The first data on the role of rhyncholites in the process of epibiota

For the first time the role of rhyncholites in the process of epibiota has been figured out. Serpulidae inlay is detected in 39 rhyncholites of 979 specimens, representing 4% of the all studied material. This fact demonstrates that rhyncholites were used extremely rarely by encrusting species as a substrate. No other epibionts were found. Polychaetes were found in the genus Hadrocheilus (87%) and in the genus Akidocheilus. Size of the inlaid rhyncholites ranges from 7 to 23 mm. Serpulidae cover usually only the ventral side of rhyncholites, herewith, at 48,7% of the samples epibionts with different degrees of intensity are developed throughout the ventral surface, at 30,7% of the samples they are observed only on the ventral side of the hood and at 20,6% serpulidae are present only on the ventral surface of the arm. At four exemplars of the genus Hadrocheilus (10 % of the total amount) polychaetes are developed on the dorsal surface, but they are always and usually very wide developed on the ventral side of rhyncholites. No samples were found in which serpulidae were found only on the dorsal surface. Among the remains of polychaete worms, large and small tubes were identified and described. The presence of serpulidae on the handle of rhyncholites, that during the life of the cephalopod mollusk was located in a horny jaw, is a clear indication of the settlement’s epibionts on isolated skeletal structures of the already dead cephalopod. Cases when serpulidae are observed only on the ventral side of the hood in representatives of the genus Akidocheilus, suggest that planktonic trochophore – larvae of polychaetes can settle on the inner surface of the mandible of living ammonoids, where they turned into an adult worm. At the same time, polychaetes gained access not only to traditional prey, represented by various microscopic organisms, but also to additional food resources associated with the life activity of cephalopodas.

rhyncholites, serpulidae, epibiota, Lower Cretaceous, South–Western Crimea

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