Several hypotheses about the influence of preservation on Bivalvia rates of evolution estimates (... more Several hypotheses about the influence of preservation on Bivalvia rates of evolution estimates (marine and freshwater families) were tested in a previous paper. However, the database used for those tests had a patchy quality and our results were provisional. Now an improved database dealing with only marine families has been used in order to test again those hypotheses. We removed freshwater families from the early database and we test the statistical hypotheses on these two data sources. Diversification patterns remain stable in general with these different databases; however, only the improved database shows the mass extinction at the end of the Triassic times. Statistical conclusions in the previous paper are generally confirmed in the present study. Since the presence of taxa having shell biominerals with different stability (aragonite or calcite) is not independent from geologic time (as expression of the fossil record rarefaction), the estimates of rates of evolution will be ...
ABSTRACT Preface The study of global biodiversity changes is a strong issue these days, as we bec... more ABSTRACT Preface The study of global biodiversity changes is a strong issue these days, as we become aware of the fragility of the Earth system and the urgent need to understand it better to keep it working. One of the key aspects of biodiversity is the distribution of organisms, and biogeography is the discipline which tries to recognize and characterize the causes of that distribution. It is closely linked to ecology, since the distribution of organisms is related to ecologic factors, but it cannot ignore other matters, such as species origin, dispersal, and extinction, and thus it becomes a historic science. Introducing the important time dimension, scientists are turning their interest to the past distribution of organisms, and paleobiogeography is now a complex subject which processes information provided by both Biology and Earth Sciences. It is conceptually and philosophically equivalent to neobiogeography. Nevertheless, its methods are somewhat different, since it is seriously limited by the incompleteness of the fossil record. On the other hand, it has direct access to the time involved, a key ingredient of organic evolution. This book is a synthesis of many years of research on Mesozoic bivalve mollusks from South America. The task of updating and processing all the information was triggered by a Symposium on ‘‘Seaways and landbridges: Southern Hemisphere biogeographic connections through time’’, organized by Dr. Silvio Casadío (CONICET and Universidad Nacional de Río Negro) and Dr. Miguel Griffin (CONICET and Universidad Nacional de La Plata), held at the Universidad Nacional de Río Negro, General Roca, Río Negro Province, Argentina, April 26–May 1, 2011, and who kindly encouraged us to complete this contribution. After that memorable meeting we put together our knowledge and skills to produce this book together, and present a picture of present-day knowledge on Triassic and Jurassic bivalve distribution in the Southern Hemisphere. Benthonic bivalves have been widely used in biogeography and paleobiogeography, but data from the Southern Hemisphere Mesozoic are still few and scattered. We trust this book will encourage future research on this subject to build better databases and allow the application of more sophisticated methodology. Through the book we analyze the subject from several viewpoints. From a merely descriptive perspective, bivalve distribution shows latitudinal gradients and distributional patterns, both at regional and global scales, which are the basis for the recognition of biochoremas (i.e., paleobiogeographic units of different ranks). Moving forward toward a causal paleobiogeography, these organisms also provide interesting insight into particular biogeographic questions, such as bipolarity and its origin. The evolution in time of the recognized biochoremas can be discussed in relation to paleoclimates and paleogeography. Finally, some of the results obtained from the analysis of the distribution of past bivalve biotas were even used to propose and discuss the development of marine corridors and argue about the distribution of continents in the past.
Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits w... more Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits worldwide are reviewed in terms of their validity, stratigraphic range, paleogeographic distribution, paleoautecology, and shell mineralogy. Data were originally compiled at species level and are arranged systematically. A brief discussion for each genus includes synonymy, taxonomic status, and included subgenera, as well as current uncertainties about their validity and range. The distribution of each genus is also shown on paleogeographic maps. Type species and first and last appearances of each genus are also mentioned. We recognize as valid 281 genera and their included subgenera, and we further discuss 148 genera (arranged alphabetically) that were mentioned for the study interval but are not included for different reasons. The purpose of this paper is to provide an updated critical assessment of all available basic information for each genus, in order to obtain a sound database to s...
"Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits ... more "Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits worldwide are reviewed in terms of their validity, stratigraphic range, paleogeographic distribution, paleoautecology, and shell mineralogy. Data were originally compiled at species level and are arranged systematically. A brief discussion for each genus includes synonymy, taxonomic status, and included subgenera, as well as current uncertainties about their validity and range. The distribution of each genus is also shown on paleogeographic maps. Type species and first and last appearances of each genus are also mentioned. We recognize as valid 281 genera and their included subgenera, and we further discuss 148 genera (arranged alphabetically) that were mentioned for the study interval but are not included for different reasons. The purpose of this paper is to provide an updated critical assessment of all available basic information for each genus, in order to obtain a sound database to study the generic paleodiversity of marine bivalves in the time interval from the Induan (Early Triassic) to the Sinemurian (Early Jurassic). This was a critical time for bivalve evolution and diversification, which began with the recovery from the Permian–Triassic extinction and ended with the recovery from the Triassic–Jurassic extinction.
Keywords: Bivalvia, paleoecology, paleogeography, Triassic, Early Jurassic"
Several hypotheses about the influence of preservation on Bivalvia rates of evolution estimates (... more Several hypotheses about the influence of preservation on Bivalvia rates of evolution estimates (marine and freshwater families) were tested in a previous paper. However, the database used for those tests had a patchy quality and our results were provisional. Now an improved database dealing with only marine families has been used in order to test again those hypotheses. We removed freshwater families from the early database and we test the statistical hypotheses on these two data sources. Diversification patterns remain stable in general with these different databases; however, only the improved database shows the mass extinction at the end of the Triassic times. Statistical conclusions in the previous paper are generally confirmed in the present study. Since the presence of taxa having shell biominerals with different stability (aragonite or calcite) is not independent from geologic time (as expression of the fossil record rarefaction), the estimates of rates of evolution will be ...
ABSTRACT Preface The study of global biodiversity changes is a strong issue these days, as we bec... more ABSTRACT Preface The study of global biodiversity changes is a strong issue these days, as we become aware of the fragility of the Earth system and the urgent need to understand it better to keep it working. One of the key aspects of biodiversity is the distribution of organisms, and biogeography is the discipline which tries to recognize and characterize the causes of that distribution. It is closely linked to ecology, since the distribution of organisms is related to ecologic factors, but it cannot ignore other matters, such as species origin, dispersal, and extinction, and thus it becomes a historic science. Introducing the important time dimension, scientists are turning their interest to the past distribution of organisms, and paleobiogeography is now a complex subject which processes information provided by both Biology and Earth Sciences. It is conceptually and philosophically equivalent to neobiogeography. Nevertheless, its methods are somewhat different, since it is seriously limited by the incompleteness of the fossil record. On the other hand, it has direct access to the time involved, a key ingredient of organic evolution. This book is a synthesis of many years of research on Mesozoic bivalve mollusks from South America. The task of updating and processing all the information was triggered by a Symposium on ‘‘Seaways and landbridges: Southern Hemisphere biogeographic connections through time’’, organized by Dr. Silvio Casadío (CONICET and Universidad Nacional de Río Negro) and Dr. Miguel Griffin (CONICET and Universidad Nacional de La Plata), held at the Universidad Nacional de Río Negro, General Roca, Río Negro Province, Argentina, April 26–May 1, 2011, and who kindly encouraged us to complete this contribution. After that memorable meeting we put together our knowledge and skills to produce this book together, and present a picture of present-day knowledge on Triassic and Jurassic bivalve distribution in the Southern Hemisphere. Benthonic bivalves have been widely used in biogeography and paleobiogeography, but data from the Southern Hemisphere Mesozoic are still few and scattered. We trust this book will encourage future research on this subject to build better databases and allow the application of more sophisticated methodology. Through the book we analyze the subject from several viewpoints. From a merely descriptive perspective, bivalve distribution shows latitudinal gradients and distributional patterns, both at regional and global scales, which are the basis for the recognition of biochoremas (i.e., paleobiogeographic units of different ranks). Moving forward toward a causal paleobiogeography, these organisms also provide interesting insight into particular biogeographic questions, such as bipolarity and its origin. The evolution in time of the recognized biochoremas can be discussed in relation to paleoclimates and paleogeography. Finally, some of the results obtained from the analysis of the distribution of past bivalve biotas were even used to propose and discuss the development of marine corridors and argue about the distribution of continents in the past.
Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits w... more Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits worldwide are reviewed in terms of their validity, stratigraphic range, paleogeographic distribution, paleoautecology, and shell mineralogy. Data were originally compiled at species level and are arranged systematically. A brief discussion for each genus includes synonymy, taxonomic status, and included subgenera, as well as current uncertainties about their validity and range. The distribution of each genus is also shown on paleogeographic maps. Type species and first and last appearances of each genus are also mentioned. We recognize as valid 281 genera and their included subgenera, and we further discuss 148 genera (arranged alphabetically) that were mentioned for the study interval but are not included for different reasons. The purpose of this paper is to provide an updated critical assessment of all available basic information for each genus, in order to obtain a sound database to s...
"Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits ... more "Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits worldwide are reviewed in terms of their validity, stratigraphic range, paleogeographic distribution, paleoautecology, and shell mineralogy. Data were originally compiled at species level and are arranged systematically. A brief discussion for each genus includes synonymy, taxonomic status, and included subgenera, as well as current uncertainties about their validity and range. The distribution of each genus is also shown on paleogeographic maps. Type species and first and last appearances of each genus are also mentioned. We recognize as valid 281 genera and their included subgenera, and we further discuss 148 genera (arranged alphabetically) that were mentioned for the study interval but are not included for different reasons. The purpose of this paper is to provide an updated critical assessment of all available basic information for each genus, in order to obtain a sound database to study the generic paleodiversity of marine bivalves in the time interval from the Induan (Early Triassic) to the Sinemurian (Early Jurassic). This was a critical time for bivalve evolution and diversification, which began with the recovery from the Permian–Triassic extinction and ended with the recovery from the Triassic–Jurassic extinction.
Keywords: Bivalvia, paleoecology, paleogeography, Triassic, Early Jurassic"
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Keywords: Bivalvia, paleoecology, paleogeography, Triassic, Early Jurassic"
Keywords: Bivalvia, paleoecology, paleogeography, Triassic, Early Jurassic"