ASPIDELLA-LIKE STRUCTURES FROM THE EDIACARAN WOOD CANYON FORMATION, NYE COUNTY, NV, USA

The late Ediacaran lower Wood Canyon Formation in Nye County, Nevada, has shown significant paleontological promise in recent years. Investigations in the Johnnie Range between the Amargosa Desert and Pahrump Valley have revealed a diverse assemblage of pyritized tubicolous fossils, with rare examples showing the preservation of bilaterian-grade throughguts, limited specimens of erniettomorphs, and abundant trace fossils approaching the Cambrian boundary. Here, we report both in-situ and float examples of Aspidella-like structures from sandstones near the Stirling Quartzite-Wood Canyon boundary. These structures range in size from approximately >1 to 5 centimeters in diameter and show the quintessential discoidal morphology of Aspidella, with visible concentric rings. Preserved in positive relief on the surfaces of desert-varnished coarse quartz sand beds, these specimens are generally not closely clustered – with the exception of multiple individuals (>10) found on pieces of float (with bedding surfaces of approx. 550 cm2 and 273 cm2). Similar structures have been reported from the region, including Hagadorn and Waggoner’s description of Nimbia from Nye County (2000, Journal of Paleontology) and Sappenfield et al.’s report of medusozoan strandings from Death Valley (2017, Geological Magazine). Comparison of previously reported Aspidella-like structures may reveal ontogenetic changes or perhaps suggest taxon separation. Given the absence of associated frond petalodia, we suggest that these structures could represent free-living jellies, much like the inference of Sappenfield et al. (2017). These possible Aspidella, if biological, serve to bolster previous reports of the preservation potential of soft-bodied organisms, such as Ernietta, from this region.