bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutritional and seasonal effects on fibre production in llamas
Authors: Russel A J F , Redden Hilary
Published: January 2018

There is a scarcity of information in the scientific literature on the effects of seasonal and nutritional factors on fibre production in the South American camelids. Without such information it is difficult to develop systems of management incorporating nutritional regimes and fibre harvesting strategies which will optimise the efficiency of fibre production. This paper presents preliminary results from an experiment designed to provide basic information on the effects of season and nutrition on fibre growth in llamas.

The experiment was conducted on 12 adult entire male llamas which were individually penned indoors under conditions of natural photoperiod and ambient temperature in north-east Scotland.

Two levels of nutrition were applied: the lower level (L) was calculated to supply approximately maintenance energy requirements (calculated as 0.44 MJ/kg0.75) and the higher level (H) to supply twice maintenance. The feeding comprised only hay for the L level and hay plus a proprietary cattle concentrate for the H level.
Effect of isolation stress on b-endorphin and lh levels in ovariectomized ewes
Authors: A.M.X. Eloy , R.G. Rodway
Published: January 2018

The sheep is a highly social animal and isolation from others members of the same species causes acute emotional stress (Kilgour & De Langen, 1970). Emotional or psychological stress rather than physical stress appears to activate the hypothalamo-pituitary-adrenal system (Mason, 1968). As part of a study of the effect of stress on reproduction, we have investigated the effect of temporary isolation of sheep on the release of β-endorpbin and concomitant secretion of LH. Previous reports have shown that isolation causes β-endorphin release from the pituitary (Matven, 1987 and Al-Gahtani & Rodway, 1991), but there is little information available on the effect of isolation stress on LH release. The purpose of this work was to examine the temporal relationship between β-endorphin release and LH secretion in sheep during isolation.
A comparison of the rate of genetic gain and inbreeding in a Centralised and a dispersed open nucleus breeding system for sheep
Authors: Roden Janet A.
Published: January 2018

Open nucleus breeding systems have been shown to result in higher genetic gains and lower rates of inbreeding than closed systems. The organisation of an open nucleus system is, however, complex and the long term success depends upon a consistency of objectives among, and strong commitment from the participating breeders. Initial genetic differences between flocks ultimately result in a greater advantage of the open nucleus system, but the short term effect, for the better flocks, is a reduction in genetic gain compared to closed flock selection. The open nucleus system also involves the physical transfer of breeding stock between flocks, which may represent a risk to sheep health.

There are, at present, a number of sire referencing schemes operating in pedigree sheep populations. These schemes involve the mating of ‘reference’ sires to randomly nominated ewes in a number of flocks. The genetic links that are created between flocks enable accurate comparisons of estimated breeding values and therefore accurate selection across flocks.
Effect of Soybean (Glycine max) Row Spacing on Chemical Control of Sicklepod (Cassia obtusifolia)
Authors: Shaw David R. , Bruff Stacey A. , Smith Clyde A.
Published: January 2018

Sicklepod control with seven chemical treatments was evaluated in 25-cm and 97-cm soybean row widths. Metribuzin applied preplant incorporated followed by metribuzin applied preemergence, and metribuzin applied preplant incorporated followed by either imazaquin or chlorimuron applied postemergence controlled sicklepod over 90% early in the season, and row spacing did not influence control at that evaluation. In late season ratings, all herbicide treatments controlled sicklepod better in 25-cm rows than in 97-cm rows. However, only imazaquin applied sequentially or metribuzin followed by chlorimuron in 25-cm rows controlled sicklepod greater than 80% late in the season. Sicklepod control in 25-cm row soybean with either imazaquin or metribuzin plus chlorimuron applied preplant incorporated was equivalent to or better than sequential preemergence and postemergence treatments of these three herbicides in 97-cm rows. All treatments resulted in lower yields than the weed-free check in the 97-cm rows, whereas all herbicide treatments except the sequential application of metribuzin gave yields equivalent to the weed free check in 25-cm rows.
Effects of Preplant Treatment Interval and Tillages on Herbicide Toxicity to Winter Wheat (Triticum aestivum)
Authors: Ogg Alex G. , Young Frank L.
Published: January 2018

Glyphosate plus 2,4-D at 0.3 + 0.5 or 0.4 + 0.7 kg ae ha-1applied 31 to 1 d before seeding did not affect wheat yields or grain test weights, in field experiments in conventionally tilled and no-till winter wheat. In the conventionally-tilled system in each of two years and in the no-till system in a year with 48 mm rain within 7 d before wheat was seeded, picloram applied at 0.14 kg ai ha-1from 31 to 1 d before seeding reduced crop yields by 7 to 8%. In the conventionally-tilled system in a year with only 2 mm rain within 7 d before wheat was seeded, 2,4-D at 3.4 kg ae ha-1and dicamba at 0.14 kg ae ha-1applied 30 to 1 d before seeding, reduced wheat yields by 7 and 4%, respectively. Grain test weights in both tillage systems were increased slightly by picloram at 0.14 kg ha-1, but were decreased slightly by dicamba at 0.14 kg ha-1, in the year with little rain before sowing. Test weights did not differ among herbicides or tillage systems in the year with significant rain a few days before seeding.
Itchgrass (Rottboellia cochinchinensis) Interference in Sugarcane (Saccharumsp.)
Authors: Lencse Reed J. , Griffin James L.
Published: January 2018

Field studies were conducted in the northern and southern cane belt areas of Louisiana to determine the effect of itchgrass on sugarcane growth and yield. Itchgrass was allowed to interfere with sugarcane season-long, early-season from emergence in the spring until layby (last cultivation) in mid-June, and late-season from layby until harvest. Itchgrass germination occurred throughout the growing season. Populations of millable sugarcane stalks and yields of cane and sugar were similar for no interference, early-, and late-season interference. Season-long itchgrass interference reduced sugarcane stalk populations and cane and sugar yields an average of 34, 42, and 43%, respectively, compared with no interference.
Two Approaches to Weed Control Decision-Aid Software
Authors: Mortensen David A. , Coble Harold D.
Published: January 2018

The number of computer applications for purposes of weed control decisions has increased dramatically in the past eight yr. During this time, many efficacy-, and population-based weed control decision aids have been developed. The complexity of decisions range from those based on optimal weed control (independent of net profitability) to those predicting weed population effects before most profitable treatments are selected. While the number of software applications has increased sharply, national software databases have not been funded and tracking has been made difficult. The purpose of this paper is to review the criteria upon which efficacy- and population-based weed control decision aids are founded, and to identify software currently available in each of the two categories.
Historical reasons for the focus on broad monetary aggregates in post-World War II Britain and the ‘Seven Years War’ with the IMF
Authors: Goodhart Charles A. E. , Needham Duncan J.
Published: January 2018

The British monetary authorities have traditionally focused on broader monetary aggregates than their counterparts elsewhere. The reasons include: the willingness of UK banks to allow customers to make payments by drawing on time deposits, the particularities of the UK approach to managing the national debt and the foreign exchange reserves, and the flow-of-funds system of national accounts developed after World War II. This article outlines these reasons, and explores the implications for the UK's often fractious relationship with the International Monetary Fund during the 1950s and 1960s. It explains why IMF conditionality on loans to the UK focused on broad aggregates.
Universities: From Local Institutions to Global Systems? Implications for Students, Staff and Institutions
Authors: Holm-Nielsen Lauritz B.
Published: January 2018

The main resource for a country’s endogenous growth is its human and cultural capital. Universities play a very important, but not the only, role in maintaining and building this resource. Universities are institutions situated amongst strong and changing forces. They are caught between government, market and academia. In many institutions, this has led to a strengthening of the executive leadership at the expense of the influence of collegial bodies, and external (to the institution) members have been introduced into the governing bodies. This development has resulted in diminished state control, and more flexible and autonomous systems, but also to expanded reporting and accounting, which often in reality limit freedom and are perceived as control. Will academic creativity thrive within this reality? How would research universities evolve? This article claims that today’s university development starts out from Wilhelm von Humboldt’s universe but will play out in that of his brother Alexander’s.
Hypothyroidism in patients with Bipolar I Disorder treated primarily with lithium
Authors: Fagiolini Andrea , Kupfer David J. , Scott John , Swartz Holly A. , Cook David , Novick Danielle M. , Frank Ellen
Published: January 2018

Aims – This study evaluated the frequency and clinical significance of abnormal Thyroid Stimulating Hormone (TSH) and Free Thyroxine Index (FTI) in patients with bipolar I disorder treated primarily with lithium. Method – We evaluated the medical records of 143 participants in the Pittsburgh study of Maintenance Therapies in Bipolar Disorder who did not have a thyroid abnormality at entry. Results – Thirty-six percent of the 143 patients developed abnormal TSH and/or FTI values. Thirty-eight percent of the 135 patients who received lithium developed abnormal TSH and/or FTI, spent significantly longer time in the acute treatment phase (t = -3.6, df = 133, p = .0004), and had significantly higher mean Hamilton Scale for Depression scores over the course of the maintenance phase (t = -2.3, df = 71.6, p = .03). Time on lithium and development of abnormal TSH and/or FTI were positively correlated (r = .25, p = .004). Conclusions – Thyroid dysfunction can be frequent in patients exposed to lithium treatment for bipolar I disorder; it also appears to be correlated with a slower response to acute treatment, and may be related to poorer quality of long-term remission. A prospective study is needed to confirm our findings and determine whether more aggressive thyroid replacement can optimize thyroid function to facilitate clinical recovery.

Declaration of Interest: Supported in part by National Institute of Mental Health Grants MH 029618 (Drs. Frank and Fagiolini) and MH 030915 (Drs. Kupfer and Fagiolini), and the Bosin Memorial Fund of The Pittsburgh Foundation (Drs. Fagiolini, Kupfer, Cook, Scott, Novick and Frank). Dr. Fagiolini is on the advisory board and a consultant to Pfizer Inc, and Bristol Myers Squibb, and is on the speaker bureau of Bristol Myers Squibb, Eli Lilly Italy, Pfizer Inc, and Shire. Dr. Frank is on the advisory board of Pfizer Inc. and Eli Lilly & Company, and is a consultant to Pfizer Italia and Sender Amerique. Dr. Kupfer is on the advisory board of Pfizer, Inc., Forest Pharmaceuticals, Inc., and Solvay-Wyeth Pharmaceuticals, and is a consultant to Servier Amerique.
Statistical anatomy of tyrannosaurs
Authors: Abler William L.
Published: January 2018

Since dinosaur fossils are not numerous enough for statistics, the idea of studying dinosaurs at all has been questioned. Teeth of Judith River tyrannosaurs (late Cretaceous of south-central Alberta, Canada) are sufficiently numerous and rich in anatomical structures for statistical analysis: 1. No difference was found between widths of serrations of anterior and posterior rows (Mann-Whitney U test, two-tailed; n = 24 tooth fragments: p> .05; anterior and posterior x = 0.4 mm): 2. Reversals in uniform trends in serration width within each serration row were more numerous for the anterior (reversals = 51; non-reversals = 74) than for the posterior (reversals = 45; non-reversals = 135) serration rows (χ2 (2×2) = 7.82; d.f. = 1; p< .01); 3. Serrations of the anterior row are more steeply angled toward the point of the tooth than are those of the posterior row (Mann-Whitney U test, two-tailed, n = 21 tooth fragments; p< .01; anterior x̄ = 8.9°; posterior x̄ = 5.0°): 4. Small teeth (mean length = 9.8mm) show less tendency to be scratched than large ones (mean length = 25.0mm) (t(d.f. = 234) = 4.64; p< .01); 5. Inter-serrational slots of posterior row require less force (x̄ = 0.14 newton) to cut standard nylon filament (diameter = 0.04mm; tensile strength = 0.42 newton) than did slots of the anterior row (x̄ = 0.24 newton; Mann-Whitney U test, two-tailed; p< .05; n = 17 fragments); 6. There is a significant difference between edge radii r (expressed in microns μ) of serrations of three classes of tyrannosaur teeth: unerupted/partially erupted (x̄ = 78.2μ), vs. fully erupted but still attached to bone (x̄ = 94.7μ), vs. shed (x̄ = 139.3μ) teeth (two factor analysis of variance, F(2,173) = 10.86; p< .05). Teeth of Judith River tyrannosaurs possess numerous structures, both interior and exterior (see figure) whose geometry differs markedly from that of, e.g., troodon teeth (which may possess a radix, but no other differentiated internal structures), or thecodont teeth (which possess a peak of interior enamel intruding into each denticle and tilted toward the point of the tooth). Statistical anatomy of teeth may offer a rich source of information for studying taxonomy, evolution, and migration of tyrannosaurs.
Functional significance of variations in the central fold of shells of late Ordovician through Devonian biconvex brachiopod genera
Authors: Alexander Richard R.
Published: January 2018

Flume experiments with models of Mid-Paleozoic atrypids, orthids, rhynchonellids, and spiriferids indicate that the central fold functions efficiently to separate lateral-margin incurrents from the anterior-medial margin excurrent in five of nine possible life orientations of the shell relative to the current direction and substrate. Anterior-medial incurrents and lateral excurrents are effectively separated in four of the nine orientations used with models of spiriferids and atrypids, but nonpediculate brachiopods drawing in water anterior-medially could not take advantage of reversing tidal currents to feed. The risk of refiltration of medial excurrent water is reduced with increasing relief of the central fold above the commissural plane. Downcurrent turbulance increases with increasing relief of the central fold. Eddies with a large radius of curvature are generated by large chevron-shaped central folds at low current velocities (5 cm/sec) and boomerang against the downcurrent lateral margin of models. Flume experiments on models also reveal that a well-developed sinus accelerated erosion of the supporting sediment around the weight-bearing posterior of the valves. Shells with high relief in the sinus destabilized comparatively quickly from valves-erect orientations when subjected to moderate current velocities (25 cm/sec).

Morphospace (ternary) diagrams of sinus shape for Late Ordovician (Caradocian) through Devonian (Famennian) genera show the realized field among the potential morphotypic extremes, namely, 1) rectimarginate (no fold), 2) isoclinal, chevron-shaped, and 3) M-shaped anterior commissural outlines. Morphospace plots through successive stages suggest centripetal selection for taxa with moderately developed folds in the atrypids and spiriferids, with occasional evolution of “outlier” genera with chevron-shaped central folds. Orthids display progressive loss of rectimarginate genera through the Devonian. Weak directional selection is suggested by the succcessive stage-level plots of the rhynchonellid genera which expanded toward the extremes of chevron- and M-shaped central folds in potential morphospace during the Devonian.
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.
Sedimentary dynamics and structural control of Neogene tropical biofacies during the formation of the Central American Isthmus
Authors: Coates Anthony , Obando Jorge , Gonzalez Herman
Published: January 2018

The central evolutionary, ecological and paleoceanographic questions of the American tropical Neogene relate to how and during what time the Central American Isthmus formed. Geographically, closure was located between the southern edge of the Chortis Block in southern Nicaragua and the Atrato Valley in Colombia. In this region we describe, on the Caribbean side, five Neogene sedimentary basins. They are the Atrato, Chucunaque, Gatun, Bocas del Toro, and Limon Basins. On the Pacific side the Neogene sediments formed as part of the Central American Trench and are well exposed in a series of uplifted blocks on the Nicoya, Osa and Burica Peninsulas. Our analysis allows 1) a construction of the sequence of contrasting sedimentary environments which characterize the different basins, giving a composite geological history of the isthmus for the Late Neogene and 2) identifies the comparable biofacies from the different basins which allow and constrain the evolutionary and ecological questions to be posed concerning the effect of the isthmus as a biogeographic barrier. Temporally, from it's partial emergence in the Middle Miocene, the isthmus shallows by the Early Pliocene (3.5–3.4 Ma) to less than 50 m (Duque-Caro, 1990) when there is a marked differentiation of shelf marine macrobenthic species between the Caribbean and the Pacific. The evidence from reliably dated, large, diverse exchanges of North and South American vertebrates on land constrains the final closure date to not later than 2.8–2.5 Ma (Marshall, 1988). Given that no conclusive evidence for final closure can come exclusively from a study of sedimentary facies, when depths of less than 50 m are involved, the present window of almost 1 Ma, during which final closure must have occurred, will only be narrowed further by the detailed study of very shallow-water fossil clades and complementary molecular data. Present studies indicate that such clades are abundantly preserved.
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.
The palaeozoic pelecypod family Rhombopteriidae and the evolution of the Ostreina
Authors: Johnston Paul A.
Published: January 2018

Though long suspected to be critical to the understanding of the evolution of the pelecypod subclass Pteriomorphia, the mid-Palaeozoic family Rhombopteriidae was too poorly known to allow clarification of its relationships. Furthermore, numerous species were assigned to the nominate genus, Rhombopteria, many of which belong in other genera or even other subclasses. Consequently, the morphologic concept entailed by Rhombopteria was confused as were functional morphologic investigations.

Silicified rhombopteriids discovered in the Lower Devonian of Australia are referred to a new genus, and reveal internal shell characters essential for understanding rhombopteriid relationships. The family Rhombopteriidae is revised to include only three genera, Rhombopteria, Prantliella and the new Australian genus.

New data provided by the Australian material indicate that rhombopteriids were non-byssate, dimyarian pteriomorphs that lived pleurothetically on the left valve as do gryphaeid oysters. The Rhombopteriidae are assigned to the Ostreina and are the sister group of all other ostreinans including the Ostreoidea, Pseudomonotidae and Terquemiidae. Important characters common to rhombopteriids and gryphaeid oysters include: 1) left-sided pleurothetic habit; 2) absence of byssal notch or sinus throughout ontogeny; 3) Quenstedt muscle scar; 4) proximal gill weal; 5) circumferential curb; 6) commissural shelf; and 7) posteroventral palliobranchial fusion as evidenced by a branchitellum and posterior radial fold and sulcus. Outgroup comparison with Umburridae indicate that characters 1–4 are symplesiomorphic for the Order Ostreoida. Characters 5–7 are autapomorphies for a clade including the Rhombopteriidae, Pseudomonotidae, Terquemiidae and Ostreoidea.

Rhombopteriids were probably derived from left-sided pleurothetic, umburrid-like ancestors which, in turn, descended from primitive, equivalved, orthothetic prionodonts. Thus, a right-sided pleurothetic stage was never part of the evolutionary pathway of oysters. The inequivalved shell of eupteriomorphs evolved initially for a left-sided pleurothetic semi-infaunal habit. Retained as an adaptation in rhombopteriids and oysters, the inequivalved shell is an exaptation in Pterioida (winged shells), Pectinina (scallops) and Pseudomonotidae, having been coopted for a right-sided pleurothetic orientation, and having the effect of enhancing stability in an epifaunal habit. Evolution of right-sided pleurothetic pteriomorphs, including the Pseudomonotidae, Pectinina and Pterioida, from separate left-sided pleurothetic rhombopteriid-like or umburrid-like ancestors, is explicable by paedomorphic retention of the byssus and epifaunal habit of the early post-larva. A right-sided pleurothetic orientation would follow ‘automatically’ owing to hydrodynamic and mechanical constraints on the already evolved, inequivalved shell, byssally attached by the anterior margin on the substrate surface.
Cambrian explosion and Permian quiescence: implications of rugged fitness landscapes
Authors: Kauffman Stuart A.
Published: January 2018

The Cambrian explosion witnessed the formation of a large number of the higher taxa extant today. The higher taxa are said to have “filled in” from the top down, with species that found phyla giving rise to daughter species which found classes, then orders, and so on. During the Permian extinction, in contrast, 96% of all species go extinct. During the rebound, a large number of new families are created, a few new orders are created, but no new phyla are created. The higher taxa are said to have “filled in” from the bottom up. The profound asymmetry between the Cambrian and Permian has been a deep puzzle. I shall suggest that this asymmetry is a nearly inevitable consequence of adaptive evolution on rugged, multipeaked fitness landscapes.
Biogeographic analysis of middle Visean articulate brachiopod genera
Authors: Kelley Patricia H. , Sablock Peter E. , Raymond Anne , Isaacson Peter E.
Published: January 2018

Climate models as well as the distribution and migration patterns of land plants and articulate brachiopods from the Early and Middle Carboniferous suggest that Visean latitudinal temperature gradients were relatively weak, and that the high latitudes may have been warmer than they were during the late Namurian and Westphalian. Biogeographic analysis of middle Visean brachiopod genera from Laurussia and North China supports these conclusions. Cluster analysis, multidimensional scaling and principal components analysis reveal longitudinal differentiation among brachiopod assemblages from Laurussia and the North China plate. Based on their faunal similarity, localities from the east coast of Laurussia (Urals, Moscow Basin, Donets Basin) and North China group together; localities from south central coast of Laurussia (Maritime Canada, England, Ireland and Belgium) group together, and localities from the southwest and west coast of Laurussia (Canada and the United States) group together. On recent Early Carboniferous reconstructions, the east Laurussian localities lie in equatorial, subtropical, and middle latitudes, but exhibit no paleolatitudinal differentiation. This may be the expected result for a biogeographic unit on the east coast of a large paleocontinent during an interval with a well-developed circum-equatorial current. On recent Early Carboniferous reconstructions, all of the localities from south central Laurussia lie near the paleoequator.

West Laurussian assemblages show paleolatitudinal differentiation, which may be the expected result for a biogeographic unit along the west coast of a large paleocontinent influenced by high-latitude westerlies. Within the cluster analysis, assemblages from the Appalachians, Midwest, and Southwest clustered separately from Cordilleran (Idaho, Utah, Montana, Wyoming and Nevada) assemblages. Recent paleogeographic reconstructions for the Early Carboniferous suggest that the Cordilleran localities were paleoequatorial and that the Appalachian, Midwestern and Southwestern localities lay in the southern paleo-subtropical belt. However, the relative diversity of assemblages from these two clusters suggests that the Early Carboniferous paleoequator lay to the south of the Cordilleran localities. Throughout the Early and Middle Carboniferous, individual assemblages within the Appalachian-Midwest-Southwest cluster have higher diversities than individual assemblages within the Cordillera cluster.

We have avoided a hierarchical ranking of these biogeographically distinct groups of assemblages into realms and provinces pending species and community level-analyses of Visean brachiopod communities which are in progress.