THE JONES BRANCH LOCAL FAUNA: AN EARLY ARIKAREEAN MAMMALIAN ASSEMBLAGE FROM THE LATE OLIGOCENE MARGINAL MARINE BASAL CATAHOULA CLAY, WAYNE COUNTY, MISSISSIPPI

A preliminary report on a diverse assemblage of mammals from near Waynesboro, southeastern Mississippi, was presented at the annual meeting of the Southeastern Association of Vertebrate Paleontology in 2013. Continued work at the site, and further study of new and previously recovered fossils, prompts the update provided here. The fossils are derived from a lag deposit at the base of the Catahoula Formation that rests unconformably on interbedded marl-clay beds of the subjacent marine Paynes Hammock Formation. To date, the mammalian component of the fauna includes a leporid, rodents, carnivores, artiodactyls, perissodactyls, and a small dugong. Additionally recovered is a single, enigmatic upper molar that may belong to a second North American Oligocene primate.

Regarding the age of the fauna, the presence of a eutypomyid castorid, the tapir Protapirus, and the anthracothere Elomeryx support an early early Arikareean age, as those taxa are reported to last occur in that NALMA subage. All three of those occurrences are firsts for the Gulf Coastal Plain. Although not yet studied in detail, the rhinoceros material appears to be referable to Subhyracodon, another taxon that last occurs in Ar1, and the horses include Miohippus and Anchippus. In addition to the anthracothere, other artiodactyls include the giant entelodont Daeodon, which first appears in Ar1, a peccary, a very small taxon resembling Hypisodus or a small species of Hypertragulus, and a small protoceratid similar to Prosynthetoceras orthrionanus from the later Arikareean Toledo Bend Local Fauna of easternmost Texas. Like the Toledo Bend LF, the Jones Branch LF lacks camels and oreodonts. Two of three small carnivores appear representative of small borophagine canids, and the third is a “mustelid-like” species superficially resembling “Plesictis.” The sirenian is a very small species, even smaller than the two known western Atlantic Oligocene dugongids, Metaxytherium albifontanum and Crenatosiren olseni. As noted above, a small enigmatic upper cheek tooth suggests the occurrence of a primate-like species. The tooth is not that of Ekgmowechashala, known from the early Arikareean of Oregon and South Dakota, and possibly from the Toledo Bend LF, thus inferring that a second late occurring primate may have persisted into the Oligocene along the Gulf Coast.