A QUANTITATIVE VIEW INTO THE TAPHONOMY OF KIMBERELLA QUADRATA FROM NILPENA EDIACARA NATIONAL PARK, SOUTH AUSTRALIA

The Ediacaran period records the appearance of complex, multicellular life in Earth’s history. Nilpena Ediacara National Park (NENP), South Australia, preserves one of the most morphologically and taxonomically diverse assemblages of this period within the Ediacara Member. Kimberella quadrata was a bilaterally symmetrical, benthic organism often interpreted as a possible stem mollusc (Fedonkin et al. 2007) due to its more complex morphology and feeding mode (Ivantsov and Fedonkin 2001; Ivanstov 2012). Although common in the White Sea region in Russia, Kimberella often occurs as isolated specimens. However, a new fossiliferous bed recently excavated at NENP preserves nearly 50 specimens of Kimberella, allowing a comprehensive insight into their palaeobiology and preservation within a single population. When tested using Spatial Point Pattern Analysis the Kimberella best-fit a spatially random pattern and their locations were additionally independent to all other taxa on the surface. This implies that Kimberella had no preference or aversion to conditions in their ecosystem at time of preservation. Landmarked-based geometric morphometrics was used to capture and analyse their shape using a combination of both fixed and sliding semi-landmarks. A generalised Procrustes analysis revealed the most likely shape in life, which was bilaterally symmetrical. The Principal components analysis describes the patterns of taphonomy and how preservation changes with growth within this single population. The pattern of taphonomy observed shows that larger specimens become more ovate, with the midline offsetting to the side and flatter relief. Whereas the smaller specimens maintain a teardrop shape with the midline still centred and high relief. Results from a multivariate regression also demonstrated the same preservation change with size. These results observed for this population were comparable to the South Australian Museum collection specimens, indicating these results likely reflect the overall taphonomic pattern for Kimberella in South Australia.