# Dawn of diverse shelled and carbonaceous animal microfossils at ~ 571 Ma

## TL;DR

This paper reports the discovery of diverse animal microfossils in Brazil, dating back to 571 million years ago, suggesting an earlier diversification of metazoans than previously known.

## Contribution

The study presents the earliest known record of biomineralized and carbonaceous animal microfossils, predating the Ediacaran biomineralized macrofossils.

## Key findings

- Microfossils from the Bocaina Formation are dated to 571 ± 9 Ma, earlier than the Cloudina-Corumbella-Namacalathus biozone.
- The microfossils include biomineralized structures similar to cloudinids, protoconodonts, anabaritids, and hyolithids.
- The discovery indicates an earlier diversification of metazoans, including organo-phosphatic animal coverings.

## Abstract

The Ediacaran-Cambrian transition documents a critical stage in the diversification of animals. The global fossil record documents the appearance of cloudinomorphs and other shelled tubular organisms followed by non-biomineralized small carbonaceous fossils and by the highly diversified small shelly fossils between ~ 550 and 530 Ma. Here, we report diverse microfossils in thin sections and hand samples from the Ediacaran Bocaina Formation, Brazil, separated into five descriptive categories: elongate solid structures (ES); elongate filled structures (EF); two types of equidimensional structures (EQ 1 and 2) and elongate hollow structures with coiled ends (CE). These specimens, interpreted as diversified candidate metazoans, predate the latest Ediacaran biomineralized index macrofossils of the Cloudina-Corumbella-Namacalathus biozone in the overlying Tamengo Formation. Our new carbonate U–Pb ages for the Bocaina Formation, position this novel fossil record at 571 ± 9 Ma (weighted mean age). Thus, our data point to diversification of metazoans, including biomineralized specimens reminiscent of sections of cloudinids, protoconodonts, anabaritids, and hyolithids, in addition to organo-phosphatic surficial coverings of animals, demonstrably earlier than the record of the earliest known skeletonized metazoan fossils.