TERRESTRIAL CARNIVORES, ARTIODACTYLS, PERISSODACTYLS, AND PROBOSCIDEANS OF THE FORT POLK MIOCENE SITES OF LOUISIANA

Terrestrial Miocene mammals have been recovered from outcrops of the Castor Creek Member of the Fleming Formation on Fort Polk in western Louisiana for the last eighteen years. Most fossils are associated with concentrations of soil-formed nodules produced in a period of regression. Small vertebrates are usually recovered by dissolving these concentrations in dilute acetic acid and screening the residue. Over 6,000 catalogued small mammal specimens, mainly rodents, have been recovered, providing information on environments of the larger mammals. Percentages of the abundant rodent types were used for estimation of relative amounts of forest and open areas at Fort Polk sites. Cricetid rodents prefer wooded areas. Low percentages of cricetids had been interpreted to indicate a relatively more open and possibly drier situation at Discovery Site, the stratigraphically highest site.

Over the years, occasional specimens of larger mammals, Carnivora (Cynarctus, Bassariscus, and Miomustela), Artiodactyla (Dyseohyus, cf. Merychyus,?Aepycamelus, cf. Pseudoparablastomeryx, Prosynthetoceras), Perissodactyla (Merychippus, Cormohipparion, Aphelops), and Proboscidea (Gomphotherium) have been recovered, through surface search, quarrying, and screening. Texas and Louisiana sites in the Fleming Formation are difficult to correlate due to their occurrence in relatively isolated outcrops in heavily vegetated areas, and research at most Texas sites did not involve much screening. The Louisiana artiodactyls and perissodactyls such as Prosynthetocerus francisi provide the strongest support for considering the Fort Polk Miocene sites to fall in the early late Barstovian Land Mammal Age. The Fort Polk Miocene sites, even the stratigraphically lowest marine one, are correlative to the Cold Spring Local Fauna from east Texas and fall after the Middle Miocene Climatic Optimum, in a cooler period marked by marine regression.