Produced by the Population Genetics and Evolution class, Furman University

The Ordovician: The 'bioerosion revolution'
During the Ordovician period, there was a significant increase in "boring fauna" that caused the bioerosion of hard carbonate substrates produced by organisms such as corals and carbonate sponges (stromatoporoids). There were over six different macroboring "ichnogenera" (trace fossil genera), separate from Oichnus drill borings on mollusc shells (Wilson and Palmer 2001). One of the macroborings is known as Trypanites, which is an important bioeroder of calcium carbonate substrates (Wilson and Palmer 2006). They were worm boring organisms that excavated over 40% of the corals that have been examined (Tapanilla et al. 2004). Palaeosabella were long and cylindrical, and they were very similar to Trypanites. However, the most common borings were made by Gastrochaenolites, which bored into thick shells and carbonate hardgrounds. A few other important types include Petroxestes, which are the earliest know borings by bivalves, and Cicatricula, which are possibly the earliest borings of true sponges. While the different types of macroborings have been discovered, it is still hard to measure the intensity of boring. This is the number of borings per unit of hard substrate area; however, it is difficult to measure due to the amount of time it has been exposed to the elements of the seafloor Wilson and Palmer 2006). The importance of this 'bioerosion revolution' is that is demonstrates that many organisms were adapting to the hard parts evolved by other species; either as preators adapting drilling strategies, or as anchoring strategies to hold fast to the hard substrate.

Page by Lindsay Gerzel
Penetration of Clathrodictyon by Trypanites (T). Tapanila et al. 2004.

Tapanila L, Copper P, Edinger E. 2004. Environmental and substrate control on Paleozoic Bioerosion in corals and stromatoporoids, Anticosti Island, Eastern Canada. Palaios 19:292-306.

Wilson MA, Palmer TJ. 2006. Patterns and processes in the Ordovician bioerosion revolution. 2006. Ichnos 13:109-112.

Wilson MA, Palmer TJ. 2001. The Ordovician bioerosion revolution. GSA Annual Meeting. November 7, 2001.