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

摘要

One hundred Selenichnites rossendalensis (excavations), sometimes with associated trackways, have been found at Joggins Fossil Cliffs (Nova Scotia, Canada; Pennsylvanian). The majority of the Selenichnites found in this study contain only one lunate cast and some are distinguished by linear ridges that project behind a single lunate cast. A detailed investigation of the morphology and orientation of these Selenichnitesattributable to xiphosurans, relatives of modern horseshoe crabs (Limulus polyphemus)yields an understanding of xiphosuran digging behavior. Statistical analysis of 96 lunate casts from two populations of Selenichnites separated by several hundred thousand years shows, with 99% confidence, that the prosomas (heads) of the younger population are smaller. Further study of the wealth of Selenichnites at Joggins will be useful to determine which factors control xiphosuran body-size changes and the timescale on which those changes can be seen manifest in a population. The smallest known Selenichnites (7mm wide) is also reported.