The Ediacaran Period (635 – 541 Ma) is a critical transition in the history of the Earth and life. It is marked by the appearance of enigmatic Ediacara-like fossils and macroalgae, which had existed since the early Proterozoic, but started to diversify morphologically and ecologically during this geological period. Nevertheless, paleontologists have been studying Ediacaran fossils for more than a century, the key questions about these fossils remain unanswered, including their phylogenetic affinities, taphonomic history, ecology, and paleoenvironmental distribution. Thus, new ways of investigation need to be employed to unveil enigmas of Ediacaran organisms. As well as, scientists need to engage other representatives of Ediacaran assemblages, such as macroalgae, to fully understand how those communities operated in the past. The chapters of this original research in this dissertation demonstrate innovative approaches and methods for studying the paleoecology and taphonomy of Ediacaran macrofossils. The second chapter presents the results of a geochemical analysis to resolve taphonomic and paleoecological questions about the Ediacara-like discoidal holdfast fossil Aspidella. Stable isotope data of organic carbon, carbonate carbon/oxygen, and pyrite sulfur were integrated with iron speciation data to reconstruct the taphonomy, paleoecology, and paleoenvironments of Aspidella fossils. The third chapter presents results from a comprehensive analysis of macroalgae from Proterozoic to early Paleozoic. In this study, a database of macroalgal fossil was updated and analyzed in order to gain insights into the big-picture evolutionary patterns of macroalgal morphology and ecology through time. These methods and approaches offer new opportunities to test major paleobiologic and geobiologic hypotheses, thus improving our understanding of the history of the biosphere and the Earth system. / Ph. D.

Saltville, Virginia (Smyth County and Washington County) has been known for its late Pleistocene megafauna since the 1700s. Based on reviews of past excavations and material in collections, the most prominent fossils found at Saltville are proboscideans. Teeth of Mammuthus (mammoth) and Mammut (mastodon) from East Tennessee State University Museum of Natural History, Virginia Museum of Natural History, and Smithsonian were the focus of this research. Evidence of sedimentary abrasion and degree of concretion development was used to address the taphonomic history of the assemblage. Evidence of root resorption, tooth expectoration, and eruption and wear of proboscidean molars was used to understand age-related patterns in the proboscidean assemblage. The Saltville proboscidean assemblage contains a disproportionate amount of juvenile mammoth and mastodon teeth, some of which were lost in life. This assemblage has also been modified extensively by sedimentary abrasion.

Thesis (Ph. D.)--University of Chicago, Department of Geophysical Sciences, December 2003. / CD-ROM contains figures 2.1-4.8 and A.1 in PDF format. Includes bibliographical references. Also available on the Internet.

The early Pliocene age Gray Fossil Site (GFS) was relatively recently found, with much still to be discovered and examined, and represents one of only a few sites of its age in eastern North America. It has been noted that the diverse faunal remains found at GFS are unique compared to what have been found at other fossil sites in North America from the same time period. Studying mammalian community structures at fossil sites can provide an abundance of information about the past environment and species adaptations to it, such as niche occupation of species, resource partitioning, and interactions between organisms and their environment. The main questions being asked in this study are: 1) what is the mammal community structure like at GFS?, and 2) how does the community structure at GFS compare to other contemporaneous sites? While studies of the fauna and flora have helped us to understand the ecosystem at GFS, detailed study of the mammal community will help us better understand this unique site. It is expected that the community structure and niche occupation of the mammals at GFS will be different from other contemporaneous sites, dominated by mammals adapted for life in the warm oak, hickory forest present at the site. A taxon-free approach to analysis will be used so that environments not sharing the same taxa or of different ages can be compared to one another. Each mammal species from GFS (48 total) and five well-known contemporaneous sites are categorized by body size, locomotor mode, and dietary preference to characterize the niches occupied by each species. Categorizations for each species will come from published works and measurements / ecomorphological analysis of specimens. Preliminary results show that GFS is different from other sites in that there are more brachyodont and tree dwelling/climbing adapted species present, and there are fewer running species present. The initial findings are likely associated with the site being a closed, forested ecosystem, compared to the more open environments of the other sites. Moving forward, descriptions pertaining to specifically how GFS and its mammal community structure compare to the niche occupation of similar species at other sites will be discussed. This project will also examine what more this analysis can reveal about the ecosystem at GFS, particularly how the herbivorous mammals can provide greater insight into what environmental conditions were like, including what vegetation was predominant at GFS.

Geographic Information Systems (GIS) can be a powerful paleontological tool. This project’s goal was to digitally reconstruct a large, mostly-articulated mastodon (Mammut sp.) excavated from the Gray Fossil Site during the 2015 to 2018 field seasons. This was done by compiling total station survey data, field notes, sketch maps, and cataloged specimen data within ArcGIS Pro. Field drawn sketch maps were geo-referenced to relevant survey points. Then, a polygon layer was created by tracing the spatially referenced field drawings. Each polygon was given the specimen’s designated field number and connected to a table containing all associated field data. The result was a polygon layer that displayed all major bones and bone fragments of the mastodon which was linked to museum catalog information. Researchers can use this digital product to interpret site taphonomy, examine the distribution of skeletal elements or fossil taxa, or potentially identify areas of interest for future excavations. This workflow will streamline future specimen digitization efforts at the Gray Fossil Site.

Cricetidae, which includes a wide range of mice, rats, and voles, is the second-most diverse and abundant family of mammals. Distributed across the Americas and Eurasia, this rodent family has been extensively studied for its success and adaptability in the face of climate and habitat change, and its utility for ecological reconstruction and the biochronology. While cricetids are known from many fossil sites in western North America, few have been found and studied from the terrestrial sites in the east prior to the Pleistocene. The Gray Fossil Site (GFS) in eastern Tennessee is well-known for its diverse flora and fauna, particularly large mammals. Small mammals from the site have remained understudied, and although a few studies have mentioned cricetids, a comprehensive investigation is needed to describe the large number of cricetid specimens found at GFS. This project uses qualitative and quantitative methods to examine the morphology of fossil cricetids from GFS, focused on molars and jaw elements because of their abundance and the rich taxonomic and ecological information they provide. Materials have been studied using a stereomicroscope and photographed using a digital microscope camera. Occlusal morphology is described and compared to modern cricetids and published records from across North America. Specimens from GFS include at least 5 taxa, and the two most abundant taxa at the site are the woodrat Neotoma, which has high-crowned molars and still lives in the region today, and the deer mouse-like Postcopemys, which has low-crowned molars. While many GFS specimens can be categorized into these two genera, distinctive morphological variations seen in some individuals suggest the presence of new species. The array of cricetids present is distinct from those at contemporaneous sites and reinforces the spatial and temporal uniqueness of the Gray Fossil Site. Situated in the biodiversity hotspot in the Appalachian region today, GFS provided habitats for cricetid taxa with diverse body sizes and dietary preferences in the Pliocene.

The early Pliocene age Gray Fossil Site (GFS) is a fossil site that preserves diverse fauna and flora and represents one of only a few sites of its age in eastern North America. The assemblage of fauna found at GFS is unique compared to what has been found at other contemporaneous fossil sites across the continent. While studies of the fauna and flora have helped us to understand the ecosystem at GFS, detailed study of the diverse mammal community will help us better understand this unique site. Studying mammalian community structures at fossil sites can provide an abundance of information about the past such as, ecological inferences and climate conditions. To understand the paleoenvironment at GFS, I have gathered data from twenty modern communities and five well-known contemporaneous sites. Mammal species from each of these 26 sites have been categorized by body size, locomotor mode, and cheek tooth crown height to characterize the niches occupied by each species. Proportions of species within categories have been compared and analyzed across modern and fossil sites using discriminant function analysis (DFA). Results of the DFA demonstrate that modern communities with different climates and habitats can be distinguished based on the body size, locomotion, and cheek tooth crown heights of mammals living there. Moreover, functions can be used to infer conditions of past sites. Species diversity within categories was also compared across all sites. Results show that GFS has more brachydont and scansorial species present, and fewer cursorial species than occur at other contemporaneous sites. The results of the discriminant functional analysis indicate that the GFS community structure is most similar to modern temperate forest regions of the Himalayan Mountains in China and modern Washington Co., TN. Proportions of brachydont, gliding, and scansorial species appear to be driving variables behind these results.

Carbonaceous fossil preservation is an important taphonomic window that provides critical perspectives on the evolutionary history of life. However, phylogenetic interpretation of carbonaceous fossils is not straightforward. This is largely because critical biological information is usually lost during fossilization and three-dimensional morphologies are flattened into two-dimensional compressions. Hence, innovative techniques and methods are required in order to better understand the evolutionary significance of these fossils. To achieve this goal, this dissertation is focused on using an array of innovative research techniques to investigate the paleobiology, biostratigraphy, and taphonomy of carbonaceous fossils in critical times of early life evolution, including Neoproterozoic and Cambrian. Chapters 2 to 5 in this dissertation present original research that helps to decipher hidden biological structures of various carbonaceous fossils using a series of research methods. An improved understanding of these carbonaceous remains will ultimately advance our knowledge regarding the early evolutionary history of life on Earth. Chapter two describes new cellular structures of the carbonaceous compression macrofossil Chuaria using backscattered electron scanning electron microscopy. The data show that Chuaria, which is one of the most common fossils in Neoproterozoic and whose phylogenetic interpretation has been uncertain, is likely a multicellular eukaryote. Chapter three is aimed to resolve a long debate on the depositional age of the Gouhou Formation in the Huaibei region of North China and to constrain the Precambrian-Cambrian (P-C) boundary in this area. Using a low manipulation maceration technique, this study reveals a diverse assemblage of organic-walled microfossils from the lower Gouhou Formation, suggesting that the lower Gouhou Formation is Tonian in age and the P-C boundary may be located within the Gouhou Formation. Chapter four reports a group of problematic carbonaceous compression macrofossils from the Hetang Formation in South China. Taphonomic analysis using optical and electron microscopy tentatively suggests that these carbonaceous macrofossils are probably carapaces of bivalved arthropods. The last chapter describes a group of sponge fossils with carbonaceous preservation from the early Cambrian Hetang Formation in South China. Using an array of electron microscopy techniques, this study reveals that siliceous spicules of the Hetang sponges have large axial filaments and large proportions of organic material, suggesting early sponge in the Precambrian and Cambrian may have had weakly mineralized or entirely organic skeletons. Results from this study helps to reconcile the apparently conflicting molecular clocks, biomarker fossils, and spicular fossils of early sponges. / PHD / Carbonaceous fossils can provide important information about the life on Earth in deep time. However, biological interpretation of carbonaceous fossils is not always straightforward, largely because critical biological information is usually lost during fossilization. To address this matter, this dissertation presents original research that helps to decipher hidden biological structures of various carbonaceous fossils using a series of innovative research techniques and methods. Specifically, Chapter two describes new cellular structures of the carbonaceous compression macrofossil Chuaria using backscattered electron scanning electron microscopy. The data show that Chuaria, which is one of the most common fossils in Neoproterozoic and whose biological interpretation has been uncertain, is likely a multicellular eukaryote. Chapter three is aimed to resolve a long debate on the depositional age of the Gouhou Formation in the Huaibei region of North China and to constrain the Precambrian-Cambrian (P-C) boundary in this area. Using a low manipulation maceration technique, this study reveals diverse organic-walled microfossils from the lower Gouhou Formation, suggesting that the lower Gouhou Formation is Tonian in age and the P-C boundary may be located within the Gouhou Formation. Chapter four reports a group of problematic carbonaceous compression macrofossils from the Hetang Formation in South China. This study, using optical and electron microscopy, suggests that these carbonaceous macrofossils are probably carapaces of bivalved arthropods. The last chapter describes a group of sponge fossils with carbonaceous preservation from the early Cambrian Hetang Formation in South China. Using an array of electron microscopy techniques, this study reveals that the Hetang sponges developed spicules with large proportions of organic material, suggesting early sponge in the Precambrian and Cambrian may have had weakly mineralized or entirely organic skeletons. Therefore, an improved understanding of these carbonaceous remains presented in this dissertation will ultimately advance our knowledge regarding how the early life on Earth evolved through time.

There is general agreement that a range of paleodepths and environments are represented in the individual shell units of the middle Pliocene to earliest Pleistocene Tamiami Formation of southwest Florida, but maximum depths remain poorly constrained. Here, benthic Foraminifera abundances are used as a paleoenvironmental proxy to compare the upper Tamiami from quarries in Sarasota, Florida to Recent modern coastal, bay, and reef habitats of Florida, the Grand Cayman Islands, and Puerto Rico, ranging in depth from 0 to 55 meters. I used: (1) ordination techniques, including detrended correspondence analysis (DCA) and cluster analysis, to compare upper Tamiami foraminiferal assemblages with potential modern analogs; (2) Ammonia-Elphidium (AEI) and FORAM (FI) indices to reconstruct past oxygen levels and environmental stress levels, respectively; and (3) diversity indices and rarefaction to investigate habitat-specific diversity change through time.Results indicate that the upper Tamiami units represent several distinct environments. APAC quarry, Fruitville Member Unit 4 samples group in DCA and cluster analyses with modern shallow, tropical, mangrove-proximate lagoon samples from Puerto Rico; AEI values of both Unit 4 and these lagoonal samples are consistent with high nutrients. APAC quarry, Fruitville Member Unit 3 and Pinecrest Member units 5 and 7, however, group with tropical shallow, open coast environments up to 12 m in depth and have relatively low FORAM indices suggesting stress and AEI values comparable to modern mesotophic, shelf habitats. SMR samples group with modern mangrove environments from White Water Bay at depths approximately 0 to 0.3 m, with FORAM and AEI indices indicating low oxygen and possibly high nutrients. Species richness measured by individual rarefaction in the fossil units is highest in the lowest APAC units sampled and progressively declines in younger APAC units, while SMR beds have the lowest richness of all fossil samples. The lower portion of Unit 7 contains the highest richness of all fossil and modern units, while other fossil units have either lower or comparable richness, diversity, and evenness when compared to modern habitat analogs as identified in cluster and DCA analyses. Thus, there is no clear evidence for wide-scale decline in foraminiferal biodiversity from the Plio-Pleistocene to now. Significantly, the identification of modern habitat analogs for the upper Tamiami units make it possible to compare biodiversity trends in other fauna (e.g., mollusks) thought to have experienced significant extinction.

Stratigraphic analyses of lacustrine sediments provide powerful tools for reconstructing past environments. The records that result from these analyses are key to understanding present-day climate mechanisms and how the natural environment may respond to anthropogenic climate change in the future. This doctoral dissertation research investigates climate and environmental history at Laguna Saladilla (19° [degrees] 39' N, 71° [degrees] 42' W; ca. 2 masl), a large (220 ha) lake along the north coast of Hispaniola. I reconstructed changes in vegetation and environmental conditions over the mid to late Holocene based on pollen, microscopic charcoal, and diatoms in an 8.51 m sediment core recovered from the lake in 2001. Fieldwork in December 2009 included the use of ground penetrating radar to identify subaqueous deltas that indicate past positions of the Masacre river, which flows into the lake from the Cordillera Central. Laguna Saladilla was deeper and more saline from the base of the sediment profile approximately 8030 cal yr BP to about 3500 cal yr BP. Mangrove (Rhizophora) pollen percentages were highest around 7650 cal yr BP, when mollusk shells in the core suggest marine conditions. The lake became progressively brackish ca. 3500 cal yr BP, followed by a transition ca. 2500 cal yr BP to its current freshwater state. This shift in water chemistry was likely due in part to a change in the position of the Masacre river. Diatoms show that lake levels decreased as evaporation/precipitation ratios increased. Amaranthaceae and other herbs dominated the pollen record under the drier conditions of the last 2500 cal yr BP; pollen of fire-adapted taxa, particularly Pinus, increased in the last 800 years. Patterns of microscopic charcoal influx at Laguna Saladilla over the Holocene are similar to patterns at Lake Miragoane, Haiti and Laguna Tortuguero, Puerto Rico. The changes in fire frequency or extent indicated by these Caribbean charcoal records may be driven by increased winter insolation at ca. 5000 cal yr BP that led to earlier winter drying. Comparing the charcoal record to archeological data and other paleoenvironmental records facilitated the disentangling of changes in climate from anthropogenic impacts.