Life history and autecology of an Ediacaran index fossil: Development and dispersal of Cloudina

• Two different morphotypes of the Cloudina apical cone
• Ontogenetic sequence of Cloudina inferred by fossils
• Sexual and asexual reproduction and dispersal strategies in Cloudina

Cloudina is the best-known biomineralizing metazoan and a potential index fossil in the late Ediacaran Period, yet many aspects of its biology remain poorly understood. Previous reports have shown that Cloudina tubes grow from a basally closed funnel (or apical element), with occasional dichotomous branching. New material from the Ediacaran Beiwan Member of the Dengying Formation, South China, includes two distinct morphotypes—tubes with rounded versus pointed conical apices. In branching specimens, one of the daughter branches tends to have a conical apex. It is hypothesized that cloudinids with a spherical apex were derived from sexual reproduction, with their spherical termination representing the embryonic shell, whereas those with a conical apex are daughter branches detached from their parent tubes through asexual reproduction. These interpretations imply that Cloudina could reproduce both sexually and asexually, producing spherical embryonic shells and conical propagules, respectively. This strategy may have served to enhance dispersal, which was critical for the ecological success of early gregarious and sedentary animals such as Cloudina.

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