bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the measurement of size-independent morphological variability: an example using successive populations of a Devonian spiriferid brachiopod
Authors: Flessa Karl W. , Bray Ron G. 
Published: July 2016

More than 500 undistorted, unfragmented pedicle valves of Ambocoelia umbonata (Conrad) (Spiriferida, Brachiopoda) were recovered from each of four levels within a Middle Devonian fossil cluster. The fossil cluster, an ellipsoidal shell accumulation measuring one meter in diameter and 2 cm in thickness, was exhumed from an exposure of the Ludlowville Shale (Hamilton Group) of western New York. Size frequency histograms indicate that the brachiopod experienced very high levels of juvenile mortality, due, probably, to the effects of high bottom turbidity. Sedimentological and paleontological evidence indicates that the cluster represents a sequence of in situ benthic associations.Size-independent variation was estimated by calculating the eigenvalue of the minor axis on a log-transformed plot of pedicle valve lengths and widths. The eigenvalue technique eliminates the effect of allometrically induced shape changes and is applicable to multicharacter analyses of morphological variability.Size-independent variability among the larger individuals of Ambocoelia decreases in successively younger cluster populations. The decrease is not correlated with any observed or inferred change in substratum, diversity, equitability or turbidity.
Formation and paleontologic recognition of structures caused by marine annelids
Authors: Ronan Thomas E. 
Published: July 2016

Laboratory and field collected sediments were x-rayed to document the array of biogenic sedimentary structures produced by the burrowing and feeding behavior of six species of marine intertidal annelid (Glycera robusta, Nephtys caecoides, Pectinaria californiensis, Notomastus magnus, Eupolymnia crescentis, and Cirriformia spirabrancha). Polychaete burrows were found to vary greatly in structural complexity with both errant (N. magnus) and relatively sessile forms (C. spirabrancha) producing a variety of biogenic structures. Sediment mixing by the tentacle-feeding polychaete C. spirabrancha was observed by sequentially x-raying an experimental field enclosure stratified with an opaque substance. The experiment demonstrates that tentacle-feeding polychaetes can influence the topography of the sediment-water interface and transport substantial amounts of near surface material downward.Criteria by which fossil biogenic sedimentary structures, presumably produced by soft-bodied organisms, can be assigned a feeding function have been advanced by Walker (1972). Some of the assumptions inherent in feeding function analysis were applied, with varying degrees of success, to the biogenic structures of modern soft-sediment polychaetes.
The relationship of the scleractinian corals to the rugose corals
Authors: Oliver William A. 
Published: July 2016

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.
Bivalve Species Duration, Areal Extent and Population Size in a Cretaceous Sea
Authors: Koch Carl F. 
Published: July 2016

Geographic distribution, species duration, and population size of 41 bivalve species which coexisted during the uppermost biozone (Sciponoceras gracile zone) of the Cenomanian were measured. Average species duration and correlation between geographic distribution, species duration, and population size were computed for five groups: total, infaunal, epifaunal, cemented epifaunal, and uncemented epifaunal bivalves.Average species duration for all bivalves is less than 2 Myr. Infaunal bivalves averaged slightly higher, epifaunal slightly lower. Positive correlation was measured between species duration and geographic distribution for all five groups and statistical significance of the relationships was demonstrated for all but infaunal forms. In general no correlation was found between species duration and population size, and between population size and geographic distribution with the following exceptions: species duration and population size were significantly correlated for infaunal bivalves and uncemented epifaunal bivalves, and population size and geographic distribution were correlated for uncemented bivalves. Because these 41 fossil species coexisted at the same time and were distributed in the same space, differences in the relationships of species duration, geographic distribution and population among the various life habits indicate differences in ecological strategy and the evolutionary consequences of that difference.
The improbability of animal phyla with few species
Authors: Strathmann Richard R. , Slatkin Montgomery 
Published: July 2016

At present there are many animal phyla that contain only a few species. The existence of these small phyla can be used to test assumptions about speciation and extinction in multicellular animals.We first model the number of species in a monophyletic clade with a birth and death process that assumes rates of speciation and extinction are constant. If no new phyla have evolved since the Cambrian and speciation and extinction rates for minor phyla are similar to or greater than those estimated from fossils, then our model shows that the probabilities of minor phyla surviving to the present are small. Random variation in extinction and speciation rates does not improve the chances for persistence. If speciation rates exceed extinction rates at the initial radiation of the clade, but before the clade becomes large, speciation rates come to equal extinction rates and both are low, persistence from before the Ordovician up to the present becomes likely. These models show that if speciation and extinction rates are independent of the number of species in a clade, then conditions before the Ordovician strongly influence today's distribution of species among taxa.We also discuss a model in which speciation and extinction rates depend on the number of species in a clade. This alternative model can account for the persistence of phyla with few species to the present and predicts a short duration for phyla that did not exceed a threshold number of species.
Character diversification and patterns of evolution in early vascular plants
Authors: Knoll Andrew H. , Niklas Karl J. , Gensel Patricia G. , Tiffney Bruce H. 
Published: July 2016

Available data on the stratigraphic ranges of latest Silurian and Devonian vascular plant macro-fossils (sporophytes) and spores provide insights into the tempo and mode of early tracheophyte evolution. Patterns of diversification, origination, and extinction conform in general to the predictions of Sepkoski's kinetic model of diversification. Rates of generic origination and extinction vary not only through time but also between organ systems for a single time interval. This fact, coupled with data on longevity and turnover and comparative morphological observations, can be used to document mosaic evolution in early vascular plant history. Mosaic evolution is an important theme in plant evolution; indeed, what we recognize as macroevolutionary events often correlate with brief periods of pronounced mosaicism. Such evolutionary patterns reflect the developmental biology of tracheophytes in which individual organs often have life spans that are considerably shorter than the life of the whole plant. Under these conditions, individual organs or organ systems can respond to different sets of evolutionary pressures.The major period of early vascular plant diversification occurred during the late Early and early Middle Devonian Period, 30 Myr or more after the origin of the group. Such lags in diversification are not uncommon in the fossil record. Sometimes they reflect extrinsic controls on diversification, but in other cases they appear to be a consequence of intrinsic rates of origination and extinction.
Aerosol suspension feeding and current velocities: distributional controls for late Osagean crinoids
Authors: Kammer Thomas W. , Ausich William I. 
Published: July 2016

Distributional patterns of late Osagean (Mississippian) crinoids from the east-central United States are examined using multivariate analysis of crinoid species diversity and species abundance data. We confirm previous hypotheses that three well-defined crinoid associations existed during the late Osagean. These associations were dominated, respectively, by 1) monobathrid camerates preserved in carbonate packstones; 2) poteriocrine inadunates in higher-energy siltstones and sandstones; and 3) disparid inadunates, cyathocrine inadunates, and flexibles in mudstones where neither monobathrids nor poteriocrines dominated. In conjunction with petrologic data on the enclosing sediments, the analyses suggest that these associations occurred along a spectrum of increasing current velocity at the seafloor. Camerates, poteriocrine inadunates, and flexibles are interpreted to display preferences for specific environmental conditions, whereas disparid and cyathocrine inadunates are inferred to be environmental generalists.The different environmental distributions of the major crinoid groups are interpreted to be a function of the mode or modes of aerosol filtration feeding used by each group. This inference is possible through functional morphologic and morphometric studies of crinoid arms, because the skeletal elements of the arms, which are commonly preserved, are directly involved in feeding.
Asymmetrical patterns of origination and extinction in higher taxa.
Authors: Gilinsky Norman L. , Bambach Richard K. 
Published: July 2016

Using Sepkoski's compendium of fossil marine families (1982a, and updates), we have analyzed the changing pace of familial origination and extinction within 55 extinct and 44 extant higher taxa of marine organisms. Eight different metrics were calculated, and least-squares regression analysis was used to identify within-taxon trends in the data. All metrics and analyses gave essentially the same results. Origination metrics decline significantly with time during the histories of higher taxa, while extinction metrics increase significantly. The number of statistically significant declines of origination metric, however, substantially and invariably exceeds the number of statistically significant increases of extinction metric for each pair of corresponding metrics analyzed. It follows, therefore, that temporal trends in the pace of origination and extinction within higher taxa are highly asymmetrical.Further analysis shows that truncating data from temporal endpoints has little effect upon the intensity of origination trends, implying that declining pace of origination is a sustained property of the long term histories of taxa. Such truncation, however, reduces the intensity of extinction trends to statistical insignificance and confirms Van Valen's (1985a) suggestion that extinction behaves largely as a stationary process. If the histories of higher taxa are characterized by substantial declines in the pace of origination while the pace of extinction remains largely stationary, it follows that declining pace of origination is an important controlling factor in long term taxic evolution.
From regional to total geographic ranges: testing the relationship in Recent bivalves
Authors: Jablonski David , Valentine James W. 
Published: July 2016

Geographic range appears to be an important aspect of the biology of species, but ranges cannot be unambiguously determined from the fossil record: ancient species can rarely be traced to the full extent of their original geographic ranges, and some ancient provinces are far better characterized than others. Here we test the degree to which paleogeographic range data for species within ancient provinces can be used to estimate the relative magnitudes of total geographic ranges, focusing on the 212 living bivalve species of the Oregonian Province, a north-south (N-S) province of the northeastern Pacific shelf.We break the total range of each species into its within-province and extraprovincial components. Nonparametric rank correlation tests and simple linear regressions yield highly significant correlations, both between within-province and total ranges (which are not independent variables) and between within-province and extraprovincial ranges. The strongest correlations are obtained when north-ranging species are excluded. These north-ranging species are thermally tolerant and have access to broad east-west (E-W) provinces, thus weakening the relation between their within-province and total ranges. On a coarser scale, we also found that the extraprovincial ranges of species with small within-province ranges (<650 km, ca. 25% of focal province) are significantly less than those for species with large within-province ranges (> 1950 km, ca. 75% of focal province). The significant correlations of within-province range with both total and extraprovincial ranges hold for species with within-province ranges >650 km, so caution is needed regarding species that extend into a focal province only a short distance from its edges. We conclude that within-province geographic range can generally be used to rank species by total geographic range and thus is an adequate proxy in most comparative studies of the paleobiologic consequences of range magnitudes.
The continuum in soft-bodied biotas from transitional environments: a quantitative comparison of Triassic and Carboniferous Konservat-Lagerstätten
Authors: Briggs Derek E. G. , Gall Jean-Claude 
Published: July 2016

The exceptionally preserved Triassic (Anisian) Grès à Voltzia fauna from the Vosges of northeastern France is compared with four major Carboniferous Konservat-Lagerstätten. The problem of comparing faunas with different types of preservation and degrees of taxonomic determination is addressed with a newly devised similarity coefficient. This coefficient quantifies and combines data from different levels in the taxonomic hierarchy and allows comparisons between biotas in a consistent direction regardless of relative diversity. The rank order of similarity between the four Carboniferous Konservat-Lagerstätten and the Grès à Voltzia is as follows: 1. Mazon Creek (Westphalian D) of Illinois; 2. Glencartholm (Visean) of southern Scotland; 3. Bear Gulch (Namurian) of Montana; and 4. Blanzy-Montceau (Stephanian) of France. These occurrences represent conditions transitional between nearshore fully marine and fresh water. The Grès à Voltzia fauna is significantly closer to the Mazon Creek fauna than to the others; the taxonomic overlap with Blanzy-Montceau and Bear Gulch is limited.Stratigraphic age has an insignificant influence on the result; indeed, the fauna closest in age to the Grès à Voltzia, that of Blanzy-Montceau, is least similar. Taphonomic factors are important in determining the range of organisms preserved. The Glencartholm fauna is represented only by forms with either mineralized or robust chitinous skeletons, implying a greater degree of decay prior to the onset of diagenetic mineralization than in the other Konservat-Lagerstätten. Environment, however, is the major control on similarity. The Mazon Creek biota, like that of Grès à Voltzia, represents settings transitional between terrestrial and marine-influenced delta. Groups common to both Konservat-Lagerstätten include medusae, brachiopods, polychaetes, bivalve and gastropod molluscs, limulids, scorpions, spiders, branchiopods, ostracodes, malacostracans, cycloids, euthycarcinoid and myriapod uniramians, insects, fish, and tetrapods. There is a striking continuity between the faunas of Carboniferous and Triassic transitional sedimentary environments. Groups that were adapted to fluctuating conditions (e.g., shifting salinity) show strong congruence at the family and lower levels and were little affected by Permian extinctions. The major taxonomic contrasts are in the eumalacostracans and insects: many of the groups represented in the Grès à Voltzia appeared in the Permian and radiated across the Permo-Triassic boundary as Paleozoic forms became extinct.
Landmark-based morphometrics of spiral accretionary growth
Authors: Johnston Mark R. , Tabachnick R. Elena , Bookstein Fred L. 
Published: July 2016

Many organisms continue to grow their skeletons throughout ontogeny. In the shells of molluscs, protists, and brachiopods and in bovid horns, accretionary spiral growth provides a detailed and continuous growth history. Although a shell may be described as a single static form, the overall morphology is a summation of the ongoing accretionary process. For this reason, an explicitly ontogenetic characterization of form provides insight into the final form achieved. Analysis of landmark transformations offers direct access to major components of morphological variation, both among adult individuals and through an individual's ontogeny. Parameters of preconceived, abstract geometric models can also be used to characterize morphological variation, but there is no guarantee that these parameters will coincide with the major features of shape variation.In order to locate landmarks at equivalent ontogenetic stages, features that indicate ontogenetic stage of coiled forms must be identified (e.g., growth increments, age, size, whorls). The gastropod Epitonium (Nitidiscala) tinctum exhibits prominent varices that provide landmark locations throughout ontogeny. Recent specimens of this species were obtained from three localities in Baja, Mexico. The morphological variation among individuals, treated as whole shells and within individual ontogenies, was analyzed using shape coordinates of landmark configurations. Deformation of shape is expressed in the uniform and nonuniform shape subspaces. The empirical components of shape variation found are similar to those generated by two parameters of an equiangular spiral: θ, the angle between consecutive varices, and W, the whorl expansion rate. The distribution of individuals is examined within morphospaces constructed from these shape features.Three scales of analysis are necessary to characterize adequately the shape variation within and among specimens. The smallest scale is equivalent to increment-by-increment changes in θ and W. The middle scale comprises variation equivalent to whorls resulting from systematic changes in θ and W during an individual's ontogeny. Finally, there is the overall ontogenetic trajectory. Mean shape must be a function of initial shape and ontogenetic trajectory in shape. Mean forms that are found to have similar shapes at the same arbitrary growth increment may achieve that shape in different ways.
Faunal interchange and Miocene terrestrial vertebrates of southern Asia
Authors: Barry John C. , Morgan Michele E. , Winkler Alisa J. , Flynn Lawrence J. , Lindsay Everett H. , Jacobs Louis L. , Pilbeam David 
Published: July 2016

Problems of stratigraphic completeness and poor temporal resolution make analysis of faunal change in terrestrial sequences difficult. The fluvial Neogene Siwalik formations of India and Pakistan are an exception. They contain a long vertebrate record and have good chronostratigraphic control, making it possible to assess the influence of biotic interchange on Siwalik fossil communities. In Pakistan, the interval between 18 and 7 Ma has been most intensively studied and changes in diversity and relative abundance of ruminant artiodactyls and muroid rodents are documented with temporal resolution of 200,000 years. Within this interval, diversity varies considerably, including an abrupt rise in species number between 15 and 13 Ma, followed by a decline in ruminant diversity after 12 Ma and a decline in muroid diversity in two steps at 13 and 10 Ma. Significant changes in relative abundance of taxa include an increase in bovids between 16.5 and 15 Ma, a decrease in tragulids after 9 Ma, and a very abrupt increase in murids at 12 Ma. Megacricetodontine rodents also decrease significantly at 12 Ma, and smaller declines are recorded among myocricetodontine and copemyine rodents after 16 Ma. An increase of dendromurine rodents at 15.5 Ma is also observed. There is also a trend of progressive size increase among giraffoids and bovids throughout the sequence.We have also investigated relationships between biotic interchange and diversity, body size, and relative abundance, concluding that (1) the rapid increase in ruminant and muroid diversity was largely due to immigration, whereas in situ speciation had only a secondary role; (2) during intervals of increasing diversity, resident lineages did not have higher than average rates of in situ speciation; (3) during intervals with rising diversity, greater extinction did not accompany increased immigration; (4) during intervals with falling diversity, there may have been greater extinction in recently invading lineages; and (5) change in diversity was independent of changes in relative abundance and body size.