Wood Conservation at the Gray Fossil Site in Northeastern Tennessee

The Gray Fossil Site in northeastern Tennessee preserves materials from a 5-million-year-old ecosystem, including wood from nearby trees. When excavated, the wood is saturated due to a modern local high water table. Moisture in the wood prevents further dendroecological research, which would provide important, annual-scale climate information from tree rings visible in the wood. In order to analyze climate-sensitive wood variables, wood samples must be dried with minimal cracking prior to further research. To test the best method for drying wood samples, a variety of methods were studied. Cotton string, wrapped firmly around a sample, and a sandbox, comprised of a sample surrounded equally on all sides by sand within a five gallon container, were both be used to test the effects of minimizing expansion and contraction during drying. A vacuum oven, a microwave, and a refrigerator were used to monitor the rate at which the wood dries under different temperature conditions, and a control sample was dried in a fume hood as a comparison. An alcohol replacement test provided data on the rate of non-water evaporation. Drying methods were evaluated by measuring the drying speed of each sample and the degree of visible surface cracking. Of the methods tested, wrapping wood samples in cotton string at an even pressure, then allowing the sample to dry in a fume hood is the best practice for drying the wood from the Gray Fossil Site. The string resulted in the least cracking, and one of the shorter drying times without destroying the sample, as the vacuum oven and microwave tests did. This work not only provides a comparison of standard drying methods for saturated fossils of the non-wood varieties, but lays the groundwork for further studies examining the wood, tree rings, and climate at the Gray Fossil Site

New mammutids (Proboscidea) from the Clarendonian and Hemphillian of Oregon – a survey of Mio-Pliocene mammutids from North America

A survey of Miocene-Pliocene Mammutidae from North America is provided. Two important but undescribed specimens from Unity (Clarendonian) and Hermiston (Hemphillian) are reported, and a previously described mandible from Black Butte (Clarendonian) is revisited. The Unity specimen, a maxilla with a tusked longirostrine mandible, represents Zygolophodon proavus. Upper and lower tusks are well developed. Mammutid species are best characterized by traits of the mandible, the upper tusks and lower and upper dentitions. However, they are rarely preserved in a single individual, as in the Unity specimen. A second mammutid mandible from the nearby, stratigraphically similar Black Butte locality has a short, tuskless symphysis and was described as “Mammut (Pliomastodon) furlongi". We question the independence of this species, because both types of mandibles are coeval in several Eurasian localities. The widespread geographic and stratigraphic co-occurrence of different mandible types cannot be explained through a phylogenetic model alone. Therefore, we discuss whether these parallel mammutid occurrences can be interpreted as resulting from species diversity, intraspecific variability, pathological abnormities, or as a sex-linked morphological difference. The Hermiston maxilla from the upper Hemphillian represents Mammut matthewi. The large upper tusk differs from Z. proavus. The morphology of the mandible, however, remains unknown, thus its precise evolutionary stage is uncertain. The maxillary molars of the Hermiston specimen are larger than in Z. proavus however, we observe a high degree of variability in the size of mammutid molars so this character alone is not indicative of a specific evolutionary stage. The relatively small number of localities with informative specimens and the conservative dental morphology of mammutids throughout the Miocene and Pliocene obscures the potential occurrence of synchronous North American taxa. Our results favor the interpretation of a continuous and endemic evolution from Zygolophodon to Mammut and make an independent immigration of the genus Mammut from Eurasia less probable. Therefore, the genus name Mammut should be avoided for Eurasian mammutids

Identifying Dietary and Migratory Patterns of Illinois Woolly Mammoth Populations Using Isotope Analysis of Carbon, Oxygen, and Strontium

The extinct woolly mammoth (Mammuthus primigenius) ranged from Alaska to the Northeastern Seaboard throughout the Late Pleistocene (100-10 Ka). Although it is recognized that woolly mammoths coincided with and lived in a region heavily influenced by glacial ice sheets, little is known about their dietary or migratory behavior. This study classifies and provides insight into the diet and mobility of Midwestern mammoths by analyzing stable isotopes of carbon, oxygen, and strontium preserved in the tooth enamel of these extinct elephantids. A woolly mammoth tooth from Moline, IL, was bulk-sampled and micromilled to extract the aforementioned isotopes from the base of the enamel. Dated to 16,410 ±110 BP (20,085-19,530 calBP), measured 13C (-12.6‰ to -11.1‰, PDB) values indicate that the terminal LGM landscape of western Illinois was dominated by C3 vegetation, which is typical of a cooler climate. This cooler climate during the LGM is also reflected by the resulting high 18O values (-10.8‰ to -8.1‰, PDB). The ratios of 87Sr/86Sr isotopes retained in the tooth enamel were mapped using GIS onto a regional isoscape to determine the mobility of one mammoth across its lifetime. The mobility patterns were compared to seasonal and annual dietary shifts to better understand the underlying cause for migrations. Preliminary analyses of the 87Sr/86Sr values (0.7907 – 0.7156) suggest that there were regional population movements around the northern Mississippi River Valley. The data reveals the climate and landscape during the terminal Pleistocene in western Illinois and how woolly mammoths responded to it

Variability in Bioavailable 87Sr/86Sr in the North American Midcontinent

Strontium (Sr) isotope tracers are useful for understanding provenance and mobility in biological materials across multiple disciplines. However, the impact of these techniques is highly dependent on the construction of appropriate comparative baselines (i.e., an isoscape). We present the results of a systematic survey of 87Sr/86Sr values from grasses in the North American Midcontinent with a particular emphasis on sedimentary systems. Although 87Sr/86Sr values are highly variable across the region, the Sr isoscape shows multi-scalar patterns that are dependent on local-to-regional trends in surficial geology. High values are found in bedrock-dominated areas such as the Black Hills (SD) and Ozark Uplift (MO), or formerly glaciated areas where surface deposits are dominated by ice-transported Precambrian clasts. The lowest values are found in river valleys that incorporate eroded Neogene sediments into terrace formation. Intermediate values are found in upland loess and alluvial deposits which blanket much of the study area. We demonstrate trends in large-scale variability of the Midcontinent’s 87Sr/86Sr isoscape and suggest that future refinement focus on sub-regional trends in Sr isotope variability

Paleontology and Paleoecology of Interglacial Guano Deposits in Mammoth Cave, KY

Mammoth Cave guano deposits contain a rich record of troglofauna spanning the last 125,000 years. In particular, chiropteran remains from Chief City provide insight into ecosystem dynamics of the cave area during the last interglacial. This paper presents results of paleontological excavations undertaken in 2008. Sub-fossil remains (N=1134) in Chief City guano deposits are dominated by chiropteran taxa. Although all identified taxa are extant, the combination of Myotis leibii and Tadarida brasiliensis is an association without modern analogue. Stable isotope analyses of guano indicate a C3 prey signature characteristic of forested habitat. This was unexpected given the prevalence of T. brasiliensis, a species that is typically associated with open environments. Ecomorphological consideration of wing shape trends in these assemblages indicate that interglacial faunas are dominated by fast-flying, open-space taxa (T. brasiliensis) while late Holocene and Historic assemblages contain more taxa that utilized closed forest or forest gaps

Late Pleistocene proboscidean population dynamics in the North American Midcontinent

Understanding megafaunal population dynamics is critical to testing and refining scenarios of how extinctions occurred during the terminal Pleistocene. Large-scale, collections-based, chronological, and taphonomic analyses of midwestern Proboscidea suggest divergent population histories in mammoths and mastodons after the Last Glacial Maximum (LGM). Although extinction of both taxa occurred in the very late Bølling-Allerød (B-A) or early Younger Dryas (YD), Mammuthus is dominant during the LGM with a decreasing presence in the region until extirpation. Mammut americanum however, is absent during the LGM but becomes the dominant taxon during the subsequent B-A. Trace and physical evidence of large carnivores in post-LGM proboscidean assemblages is extremely rare, suggesting apex predators had minimal impact on mammoth and mastodon populations at this time. The ultimate mechanism(s) of extinction remain unclear; however, the wide geographic distribution of late Mammut and an increase in the frequency of multi-animal death assemblages is consistent with a large, destabilized population experiencing periodic boom-bust cycling at the end of the B-A. We suggest this pattern is due to the collapse of trophic controls on proboscidean populations prior to the LGM and a subsequent system-wide shift from top-down to bottom-up regulatory mechanisms in Proboscidea

American Mastodon Mitochondrial Genomes Suggest Multiple Dispersal Events in Response to Pleistocene Climate Oscillations

Pleistocene glacial-interglacial cycles are correlated with dramatic temperature oscillations. Examining how species responded to these natural fluctuations can provide valuable insights into the impacts of present-day anthropogenic climate change. Here we present a phylogeographic study of the extinct American mastodon (Mammut americanum), based on 35 complete mitochondrial genomes. These data reveal the presence of multiple lineages within this species, including two distinct clades from eastern Beringia. Our molecular date estimates suggest that these clades arose at different times, supporting a pattern of repeated northern expansion and local extirpation in response to glacial cycling. Consistent with this hypothesis, we also note lower levels of genetic diversity among northern mastodons than in endemic clades south of the continental ice sheets. The results of our study highlight the complex relationships between population dispersals and climate change, and can provide testable hypotheses for extant species expected to experience substantial biogeographic impacts from rising temperatures

Human Responses to Bison Nutritional Variability: An Illustration from the Central Plains

The relation of prehistoric human groups to bison populations in the Central Plains has long been the subject of both speculation and debate. Recent research has shown that bison are relatively sensitive to changing environmental conditions (Bamforth, 1988; Bozell, 1995; Speth and Pany, 1978; Emerson, 1990). This sensitivity is visible in physiological and behavioral adaptations used by bison to deal with change. Ukewise, evidence for these adaptations is present in faunal assemblages from Central Plains archaeological sites. In order to determine the nature of these adaptive charaderistics, a model must be developed which goes beyond traditional presence/absence tabulations of faunal taxa. With the goal of understanding how human groups dealt with inconsistent bison resources between AD I and AD 1500, a model will be developed that utilizes research from several different fields. This paper is a synthesis of research undertaken in grassland and cultural ecology, archaeology, paleoclimatology and nutrition. Its purpose is to create a diachronic pidure of bison availability and its relevance to subsistence. It will then examine cultural implications for prehistoric human populations on the Central Plains. This paper will present a general discussion of human adaptation to dietary stresses. Then, it will explain grassland and bison ecological systems, respectively. These data will then be used to develop a model of bison use, which will be evaluated through the analysis of Central Plains archaeologicalsites