Ediacaran Fronds From the Mistaken Point Assemblage, Newfoundland
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The Ediacara Biota is a distinct group of soft-bodied organisms that flourished in late Precambrian (Ediacaran) oceans. The succession at Mistaken Point, Newfoundland, contains the most extensive collection of Ediacaran fronds in the world, with hundreds of complete specimens spanning at least 10 million years. The goals of the completed thesis were to investigate the growth strategies, preservational biases, function, and taxonomy of Ediacaran fronds through the use of qualitative morphological descriptions and quantitative morphometrics. Several of these mathematical techniques had not been previously applied to the Ediacara Biota, and strengthen traditional descriptive techniques through mathematical scrutiny. The second chapter applies standard biometric and principal components analyses to the cosmopolitan frond Charniodiscus from Newfoundland, which allowed for rigorous definition of two new closely related species that evolved differently shaped petalodiums to extract nutrients from different levels in the water column. The third chapter utilizes "landmark morphometrics" to interpret the original 3D shape of Charnia. These techniques suggest that traditional descriptions of Ediacaran fronds as sheet-like organisms are incorrect, and are a direct result of preservational processes. It was demonstrated that branch rigidity is species specific, resulting in the description of a new species of ancestral Charnia. The fourth chapter describes a new species of multifoliate rangeomorph frond that was preserved in four unique taphonomic settings. Only through comparison of specimens from all four preservational regimes was it possible to reconstruct the original morphology of this frond, and isolate taphonomically based features from true morphological characters. The final chapter reviews the biological significance of the frond morphoshape, and proposes that the present emphasis on overall shape in Ediacaran taxonomy is inherently flawed. It is recommended that a new system be erected to classify Ediacaran fronds based on branching architecture, as frond morphology most likely represents a common need to extract nutrients from the water column, and therefore represents a shared ecology, not ancestry.