The Fossil of the Week series is no longer weekly, and the beautiful specimen above is not actually a fossil, but the brand is so embedded in this blog that I’m going to use it!
My friend Al Curran, an emeritus professor at Smith College, sent me this specimen he collected 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 shell is from an oyster that most likely lived in the inlet, and the brown-orange encruster is a cheilostome bryozoan from the ocean proper. The abundant holes are borings of clionaid sponges, also fully marine in origin.
The underside of the oyster shows more of the bryozoan. It is heavily eroded, showing the sequential layers of its growth. Inside the cavity is a thin encrusting tube from a serpulid worm. These worm tubes are often found in cavities like this because they prefer cryptic spaces.
These are among my favorite types of organisms in the fossil record and the Recent. They are sclerobionts — organisms that live in or on hard substrates.
Thanks for this fun little community, Al. It is now part of Wooster’s paleoecology collections!