A New Occurrences of Protichnites Owen, 1852, in the Late Cambrian Potsdam Sandstone of the St. Lawrence Lowlands

Abstract

Late Cambrian arthropod trackways from the Potsdam Sandstone have been known since the 1850s. A site in Clinton County, New York, USA, exposes Protichnites in fine-grained, quartz-rich, rippled, micro-laminated Potsdam Sandstone. The study area includes evidence of microbial mat growth on the original surface where the trackways were produced. Ripple marks presumably underlie, and therefore were generated prior to, the microbial mat. Trackway preservation is variable over the outcrop and depositional setting indicates a high intertidal or a low supratidal environment with growth of benthic microbial mats. At least eleven distinguishable trackways of multi-legged, telson- bearing individuals show a range of widths. The trackways consist of repetitive sets of seven pairs of tracks converging in the direction of motion of the organism. A telson impression, either discontinuous or continuous, divides the trackways longitudinally and is nearly centered throughout the lengths of the trackways. The trackways are consistent in number of tracks per series, arrangement, and stride lengths with the ichnospecies holotype from the original description of Protichnites septemnotatus Owen, 1852. Variable preservation probably resulted from varying thickness of the microbial mat and/or varying water depth or wind and wave action in an intertidal pool.