AN ENCHODUS FISH JAW FROM THE COON CREEK FORMATION (CAMPANIAN) OF WEST TENNESSEE

The Coon Creek Formation is a Late Cretaceous (Campanian) deposit consisting of greenish-brown, glauconitic, sandy-marl deposited within the nascent Mississippi Embayment currently cropping-out in a North-South trending belt just west of the Tennessee River in West Tennessee. The Coon Creek Formation is best known for the immaculate preservation and abundance of invertebrate fossils, along with lesser occurrences of mosasaur, plesiosaur, turtle, and shark teeth. Fish fossils are dominated by isolated vertebrae and otoliths. One of the more prevalent fish encountered in the deposit, primarily as isolated fang teeth, is the aulopiform actinopterygian teleost genus Enchodus. Jaw fragments of fish from the Coon Creek Formation are rare; historically, only a couple of jaw fragments have been reported, one of which was collected from a pit just a few hundred meters from the site for this specimen. Herein we describe a dentary of a well-preserved specimen of Enchodus? collected by an amateur fossil collector from the Sawmill Site locality (Decatur County, Tennessee). The dentary is the lower right and is 10.5 cm long, with a height (including teeth) ranging from 2.2 cm at its highest to .9 cm at its lowest. Eleven teeth are preserved, beginning with a 1.4 cm fang tooth (d1) followed by 10 more teeth along the dentary (d2-11). tooth D8 appears to be second small germ sabre-tooth. The jaw shows several gaps with no teeth and the sabre-teeth are shorter than other Enchodus teeth from this locality, suggesting this may have been a small or juvenile individual. This specimen is tentatively identified as Enchodus ferox Leidy, 1855.