AN EXCEPTIONAL MARINE FOSSIL FISH ASSEMBLAGE REVEALS A HIGHLY PRODUCTIVE DEEP-WATER ENVIRONMENT IN THE CENTRAL AMERICAN SEAWAY DURING THE LATE MIOCENE

We report the discovery of a previously undescribed late Miocene (~ 6 Ma) marine Caribbean fossil fish assemblage located at the Chagres Formation (Panama Canal Basin). Our preliminary taxonomic results show that this assemblage is characterized by 47 species. These include microfossils, such fish otoliths (n = 821), and macrofossils, as represented by shark teeth (n = 257) and billfishes (n = 12). The billfishes are the most distinctive taxon in this assemblage, and are represented by vertebrae, rostra, and a nearly complete skeleton. The extraordinary preservation indicates that the site may be regarded as a concentration largestatten. The bathymetric ranges of related and extant species in this fossil assemblage indicate that it accumulated in between 100 m and 700m of water depth. Moreover, the relatively high abundance of the shark Isistius triangulus (a small pelagic organism that preyed on large fish and marine mammals) and bathypelagic to mesopelagic fishes which given its life habit needs nocturnal vertical migrations, suggest the presence of large fish shoals, shark schools, and that the fossil assemblage occurred in an oceanic upwelling system. Even though recent geological studies on the tectonic evolution of the Panamanian Isthmus indicate closure of the Central American Seaway around 15 Ma our study suggests the existence of a marine Caribbean-Pacific connection during the latest Miocene (~ 6Ma).