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Ecology and Morphology of Early Animals: An Analysis of the Problematic Genus Sphenothallus from the Lower Cambrian Shuijingtuo and Niutitang Formations in South China
Nakagaki, Michael Masao
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New specimens of the problematic group Sphenothallus have been recovered from the early Cambrian Shuijingtuo and Niutitang Formations in South China. The two sites from the Shuijingtuo Formation were collected from Yanjiahe and Changyang in Hubei and the equivalent Niutitang Formation from Siduping in Hunan. The ability to unite fossils in this genus is due to the pair of longitudinal thickenings which allow for species level analysis of morphology within this easily recognized genus. The morphology needed to differentiate species is subtle and may be influenced by abiotic factors. Differences between the three sampled sites representing different weathering states and paleo-environments allow us to investigate variations in preserved morphology related to abiotic factors (e.g., taphospecies and ecophenotypes). Despite differences in weathering and interpreted paleo-environments, no significant differences in preserved morphology are observed. Without abiotic biases, a logarithmic ontogenetic pattern of the organism indicates a set size of the adult as well as a set width of the longitudinal thickening throughout the organismâ s lifespan. The ability to incorporate multiple specimens from sites with differing diagenetic histories allows for greater sample sets to be created for investigating morphology, especially with early Cambrian organisms which rely on subtle character differences to identify species.
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