bluuebunny/crossref_metadata_2025_split huggingface dataset:
Paleoenvironmental control of species distributions in Neogene invertebrate taxa of the Dominican Republic
Authors: Anderson Laurie C. , Geary Dana H. , Budd Ann F. , Nehm Ross H. , Johnson Kenneth G. , Stemann Thomas A. 
Published: January 2018

Neogene deposits of the northern Dominican Republic contain a diverse fossil assemblage that is especially rich in corals and mollusks. To see if faunal change was concordant or discordant within and among taxa and decipher factors controlling distributions, we compared distributions of coral communities, the gastropod families Strombidae and Marginellidae, and the bivalve family Corbulidae. We also incorporated published ranges for the Cardiidae (Vokes, 1989), Cancellariidae (Jung and Petit, 1990), and the columbellid genus Strombina (Jung, 1986).First and last appearances of individual mollusk species were diachronous among sections. Within the sections, however, first and last appearances of mollusk species tended to coincide. Concordance of species ranges could be caused by unconformities or faults, be an artifact of sampling, or indicate similar responses by species to environmental changes. Neither stratigraphic gaps nor faults appear to correspond to concordant first or last appearances. Although the absence of mollusk taxa generally corresponds to less intense sampling, sampling intensity is highly correlated with the presence of macrofossils and therefore, taxa absence is probably real. First and last appearances do coincide with paleoenvironmental changes such as rapid deepening, introduction of marine conditions, increased intensity of erosional bottom currents, and changes from reefal to sand flat facies.Comparisons among taxa also helped elucidate other distributions patterns. For instance, comparing coral communities to strombid ranges showed that strombid diversity increased in grass flats (inhabited by free living corals) and reefal deposits, indicating similar ecologic preferences to many modern strombid species. Using the coral fauna to distinguish a grass flat community from other shallow marine facies also helped explain corbulid abundances as environmentally induced, with lower numbers in grass flat deposits.Simultaneous comparison of species distributions within diverse taxa can help explain the nature of species occurrences. For several mollusk taxa from the Neogene of the Dominican Republic, the general correspondence in distribution patterns across taxa indicates that paleoenvironmental conditions were controlling species distributions.
Thin-plate spline analysis of shape differences between a primitive and modern rhinoceros
Authors: Bales Gerald S. 
Published: January 2018

The thin-plate spline (TPS), a new technique for comparing shapes using landmark data, has been developed by Fred Bookstein and programmed for microcomputers by F. Rohlf. TPS generates a mapping function describing the deformation necessary to superimpose one set of landmarks exactly onto a second set of homologous landmarks, after first adusting for orientation and overall size. The mapping function is then used as an interpolant to plot a grid which geometrically represents the deformation. The TPS grid is a mathematically formalized equivalent to the Cartesian transformation grid (CTG) introduced in 1917 by D'Arcy Thompson, a technique which requires construction by eye, brain, and hand.TPS is used here to “replicate” Edwin Colbert's 1935 CTG analysis of shape change from Subhyracodon occidentalis, a primitive fossil rhino, to Rhinoceros unicornis, a derived living form. Twenty-two landmarks were defined on Colbert's original line drawings and coordinate data was retrieved by digitization. TPS analysis of this data was nearly instantaneous using an 80386 20MHz PC.TPS mapping of S. occidentalis onto R. unicornis produces a transformation similar to Colbert's CTG (differing most at the mandibular angle) and reveals both global and local aspects of the shape change. The global changes are dorsoventral heightening and rostrocaudal shear. Local changes include rostrocaudal shortening in the occipital and preorbital regions and rotations of the occiput and rostrum toward each other (producing the saddle-shaped skull of R. unicornis).The functional consequences of these changes may be interrelated. For example, the upward and forward displacement of the occiput in R. unicornis suggests a change in head posture (nuchal attachment and range of motion) and a change in masticatory processing (increased vertical action of the temporalis muscle). Both functional changes may relate to dietary preference.
Patterns of faunal turnover and diversity in the Siwalik Neogene record in relation to regional and global events
Authors: Barry John C. , Morgan Michèle E. , Flynn Lawrence J. , Jacobs Louis L. , Lindsay Everett H. 
Published: January 2018

The fluvial Neogene Siwalik formations of northern Pakistan contain one of the longest and richest sequences of terrestrial vertebrate faunas known. The complete sequence extends from ca. 18 Ma to 1 Ma, with the interval between 18 and 7 Ma being best sampled. Throughout this best known interval vertebrate remains are frequently abundant in channel fills and less common in large channel sands, levees, and paleosols. Although the abundance and quality of fossil preservation varies, all stratigraphic levels have some fossils and the record of most subintervals is good to excellent. As a consequence the patterns of faunal turnover and changes in diversity can be documented and analyzed for 0.5 my long subintervals.Thirteen orders of Siwalik mammals have been identified, with well sampled subintervals typically having 50 or more species. Despite the ordinal diversity, however, most Siwalik mammal species belong to just three orders: rodents, artiodactyls, and perissodactyls. Among the larger mammals, the bovids and equids are the most common and have the most species, while the murid and cricetid rodents dominate the small mammal assemblages. These Siwalik abundance and diversity patterns differ markedly from those of the Paleogene and are a result of Neogene radiations in these four families and extinction of Paleogene groups.Between 18 and 7 Ma species diversity varies considerably. Among artiodactyls and rodents the number of species first increases between 15 and 13 Ma and then falls after 12 Ma. Significant changes in relative abundance are also known, including an increase in the abundance of bovids between 16.5 and 15 Ma and a very abrupt increase of murids at 12 Ma.Data on stratigraphic ranges of rodents and artiodactyls show that faunal change in the Siwaliks was episodic, occurring as short intervals with high turnover, followed by longer periods with considerably less change. Maxima of first appearances occur at approximately 13.5 and 8.5 Ma, while maxima of last appearances come at 12.0, 9.5, and 8.0 Ma. It is thus apparent that in the Siwaliks increased extinction did not accompany or closely follow maxima of first appearances.Correlations of these faunal events to global climatic trends are ambiguous. However, it is apparent that the middle Miocene diversification of Siwalik faunas occurred during a period of global cooling, while the late Miocene decline in diversity preceded a second episode of cooling and increasing aridity.
Chemosymbiosis: towards an integrated approach for tracking trophic strategy in the fossil record
Authors: Cobabe Emily 
Published: January 2018

Chemosymbiosis can be identified in fossil taxa and followed through the fossil record with some certainty if several independent criteria are met. No hard part morphology reliably reflects a chemosymbiotic lifestyle, but soft part morphology can be used to demonstrate that chemosymbiosis is primitive in some groups. Throughout the evolutionary history of a taxon, faunal and facies associations can provide support for a chemosymbiotic interpretation. Biogeochemical evidence from fossil organic matter may, in some cases, demonstrate the δ13C depletion recognized as being chemosymbiotic in origin.Morphology of extant lucinacean bivalves indicates that the superfamily was primitively chemosymbiotic and suggests that the Ungulinidae and some of the Thyasiridae have secondarily lost their bacterial symbionts. This observation, along with facies and faunal data, suggests that the family Lucinidae has always been chemosymbiotic and that the Lucinidae are a reliable group to use in evaluating the paleobiological effects of chemosymbiosis.Biogeochemical evidence does suggest that lucinid bivalves were chemosymbiotic in the past and stable isotope analyses remain the only direct method for evaluating chemosymbiosis in the fossil record. For taxa with no extant members but with interesting faunal or facies associations, δ13C of the organic matrix is still the best hope of evaluating this trophic strategy.
Rates and patterns of molecular evolution in marine animals following the Isthmian emergence
Authors: Collins Timothy 
Published: January 2018

The marine vicariant event resulting from the Pliocene emergence of the Central American Isthmus presents a unique opportunity for calibrating rates of molecular evolution. The synchronous fragmentation of the ranges of previously widespread taxa into Western Atlantic and Eastern Pacific components (geminates) enables one to make comparisons of rates among higher taxa on the same time scale and to evaluate the regularity of rates of molecular evolution among all species sampled. Other advantages of this approach are that the time scale (approximately 3 Ma) is one of particular interest for evolutionary biologists concerned with speciation and one that minimizes the ambiguities associated with augmentation of divergence values to account for multiple hits at a site. The divergence values derived for geminate pairs are independent, allowing statistical evaluation of variance in rates.The current popularity of the relative rates test as the final arbiter of questions regarding rates and rate variation is primarily a matter of convenience and not a reflection of methodological superiority. A review of the commonly used techniques for calibrating rates of molecular evolution shows that each approach has limitations. Temporally based calibrations of rates are necessary complements to time-independent comparisons.Interpretation of transisthmian molecular comparisons in the literature have in many cases been unduly influenced and confused by molecular clock assumptions and the restriction of studies to single higher-level taxa. Analysis of the apparently contradictory published data as well as new results from sequence comparisons of fishes, urchins and snails suggests a synthesis: taxon specific rates of molecular evolution, with reduced variance within taxonomic groups and great variance among all groups sampled.
Graptolite and conodont faunas in Ordovician Vinini Formation, Roberts Mountains, central Nevada, demonstrate that the Roberts Mountains allochthon is not an exotic terrane
Authors: Finney Stanley C. , Ethington Raymond L. 
Published: January 2018

Two very different plate-tectonic models have been proposed to explain the development and emplacement of the Robert Mountains allochthon (RMA) onto the North America craton during the Late Devonian-Early Mississippian Antler Orogeny. In one model, the RMA represents a far-traveled accretionary prism that migrated eastwards over a west-dipping subduction zone. In the other, the eugeoclinal strata of the RMA were deposited on the continental rise of western North America within a closed back-arc basin. Siliciclastic sediments, especially quartz sandstones, compose much of the RMA, yet knowledge of their provenance is poor even though such knowledge is essential for evaluating the two plate-tectonic models.We have recently obtained large collections of graptolites and conodonts from turbiditic quartz sandstones in the Lower Member of the Vinini Formation in the Roberts Mountains. These sandstones of lower Whiterockian age are correlative with the lower Antelope Valley Limestone that deposited on the western shelf of North America. The diverse graptolite fauna represents the oceanic isograptid fauna. However, it also includes pendent didymograptids and rooted dendroids that were restricted to shallow shelf seas. The dendroids (Cactograptus, Dendrograptus, Desmograptus, and Dictyonema) were benthic organisms, could not have lived in a deep marine setting, and are also common in shallow-water carbonate strata of western Utah. All specimens within the turbiditic quartz sandstones of the Vinini were broken before final deposition and burial, but specimens from Utah are generally complete. The diverse conodont fauna is virtually identical to that found in the lower Antelope Valley Limestone, as well as in coeval strata in western Utah. Although it includes a few deep (cold) water, cosmopolitan species, it is dominated by species that are otherwise known only from shallow water strata deposited on the North American craton.We conclude that turbidity currents transported these exotic graptolites and conodonts down from the shelf and onto the rise along with the quartz sands in which they occur. Thus, the Whiterockian quartz sandstones in the Vinini Formation must have a North American provenance just as the fossils do. This is strong evidence that 1) the RMA is not exotic to North America, 2) the eugeoclinal strata of the RMA were deposited on the western continental rise of North America and on the eastern side of a back-arc basin, and 3) the RMA was thrust onto the western shelf of North America by closure of this back-arc basin.
Biogeography of Recent marine bivalve molluscs: implications for the geography of extinction
Authors: Flessa Karl W. , Jablonski David 
Published: January 2018

The geographic distribution of taxa appears to affect their survivorship during both background and mass extinction. Direct paleontological evidence for this tendency is strong, but inevitably incomplete on a global scale due to extreme geographic variation in preservation and sampling. As a complementary approach to the relation between biogeography and extinction, we are modelling potential survivorship patterns using a global biogeographic database for Recent shallow (< 200 m) marine bivalve molluscs. To date, we have collected information on genera from 10 superfamilies: Arcacea, Limposacea, Mytilacea, Pinnacea, Pteriacea, Pectinacea, Carditacea, Cardiacea (including Tridacnacea), Tellinacea, and Veneracea. Although these superfamilies represent only one-fourth of all marine superfamilies, they include approximately 46 percent of the extant marine genera. We used species lists or monographs to disentangle many generic assignments, thus attaining uniformity of treatment at the generic level among 115 sites or regions. These faunas together represent all latitudinal zones, all oceans, and many oceanic islands and inland seas.The expected latitudinal and inter-ocean diversity gradients are clearly seen in our data. Although high latitude faunas are consistently low in generic diversity, tropical bivalve faunas may have high, intermediate, or low generic diversities, mainly because of the relative impoverishment of Atlantic faunas and the low diversity of tropical island faunas relative to their continental shelf counterparts. Island faunas are dominated by cosmopolitans, underscoring the importance of dispersal in maintaining bivalve populations on oceanic islands.We simulated extinction of bivalve faunas by “eliminating” genera restricted to particular latitudinal zones, oceans, continental shelves or oceanic islands. Because endemism at the generic level is low (despite today's high global thermal gradient and wide dispersal of continents), extinctions comparable to the K/T and P/Tr can be accomplished only through the annihilation of faunas in several latitudinal zones or oceans. Either today's fauna is more cosmopolitan than those of the past, or major mass extinctions required truly pervasive and profound environmental upheavals.
Archaeocyath palaeoecology
Authors: Hart S. Fraser 
Published: January 2018

A well preserved archaeocyath fauna occurs in the Forteau Formation in Southern Labrador, Canada. Following on from the confirmation that archaeocyatha are aspiculate calcified sponges, detailed ecological work is now being undertaken on this fauna, a representative of the first reefal ecosystem in the fossil record.One species, Metaldetes profundus, shows considerable variability in growth form, from open bowl-shaped forms in lagoonal settings, to a branching morphology in biohermal habitats. This species also appears to colonise a variety of substrate types and for this purpose often uses exothecal structures and holdfasts. M. profundus is also the dominant species numerically, comprising 80% of the fauna, except at the top of the bioherm horizon, where Archaeocyathus atlanticus becomes dominant. In contrast to previous studies' findings, bowl-shaped Metaldetes at the top of the bioherm horizon occupy the basal region of the bioherms, not the upper areas and provide a surface on which the bioherms can develop.The unique form of Retilamina amourensis endows it with the ability to stabilise substrates so facilitating the colonization of a substrate. It is more common at the base of bioherms, providing a surface on which other archaeocyaths can settle. The calcimicrobes Renalcis and Epiphyton also appear to have played a major role in the initiation of the bioherms, occurring as 3–5cm thick layers on erosion surfaces, within which small, juvenile, upright M. profundus sticks, <1cm in diameter, are found, surrounded and supported by the dense calcimicrobe aggregate.Digital 3-D analysis is being used to document the behaviour of the archaeocyaths, together with vertical and lateral zonation within the bioherms, especially with regard to the timing of calcimicrobe encrustation. Volumetric abundances of the archaeocyaths are also being calculated.There are small faunal composition changes over the area: Archaeosycon billingsi, a solitary stick-like form is more abundant in the west than in the east and Archaeocyathus atlanticus, another stick-like form occurs in dense clusters in lagoonal environments, elsewhere being solitary.
Origin of the Bakevelliidae, evolution of the multivincular ligament and implications for the Mesozoic bivalve radiation
Authors: Heaney Michael J. , Yancey Thomas E. 
Published: January 2018

The Buckhorn Asphalt (Desmoinsean, Pennsylvanian) of south-central Oklahoma has yielded a diverse and exquisitely preserved, shallow marine Molluscan fauna, including many minute taxa. This window into the shallow marine biota of the late Carboniferous, provides insight regarding evolutionary relationships of several molluscan clades and the Mesozoic Bivalve radiation. It confirms a Pterineidae ancestry for the Bakevelliidae, and allows documentation of crucial character states such as: shell microstructure, ligament ultrastructure, geochemical composition, prodissoconch 1 and 2 stages, as well as hinge dentition and ligament details for members of both families. Three previously undescribed species of pterioid bivalve, provide new data on this clade. These forms include: 1) a pterineid closely related to Leptodesma, with an alivincular ligament type, 2) the earliest known bakevelliid, possessing a rudimentary multivincular ligament, and 3) a transitional form which has but one shallow ligamental pit located beneath the beaks. These ancestral forms consist of minute species that develop character states used as family defining features in the Mesozoic. This study extends the range of the predominantly Mesozoic bakevelliids, and documents the early evolutionary development of the ligament type which characterizes the group.Additionally, these taxa demonstrate the Carboniferous origin of the Mesozoic bivalve radiation, and provide invaluble data concerning the roots of the radiation prior to the firm establishment of Mesozoic clades. The key family defining character was established in the Carboniferous yet did not come to fruition until the Mesozoic. These taxa also enable one to establish multiple working hypotheses regarding the functional and adaptive significance of this ligament type. The multivincular ligament may: 1) conserve constructional material, 2) facilitate a more endobyssate life position, or 3) simply be a neutral character of little or no adaptive value. The exceptional preservation of the Buckhorn Asphalt biota provides a unique opportunity to evaluate such evolutionary and paleoecological relationships.
Tetrapod extinctions during the Late Triassic: evidence from the western United States
Authors: Hunt Adrian P. , Lucas Spencer G. 
Published: January 2018

Most recent workers have identified a major extinction of nonmarine tetrapods during the Late Triassic at the Carnian-Norian boundary. However, this identification is based principally on the stratigraphic distribution of tetrapods where there either is a major facies change at the Carnian-Norian boundary (Germany) or a significant unconformity that spans much of the early Norian (Argentina). Instead, we have examined the stratigraphic record of tetrapods in the western United States (Chinle Group) where there is a relatively continuous, nonmarine depositional and fossil record across the Carnian-Norian boundary that does not encompass major facies changes. The Chinle Group, because of its great area of exposure, more than one century of extensive collection and relatively complete publication, contains the world's best record of tetrapods across the Carnian-Norian boundary.The tetrapod record from the Chinle Group does not record a significant tetrapod extinction at the Carnian-Norian boundary. Instead, it documents a staggered extinction of some taxa during the late Carnian and the persistence of most taxa across the Carnian-Norian boundary. Thus, rhynchosaurs become extinct at the end of the early-late Carnian, whereas dicynodonts become extinct somewhat later, during the latest Carnian. Among metoposaurids, only the large taxa (Buettneria) disappear at the end of the Carnian. Other groups - phytosaurs, aetosaurs, rauisuchians, trilophosaurs, etc. - only exhibit some generic turnover at the Carnian-Norian boundary. The first appearance of dinosaurs, linked by some to a Carnian-Norian tetrapod extinction, is well in advance of the end of the Carnian. Thus, we conclude that the highest resolution tetrapod record of the late Carnian and early Norian does not document a significant tetrapod extinction at the end of the Carnian.