bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ostracode paleoecology of the Bangor-Pennington transition (Chesterian, Mississippian) in northeastern Alabama
Authors: Olson William , Dewey Chris 
Published: January 2018

The Pennington Formation (Chesterian, Mississippian) of northeastern Alabama is a regressive, distal lobe of the Pennington/Lee clastic wedge, located on the western flank of the Appalachians in the Tennessee structural salient. The clastic units of the Pennington include sandstone, siltstone, mudstone, clay shale and coal and are genetically related to the effects of progradation. The presence of limestones and dolostones within the southwestwardly prograding and thinning Pennington is due to the lateral equivalency and interfingering relationships of the Pennington with the upper part of the adjacent Bangor Limestone shelf.A highly diverse ostracode fauna as been collected from outcrops along the Pennington-Bangor transition in northeastern Alabama. The most common assemblage of ostracodes is dominated by kirkbyaceans and includes species of Amphissites, Polytylites, Kirkbyella, Kirkbya and Reviya. Bairdiaceans are noteably absent from this assemblage. The Kirkbyacean Assemblage is only found in middle to outer shelf palaeoenvironments where clastic input is high, but where salinity conditions are thought to have been typically marine. In middle to outer shelf limestone-producing palaeoenvironments, a Bairdiacean Assemblage is dominant, although kirkbyaceans are still present.A Sansabellid Assemblage, consisting of kloedenellaceans such as Sansabella, Geisina, Geffenina, Nufferella and Glyptopleura appears to be produced under rapidly changing nearshore, inner shelf conditions, where terrigenous input was often high and palaeosalinities may have been variable or less than normal marine. The Sansabellid Assemblage contains occasional kirkbyaceans, however bairdiaceans are noteably absent. Intermediate assemblages contain elements of the three main assemblages and reflect the transition from the inner to outer shelf.In summary, the ostracode assemblages of the Pennington-Bangor transition in northeast Alabama provide indicators of palaeoenvironmental change during the southwestward progradation of the Pennington deltaic wedge onto the Bangor Limestone shelf. The prime factors resulting in palaeoecological response appear to have been variations in terrigenous input and palaeosalinity.
Morphology and movement of the presacral vertebral column in Phenacodus vortmani and Phenacodus primaevus
Authors: Otts Charlotte 
Published: January 2018

Phenacodus vortmani and P. primaevus, members of the mammalian radiation (Tiffanian - Bridgerian) in western North America, were digitigrade five-toed ungulates who were good runners compared to their contemporaries. P. vortmani was smaller and more slender (presacral vertebral column = 463 mm) while P. primaevus was larger and more robust (presacral vertebral column = 814 mm).The presacral vertebral column in these phenacodontids consists of 7 cervical, 15 thoracic, and 6 lumbar vertebrae, with the sectional length proportions being very similar in P. vortmani and P. primaevus.Morphologies and relationships of the vertebral structure in the cervical section allow both dorsoventral and mediolateral movements in both animals. Structures in the cranial thoracic section allow some mediolateral movement but restrict dorsoventral motion, adding stability and allowing forward transfer of momentum generated in the hind limb and caudal vertebral column. Structures in the caudal thoracic and especially the lumbar sections allow greater dorsoventral movements which enabled both phenacodontids to increase stride length beyond that accomplished by the limbs alone. In the smaller P. primaevus. the orientation of the zygapophyses emphasizes dorsoventral movements and restricts mediolateral movements compared to that in P. vortmani. providing the larger animal with greater efficiency in the flexion and extension of the posterior vertebral column during running.
Large-body impact: the least unlikely cause of pulsed extinction
Authors: Raup David M. 
Published: January 2018

In the past year, a strong consensus in the geological community has developed in favor of comet or asteroid impact as the ultimate cause of the K-T mass extinction, although many paleontologists remain doubtful. The discovery of tektites and craters with argon-argon ages matching the K-T boundary has finally removed the “smoking gun” problem. It is important, therefore, to evaluate large-body impact as a possible cause of other Phanerozoic extinctions, and to do so as carefully as possible before enthusiasm for the K-T success overwhelms objectivity in this research area.Approximately 60% of all species extinctions in the Phanerozoic occurred in “pulsed” extinctions, defined as ecologically and geographically pervasive episodes in which the number of species going extinct in a geologically short interval far exceeds any reasonable estimate based on chance coincidence of independent events. In addition to the well-known mass extinctions, pulsed extinctions often mark system, series, and stage boundaries, and probably some zonal boundaries.To be plausible, any proposed cause of pulsed extinctions must be (1) geographically pervasive (regional or global), (2) effective in diverse habitats, and (3) relatively quick-acting (to inhibit survival of species by migration or adaptation). The stresses causing the extinctions must be sufficiently severe and rare to be beyond the reach of natural selection, so that species do not have prior opportunity to evolve defenses.These requirements severely limit the possibilities to phenomena that occur on time scales of one million to tens of millions of years, far longer than the tens or hundreds of years available for study by traditional actualistic approaches. In view of the Phanerozoic record, it is not surprising that the earth has not experienced a pulsed extinction in historic times (excluding human influences). This suggests that extinction is one case where the present is a not the key to the past, and a full exploration of the problem will require a substantial re-ordering of thinking.Furthermore, because pulsed extinctions involve geographically widespread species (as well as restricted taxa), and because extinction of widespread species may be qualitatively different from that of local endemics, the common extrapolation from studies of extinction in local populations is risky.Of the many phenomena suggested as causes of pulsed extinction, large-body impact is the one that most nearly satisfies the requirements, and is therefore the least unlikely of the candidates. Temporal distribution is especially critical. Currently accepted flux estimates for comet and asteroid impacts are in the appropriate frequency range to explain the extinction record, but testing the hypothesis will depend on better radiometric dating of the 100+ craters and other confirmed impact events.
The Permian-Triassic boundary in Wyoming: the case of the disappearing paraconformity
Authors: Renner James M. , Boyd Donald W. 
Published: January 2018

Long-standing interpretations of paleontologic, sedimentologic, and stratigraphic evidence from Permian-Triassic marine sequences in western Wyoming have suggested an interruption in deposition of several million years' duration between the two systems, even though physical evidence of unconformity is subtle and somewhat equivocal. We postulated that an unconformity of this duration should be more pronounced in paralic and non-marine facies in central and southeast Wyoming than in adjacent inner-shelf marine facies in westcentral Wyoming. Therefore, we correlated an erathem boundary-bearing sequence from westcentral Wyoming (where it is faunally controlled) to southeast Wyoming (where it is non-fossiliferous) and studied this sequence for evidence of hiatus. The correlations were made using surface sections, surface gamma-radiation logs, and subsurface log suites.In southeast Wyoming, the lithostratigraphic equivalent to the systemic boundary in westcentral Wyoming is located within a redbed-evaporite sequence traditionally interpreted as having accumulated in paralic and/or terrestrial depositional environments. Physical evidence of disconformity at this surface in southeast Wyoming is no greater, and is in places less, than at several other horizons within the boundary-bearing sequence. Also, petrologic examination of the terrigenous clastic units below, through, and above the boundary-bearing sequence in central and southeast Wyoming suggests notable stability of the depositional environment. Southeastward stratigraphic thinning of various units within this boundary-bearing sequence is demonstrable; however, compelling evidence of regional truncation is not evident, and the stratigraphic thinning appears to be due to primary depositional processes rather than post-depositional erosion during hiatus.We interpret slow, episodic, yet generally continuous deposition of evaporite and siliciclastic units in southeast Wyoming across the Permian-Triassic boundary. If true, then conventional biostratigraphic estimates of the duration of a hiatus separating Permian inner and middle-shelf carbonate facies from overlying Triassic siliciclastics in western Wyoming appear to be overly long, and may need re-evaluation.
Ichnology of a reworked strandplain complex: Mississippian Hartselle Sandstone of Alabama
Authors: Rindsberg Andrew K. , Pashin Jack C. 
Published: January 2018

The Hartselle Sandstone of northern Alabama represents a mesotidal strandplain complex of Hombergian (middle Chesterian) age that was reworked by a transgressing sea. Transgressive reworking resulted in complex facies patterns that can best be deciphered by ichnology. Thickly bedded, unbioturbated beach to shoreface sandstone is widespread at the base of the formation. Wavy-bedded back-barrier to shelf sandstone and shale predominate in the middle and upper parts of the formation and contain distinctive assemblages of trace fossils, invertebrates, and plants.Barriers with a broad, gently sloping beach face and muddy coastal swamps typified the Hartselle strandplain which extended across northern Alabama. Barrier and coastal-swamp deposits lack trace fossils but locally contain an indigenous lycopod flora including stumps and Stigmaria root systems.Back-barrier tidal flats and lagoon deposits have trace-fossil assemblages dominated by bivalve traces that probably represent brackish environments. Marginal-marine sandstone contains chiefly monospecific assemblages and is reworked by bivalves and unknown organisms; Lockeia, Uchirites, and Rosselia are dominant at different sites. The Lockeia assemblage includes bedding surfaces with crowded bivalve resting traces. The abundance, density, and small size of monospecific burrows suggests estuarine conditions with high food supply and rapid larval colonization. The Uchirites assemblage is characterized by bivalve trails, representing probably brackish substrates with a high sedimentation rate.Shelf sandstone and shale include bivalve resting traces and trails (Lockeia ispp., Uchirites isp. aff. U. triangularis, Walcottia rugosa, and W. imbricata), asteroid and ophiuroid resting traces (Asteriacites stelliforme and Pentichnus pratti), trilobite resting traces and trackways (Rusophycus ispp. and Petalichnus isp.), and dwelling burrows, feeding burrows, trails, and trackways of unknown organisms (Chondrites-like burrows, Phycodes isp., Haplotichnus isp., Rosselia isp., Planolites montanus, Nereites missouriensis, Tasmanadia twelvetreesi, imbricate burrows, and wavelike burrows). Some shelf areas even supported diverse calcified faunas containing crinoids, fenestrate bryozoans, and articulate brachiopods.The Hartselle Sandstone is a facies mosaic that records indundation of an extensive strandplain complex and a distinctive stratigraphic succession of lithofacies and biofacies. Hartselle ichnofacies have unique aspects, but are similar to those of other marginal-marine Carboniferous strata in eastern North America. The paleoecologic complexity of the Hartselle Sandstone helps to establish the dynamic range of Carboniferous ecosystems, which have yet to be fully explored.
Intertwining of paleontology and medicine: implications for structure-function relationships, behavior, and habitat in paleontology
Authors: Rothschild Bruce 
Published: January 2018

Medicine and paleontology have been intertwined from the start. Gideon Algernon Mantell, a family physician from Sussex, and his wife, while on patient care “rounds,” found the first English dinosaur. Nineteen years later in 1841, Sir Richard Owen established the neologism, dinosaur, to categorize these animals. It is not accidental that the first Dean of Kansas University School of Medicine was also the founder of the University's Museum of Natural History. Rheumatology and paleontology paths have also crossed in the form of Thinocetus arthritus, so named because the ligamentous fusion in a specimen mistaken for arthritis.Technology and understanding of disease processes have advanced sufficiently to allow hypotheses to be critically examined. The underlying assumptions are that:1. Disease manifestations are relatively stable through time.2. Tissue is preserved in a state amenable to analysis.3. Pathology can be distinguished from diagenesis (pseudopathology).4. Analysis of pathology as a skeletal phenomenon provides more insight than examination of isolated bones.5. Analysis of pathology as a population phenomenon provides more insight than examination of isolated skeletons.Exemplifying the intertwining nature of the fields is the presence of spine and sacroiliac involvement and the nature and distribution of erosive lesions in the great apes (Gorilla and Pan (chimpanzee), the lesser ape (Hylobates) and Old World monkeys (Theropithecus, Papio, Cercopithecus, Macaca, Presbytis, Colobus, and Erythrocebus). This allowed definitive diagnosis of spondyloarthropathy. Reproducibility of diseases across species lines has been established for spondyloarthropathy (gorilla, chimp, monkey), not only for gross or radiologic appearance of individual bones, but also for skeletal distribution. More recently, similar observations have been made for Smilodon and Mammuthus. Reactive arthritis, related to infectious agent diarrhea or sexually transmitted, is a consideration. Infectious agent diarrhea is common in Old World primates. This natural disease state provides a unique model system for in depth analysis of the contribution of genetic and environmental factors to disease pathophysiology.
Phanerozoic paleogeographic, plate tectonic and paleoclimatic reconstructions
Authors: Scotese Christopher R. 
Published: January 2018

In 1913, in the concluding remarks to his two volume compendium, Principles of Stratigraphy, Amadeus Grabau wrote, “When the science of Stratigraphy has developed so that its basis is no longer purely or chiefly paleontological, and when the sciences of Lithogenisis and Orogenesis … are given their due share in the comprehensive investigation of the history of the earth, then we may hope that Paleogeography, the youthful daughter science of Stratigraphy will have attained unto that stature that will make it the crowning attraction to the student of earth history.” It has taken nearly 80 years for Grabau's vision to be realized. The fruits of the plate tectonic revolution combined with our new understanding of global eustasy and event stratigraphy, make it now possible to map the changing geography of the earth's surface with unparalleled detail and accuracy.In this poster session, we present 28 paleogeographic maps illustrating the changing configuration of mountains, land, shallow seas, and deep ocean basins during the Phanerozoic. The plate boundaries (spreading ridges, subduction zones, and transform faults) that were active during each time interval are also shown. For the Mesozoic and Cenozoic these plate boundaries are based on a synthesis of linear magnetic anomaly data and fracture zone locations compiled by PALEOMAP Project (International Lithosphere Program). The Mesozoic and Cenozoic orientation of the continents relative to the Earth's axis of rotation has been determined using a combination of paleomagnetic data and hot spot tracks. The location of Paleozoic plate boundaries, though speculative, is based evidence of past subduction and inferred sea floor spreading. The relative longitudinal positions of the continents and the width of the intervening Paleozoic oceans have been adjusted to best explain changing biogeographic and paleoclimatic patterns.The land, sea and mountain distributions portrayed on these 28 paleogeographic reconstructions have been used as input for a series of computer simulations of paleoclimate. The paleoclimatic model, which was developed by C.R. Scotese and M. I. Ross, uses the latitudinal distribution of land and sea, as well as the orientation of ancient mountain belts to predict the distr ibution of high and low pressure cells, prevailing wind direction, relative wetness/dryness, as well as zones of coastal upwelling. This model, which takes a simple parametric approach, makes predictions which are similar to the more robust General Circulation Model (GCM), but requires far less computer resources.
Are seismic/depositional sequences chronostratigraphic units?
Authors: Scott R. W. 
Published: January 2018

Sequence Stratigraphic Analysis is claimed to be a “new globally valid system of stratigraphy … a precise methodology to subdivide, correlate and map sedimentary rocks” (Vail et al., 1991, p. 622). Sequence stratigraphic units, such as depositional sequences, depositional systems tracts, and parasequences, are time-equivalent rocks of specific durations controlled by cyclical changes in sediment supply related to eustasy. These units are bounded by regionally extensive unconformities with erosion beneath and onlapping strata above, or by physical surfaces separating either different patterns of stratal geometry or shoaling-up facies units. According to this school, precise correlations are based upon inferred time relations within depositional models.Several key concepts of sequence stratigraphy have their origins in early geological studies. For many years geologists have separated time-equivalent strata by regional unconformities related to changes in climate or sea level, e.g., J. Woodward, 1695 and T. C. Chamberline, 1909. Stratal surfaces, such as bentonites and limestone markers, have been used in place of fossils for time correlations since the first wells were drilled. Stratigraphic models have strongly influenced how we correlate strata since the time of William Smith.Two developments are, indeed, new and have sparked the current resurgence in stratigraphic research. One is the seismic technology to test the physical continuity of strata on a regional scale (50-100 km), and to test the stratal geometry of genetically related depositional packages. The second is the chart of global coastal onlap events and eustasy (Haq et al., 1988).Some key research problems are: (1) how to identify unique, time-significant stratal surfaces; (2) how to test their physical continuity; (3) how to test the time relations within depositional models; and (4) how to identify the unique, time-significant global events recorded in the stratigraphic record. These stratigraphic concepts can be tested by graphic correlation, which is a powerful technique of high precision, quantitative stratigraphy. Its application in Cretaceous sections of the Gulf Coast and Oman, and in the Plio-Pliestocene of the Gulf Coast aids the distinction between synchronous surfaces and diachronous boundaries.
Patterns of diversity on the Paleozoic shelf: implications for controls on clade history
Authors: Sepkoski J. John , Miller Arnold I. 
Published: January 2018

Global diversity often is treated as a barometer of evolutionary success of clades without reference to their occurrence in ecological or biogeographical space. But global diversity is a composite of various spatial scales: alpha diversity, the number of taxa co-occurring in local communities; beta diversity, the distinction in taxonomic composition among local communities; and gamma diversity, the distinction, or degree of endemism, among geographic provinces, It has been argued by some workers that global diversity correlates strongly with alpha (and beta) diversity but by others that provinciality is the principal control of global patterns. The distinction is important, implicating either ecological processes (“adaptation”) or physical geography (“contingency”) as the major factor in expansion of clades.We have examined the ecological half of this problem with a data base comprising 505 fossil assemblages sampled from Paleozoic strata of Laurentian North America. On the basis of associated sedimentary characteristics, each assemblage has been assigned to one of six environmental categories, ranging from onshore peritidal situations to offshore basinal conditions. For each taxonomic order and class, average numbers of genera in each category have been determined for each of 18 time units. These average alpha diversities have been contoured on time-environment diagrams and compared to patterns of global diversity.Three major generalizations are derived from these diagrams:1. Major groups tend to be environmentally conservative, maintaining their life zones of maximum and minimum alpha diversity over vast stretches of time.2. Onshore-offshore shifts are most common during early expansion or late contraction of groups, when their global diversity is rapidly waxing or (more slowly) waning.3. Maxima and minima in global diversity within the groups through time, with few exceptions, are reflected in alpha diversity as fluctuations within the environments of maximum richness and/or as variations in the range of environments occupied.The last observation indicates a tight link between local ecology and global diversity, although the direction of causation is not unambiguous: alpha diversity could be reflecting only the global pool from which species can be recruited into local communities. However, in view of the onshore-offshore shifts during early and late histories of clades we conclude that local ecology is the dominant factor in controlling global diversity, and provinciality is secondary.