Growth and disparity of form in the Ediacaran genus Charnia, with description of Charnia brasieri sp. nov. from the Ediacaran of Avalonia

Graphical abstract in support of "The Novel Ediacaran Rangeomorph Charnia brasieri from the Inner Meadow Lagerstätte. • The novel, new, Ediacaran rangeomorph fossil Charnia brasieri is described and reconstructed in 3D for the first time. • Charnia brasieri is recognized as having a branch architecture that raised the axis above the seafloor. • Computational fluid dynamics is applied to the conceptual 3D models to assess interactions with seafloor currents. • Charnia brasieri and similar forms are considered to be procumbent epibenthic suspension feeders with chemosymbionts. The Ediacaran of Newfoundland continues to yield a diverse biota of complex macro-organisms that records the early evolution of the Eumetazoa. The exceptional preservation of Rangeomorpha from the Fermeuse Formation at the Inner Meadow fossil site in Conception Bay, Newfoundland has allowed the recognition of a novel form of the genus Charnia with falcate first order branches that we describe as Charnia brasieri sp. nov. herein. Three dimensional reconstructions using pre-established conceptual models have predicted a central lumen to all first order branches, which is supported by the new Inner Meadow material. The inferred frond architecture of C. brasieri is sculpted in three dimensions herein and studied using computational fluid dynamics, which gives insights in the flow in and around the fossil organisms thereby informing its possible mode of life as procumbent epibenthic organism. The falcate branching that characterizes Charnia brasieri sp. nov. is also seen in material previously described as C. grandis from the UK and Newfoundland. In reviewing the original diagnosis and figured material, we find C. grandis to be a distinct and valid taxon, reject its recent synonymization with C. masoni , and recognize its occurrence in the Ediacaran of Newfoundland. The large Charnia with falcate branching from Newfoundland and the UK are herein attributed to C. brasieri, with large size not being considered a valid taxobase. This work strongly suggests that Charnia is a long-lived, highly stable and morphologically-diverse genus characterized by rotated and furled rangeomorph branches, as conceptualized by Martin Brasier. The taphonomic and preservational insights from this work allow recognition of the lumina of Charnia and will require reconsideration of the palaeobiology of other members of the family Charniidae.