Prey fractionation in the Archaeocyatha and its implication for the ecology of the first animal reef systems

Archaeocyaths are the most abundant sponges from the Cambrian period, forming the first animal reef communities over 500 million years ago. The Archaeocyatha are index fossils for correlating rocks of similar ages globally, because of their abundance, extensive geographic distribution, their detailed anatomy and well established taxonomy. Their ecological significance remains incompletely explored yet they are known to strongly competitively interact unlike modern sponges. This study examines the feeding ecology of the fossil remains of Siberian archaeocyath assemblages. As suspension feeders, archaeocyaths filtered plankton from the water column through pores in their outer wall. Here we outline a new method to estimate the limit on the upper size of plankton that could be consumed by an archaeocyath during life. The archaeocyaths examined were predominantly feeding on nanoplankton and microplankton such as phytoplankton and protozooplankton. Size-frequency distributions of pore sizes ...