THROWING THE KITCHEN SINK AT CLOUDINA: A REEVALUATION

One of the current major goals of the Subcommission on Ediacaran Stratigraphy (International Commission on Stratigraphy) is to define Stage-level subdivisions for the Ediacaran Period. Specifically for a terminal Ediacaran Stage, the utility of the globally distributed biomineral or lightly mineralized tubular fossils cannot be overlooked. They are easily recognized in the fossil record and occur, largely, in similar depositional environments, although with differing taphonomic histories. Of these forms, Cloudina is the most well-known and can be distinguished by its characteristic multilayered and nested tubular construction, often called a “funnel-in-funnel” morphology. Cloudina was first described in 1985 by Hahn and Pflug and since then has, perhaps unfortunately, acted as a catch-all generic moniker for any small, mineralized, nested, tubular fossil of late Ediacaran age. The literature reports Cloudina with a high degree of morphological variation, preservational quality, and variety of different taphonomic modes. As major effort towards confirming whether this genus serves as a reliable index fossil for defining the terminal Ediacaran Stage, we must first taxonomically reevaluate global examples of Cloudina using modern tools and techniques. Herein we consider both reports from the literature and new data from both hand specimens and thin sections from a variety of different occurrences (Nevada and California, United States; Mexico; Spain; South China; Namibia) using a myriad of analytical techniques (light microscopy, scanning electron microscopy, and X-ray tomographic microscopy) to tackle this issue from every possible angle.