bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isotopic and molecular characterization of modern and fossil proteins in ostrich eggshell
Authors: Johnson Beverly J. , Fogel Marilyn L. , Miller Gifford H. , Tuross Noreen 
Published: January 2018

Stable carbon and nitrogen isotopes in fossil ostrich eggshell (OES) proteins have the potential to provide paleodietary information on ostriches through the Late Pleistocene in arid and semiarid regions of the Old World. Carbon isotopes may be used as a monitor for floral composition (C3 vs. C4 plant abundance), for example. The stable isotope composition of the organic matter in modern OES and Middle Holocene fossil OES samples from Bir Tarfawi (an archaeological site in southern Egypt) are presented, as well as the nature of modern proteins in OES and the degree to which they are preserved in the fossil samples.The organic fraction was extracted from OES samples and subsequently desalted by (1) decalcification in 0.5 N EDTA, followed by dialysis against water in >6-8,000 molecular weight cut off (MWCO) tubing, or (2) hydrolysis in 6N HCl for 20 minutes at 153°, followed by the addition of concentrated HF to facilitate the precipitation of CaF2. There is good agreement between the stable isotope results of the two organic fractions from modern OES samples (δ13C = −23.51±±0.76 and −23.53±±0.39, and δ15N = +6.23±±0.15 and +6.42±±0.33 for the >6-8,000 MWCO and HF preparations, respectively). A 2± and 4± enrichment between ostrich diets and the organic fraction was found for carbon and nitrogen, respectively. These relationships support a vegetarian diet comprised almost exclusively of C3 plants. Result from the HF preparation show higher variability in both the δ13C and δ15N values in the fossil samples than in the modern. This increased variability may be due to isotopic fractionation accompanying protein degradation or to inadequate methodologies for isolating the bulk organic matter. These effects could be minimized by analyzing individual molecules throughout the study.The >6-8,000 MWCO fraction of the modern and fossil OES samples were electrophoresed on SDS polyacrylamide gels. The modern sample shows predominant bands corresponding to apparent molecular weights of 14 kilodaltons (kD), 28 kD, and 35 kD, and a light smear at the top of the gel. Preliminary results of the fossil sample show a pronounced band corresponding to an apparent molecular weight of 80 kD, and a light smear over the whole gel. Results of an enzyme linked immunosorbent assay (ELISA) on the modern material demonstrate a positive antibody-antigen reaction between the >6-8,000 MWCO fraction and osteocalcin, osteonectin, and albumin.Due to the “closed-system” nature of the ostrich eggshell matrix and the ease with which it can be accurately dated through the Late Pleistocene, it provides an ideal medium for studying protein diagenesis. Subsequent isotopic analyses, using the newly developed technologies of GC/IRMS, offer an alternative method for using the paleodiets of ostriches as a tool for paleoenvironmental reconstructions in Africa and Asia.
The isotopic record of oxygen in phosphates of fossil fish - Devonian to Recent
Authors: Kolodny Yehoshua , Luz Boaz 
Published: January 2018

The isotopic composition of oxygen in the phosphate (δ18Op)was determined in 159 fish bones and teeth from museum collections throughout the world. The fossils were both marine and fresh-water ranging in age from the Devonian to the Recent. In 45 of those we also determined the isotopic composition of oxygen and carbon of the lattice carbonate in apatite (δ18Oc and δ13C). In most cases the isotopic results are compatible with previously available geological information: the difference between marine and fresh water, the indication of previously known warm and cold time periods, and the ranking of fishes from warm to cold according to their inferred life habitat.Three fish specimen from the Devonian of the Orcadian Basin in Scotland yield results which are compatible with the thermal structure of a stratified lake. The isotopic analysis of Inocentrus vulgaris, a fish found inside Cretaceous inoceramids, yields normal marine δ18Op. Hence we favor the suggestion of Tourtelot and Rye (1969) that 18O depleted inoceramids did not deposit their shells in isotopic equilibrium with sea water.The relationship between δ18Op and δ18Oc suggests early diagenetic replacement of an originally phosphatic phase by carbonate fluor apatite (CFA). This conclusion is in accord with REE studies of fish fossils. The correlated latitudinal variation in δ18O of meteoric water and temperature should result in a small variation of δ18Op in fresh water fish. The large range in δ18Op of Recent fish is the outcome the “altitude effect” (Dansgaard, 1964) i.e. of the existence of Recent high altitudes, and sharp morphological gradients.
Late Wenlock-Ludlow graptolite extinction and evolution: perspectives from Arctic Canada
Authors: Lenz Alfred C. 
Published: January 2018

An abrupt change in the composition of graptolite faunas just below, and at, the Wenlock-Ludlow boundary has recently been demonstrated in southeastern Germany and Kirgizistan. JAEGER (1991) terms that changeover the “Big Crisis”.On a global scale, throughout all but the uppermost Wenlock, Monograptus (s.s.), Cyrtograptus, and plectograptine retiolitids are moderately diverse and very abundant. This fauna is abruptly replaced in the uppermost Wenlock by an acme of simply thecate Pristiograptus dubius types and “pristiograptids”, and a marked increase in the diversity of the plectograptines. The succeeding earliest Ludlow fauna, which too appears abruptly, is marked by a mostly new fauna of plectograptines and new forms of monograptids the earliest of which include Lobograptus, Neodiversograptus and Bohemograptus. Two “crises” are therefore manifest, the earlier one being more profound.The Cape Phillips Formation of the Arctic Islands, Canada, yields a superb late Wenlock and early Ludlow graptolite, fauna. The late Wenlock lundgreni-testis Biozone has yielded isolated specimens of about 15 species of monograptids (including Monograptus (s.s.); especially M. testis), Cyrtograptus (several species), and at least seven species of plectograptines. About half of the fauna continues from the underlying zone. The overlying uppermost Wenlock ludensis Biozone is markedly different. Pristiograptus (of the P. dubius type) and “Pristiograptus” (Pseudomonoclimacis?) with novel thecal and sicular development (four or five species) are very abundant, and ten species plectograptines, only two of which continue from the underlying zone, appear abruptly. Cyrtograptus and Monograptus (s.s.) are totally absent.The succeeding earliest Ludlow is also characterized by rather abrupt appearances, again of several or more species of plectograptines, most very small, as well as monograptids with new thecal/rhabdosomal styles; these include Lobograptus. Neodiversograptus, Bohemograptus and Colonograptus, and slightly later, Saetograptus and the reappearance of Monograptus (s.s.). Plectograptines apparently become totally extinct by about mid Ludlow.
Ruedemann's Gasport Channel revisited: investigation of a Silurian (Ludlovian) Konservat-Lagerstätte
Authors: Lo Duca Steven 
Published: January 2018

In 1925 Rudolf Ruedemann described a remarkable Silurian biota dominated by noncalcified plants and animals from the Lockport Dolomite of western New York State. Ruedemann stated that the biota was confined to a single lens of interreef strata exposed at a Gasport, New York quarry; hence, he referred to the deposit as the Gasport Channel. Apart from a brief taxonomic treatment of the biota, this deposit remained largely unstudied, principally due to the destruction of the fossil site (by quarrying activity) shortly after the publication of Ruedemann's report. Recently, several new exposures of this fossil-bearing interval were discovered, prompting renewed interest in this unusual occurrence.The stratigraphic relations of this fossil occurrence reveal that it is not a lenticular interreef channel deposit, as indicated by Ruedemann, but is instead a thin (10 cm on average), laterally continuous unit that overlies the bioherms. Based on the great lateral extent of this unit (over 100 km), and the abundance of the noncalcified dasyclad alga Medusaegraptus mirabilis within, this interval has been termed the Medusaegraptus epibole.The biota of the Medusaegraptus epibole is dominated by dendroid graptolites and noncalcified algae. Several well preserved worms (Protoscolex) have been recovered, as well as fragments of probable terrestrial plants. A typical Silurian shelly marine biota of brachiopods, bryozoa, corals, trilobites and crinoids is almost completely absent, although shelly material is represented by rare internal and external molds. Apparently, the Medusaegraptus epibole does not present a taphonomically biased view of a “typical” Silurian community, but instead presents a picture of an entirely different kind of Silurian association.Based on the sedimentology and paleontology of the Medusaegraptus epibole, this unit was likely deposited in rather shallow (10–20 m), stagnant marine water. The fossil-bearing beds represent a series of tempestites with sharp, slightly erosional bases and distinct internal grading; fossil material is concentrated near the tops of these graded beds.Other, quite similar Ludlovian Konservat-Lagerstätten from North America (basal Mississinewa Shale, Lecthaylus Shale) apparently were deposited concomitant with the Medusaegraptus epibole. Synchronous deposition of these widespread units suggests that a large-scale mechanism, such as the emplacement of dysaerobic water on the craton, may be at least partly responsible for the formation of these Silurian Konservat-Lagerstätten.
Relative importance of molecular, morphological and paleontological data in understanding evolutionary innovations
Authors: Marshall Charles R. 
Published: January 2018

Recently there have been increasing efforts to integrate morphological, molecular and paleontological data in assessing evolutionary relationships. In some instances molecules appear more reliable than morphology. For example, a DNA-DNA hybridization phylogeny of clypeasteroid echinoids appears superior to conflicting morphological phylogenies, because: 1) Of all the nodes on the morphological tree, the one drawn into question by the DNA data is the least supported (the characters are few and of relatively low quality; character quality was judged using Remane's a priori homology recognition criteria). 2) A case can be made for the conflicting characters being functional correlates. 3) The morphological tree only finds support in 1% of 500 bootstrap analyses of the DNA data. 4) On the DNA tree sister groups occupy the same paleobiogeographic realm while on the morphological tree sister groups occupy completely disparate paleobiogeographic realms.However, in other instances morphology appears more reliable than molecules. For example, a recent 18S rRNA phylogeny of amniotes unites birds and mammals to the exclusion of crocodiles. Paleontologically this result seemed highly unlikely and it was suspected that some sort of substitution bias was responsible for the 18S rRNA result. Not only were pronounced substitution biases found, but when the 18S rRNA sequences were analyzed with an algorithm designed to deal with substitution biases a paleontologically more ‘reasonable’ tree resulted (birds were closer to crocodiles, not mammals).By comparing independent data sets, it appears that both morphological features and molecules may evolve less than parsimoniously. More significantly, in these cases the unanticipated parallel evolution has an identifiable biological 'signature’. It is perhaps disappointing that the evolutionary process may produce more parallel evolution than is implied by most-parsimonious trees. But when analyzed carefully there appears to be a coherency to the unanticipated parallel evolution, a coherency that may help us understand the structure of the adaptive landscapes within which evolutionary innovation arises.
Functional vs. phylogenetic control in the evolution of the vertebral column
Authors: McShea Daniel W. 
Published: January 2018

In the evolution of morphology, the importance of both historical constraints and selection for adaptive design has been widely acknowledged, but the relative efficacy of these internal (historical or phylogenetic) and external (selective or functional) factors has been much debated. Innumerable examples can be selected to make a case either way, but disinterested evaluation requires study of instances in which the relative degrees of functional and phylogenetic control are not already known. The vertebral column is an appropriate case: as the central structure for vertebrate locomotion and support, it ought to be subject to strong selection for functional design, yet it is also deeply generatively entrenched in vertebrate development, and therefore, arguably, ought to be less plastic than other structures.For this analysis, I applied three shape metrics to the vertebral column. The metrics are univariate and measure shape as functions of degree of differentiation within a column. (The metrics were developed in another context as measures of morphological complexity.) Then, a series of tests was conducted: in each, mean shape values for a group of functionally similar mammals (e.g. aquatics) and values for a group of phylogenetically related mammals (e.g. carnivorans) were compared independently with values for a test case, a mammal which belongs to both groups (e.g. aquatic carnivoran, otter). In almost all instances in which differences in resemblance were significant, the test cases more closely resembled their functional kin than their phylogenetic kin, suggesting a predominance of functional control. Results of standard cluster analyses (unweighted-pair-group method) supported this conclusion.
Comparative paleoecology of Paleogene and Neogene mammalian faunas: body-size structure
Authors: Morgan Michele E. , Kappelman John , Badgley Catherine , Gunnell Gregg F. , Gingerich Philip D. , Maas Mary , Legendre Serge 
Published: January 2018

In mammalian assemblages, size distributions reflect conditions of vegetation and climate as well as biotic interactions among mammals. Paleogene (Wyoming/Montana) and Neogene (Siwalik) mammalian faunas depict strikingly different size distributions in the cenograms below (rank v. size of herbivorous and omnivorous species), because evolutionary increase to substantial size did not become widespread among lineages until the middle Eocene (after our record).In the Paleocene to early Eocene, substantial faunal turnover with accompanying change in guild structure occurred with little change in size distributions. While maintaining relatively small sizes, lineages of modern mammalian orders replaced species from archaic groups. However, most mammalian lineages experienced size increase, especially through the Wasatchian (early Eocene).From the middle to late Miocene, significant size increases occurred upsection within several families of Siwalik carnivores, artiodactyls, and rodents. Families of insectivores, primates, proboscideans, and perissodactyls exhibited little change in species sizes despite changes in species composition and number. The trend toward increasing size preceded the widespread development of C4 grasslands in the Siwaliks, suggesting that biotic rather than abiotic factors influenced the size increase.
Taphonomy and ecology of deep-water Ediacaran organisms from northwestern Canada
Authors: Narbonne Guy M. , Dalrymple Robert W. 
Published: January 2018

Although most occurrences of Ediacaran fossils are from shallow-shelf deposits, taxonomically-similar assemblages have recently been described from a 2.5 km-thick succession of dark mudstones and turbiditic sandstones in the Windermere Supergroup of the Mackenzie Mountains, northwestern Canada. The paleogeographic position (20-40 km seaward of the shelf edge), abundant evidence of mass flow, and the complete absence of in situ shallow-water features imply that deposition took place on a slope considerably below storm wave-base. Ediacaran fossils were not observed in axial trough deposits (lower parts of the Twitya and Sheepbed formations), but megafossils occur sporadically in lower to middle slope deposits higher in the same formations. Megafossils and trace fossils are present in upper slope settings (Blueflower Formation) at the top of the Ediacaran succession. The megafossil assemblage varies stratigraphically, but in all formations is dominated by discoid forms (e.g. Cyclomedusa, Ediacaria, Nimbia); frondose forms and vendomiids are very rare.Megafossils are preserved mainly as positive features on the soles of thin turbidite beds. Most fossiliferous beds begin with the rippled layer of the turbidite (Tc), but a few begin with the graded (Ta) or parallel-laminated (Tb) layer. Consistent orientation and high relief of individuals, evidence of mutual deformation during growth of adjacent organisms, and other taphonomic features imply that virtually all of the taxa represent benthic polypoid and frond-like organisms (not jellyfish). Slump structures occur commonly in the sandstone fill of fossils, suggesting that many of the organisms were buried alive by the turbidite and later decomposed. Other individuals, even on the same bedding plane, exhibit graded to laminated fill identical to that of the overlying turbidite bed, indicating that the depressions on the sea bottom produced by these individuals were empty at the time of turbidite deposition. Escape structures are absent, suggesting that the Ediacaran organisms were not capable of burrowing up through even thin layers of sand.Ediacaran megafossils are invariably preserved on black, wrinkled surfaces similar to those elsewhere interpreted as microbial mats. Molding of delicate features (including tentacles), preservation of open molds as negative epireliefs, and sedimentological evidence of considerable cohesion of these surfaces relative to the underlying turbiditic muds (Td,e) supports this interpretation, and suggests that microbial mats were as important in the preservation of these deep-water Ediacara faunas as they were in their shallow-water equivalents. The presence of the wrinkled mats and their associated Ediacaran fossils almost exclusively in the pyritic intervals of the succession suggests that both may have lived under exaerobic conditions in this deep-water setting.
Patterns of terrestrial plant carbon: late Mesozoic and Cenozoic
Authors: Olson Jerry , Upchurch Garland R. 
Published: January 2018

Variation in terrestrial productivity and biomass impacts evolution through linkages between productivity and biodiversity and through the types of resources available for consumption by herbivores. Geographic variation in terrestrial plant carbon is known on a global scale for extant biomes and is strongly correlated with precipitation, temperature, and the area of wetlands. Although estimates of extant terrestrial plant carbon density are still somewhat uncertain, the highest densities clearly occur in tropical and temperate rainforests, and the lowest occur in deserts, semideserts, and arctic/alpine tundra. Patterns of variation in ancient terrestrial plant carbon can be estimated through the correlation between biome/climate and carbon density, provided individual biomes show little change through time in primary productivity or density of plant carbon.Density of terrestrial plant carbon has been estimated on a global scale for the latest Cretaceous, late Paleocene/Eocene, middle-late Eocene, early Miocene, and Holocene/Recent using the biomal reconstructions of Wolfe (1984), Upchurch (this symposium), and others. Latest Cretaceous (Maastrichtian) estimates indicate a relatively low value of 700-800 gigatons, which may underestimate carbon due to the presence of extensive latest Cretaceous coastal wetlands. However, much of this figure is readliy explainable by extensive deserts in Asia and little evidence for areally extensive tropical rainforest.Major increase in terrestrial plant carbon occurred during the Paleocene/earliest Eocene in conjunction with a major areal increase in rainforest. During the early Miocene terrestrial global carbon was approximately 1200-1300 gigatons. This figure decreased by about half between the early Miocene and Holocene/Recent. The decrease in terrestrial carbon density resulted from a decrease in area of tropical and subtropical forests and increase in area of deserts, grasslands, and mediterranean woodlands/chapparal.
What is the significance of supraspecific taxa in macroevolutionary studies
Authors: Rieppel O. 
Published: January 2018

For historical reasons, Darwin insisted on continuity of evolutionary transformation, which he believed would result in the “Origin of Species”. By the title of his book, he stigmatized species as the basic unit of evolution. If evolution is a historically unique process, a species originates only once, and if it goes extinct, it is lost forever. As a consequence, no “natural laws”, or general statements can cover the origin or extinction of particular species taxa; only particular statements are possible. For reasons such as these, some authors have proposed to view species as individuals.Can higher taxa be conceived of as individuals, too? If so, higher taxa would have to perform as units of evolution as species are believed to do. To deny so would introduce a fundamental ontological difference between “species taxa” and “higher taxa” without epistemological justification. I argue that the “discovery procedure” (Nelson, 1989) for species is the same as for higher taxa, and hence that species are taxa. However, the “discovery procedure” for monophyletic taxa results in an inclusive hierarchy of “groups under groups”, which is incompatible with Darwinian causes of evolution, predicting an exclusive hierarchy of ancestors and descendants. If it is agreed that successful scientific explanation must link hypothetical causes to observed effects in a testable manner, the conclusion must be that macroevolutionary scenarios built on species, or higher taxa, are descriptive rather than explanative. The Darwinian unit of evolution is, in fact, the geographically determined population, not the species (as Darwin himself realized). The alternative is to treat the inclusive hierarchy of species and higher taxa, and the pattern it reveals through time and space, as a reflection of history, which means that causes of this historical process are not only non-Darwinian, but remain a “black box” (Nelson, 1989) until today.