A rare occurrence of matched otoliths and associated skeletal remains of Apogon townsendi (Osteichthyes) from the Caloosahatchee Formation (lower Pleistocene) of Florida

Abstract

A matched pair of otoliths (right and left saccular otoliths) and associated skeletal remains (n = 107) of Apogon townsendi (belted cardinalfish) were obtained in unconsolidated sediment from inside the valves of an articulated scallop Carolinapecten eboreus. The scallop specimen was collected in Hendry County, Florida, from the lower Pleistocene Caloosahatchee Formation, approximately 1.7 to 2.1 Ma. The recovery of this vertebrate material is highly significant because no skeletal remains of bony fish with in situ or associated otoliths are known from the Gulf or Atlantic coasts of the United States. Furthermore, the specimen represents the first fossil record of the family Apogonidae and the genus Apogon from Florida and the first report of the species Apogon townsendi in the fossil record. The length of the fossil Apogon townsendi was determined to be 4.7 cm based on the linear relationship between fish length and otolith length and utilizing modern specimens of the species for comparison and analysis. The length of the fossil Apogon townsendi indicated that it was an adult fish upon death (> 2.1 cm). Although several taphonomic scenarios are considered, including commensalism, it is believed that the apogonid died in close proximity to the empty scallop shell, which was followed by fairly rapid washing in of sediment with the fish into the valves of the scallop (i.e., sediment trapping). This determination is based on several factors including the biology, distribution, and behavior of extant Apogon townsendi. The presence and preservation of the two matched saccular otoliths and the large number of associated, fragile skeletal remains in the scallop shell suggest that the apogonid was not ingested and excreted by a piscivorous predator.