Anomia-associated bryozoans from the upper pliocene (Piacenzian) lower tamiami formation of Florida, USA

Commercial mining northeast of Sarasota, SW Florida (USA), since the 1960s has exposed Plio-Pleistocene marine shell beds of the Tamiami Formation, a complex sequence of mixed carbonate and siliciclastic beds containing a malacofauna that is a mixture of subtropical and temperate species. Material used for the current study consists of shells of the bivalve Anomia simplex d’Orbigny, 1853 encrusted by bryozoans. The shells were collected from Units 10/11 of the lower Tamiami Formation, estimated as being late Pliocene (Piacenzian). This paper describes the bryozoan fauna associated with these ‘jingle shells’, which is of relatively low diversity, totaling 29 species, and comprises one cyclostome and 28 cheilostomes. Six cheilostome species are new: Micropora stellata sp. nov., Microporella sarasotaensis sp. nov., Microporella tamiamiensis sp. nov., Pourtalesella chiarae sp. nov., Spiniflabellum laurae sp. nov., and Trypostega composita sp. nov. Of the previously described species, six are extant and have western Atlantic distributions, while 12 species are known only from the fossil record. The bulk of the assemblage comprises a limited number of species represented by hundreds of colonies, while the remaining species are rare and represented by a single or a few colonies. Colonization of the shells is likely to have happened postmortem, considering the high percentage of valves encrusted on both surfaces. A large number of overgrowth interactions have been observed among the bryozoan colonies, thus this taxonomic revision is the necessary baseline for ecological analyses aiming to establish a ranking of species in a competitive hierarchy.