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Curator’s Choice
Form and Function:
A Tribute to Adolf Seilacher
Epizoans Provide Evidence of Host Biology
Ceratites semipartitus
Middle Triassic, Germany
YPM.200327
| Since ammonoids are extinct, we cannot observe them directly. Dr. Seilacher used “hitch-hikers” on the ammonoid shell to interpret its lifestyle. This ammonoid is covered with epizoans (animals that attach themselves to the surface of other animals). These epizoans include bivalves, brachiopods, gastropods and serpulid worms. Commonly, epizoans attach to shells of dead animals as they lie with one side on the sea floor. In this case epizoans encrust both sides of this shell, indicating that they attached to the shell while the ammonoid was alive and swimming. Most of the encrusters show a preferred orientation, that facilitated feeding and respiration. The orientation of the encrusters on the host indicates that the ammonoid did not jet quickly through the water, but floated and swam slowly near the seabed. |