Animal reef-building evolved millions of years earlier than previously thought, researchers report today in Science1. Scientists have discovered fossils indicating that animal, or metazoan, reefs date to as far back as about 548 million years ago, some seven million years earlier than previously estimated. This suggests they appeared prior to the Cambrian explosion, a wellspring of diverse life that is generally thought to have driven the proliferation of reef-building.
Here’s the abstract:
Reef-building in metazoans represents an important ecological innovation whereby individuals collectively enhance feeding efficiency and gain protection from competitors and predation. The appearance of metazoan reefs in the fossil record therefore indicates an adaptive response to complex ecological pressures. In the Nama Group, Namibia, we found evidence of reef-building by the earliest known skeletal metazoan, the globally distributed Cloudina, ~548 million years ago. These Cloudina reefs formed open frameworks without a microbial component but with mutual attachment and cementation between individuals. Orientated growth implies a passive suspension-feeding habit into nutrient-rich currents. The characteristics of Cloudina support the view that metazoan reef-building was promoted by the rise of substrate competitors and predators. (paywall)
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