Produced by the Population Genetics and Evolution class, Furman University

The Cambrian: Archaeocyathans
The lower Cambrian period marked the appearance of Archaeocyathans, a type of prolific marine organism. Some species were responsible for the first reef ecosystems, an important type of ecological community even today. This group radiated into many different species during this period, but they became extinct after a brief 10 or 15 million years (Collins and Waggoner 2006). Archaeocyanthans are thought to be relatives of our modern sponges. They possessed a calcium-based backbone and two stacked cones connected by septa, suggestive of a filter feeding mechanism like that of modern sponges. The image on the right demonstrates a cross-section of the inner and outer cones connected by a matrix of septa. As seafloor dwellers, they sometimes formed communities but were often found alone. They seem to have preferred a shallow, open seabed of carbonate with high oxygen availability (Kazlev 2002). An interesting feature of Archaeocyathans is their evolutionary trend towards increasingly complex branching of its cup morphology. Its simple shape early in the Cambrian progressed to branched shapes present in the majority of genera at the end of its history, suggesting an evolutionary advantage to this morphology (Wood 2001).

Page by Tory Grimm-Oropesa
Archaeocyath with coin for scale. Photo credit: UCMP

Collins AG, Waggoner B. 2006. Archaeocyatha. University of California Museum of Paleontology. Accessed February 2010.

Kazlev MA. 2002. Metazoa: Porifera: Archaeocyatha. www.palaeos.com. Accessed February 2010.

Wood, R. 2001. AccessScience: Encyclopedia Article: Archaeocyatha. McGraw-Hill’s Access Science Encyclopedia of Science and Technology Online.Accessed February 2010.