneficial. To address this, we surveyed more than 300 gastropod fossils from the Stringocephalus Limestone Formation, from the Middle Devonian, in Germany. We used Raup’s (1966, J. Paleo. 40, 1178-1190) parameters to quantify whorl expansion rate, whorl translation rate, and distance of the generating curve in relation to the axis. In addition, we coded the degree of ornamentation on each shell. These measurements revealed relationships between shell morphology and ornamentation and provided a basis for comparison with gastropods during and after the Mesozoic Marine Revolution. Devonian shells exhibited low translation rates compared to more recent gastropods. Additionally, less ornamented shells showed a wider range of whorl expansion values. We also observed evidence of predation via durophagy through repair scars, although to a lesser degree than in samples from younger rocks.