bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution, dispersal and habitat preference of deep-sea trace fossils
Authors: Crimes T. Peter 
Published: January 2018

Cambrian deep-sea sediments have yielded few trace fossils. The first moderately diverse suite is found in an Arenig flysch sequence in Eire. There followed a gradual increase in diversity and abundance of trace fossils in deep-sea niches in the Palaeozoic and early Mesozoic. A major burst of behaviourial evolution appears to have taken place during the Cretaceous and, from then through the Tertiary, high levels of trace fossil abundance and diversity were maintained. This is confirmed by recent work on Miocene deep-sea sequences and from a superbly preserved, diverse, ichnofauna recently discovered in strata of Oligocene and Miocene age in the Makran Range of Iran.In the past, it has been inferred that there was a gradual improvement in behavioral programming in deep-sea traces, with a trend towards economy of effort and perfection. However, Lower Palaeozoic deep water traces show careful, complex, behavioral programming which was to change little through the rest of the Phanerozoic.Within the deep-sea, there are, however, significant variations in the ichnospectrum in different niches. For example, the inner parts of seep-sea sand fans, particularly the channelled areas, have a mixture of “deep” and “shallow” water traces, whereas the outer fan normally has only deep water forms.
Biostratinomy of Recent intertidal bivalves at False Bay, San Juan Island, Washington, U.S.A.
Authors: Dent Steven R. , Uhen Mark 
Published: January 2018

The importance of hydrologic processes in determining where and how a shell will be deposited is widely acknowledged, but few actualistic studies of these processes have been conducted. Additional knowledge of how the hydrologic regime influences the post-mortem distribution, orientation, and burial of modern shells can provide valuable paleoecological insights.For the purposes of biostratinomy, single and articulated shells of Macoma nasuta and Clinocardium sp. were studied in False Bay, a semicircular inlet located on the west coast of San Juan Island, WA. Dead shells of these species were the most numerous and conspicuous skeletal elements present on the tidal flats. Transects were used to quantify the valves' natural distribution, orientation and depth of burial. Shell concentrations were significantly greater toward shore and decreased toward the center of the bay. The majority of these valves were articulated (56.4%) and oriented in the convex-up attitude (71.7%).Tides and waves were the bay's dominant hydrologic forces. Spring low tides (maximum range of -0.8 m to 2.6 m) leave most of the bay subaerially exposed. During periods of immersion, waves from the Straits of Juan de Fuca underwent refraction, diffraction, and shoaling as they moved into False Bay. This influence was evidenced in the concentric sand bars which average 100 m long, 20 m wide and 0.5 m high. Painted and numbered valves were used to determine the effects of waves and tides. Shells were place in m2 areas both in a tidal channel and on a sand bar at low tide and then left for 1–2 tidal cycles. Recovery rates of shells ranged from 76.7% to 93.3%. Regardless of initial attitude, the majority were found in a convex-up attitude; convex-up valves remained in that orientation (89.8% – 97.7%) while those initially convex-down were reoriented to the convex-up position (75% – 86%). These findings confirmed that the convex-up position is the most hydrodynamically stable.The most interesting aspect of this study was the nature of valve transport. Valves placed in the tidal channel moved less than one meter while those on the sand bar showed a strong bimodal distribution: shells moved either less than 2 m or distances ranging from 10 to greater than 119 m. The long range transport was unexpected; it was caused by the flotation, under calm meteorological conditions, of subaerially exposed convex-down shells on the incoming tide. This mode of transport moved the valves considerably greater distances than either saltation or traction in bedload. Shell flotation was not correlated to valve size, handedness, nor species.
Higher taxa in the fossil record and the recognition of evolutionary events: patterns vs. processes
Authors: Fastovsky David E. , Sheehan Peter M. 
Published: January 2018

The fossil record is commonly (but not universally) invoked as an historical record with which to test evolutionary scenarios. The process by which this takes place involves the recognition of patterns of taxa in a temporal framework. The patterns are in turn interpreted as the result of some evolutionary mechanism. We submit that if the fossil record is to be a tool in evolutionary studies, the use of appropriately-defined higher taxa can be consistent with the objective of recognizing patterns from which evolutionary events can be inferred.We implemented a study to monitor the ecological diversity of “families” of dinosaurs through the last 2.2 million years of the Cretaceous in the terrestrial sediments of the Hell Creek Formation in eastern Montana. We concluded, using the Shannon index and rarefaction as monitors, that at the “family” level, the ecological diversity of dinosaurs remained constant.We suspect that the taxa we designated as “families” did not branch ancestrally at equivalent points in their respective phylogenies. Nevertheless, each is a monophyletic group, established and united by synapomorphies. We therefore measured and tracked the relative proportions of monophyletic groups through sequential time slices of the latest Cretaceous. We interpreted this as a measure of ecological diversity.The phylogenetic methods that were used to define the extinct “families” in our study are epistemologically indistinguishable from methods that are used to establish monophyletic fossil groups at any taxonomic level, including the lowest levels. Why should special significance be attributed to a taxonomic level (i.e., species) that is obtained by means no different from those used to obtain the other levels?Use of the fossil record in evolutionary reconstruction requires the recognition of patterns, and the attribution of evolutionary mechanisms to those patterns. It is unlikely that selection acts on units other than populations which arguably, are not even taxa. Recognition of historical patterns rather than causality or process, therefore, may be the unique province of the stratigraphic record.
Neogene Siwalik mammalian lineages: species longevities, rates of change, and modes of speciation
Authors: Flynn Lawrence J. , Barry John C. , Morgan Michele E. , Pilbeam David , Jacobs Louis L. , Lindsay Everett H. 
Published: January 2018

The Siwalik sequence, particularly the interval from 18 to 7 Ma, provides one of the few terrestrial data sets that allows direct measurement of temporal durations of mammalian species. Its data are drawn from a single biogeographic subprovince and superposed collections likely represent successive samples of single lineages. Observed temporal ranges underestimate total species longevities if (1) species existed in other biogeographic provinces before or after the temporal ranges recorded in the Siwaliks, or (2) the fossil record inadequately samples species durations in the Siwalik subprovince. Some data, notably from Afghanistan, China, and Thailand, bear on the first variable. The second can be controlled by considering data quality, in this case the temporal distribution of good data sets, to assess the scale of accuracy available for defining range endpoints. In general, range endpoints can be estimated to the nearest 0.1 million years.The diverse Rodentia give a mean species longevity of 2.2 million years for the Miocene Siwaliks. This includes single records, but of course ignores unretrieved rare or short-lived taxa. The diverse Artiodactyla yield 3.1 million years. The difference may reflect greater body size and longer generation time; large Perissodactyla and Proboscidea have longer temporal ranges. Carnivorous mammals also show about 3 million year durations. Given these data, the average longevity for Sivapithecus species (1.6 million years) is modest. The deposits of the Clarks Fork Basin, Wyoming, offer a Paleogene data set comparable to that of the Neogene Siwaliks. Paleocene-Eocene mammals of North America yield shorter longevities (most less than one million years).Extinction is the dominant mode of species termination for Siwalik mammals. Most taxa originated by immigration (as at about 13.5 Ma) or abrupt speciation. There are some cases for insitu transformation of lineages, for example in the genera Punjabemys, Antemus, Percrocuta, Dorcatherium, Giraffokeryx, and Selenoportax. The rodent Kanisamys shows a rate of increase in tooth size of 0.5 darwins. This overall rate is moderate by Paleogene standards, but includes an interval of more rapid change between 9.0 and 8.5 Ma.
The Oxford Clay: a paleontological laboratory
Authors: Hudson John D. 
Published: January 2018

The Lower Oxford Clay, a marine formation of Middle Jurassic (Callovian) age exposed in central and southern England, merits the attention of paleontologists and geochemists for several reasons. It was the subject of a classic of biostratigraphic and evolutionary paleontology by Brinkmann on the ammonites; sexual dimorphism and bioprovinciality in the same group has since been intensively studied by Callomon and others. Its exploitation by the brick industry has enabled the assembly of one of the most extensive collections of marine vertebrates by the Leeds brothers and later workers; these include the world's largest ever fish, and superbly preserved ichthyosaurs, plesiosaurs and crocodiles now dispersed to museums throughout Europe and beyond. Dinosaurs, while rare, are also diverse. The benthic fauna is dominated by abundant but not diverse molluscs, believed tolerant of soupy bottom conditions and periodic dysoxia. Coccoliths and dinoflagellates represent the phytoplankton. Aragonite, calcite and phosphate biominerals are excellently preserved. In our main study area burial did not exceed 500m.; organic matter is immature. Early diagenesis resulted in the formation of carbonate concretions that preserve original sediment fabrics elsewhere destroyed by compaction; later diagenesis brought about further mineralogical changes.Work since the 1970's has resulted in much improved understanding of the Lower Oxford Clay biota and its trophic relationships. It is useful to compare it to the more calcareous Middle and Upper Oxford Clay. The biostratigraphy is extremely well-known. The well-preserved fossils invite microstructural and geochemical studies. Economic concerns add impetus to the study of actual or potential hydrocarbon source rocks. Yet the Lower Oxford Clay is full of enigmas and questions still. It looks quiet-water but has many diastems, not all recognizable by classic criteria like shell beds. The fossil preservation might imply a high sediment delivery rate, but the sediment accumulation rate is low. It is organic-rich, but not anoxic. Where did the enigmatic ‘pendent’ bivalves live? Whence the nutrients to support the rich biota? To what extent do organic compounds survive from the primary producers, or does heterotrophic reworking dominate? Can we refine or quantify trophic relationships? We should also be able to use our ‘laboratory’ for experiments of wider significance for paleotemperatures or paleo-CO2 levels.In the Oxford Clay group of papers we attempt to summarize where traditional paleoecological analysis has led us to so far, and to show how the new approaches made possible by advances in isotopic and biomolecular paleontology can revise and refine our ideas, solve old problems and, no doubt, raise new ones. We believe our collaborative approach has much to offer for paleontologists and geochemists, as also exemplified by the other contributions to the symposium.
Organic stratigraphy and its applications with examples from the North American Western Interior and Antarctica
Authors: Jacobson Stephen R. , Askin Rosemary A. 
Published: January 2018

Both insoluble (particulate) and soluble (molecular) sedimentary organic matter carry signatures of physical, chemical, and biological processes. These signatures may reflect (a) primary age-diagnostic, organism-specific, and environmentally-sensitive processes; (b) secondary factors related to mode of transportation, deposition, and preservation; and (c) tertiary agents that indicate post-burial alteration of the organic matter. Application of any or all organic matter data recorded in rocks can be used to solve geologic problems.Organic stratigraphy may be applied to hydrocarbon exploration. Our example uses both particulate and molecular data to reconstruct the age relations of Cretaceous-Lower Tertiary sediments in Wyoming, to determine the age of thrust fault motion, and to demonstrate constraints on the timing of upward petroleum migration to available trapped reservoirs.Another perspective helps establish chronostratigraphic frameworks for correlations of global sea-level change. Our example from Antarctic sediments that span the Cretaceous-Tertiary boundary reflects perturbations in relative sea-level and the consequential changes in the distribution of organic particulates from marine and terrestrial regimes. These data can be compared to age-equivalent data from other parts of the world, and test global sea-level change.Both of these applications demonstrate the versatility of organic matter in solving geologic problems. Data from contemporaneous land plants, freshwater and marine organic-walled micro-organisms provide clues on their lifestyle and subsequent afterlife alteration. Organic stratigraphy represents a long anticipated integration of several paleontological disciplines. It combines aspects of palynology, organic geochemistry, paleobotany, and coal petrography into a coherent science, with an enhanced capability to provide significant applications in the future.
Permian Triassic geologic evolution in the southern Kitakami Belt, Japan
Authors: Kamada Kotaro 
Published: January 2018

Before opening of the Japan Sea, the Japanese islands were attached to the eastern margin of the Asian continent. The Southern Kitakami Belt is regarded as a micro-continent in an accretional complex of the islands, that accreted before the Early Cretaceous. But its tectonic setting and location between the belt and the Asian continent is still an unresolved argument.Permo-Triassic sequences in the Southern Kitakami Belt are composed of shallow to off-shore deposits. These deposits are composed of clastics, carbonates with volcaniclastics. But there was no volcanic activity in the belt in the Middle to Late Permian. From the viewpoint of the sedimentary character and history, the Middle Permian to Middle Triassic sequences differ from their previous and their following successions in the belt. And the sedimentary basin of Middle Permian to Middle Triassic was bounded by transform faults. Magmatic arc was replaced by passive margin as hinterland of the Southern Kitakami Belt during the Middle Permian to Middle Triassic. It means that the sedimentary basin moved from the margin of Yangtze Platform to Sino-Korean Platform at that time.
Demise of the middle Paleozoic crinoid fauna: gradual or mass extinction?
Authors: Kammer Thomas W. , Ausich William I. 
Published: January 2018

There are essentially three major crinoid faunas of the Paleozoic: 1) the lower Paleozoic (Ordovician) fauna dominated by disparids and diplobathrid camerates; 2) the middle Paleozoic (Silurian-middle Mississippian) fauna dominated by monobathrid camerates, cladids, and flexibles; and 3) the upper Paleozoic (middle Mississippian-Permian) fauna dominated by cladids. Change from the middle Paleozoic fauna to the late Paleozoic fauna, at or near the Osagean-Meramecian boundary, was characterized by Laudon (1948) as “one of the most remarkable faunal breaks in the entire Paleozoic era”. The monobathrids that had reached their zenith in the Osagean (Tournaisian-Visean) became a very minor component of late Paleozoic faunas. Conventional thinking has implied that a mass extinction of crinoids occurred at the Osagean-Meramecian boundary.We have biostratigraphically subdivided the late Osagean and early Meramecian into four zones (times A-D, oldest to youngest, all within the Gnathodustexanus zone) in order to study the origination and extinction of all crinoid species during the changeover from the middle to upper Paleozoic faunas. Rather than a mass extinction, a monotonic turnover of species fits a pattern of gradual extinction as extinctions outpaced originations. Data are based on 216 species (taxonomically updated) from 69 localities and are as follows:The pattern of originations and extinctions for monobathrids is very similar to the pattern for all crinoid species.The above data have maximum diversity during Time B of the late Osagean followed by declining diversity in times C and D into the early Meramecian. Late Meramecian crinoid faunas (after time D) were less diverse with a maximum of about 45 species. The gradual decline of crinoids across the Osagean-Meramecian boundary cannot be explained as sampling bias (Signor-Lipps effect), because ranges of crinoids thought to be extinct at the boundary are extended into the early Meramecian as well as disappearing at various tinles prior to the boundary.The decline in diversity and the monotonic turnover of species are hypothesized to be the result of habitat reduction as the Eastern Interior Basin of North America was gradually infilled with clastic sediments at the end of the Acadian Orogeny. Most notable in this regard was the smothering of the Keokuk Limestone carbonate bank. Changes in sea level also contributed to habitat reduction. Lowering of sea level at the end of the Osagean caused restriction of open marine environments. A transgression in the early Meramecian was followed by shoaling and restriction during deposition of the late Meramecian Salem and St. Louis limestones.
Pseudoplankton: hitch-hikers through time or stuck in the mud?
Authors: Kauffman Erle G. , Meyer Christian A. , Villamil Tomás , Harries Peter J. 
Published: January 2018

Pseudoplanktic life modes have typically been invoked to explain the presence of abundant fossils belonging to normally low-oxygen intolerant taxa within oxygen-deficient black shales facies (e.g., bivalves, crinoids, barnacles, serpulid worms, brachiopods, gastropods, bryozoans, foraminifers, corals, hydrozoans, and sponges). The same explanation has been used for exceptional paleobiogeographic distribution of benthic species. However, detailed paleoecologic, population, and taphonomic analyses of numerous black-shale biotas in conjunction with recently published models for oxygen-deficient basins suggests that this hypothesis is no longer required to explain the distribution of these taxa in supposedly non-viable habitats. Actual examples that could be interpreted as evidence for pseudoplanktic life habit (i.e., colonization on both sides of ammonites) are very rare. For example, less than 2% of the encrusted ammonites (N = 1240) in the Jurassic Posidonienschiefer show pseudoplanktic colonization patterns. These could be interpreted as flipped specimens within the benthic zone. The remainder are stable “shell-island” substrates with ammonites (and large bivalve shells) colonized on one side only. Most logs believed to be colonized on the lower surface by bivalves and/or crinoids in floating position actually have evidence for benthic encrustation on the tops and sides of the logs, and have obvious current shadows of dead shells.The data show that: 1) the abundance of these taxa greatly exceeds the expectations of pseudoplanktic rain as well as the number of potential hosts; 2) they commonly occur as short-term event communities rather than as the normal populations expected of continuous pseudoplanktic rain; 3) specimens are commonly found in epibenthic life position; 4) their occurrence patterns show strong facies control usually reflecting benthic oxygen gradients; 5) many preserve a large prodissoconch or protoconch suggesting a long-term planktotrophic larval stage. Most of these “pseudoplanktic” groups appear to have had a benthic life habit.Moreover, most oxygen-deficient environments disappeared by the end of the Cretaceous along with some of the dominant pseudoplanktic taxa. Drifting logs and seaweeds are common today, but generally lack specific “pseudoplanktic” faunas, with the exception of boring bivalves, gooseneck barnacles, serpulid worms, and bryozoans. Epibenthic bivalves and crinoids are very rare to absent on potential “pseudoplanktic” hosts in modern seas, yet are the main groups of organisms designated as pseudoplankton in the fossil record.
Morphometric studies of radiolarian evolution
Authors: Lazarus Dave 
Published: January 2018

Radiolarians are the most diverse of the 4 major fossil forming plankton groups, with several hundred living species, and an equally diverse range of biologic specializations for planktonic existence. Studies of radiolarian evolution are mostly from the Cenozoic, where the opaline silica skeletons of radiolarians are well preserved in most areas of the world's oceans. Cenozoic radiolarian skeletons are mostly too small (50-150 μm) and delicate to easily manipulate individually. Washed sieved skeletons are strewn at random orientations onto glass microslides and viewed in transmitted light. At the required magnifications, most skeletons cannot be viewed in their entirety within a single focus-plane. Many (perhaps the majority) of taxonomic characters in radiolarians are not visible in the skeleton outline, but are internal. These characteristics make normal image analysis techniques more difficult to employ. Computer assisted manual digitizers (one version working in 3 dimensions) have sometimes been used to measure skeletons. Distance, angle, area, and shape outline measurements have all been used to quantify radiolarian morphology.Radiolarian skeletal growth is determinate, and relatively little ontogenetic or within-population allometric variation is seen. Geographic variation in radiolarian species morphology is common, but little studied. Perhaps due to the effort involved, most ordinary taxonomic work does not employ morphometric data: its use has largely been in species-level evolutionary studies. Phyletic trends in size, shape, and in other characters have long been used to delineate stratigraphically useful chronospecies, and some of these anagenetic series have been morphometrically measured. Cladogenesis has also been morphometrically quantified in a few cases. Most studies of both cladogenesis and anagenetic evolution have documented gradual rates of morphologic change.Integrated studies of paleogeographic variation and temporal change are still needed, as is better information on modern radiolarian biology. Much more efficient measurement tools are also needed, to handle the very large number of specimens required by integrated studies.