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Although mass extinctions are typically brief geological events, they disproportionately affect the tempo and mode of the history of life. Mass extinction is considered a governing influence on the diversification, migration, and ecological innovation of biota. Diverse and widespread clades are often obliterated at extinction boundaries and previously obscure taxa sometimes rise to prominence in the wake of extinction. While much is known about the proximate causes and consequences of mass extinction, relatively less study has focused on subsequent recovery periods, especially on timescales of tens of millions of years. Climate change is also considered a fundamental force that shaped the origination and distribution of taxa, however relatively few studies have tested this correlation in deep time. The Upper Cretaceous through lower Paleogene (84 - 46 Ma) Gulf Coastal Plain of the United States (GCP; Alabama, Mississippi, Georgia, and Texas) contain the Cretaceous-Paleogene (K-Pg) mass extinction and a global warming event at the Paleocene-Eocene boundary known to have affected marine organisms. I analyzed molluscan-dominated assemblages to better understand how these forces shaped the diversity and ecological characteristics of assemblages at the local and regional level. I also derived temperature estimates from mollusk shells to assess how climate change affected these organisms. Because of vagaries in the architecture of the fossil record, biases must first be accounted for to remove the spurious effects of preservation and unequal sampling. By doing so, this dissertation represents a synoptic treatment of the diversity and ecological trends of GCP marine assemblages in the 20 million years following the K-Pg extinction. Abundance data were collected from bulk samples, museum collections, and the literature, resulting in a data matrix of 153 samples, 1494 taxa, and 52,585 individuals spanning ~14 fossiliferous horizons in the GCP during the Paleocene to middle Eocene (65.5 - 46.6 Ma). These faunas are dominated by molluscs (bivalves and gastropods) with less common bryozoans, corals, echinoderms, and brachiopods. A subset of these data contains body size measurements. Geochemical data were analyzed from two late Paleocene units and one early Eocene unit. Chapter 1, published in Geology (Sessa et al., 2009), examines the effect of temporally heterogeneous lithification on recovery patterns following the K-Pg extinction. Lithification has been advanced as a potential bias on diversity patterns, and this is one of the first studies to quantify the magnitude of this bias. Lithified units are significantly less diverse than their unlithified counterparts, primarily because small taxa are obscured in lithified rocks. In the GCP, this bias results in the artificial protraction of the K-Pg recovery interval by 7 Myr. Chapter 2 explores the climatic and water mass properties of the GCP during the late Paleocene through early Eocene, a period of extreme global warmth. Temperature estimates from the oxygen isotopes of bivalve shells show a 3°C increase from the late Paleocene through early Eocene. Carbon isotopic profiles from bivalve shells suggest that the GCP water mass became progressively more stratified through this interval. While climatic changes had little effect on the diversity and ecology of assemblages (Chapter 3), the results of Chapter 2 are significant for the calibration and validation of models that reconstruct past greenhouse climates. Chapter 3 analyzes the diversity, ecological structure, and turnover patterns of Late Cretaceous and early Paleogene assemblages. After accounting for unequal sampling intensity, bin duration, and preservation, I found that regional GCP diversity recovered to pre-extinction values in ~2.7 Myr, nearly 20 Myr sooner than suggested by unstandardized estimates. The ecological composition of assemblages was also changed by the K-Pg extinction and was tightly correlated to periods of diversity recovery, expansion, and subsequent equilibrium.
This book is the culmination of many years of research by a scientist renowned for his work in this field. It contains a compilation of the data dealing with the known stratigraphic ranges of varied behaviors, chiefly animal with a few plant and fungal, and coevolved relations. A significant part of the data consists of ``frozen behavior'', i.e. those in which an organism has been preserved while actually ``doing'' something, as contrasted with the interpretations of behavior of an organism deduced from functional morphology, important as the latter may be. The conclusions drawn from this compilation suggest that both behaviors and coevolved relations appear infrequently, following which there is relative fixity of the relation, i.e., two rates of evolution, very rapid and essentially zero. This conclusion complies well with the author's prior conclusion that community evolution followed the same rate pattern. In fact, communities are regarded here, as in large part, expressions of both behavior and coevolved relations, rather than as random aggregates controlled almost wholly by varied, unrelated physical parameters tracked by organisms, i.e., the concept that communities have no biologic reality, being merely statistical abstractions. The book is illustrated throughout with more than 400 photographs and drawings. It will be of interest to ethologists, evolutionists, parasitologists, paleontologists, and palaeobiologists at research and post-graduate levels.
The hominin fossil record documents a history of critical evolutionary events that have ultimately shaped and defined what it means to be human, including the origins of bipedalism; the emergence of our genus Homo; the first use of stone tools; increases in brain size; and the emergence of Homo sapiens, tools, and culture. The Earth's geological record suggests that some evolutionary events were coincident with substantial changes in African and Eurasian climate, raising the possibility that critical junctures in human evolution and behavioral development may have been affected by the environmental characteristics of the areas where hominins evolved. Understanding Climate's Change on Human Evolution explores the opportunities of using scientific research to improve our understanding of how climate may have helped shape our species. Improved climate records for specific regions will be required before it is possible to evaluate how critical resources for hominins, especially water and vegetation, would have been distributed on the landscape during key intervals of hominin history. Existing records contain substantial temporal gaps. The book's initiatives are presented in two major research themes: first, determining the impacts of climate change and climate variability on human evolution and dispersal; and second, integrating climate modeling, environmental records, and biotic responses. Understanding Climate's Change on Human Evolution suggests a new scientific program for international climate and human evolution studies that involve an exploration initiative to locate new fossil sites and to broaden the geographic and temporal sampling of the fossil and archeological record; a comprehensive and integrative scientific drilling program in lakes, lake bed outcrops, and ocean basins surrounding the regions where hominins evolved and a major investment in climate modeling experiments for key time intervals and regions that are critical to understanding human evolution.
The literature of paleobiology is brimming with qualifiers and cautions about using species in the fossil record, or equating such species with those recognized among living organisms. Species and Speciation in the Fossil Record digs through this literature and surveys the recent research on species in paleobiology. In these pages, experts in the field examine what they think species are - in their particular taxon of specialty or more generally in the fossil record. They also reflect on what the answers mean for thinking about species in macroevolution. The first step in this approach is an overview of the Modern Synthesis, and paleobiology’s development of quantitative ways of documenting and analyzing variation with fossil assemblages. Following that, this volume’s central chapters explore the challenges of recognizing and defining species from fossil specimens, and show how with careful interpretation and a clear species concept, fossil species may be sufficiently robust for meaningful paleobiological analyses. Tempo and mode of speciation over time are also explored, exhibiting how the concept of species, if more refined, can reveal enormous amounts about the interplay between species origins and extinction and local and global climate change.
South American ecosystems suffered one of the greatest biogeographical events, after the establishment of the Panamian land bridge, called the “Great American Biotic Interchange” (GABI). This refers to the exchange, in several phases, of land mammals between the Americas; this event started during the late Miocene with the appearance of the Holartic Procyonidae (Huayquerian Age) in South America and continues today. The major phases of mammalian dispersal occurred from the Latest Pliocene (Marplatan Age) to the Late Pleistocene (Lujanian Age). The most important and richest localities of Late Miocene-Holocene fossil vertebrates of South America are those of the Pampean region of Argentina. There are also several Late Miocene and Pliocene localities in western Argentina and Bolivia. Other important fossils have been collected in localities of Pleistocene age outside Argentina: Tarija (Bolivia), karstic caves of Lagoa Santa and the recently explored caves of Tocantins (Brasil), Talara (Perú), La Carolina (Ecuador), Muaco (Venezuela), and Cueva del Milodon (Chile), among others. The book discusses basic information for interpreting the GABI such as taxonomic composition (incorporating the latest revisions) at classical and new localities for each stage addressing climate, environments, and time boundaries for each stage. It includes the chronology and dynamics of the GABI, the integration of South American mammalian faunas through time, the Quaternary mammalian extinctions and the composition of recent mammalian fauna of the continent.
This 3-volume handbook brings together contributions by the world ́s leading specialists that reflect the broad spectrum of modern palaeoanthropology, thus presenting an indispensable resource for professionals and students alike. Vol. 1 reviews principles, methods, and approaches, recounting recent advances and state-of-the-art knowledge in phylogenetic analysis, palaeoecology and evolutionary theory and philosophy. Vol. 2 examines primate origins, evolution, behaviour, and adaptive variety, emphasizing integration of fossil data with contemporary knowledge of the behaviour and ecology of living primates in natural environments. Vol. 3 deals with fossil and molecular evidence for the evolution of Homo sapiens and its fossil relatives.