Eocene Terrestrial Mammals From Central Georgia

Descriptions of fossils of Eocene terrestrial mammals from the southeastern United States are rare, and particularly so in the Eocene sediments of Georgia. Here we describe a small collection of fossilized teeth and tooth fragments representing four mammalian taxa. The fossils were recovered by surface collecting overburden sediments and screen washing in situ Clinchfield Formation sediments exposed in an inactive kaolin mine, Hardie Mine, in Wilkinson County, Georgia. The Clinchfield Formation has been described as a Late Eocene coastal unit with abundant gastropods, bivalves, sharks, and rays. This is the first detailed description of terrestrial mammals from this unit. Although limited in diversity, this collection represents the most diverse Eocene-aged mammalian fauna described for the state

Generation of a Convalescent Model of Virulent Francisella tularensis Infection for Assessment of Host Requirements for Survival of Tularemia

Francisella tularensis is a facultative intracellular bacterium and the causative agent of tularemia. Development of novel vaccines and therapeutics for tularemia has been hampered by the lack of understanding of which immune components are required to survive infection. Defining these requirements for protection against virulent F. tularensis, such as strain SchuS4, has been difficult since experimentally infected animals typically die within 5 days after exposure to as few as 10 bacteria. Such a short mean time to death typically precludes development, and therefore assessment, of immune responses directed against virulent F. tularensis. To enable identification of the components of the immune system that are required for survival of virulent F. tularensis, we developed a convalescent model of tularemia in C57Bl/6 mice using low dose antibiotic therapy in which the host immune response is ultimately responsible for clearance of the bacterium. Using this model we demonstrate αβTCR+ cells, γδTCR+ cells, and B cells are necessary to survive primary SchuS4 infection. Analysis of mice deficient in specific soluble mediators shows that IL-12p40 and IL-12p35 are essential for survival of SchuS4 infection. We also show that IFN-γ is required for survival of SchuS4 infection since mice lacking IFN-γR succumb to disease during the course of antibiotic therapy. Finally, we found that both CD4+ and CD8+ cells are the primary producers of IFN-γand that γδTCR+ cells and NK cells make a minimal contribution toward production of this cytokine throughout infection. Together these data provide a novel model that identifies key cells and cytokines required for survival or exacerbation of infection with virulent F. tularensis and provides evidence that this model will be a useful tool for better understanding the dynamics of tularemia infection

Vertebrate Fossils From a New Locality in Wilkinson County, Georgia

Recent exploration of a fossiliferous horizon in an active kaolin mine in Wilkinson County, Georgia has produced an array of fossils of marine vertebrates. The objective of this study is to identify and curate this new fossil collection. The collection is dominated by Eocene-aged sharks teeth belonging to the Sand Tiger Shark (Charcharis), but also includes teeth from Tiger Sharks (Galeocerdo), Snaggletooth Sharks (Hemipristis), Angel Sharks (Squatina), Sawfish Sharks (Pristis), Extinct Sawfish (Propristis), and Megatooth Sharks (Carcharocles). Rays are represented by a number of dental plates and tail spines (cf. Myliobatis). At least one species of turtle (Trionychidae) is represented by multiple shell fragments. Several vertebrae from an extinct “sea snake” (Pterosphenus) have been recovered as well. Additionally, two cetacean vertebrae have also been recovered. Most of these taxa have been interpreted as shallow water, near shore animals. These fossils add to our knowledge of the geographic distribution of these taxa and the paleoenvironments of central Georgia during the Eocene

DESCRIPTION OF EOCENE-AGED MAMMAL FOSSILS FROM WILKINSON COUNTY, GEORGIA

Eocene-aged fossils are known from many localities across the United States (US) with the richest beds being found in the western US. However, descriptions of Eocene-aged terrestrial mammal fossils from the southeastern US are rare, and particularly so in the Eocene sediments of Georgia. The materials analyzed in this study were obtained from several years (1998 to 2005) of surface collecting in fossiliferous sediments exposed in an inactive kaolin mine in Wilkinson County, central Georgia. At this locality, the removal of overburden and excavation of kaolinite has exposed Eocene-aged sediments of the Clinchfield Formation. The Clinchfield sediments represent deposits laid down in a near-shore environment and contain a variety of invertebrate and vertebrate fossils. The vertebrate material described to date includes numerous species of sharks, a chimaeroid fish, a colubrid snake, two genera of paleopheid snakes, five species of turtles, and an auk. Fossils of terrestrial mammals from this unit have not been previously described. Here we describe a small collection of fossilized teeth or tooth fragments representing four mammalian taxa. Although limited in diversity, this collection represents the most diverse Eocene-aged mammalian fauna described for the state. The taxa recovered from this locality include a carnivore, lagomorph (rabbit), brothotherid (large herbivore), and primitive rhinoceros