LATE PLEISTOCENE RODENTS FROM CLARK QUARRY, A VERTEBRATE FOSSIL LOCALITY IN SOUTHEASTERN GEORGIA

Clark Quarry is a Late Pleistocene fossil locality near Brunswick, GA, United States with a diverse vertebrate fauna. Morphological descriptions of Mammuthus columbi (Columbian Mammoth), snakes, amphibians, and birds from Clark Quarry have previously been completed along with a stable isotope analysis of M. columbi and Bison latifrons (Long-horned Bison) enamel. Herein, the rodent fauna is described using primarily teeth recovered by screen-washing quarry sediment. Nine rodent taxa have been identified, two of which are the extinct species Synaptomys australis (Florida Bog Lemming) and Neochoerus aesopi (Late Pleistocene Capybara). Of the remaining seven taxa, Erethizon dorsatum (North American Porcupine) and Neofiber alleni (Round-tailed Mustkrat) are extralimital compared to modern distributions. This is the first reported occurrence of Reithrodontomys humulis (Eastern Harvest Mouse) and Erethizon dorsatum from the Late Pleistocene of Georgia. The rodent fauna of Clark Quarry suggests a mostly open, grass-dominated environment with vegetated aquatic habitats nearby. This paleoenvironmental assessment agrees with previous paleoecological studies of M. columbi, B. latifrons, snakes, and birds from Clark Quarry

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

#35 - Enamel isotopes reveal late Pleistocene ecosystem dynamics in southeastern North America

The end of the late Pleistocene (~10,000 years ago) witnessed the extinction of over seventy percent of North America’s megafaunal genera. Although this pattern has been extensively investigated, its causal mechanisms remain elusive. Much of this difficulty is related to the spatial and temporal discontinuity of sites dating to the period leading up to the extinctions. Due to its removal from glacial conditions, southeastern North America provides a unique window into ecosystem dynamics just prior to human arrival in the region. In this study, we present new stable carbon and oxygen isotope data from Mammuthus columbiand Bison latifronsteeth collected from a well-dated Last Glacial Maximum (~20,000 rcybp) locality called Clark Quarry in coastal Georgia, USA. We compare these data to those from similarly aged (middle and late Rancholabrean) localities from Florida and demonstrate the presence of a vegetation gradient with elevated levels of C3vegetation at higher latitudes. We hypothesize that this pattern may have contributed to previously described migratory patterns of mastodon (Mammut) populations in southeastern North America. Serially-sampled δ13C and δ18O values suggest that Clark Quarry Mammuthus and Bison changed their diet seasonally with the incorporation of elevated quantities of C4vegetation during warmer periods. Our data indicate more exaggerated seasonal dietary variability in these taxa at Clark Quarry relative to those collected from the interglacial locality of Waccasassa River in Florida, providing additional evidence for the significant influence of glacial dynamics in structuring North American ecosystems

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

Pleistocene Rodents from Southeast Georgia

Late-Pleistocene fossil sites are uncommon in Georgia. However, Clark Quarry, a locality near Brunswick, Georgia, has yielded a large and diverse collection of vertebrate skeletal material dominated by cranial and post-cranial fossils of Columbian mammoths (Mammathus columbi) and giant bison (Bison latifrons). Screen washing of the fossiliferous sediment associated with the bones of the megafauna has produced a large number of microfossils. Here I describe fossil rodents from Clark Quarry. Cranial and post-cranial material of eight rodent taxa have been identified to date. Of these, five are found in the area today: Sigmodon hispidus, Peromyscus sp., Oryzomys palustris, Neofiber alleni, Reithrodontomys humulis. For the other three, the Florida bog lemming (Synaptomys australis) is now extinct, Clark Quarry is south of the current range of the groundhog (Marmota monax), and the capybara (Hydrochoerus) is only found in Central and South America today. The typical habitat of the species in this locality indicate that the environment was likely grassy marshland. The fossils found in Clark Quarry provide a glimpse of the diversity of Late-Pleistocene rodent fauna in Georgia

Pleistocene Rodents from Southeast Georgia

Late-Pleistocene fossil sites are uncommon in Georgia. However, Clark Quarry, a locality near Brunswick, Georgia, has yielded a large and diverse collection of vertebrate skeletal material dominated by cranial and post-cranial fossils of Columbian mammoths (Mammuthus columbi) and giant bison (Bison latifrons). Screen washing of the fossiliferous sediment associated with the bones of the megafauna has produced a large number of microfossils. Here we describe fossil rodents from Clark Quarry. Cranial and post-cranial material of eight rodent taxa have been identified to date. Of these, five are found in the area today: Sigmodon hispidus, Peromyscus sp., Oryzomys palustris, Neofiber alleni, Reithrodontomys humulis. For the other three, the Florida bog lemming (Synaptomys australis) is now extinct, Clark Quarry is south of the current range of the groundhog (Marmota monax), and the capybara (Hydrochoerus) is only found in Central and South America today. The fossils found in Clark Quarry provide a glimpse of the diversity of Late-Pleistocene rodent fauna in Georgia

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

FOSSIL SHARKS AND RAYS FROM A NEW LOCALITY IN WILKINSON COUNTY, GEORGIA

Fossils of marine organisms have been described from Eocene units of the southeast. In Georgia, they are generally found within the quartz dominated nearshore deposits of the Clinchfield Formation of the Barnwell Group. Recent exploration of a fossiliferous horizon in an active kaolin mine in Wilkinson County, Georgia has produced an array of marine fossils. The fossils were recovered by surface collecting overburden sediments exposed by mining operations. Thus far, the collection includes bivalves, gastropods, echinoderms, teeth of chondrichthyans, many vertebrae of osteichthyans, at least one species of turtle (Trionychidae) represented by multiple shell fragments, several vertebrae from an extinct “sea snake” (Pterosphenus), and two cetacean vertebrae. Here we describe the chondrichthyans. Based on frequency of occurrence, the collection is dominated by shark teeth belonging to the Sand Tiger Shark (Charcharis). Tiger Sharks (Galeocerdo), Snaggletooth Sharks (Hemipristis), Angel Sharks (Squatina), Sawfish Sharks (Pristis), Extinct Sawfish (Propristis), and Megatooth Sharks (Carcharocles) are also present. Rays are represented by a number of dental plates, isolated teeth, and tail spines (cf. Myliobatis). 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 enhance our understanding of the paleoenvironments of central Georgia during the Late Eocene