MOLLUSKS FROM THE MIDDLE TO UPPER EOCENE OCALA LIMESTONE (FLORIDA, USA)

In Florida, the middle to upper Eocene Ocala Limestone occurs in limited exposures across the Panhandle and in widespread exposures around the northwestern portion of the peninsula. This relatively pure carbonate unit contains a wide variety of fossil invertebrates, some of which (e.g., Echinodermata and Bryozoa) have received considerable attention. However, the Mollusca has yet to be thoroughly examined and documented, which is most likely due to the moldic preservation of shells originally consisting of aragonite (e.g., bivalve genera Clavagella and Pholadomya and gastropod genera Campanile and Entemnotrochus). Shells originally consisting of calcite are preserved as body fossils – these include oysters (e.g., Nayadina and Hyotissa) and scallops (e.g., Amusium and Chlamys).

As a function of these varied modes of preservation, a comprehensive treatment of this molluscan fauna, particularly the moldic mollusks, currently does not exist. This is due, as alluded to previously, to the difficultly in studying moldic invertebrates, as workers must contend with only internal and external molds, rather than the complete body fossils. Researchers at the Florida Museum of Natural History (FLMNH) have circumvented this problem by creating replicas of the body fossils. This technique utilizes Room Temperature Vulcanizing (RTV) silicone rubber “peels,” which allow for the moldic mollusks to be studied in greater detail.

This preliminary report, based on currently curated material in the FLMNH Invertebrate Paleontology (IP) collection, documents 30 families of Bivalvia (55 genera), 35 families of Gastropoda (60 genera), and one family/genus of Cephalopoda. These mollusks indicate a variety of life modes, from rock boring to algal grazing and reflect a variety of shallow marine depositional settings (e.g., hardgrounds and firm muds). With additional curatorial efforts, we plan to provide a comprehensive overview of the mollusks found in the middle to upper Eocene Ocala Limestone.