Brasier Highlights: Stromatolites
Discover specimens that are not currently on display
The Cambrian Explosion: Archaeocyathids
The Cambrian Explosion was a period of animal evolution that saw the replacement of the enigmatic Ediacaran organisms with representatives of many modern animal groups, many of which had hard, mineralising skeletons. Cloudina and Namacalathus disappeared along with the Ediacaran organisms, and their position alongside stromatolites in reefs was occupied by a curious group of skeleton-building sponges called archaeocyathids.
Like modern sponges, Archaeocyathids grew as vase-shaped columns that fed by filtering tiny particles, such as plankton, from the water column. Archaeocyathids declined towards the end of the Cambrian, possibly due to competition with other groups of sponges, but they were incredibly abundant and diverse in their heyday.
The last of the Archaeocyathids went extinct at the end of the Cambrian, and corals soon emerged as the predominant reef-building organisms of the next geological period, the Ordovician. These corals were very different from the ones that we see in reefs in the modern day, but the importance of corals to reef-building has persisted since.
Left: An archaeocyathid fossil from the Cambrian of Australia. This is an exceptional specimen from the Brasier Collection, with individual feeding pores that can be made out along the length of the body. Right: A cross-section of an Australian archaeocyathid, also from the Brasier collection. The chambered wall is clearly visible.