The Fossil of the Week series is no longer weekly, and the gnarly specimen above is not actually a fossil, but the brand is so embedded in this blog that I’m still using it for occasional contributions.
Like the specimen posted last week, the above holey shell is a gift from my friend Al Curran, an emeritus professor at Smith College, He collected it on Anastasia Island, Florida, at the Matanzas Inlet. This location has very strong tidal exchanges and a mix of shells from the inter-coastal waterway and the open Atlantic Ocean.
The calcareous shell is from a bivalve, probably the common Mercenaria merenaria. The network of holes are borings of clionaid sponges, producing the trace fossil Entobia. This surviving remnant of this bivalve shell shows the incredible destructive power of bioerosion. The missing carbonate has been converted to microscopic chips, contributing to muddy carbonate sediments along the Florida coastline.
The wonderfully complex interior of these clionaid sponge borings.
Thanks again to Al Curran!