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The archaeocyathids are a rather obscure group of calcifying sponges. They were abundant during the early Cambrian, but declined in diversity and abundance during the late Cambrian, with the last species going extinct just before the start of the Ordovician.

They were the dominant reef-building organisms of the early Cambrian, and some of the first metazoan (muticellular) reef builders, constructing reef mounds alongside those made by stromatolites.

An archaeocyathid fossil from the Brasier Collection

An unusually well-preseved archaeocyathid from the Cambrian of Australia. This fossil is part of the Brasier Collection.


Archaeocyathids fed in a similar way to modern sponges, filtering plankton from the water column through pores in their sides. Their decline in the late Cambrian has been attributed to competition from more modern sponges.

The Brasier Collection contains a remarkable diversity of archaeocyathids, including the material associated with Brasier's 1976 publication Early Cambrian intergrowths of archaeocyathids, Renalcis, and pseudostromatolites from South Australia. It also contains material from other sites in Australia, Russia and Antarctica, such as hand specimens, polished rock slices, and thin sections.

Fossil stromatolites and archaeocyathids from the Brasier Collection


In this fossil, also from the Cambrian of Australia, stromatolites have grown up between the near-circular archaeocyathids, creating bands in the sediment.