Abstract

Charniodiscus is a leaf-shaped Ediacaran (terminal Neoproterozoic) fossil with a worldwide distribution, but the scarcity of complete specimens has previously hindered evaluation of its taxonomy and ecology. The presence of hundreds of complete (fronds with stem and disc attached) Charniodiscus specimens from the Avalon Zone of Newfoundland has allowed for detailed morphometric analysis of Charniodiscus specimens and permits determination of characteristics which vary with growth (e.g., stem length, frond width, and disc diameter) versus those that reflect taxonomic differences (e.g., number of primary segments, presence of a distal spine, shape ratios). This has led to the recognition of three species of Charniodiscus in the Mistaken Point biota, including numerous specimens of two new taxa, C. procerus n. sp. and C. spinosus n. sp., and rare specimens of the Australian species C. arboreus. C. procerus n. sp. and C. spinosus n. sp. represent similar, yet ecologically distinct forms of upper-level filter feeders with diverging feeding strategies in order to reduce the competition for resources. Ratio plots and principal components analyses (PCAs) confirm the existence of five (possibly six) morphologically distinct species of Charniodiscus worldwide.

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