DECONSTRUCTING TAPHONOMY TO RECONSTRUCT MORPHOLOGY: CHARACTERIZING THE LIFE HABIT AND MORPHOLOGY OF ATTENBORITES JANAE FROM THE NILPENA EDIACARA NATIONAL PARK

Attenborites janae is a recently described fossil taxon from the Ediacara Member of the Nilpena Ediacara National Park that was proposed as potentially pelagic in its initial description in 2017. Subsequently, 50 new specimens were excavated from the same site for a total population of 105 individuals. Of these, 102 are found on or in association with bedding plane TB-ARB, and 3 are found on separate bedding planes. The taphonomic characteristics of this essentially doubled population of Attenborites were compared to those of known benthic Ediacaran organisms and Cambrian medusoids to test the pelagic hypothesis for this taxon. Additionally, the effects of biostratinomy on the taxon’s fossil morphology were constrained to reconstruct the in vivo morphology of Attenborites.

A key morphological characteristic of the fossil Attenborites janae are its subparallel longitudinal ridges. The variety in number and patterning of these ridges across specimens indicates that they formed biostratonomically during burial and preservation and are not true morphological characteristics. The in vivo morphology of Attenborites was reconstructed by importing laser scans taken of individual specimens into the 3D modeling software Blender. These scans were simulated to inflate until the ridges were smoothed out without stretching the fossil material. This virtual reinflation technique reconstructed the true morphology of Attenborites as an ellipsoidal form with a relatively smooth surface and represents the first retrodeformation of a soft-bodied fossil.

The random spatial distribution of Attenborites on TB-ARB in conjunction with taphonomic data confirmed a pelagic life habit as most parsimonious for Attenborites, making this the first known macroscopic inhabitant of the water column. Developing methods to identify the life habit of Attenborites led to the creation of criteria for the preservation of pelagic Ediacaran taxa. These criteria are based in the unusual taphonomy of the Ediacaran Period that results from the extensive organic mat cover of the seafloor. These criteria are key in resolving debate over the ecological affinity of proposed pelagic Ediacaran fauna as they eliminate reliance on morphological similarity between Ediacaran forms and medusoids for the identification of pelagic Ediacaran taxa.