Xiphosuran Digging Traces at the Late Carboniferous Joggins Fossil Cliffs UNESCO World Heritage Site, Nova Scotia, Canada

A significant discovery at the Joggins Fossil Cliffs UNESCO World Heritage Site reveals new insights into the behavior and evolution of xiphosurans, ancient relatives of modern horseshoe crabs. Researchers identified 100 Selenichnites rossendalensis, some with associated trackways, dating back to the Late Carboniferous period (Pennsylvanian). Detailed morphological analysis of these digging traces, particularly lunate casts, indicates that xiphosurans used linear ridges behind their prosomas (heads) during excavation. Statistical analysis of 96 lunate casts from two populations, separated by several hundred thousand years, shows a significant reduction in prosoma size with 99% confidence, suggesting evolutionary changes in body size over time. The smallest known Selenichnites, measuring just 7 mm wide, were also documented. This study highlights the potential of Joggins Fossil Cliffs to uncover factors controlling xiphosuran body-size changes and their temporal scales.

Buhler, P. B., & Grey, M. (2016). Xiphosuran Digging Traces at the Late Carboniferous Joggins Fossil Cliffs UNESCO World Heritage Site, Nova Scotia, Canada. Ichnos, 24(3), 179–190. https://doi.org/10.1080/10420940.2016.1244055