NEW INSIGHT INTO THE GLOBAL RECORD OF THE EDIACARAN TUBULAR MORPHOTYPE: A COMMON SOLUTION TO EARLY MULTICELLULARITY

The Ediacaran tubular morphogroup is globally distributed, has intriguing links to metazoan phyla, and is the most commonly occurring morphogroup in the Nama Assemblage (~550-538 Ma) of the Ediacara Biota, the oldest record of multicellular animals. However, tubular taxa of the older White Sea Assemblage (~558-550 Ma) are comparatively understudied despite their high abundance and potential to contextualize the high diversity of tubular organisms in the Nama Assemblage, which is critical for determining the scale of the purported radiation of tubular taxa in the Nama Assemblage and for understanding their role in Earth’s earliest complex communities. This is further complicated by a mass extinction occurring between the White Sea and the Nama assemblages. To test whether the radiation of tubular organisms in the Nama Assemblage represents a true increase in diversity, we constructed a database of all non-biomineral Ediacaran tubular taxa. Synthesis of the database informs the proposal of three new form-based subgroupings including tubiform, conotubular, and ovatubular taxa. Further, it reveals that tubular organisms are represented by the same number of genera in the White Sea and the Nama assemblages, demonstrating that the number of non-biomineral tubular genera did not increase across the White Sea-Nama transition. However, the variability of the original compositions of tubular organisms in the Nama Assemblage is found to increase. Thus, a tubular form is shown to have been a commonly converged solution to multicellularity prior to the Nama Assemblage, but understanding of the Nama Assemblage as a period of increased tubular complexity is upheld.