AUTHOR=Pérez-Pinedo Daniel , McKean Christopher , Taylor Rod , Nicholls Robert , McIlroy Duncan 

TITLE=Charniodiscus and Arborea Are Separate Genera Within the Arboreomorpha: Using the Holotype of C. concentricus to Resolve a Taphonomic/Taxonomic Tangle

JOURNAL=Frontiers in Earth Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2021.785929

DOI=10.3389/feart.2021.785929

ISSN=2296-6463

ABSTRACT=<p><italic>Charniodiscus</italic> is one of the most iconic and first described of the Ediacaran frondose taxa. Since the diagnosis of the holotype of <italic>C. concentricus</italic> in 1958, the scarcity and poor preservation of unequivocal specimens has resulted in genus-level taxonomic uncertainty. Since the recent reinterpretation of <italic>C. concentricus</italic> as a multifoliate frond, other <italic>Charniodiscus</italic> species—all of which are bifoliate—have been left in taxonomic limbo, with most authors comparing them to the clade Arboreomorpha and also the Rangeomorpha. Reconsideration of the taphonomy of the holotype of <italic>C. concentricus</italic> has revealed that the frond is bifoliate as first described, and also that the frondose portion was broadly conical rather than planar as previously inferred. The conical frond of <italic>Charniodiscus</italic> is thus morphologically quite different from all other frondose taxa within the Arboreomorpha. Our emendation of the generic diagnosis of <italic>Charniodiscus</italic> to encompass bifoliate arboreomorphs with conical fronds without a backing sheet distinguishes <italic>Charniodiscus concentricus</italic> and <italic>C. procerus</italic> from more planar leaf-like arboreomorphs such as <italic>Arborea arborea, A. longa and A. spinosa,</italic> all of which have a distinctive backing sheet. Additionally, we find no evidence of rangeomorph-type fractal branching in <italic>Charniodiscus</italic>.</p>