SIGNIFICANCE OF EARLY PALEOCENE FISH OTOLITHS FROM TWO CLAYTON FORMATION (DANIAN) SITES IN CENTRAL ARKANSAS

The published record of Paleocene bony fish otoliths is quite limited worldwide, and this is especially evident in North America. Only three studies on Paleocene otolith assemblages have been published from North America, and only one of these is from the United States. Consequently, the occurrence of otoliths in the Clayton Formation (Paleocene, Danian) at two sites in central Arkansas (Hot Spring and Saline counties) is quite significant. Approximately 300 otolith specimens from the sites were preserved well enough for identification, but there were hundreds of broken and unidentifiable specimens. The teleostean otolith assemblage from the Clayton Formation represents the oldest known Paleocene otoliths in the United States and the first occurrence of Paleocene otoliths in Arkansas. The otoliths are important in providing pertinent taxonomic, paleoecologic, and evolutionary data that would not be possible based solely on the skeletal remains of bony fishes. Additionally, skeletal remains of bony fishes are quite limited in the Clayton Formation at the I-30/Rockport Site and the McNeil Creek Site making the otoliths even more useful. Limitations to this study are duly noted as many of the otoliths are poorly preserved and extremely friable. Even with these deterrents, analysis of the otoliths indicated the presence of bony fishes representing at least 8 orders, 14 families, and 25 taxa. The otolith assemblage represented primarily neritic fishes expected in tropical and subtropical, coastal and shallow marine settings. The otoliths were dominated by ariids (sea catfishes), albulids (bonefishes), and heterenchylids (mud eels) at both the I-30/Rockport Site and the McNeil Creek Site (approximately 70% and 80% respectively). The heterenchylids are of special interest since the extant forms represent a small family of burrowing eels with a center of diversity on the Atlantic coast of Africa. Their abundance in the Paleocene points to greater diversity and distribution in the geologic past. The early Paleocene Clayton Formation otoliths (primarily NP1 – NP2 calcareous nannofossil zones or approximately 63 – 66 Ma) afford an exceptional opportunity to examine the bony fishes not long after the Cretaceous/Paleogene extinction and to glean insight into the paleoecology of the early Paleocene in central Arkansas.