THE FIRST DISASTER TAXA: VENDOTAENIDS AND THE EDIACARAN EXTINCTION

The Ediacaran-Cambrian boundary marks a critical transition point in the history of life, with the radiation of modern animal phyla preceded by two extinction events that together constitute the Kotlinian Crisis. This crisis is defined by an observed drop in diversity between the White Sea and Nama assemblages, followed by the complete disappearance of the Ediacaran biota at the end of the Ediacaran period. However, some taxa persisted through the crisis. Vendotaenia, a planktonic macroalgae, is one such organism, which has been suggested to have thrived during the crisis, though this observation lacks quantitative support. Here, we document a large number of Vendotaenia specimens from drill core samples of the Nama Group in Namibia, which encompasses the decline of the Ediacaran biota at the end of the Ediacaran Period. We used integrated observations from light and scanning electron microscopy to analyze the morphology and taxonomic affinity of the Vendotaenia specimens. Our analysis reveals that the observed vendotaenids represent a single morphotype of tubular macroalgae which were likely planktonic in nature. Their abundance and temporal occurrence after the first extinction pulse make Vendotaenia a classic example of a disaster taxon. Thus, like Phanerozoic mass extinctions, the Kotlinian Crisis is characterized by the decimation of many species, a transient proliferation of several disaster taxa, and subsequent diversification of a new cohort of life.