bluuebunny/crossref_metadata_2025_split huggingface dataset:
The genesis and preservation of biomarkers in the sedimentary record: an experimental study of the alga Emiliania huxleyi
Authors: Briggs Derek E.G. , Getliff John M. , Leftley John W. , Maxwell James R. , Parkes R. John. , Teece Mark 
Published: January 2018

The distribution of molecular markers in sediments provides a reservoir of unique information concerning biogeochemical processes in the geological past, and how these processes respond to environmental change. However, sedimentary systems themselves are biologically dynamic and these markers, and their precursors, have been subjected to bacterial degradation and modification. Recent research indicates that key changes in sedimented organic matter take place during the earliest stages of sediment burial and diagenesis where bacterial activity is also intense. Hence, effective interpretation of the distribution of biomarkers from deep sediment layers and sedimentary rocks requires knowledge of the rates and processes of bacterial decomposition under a range of environmental conditions.Algae are important primary producers in the marine environment. The prymnesiophyte alga Emiliania huxleyi was selected as a subject for study as it is a source of long chain ketones which are geochemically important biomarkers. The ratio of the ketones C37:2 to C37:3 is temperature sensitive and has been used as a palaeotemperature indicator (UK37).Preliminary sediment slurry incubations were carried out to optimize experimental design (concentration of decay organism, concentration of sediment in slurry, ability to obtain defined microbial environments over long term incubations, aerobic and anaerobic), and quantitative analytical scheme (extraction and separation technique, type and concentration of internal standards). Subsequent experiments on aerobic bacterial degradation of E. huxleyi demonstrated rapid increase in bacterial activity and biomass. This was accompanied by major changes in lipid classes. The dominant aliphatic hydrocarbons, three isomers of nC31:2, were rapidly degraded and completely removed by 78 days. In contrast, in preliminary anaerobic incubations, the same compounds remained unchanged. By 78 days a significant reduction in the total algal sterols was accompanied by a small increase in total stanols; hence the cholestanol/cholesterol ratio increased markedly. The abundance of the long chain unsaturated ketone C37:3 decreased relative to C37:2 resulting in an increase in the UK37 ratio. The reasons for these changes are unclear. However, they indicate that bacterial degradation may have to be taken into account in the interpretation of UK37 ratios in terms of paleotemperatures.Further experiments are in progress to clarify the interpretation of these results and provide information on the more recalcitrant biomarkers.
New material of the ichthyosaur

Mixosaurus nordenskioeldii

from the Triassic of British Columbia, and the interspecific relationships of

Mixosaurus
Authors: Brinkman Donald B. , Nicholls Elizabeth L. , Callaway Jack M. 
Published: January 2018

New material of Mixosaurus nordenskioeldii from the Middle Triassic Sulphur Mountain Formation of Wapiti Lake, British Columbia, includes cranial elements with complete upper and lower dentitions, and associated post-cranial material. It demonstrates that skulls with a Phalarodon-like dentition are associated with a Mixosaurus type of post-cranium. The upper and lower dentitions differ in the degree of anteroposterior elongation of the molariform teeth and in the rate of tooth differentiation. These new specimens demonstrate that the separation of the Svalbard material into Phalarodon and Mixosaurus (Merriam, 1911; Wiman, 1916) represents a separation of upper and lower dentitions and confirms that Phalarodon fraasi is the junior synonym of Mixosaurus nordenskioeldii.Mixosaurus nordenskioeldii is more derived than M. cornalianus in the following characters: 1) Anterior end of both jaws edentulous, 2) Posterior crushing teeth laterally compressed domes, elongate anterolaterally, 3) Skull with large parietal crest, extending well forward between the orbits, 4) Sixth digit present in manus (developed from a neomorph in M. cornalianus).A well preserved stapes is present in the new material of Mixosaurus from British Columbia. This is one of the oldest preserved ichthyosaur stapes and demonstrates that this element was primitively long and slender in the Ichthyopterygia.The cheek region in Mixosaurus is formed by two large bones traditionally identified as the quadratojugal and the squamosal. The homologies of these elements are reinterpreted as the squamosal and the supratemporal.
Late Cenozoic turnover in the Caribbean reef coral fauna
Authors: Budd Ann F. , Stemann Thomas A. , Johnson Kenneth G. 
Published: January 2018

Study of the stratigraphic ranges of reef coral species in scattered sequences (Dominican Republic, Bahamas, Costa Rica, Jamaica, and Florida) suggests that a major episode of faunal turnover occurred in the Caribbean region between early Pliocene and mid Pleistocene time. In a data set composed of all reef corals except the families Mussidae and Oculinidae and the genera Cladocora and Madracis, approximately 90% of the Mio-Pliocene fauna, composed of as many as 65–70 species, became extinct during this time interval. Ten of 27 genera became extinct. Despite the high numbers of extinctions, the total number of species in the Caribbean reef coral fauna dropped only slightly over the time interval, due to similar numbers of originations and extinctions in the fauna. With one possible exception, new species arose in surviving genera, and no new genera formed.Although similar numbers of species became extinct within early Pliocene, late Pliocene, and early Pleistocene time units, shallow water communities experienced higher numbers of extinctions during the late Miocene and early Pliocene. Deeper water communities experienced higher numbers of extinctions during the late Pliocene and early Pleistocene. Species surviving the turnover episode occur in deeper water communities and belong predominantly to the family Agariciidae. Nearshore grass flat communities contain the highest number of early extinctions. No difference in extinction patterns could be detected between taxa which reproduce primarily by fragmentation and those that reproduce primarily by larval recruitment. Although originations appear evenly distributed among community types, a large number occur in Florida along the northern margin of faunal distribution.The increased extinctions in shallow water communities and increased originations in the north suggest that turnover occurred primarily in response to change in abiotic factors such as temperature and siltation, and not in response to species-area effects associated with sea level change.
Arthropods from North Greenland: exceptional data in the ‘Cambrian explosion’ debate
Authors: Budd Graham E. 
Published: January 2018

'Sirius Passet’ fauna arthropods from the Lower Cambrian Buen Formation of North Greenland form the major component of this exceptionally preserved biota. Early mineralisation of body cavities led to internal anatomy being preserved more readily than external structures such as limbs. Musculature and gut are known in three dimensional form. Many of the taxa present are more easily compared to extant arthropods than to flattened fossil material such as from the Burgess Shale.The most common arthropod is represented by some 1600 specimens. Although widely differing in preservational style, these specimens may be reconciled to provide a coherent model of the three-dimensional anatomy of the arthropod. The affinities of this arthropod lie with the ‘Cheliceromorph’ rather than the Crustacean biramous-limbed arthropods, and may represent a fairly advanced lineage within the clade.Recent discussions of the patterns produced by the early metazoan radiations have concentrated on data available from the Burgess Shale. The continuing discovery and description of other Cambrian lagerstätten such as from North Greenland and Chengjiang has highlighted the degree to which the Burgess Shale fauna should be considered to be an aliquot taken from the foment of the ‘Cambrian Explosion’. The discovery of more taxa is tending to flesh out the bare bones of the Burgess fauna. Conclusions about phylogentic patterns drawn from the Burgess Shale alone may thus be premature.Body patterning in the arthropods, and the validity of the ‘Bauplan’ concept may be investigated by consideration of the actual mechanisms available for profound morphological change. One promising route is provided by the ‘homeotic’ and other hierarchically arranged developmental genes. When the mode of action of these genes is considered in conjunction with phylogenetic methods, it may prove possible to assess evolutionary pathways in terms of the feasibility of the morphological changes required by them rather than relying on what seems inherently reasonable or on marginal advantages in parsimony. Exceptionally preserved biotas also contain the evidence for the evolution of the developmental mechanisms themselves.
Shell-crushing by two duck species,

Tadorna tadorna

and

Somateria mollissima

in the Wadden Sea. Paleoecologic implications
Authors: Cadee Gerhard C 
Published: January 2018

Shell fragments from faeces of the mollusc-eating eider (Somatera mollissima) and shelduck (Tadorna tadorna) were studied in the Dutch Wadden Sea. Both species crush shells internally in their gizzard.Shelducks feed mainly on the small gastropod Hydrobia ulvae, which they do not always succeed in breaking: in some cases even surviving Hydrobia were collected from the faeces. This indicates that shelduck may help dispersion of Hydrobia and that not only Hydrobia fragments but also intact empty shells are contributed to the sediment by this predator.Eiders feed mainly on mussels (Mytilus edulis) and cockles (Cerastoderma edule). When these are scarce, they take shorecrabs or the gastropod Littorina littorea. Their crushing method is usually successful; only some Littorina shells were found intact but not alive in their faeces. Shells are crushed to fragments ranging from less than 0.1 to 8 mm, with a peak in the 2 – 4 mm size fraction, 20% was < 1 mm.Annual shell carbonate production in the Dutch Wadden Sea is ca 150.000 tonnes. The annual average number of eiders is 63.000 with a maximum of up to 200.000 in winter. Annually they consume 3200 tonnes meat (ash-free dryweight). If they fed fifty/fifty on mussels and cockles they would produce ca 75.000 tonnes shell-fragments. As they feed partly on non-molluscan food this is an upper limit, but it implies that they are the main producers of shell-fragments (of all sizes, even the smallest) in the Wadden Sea. The typically square shell-fragments they produce, are easily recognisable in Wadden Sea sediments.Others predators (shorecrabs, shrimps, flatfish, other mollusc-eating birds like knot and curlew) produce additional shell-fragments. However, some predators e.g. seastars (Asterias rubens) leave intact the shells they consumed.Shell-fragments in sediments, therefore, may give an indication of predation pressure, but as non-crushed shells may be left over by some predators, total predation pressure on molluscs cannot be estimated in fossil faunas.
Time averaging and temporal persistence in chemoautotrophic molluscan-dominated death assemblages on the Louisiana continental slope
Authors: Callender W. Russell , Powell Eric N. 
Published: January 2018

Petroleum seeps on the Louisiana continental slope produce luxurious communities based on chemoautotrophic symbiotic bacteria. Petroleum seeps are typical cold seep communities and generate classic autochthonous death assemblages. Fossil cold seep communities are well-known, common and widespread. Most fossil analogues are dominated by lucinids, but petroleum seeps are not. A combination of sample collection and in situ experimentation has been used to determine rates of taphonomy and time averaging in petroleum seep assemblages.Cores were obtained and sectioned from seep sites in Green Canyon lease blocks 272, 234, and 184 and Garden Banks lease block 386. Lucinids and thyasirids were selected for dating time-since-death to determine the importance of time averaging in these assemblages. Dating was accomplished by measuring the free amino acid content of the shells. Time-since-death became progressively older with depth; accordingly little time averaging had occurred in these autochthonous assemblages. Lucind and mussel shells were placed on the sea floor and recovered 3 yr later. Comparison of each species to the controls left on a laboratory shelf for 3 yr shows that taphonomic alteration was rapid. Mussels were more severely altered than lucinids. Mussels were more heavily dissolved, had more altered edges, were more prone to fragmentation and exhibited greater weight loss than lucinids. The rapid taphonomic loss of the mussels suggests that the preponderance of lucinids in the fossil record is an artifact of preservation. Taphofacies analysis suggests the same; thus verifying an important assumption of taphofacies analysis that taphonomic signatures record biases in preservation by identifying inter-species differences in the rates of important taphonomic processes. Significant variability in taphonomic rates exists between shells from locations 10 m apart indicating significant local variation in the taphonomic process. Local variability in taphonomic and community attributes is characteristic of many autochthonous assemblages.
Morphometric description of cosmopolitan Early Cretaceous inoceramid bivalves
Authors: Crampton James S. 
Published: January 2018

Inoceramidae (Bivalvia) was a diverse, cosmopolitan family of large Cretaceous bivalves which occupied a wide range of marine environments, and experienced high rates of speciation. For biological and taphonomic reasons inoceramid taxonomy has been based almost exclusively on only two characters: shape and ornament. These characters commonly display high degrees of intraspecific variability. Previous biometric studies, using linear and angular measurements (eg. shell length, umbonal angle), have successfully discriminated between closely related species, and have overturned earlier qualitative taxonomies. Even comprehensive linear and angular measurements suffer from several disadvantages. They are restricted by instrumental limitations, are time consuming to gather, and neglect much information inherent in outline shape. Hence, the present study attempts to quantify differences in inoceramid shape and ornament using outline shape analysis complemented by a few simple distance measures. A digitised outline can be exactly described by a set of elliptic Fourier coefficients, and sets of such coefficients are treated as variables in a multivariate analysis of shape.These methods have been used to examine the cosmopolitan, morphologically highly plastic, and highly subdivided Albian species Birostrina concentrica (Parkinson) and related forms. Collections from New Zealand (southern high latitude), England (northern high latitude), and Switzerland (Tethyan) show significant differences in the shape and maximum size of individuals. Preliminary analyses, however, have shown that within any region it is difficult to identify distinct sub-groupings based on shape or ornament. Furthermore, the total volume of morphospace occupied by B. concentrica (s.l.) can be accounted for largely by changes in morphology through ontogeny. In other words, for example, the change in shape of an individual through ontogeny can exceed the morphological distance between described subspecies. Ongoing morphometric examination of populations from different stratigraphic horizons is helping to unravel evolutionary and biogeographic patterns which are otherwise difficult to demonstrate.Shape analysis is a tool that is largely underexploited by macropalaeontologists, and is particularly useful for the description of taxa with few landmarks or easily defined characters.
Onshore-offshore patterns in Late PreCambrian and Lower Palaeozoic trace fossils
Authors: Crimes T. Peter , Hunt N. Chris 
Published: January 2018

There was a dramatic increase in abundance and diversity of trace fossils in Upper Precambrian and Lower Cambrian shallow water seas. The trace-producing animals rapidly filled all the available niches and in low energy, muddy, environments they evolved winding, meandering and patterned habits. Traces such as Taphrhelminthopsis, Helminthoida, Nereites, Paleodictyon and Squamodictyon had all evolved in clastic shelf seas during the pre-trilobite Lower Cambrian.Significant colonisation of the deep oceans seems to have mostly been delayed until the Ordovician. A recently described suite of trace fossils from a flysch sequence in Eire includes such deep water types as: Glockerichnus, Helminthopsis, Lorenzinia, Paleodictyon and Taphrhelminthopsis. This migration into the deep sea is accompanied by a virtual absence of such traces from shallow water sequences after the Cambrian.Deep water trace fossils therefore seem to have evolved initially in shallow water clastic seas and then migrated in to the deep ocean, thereby providing an exciting example of an onshore-offshore pattern. This may be of particular significance in that it is presumably mimicked by body fossil migrations in these early seas.
The pliocene record of climatic change: equator-to-pole biotic response
Authors: Cronin Thomas M. , Dowsett H.J. 
Published: January 2018

Pliocene faunal events in tropical and subtropical regions of the Americas and the Caribbean have been causally linked to global climatic events, particularly, progressive cooling and increased amplitude of climatic cycles between 3.5 and 2.0 Ma. However, the rate and magnitude of Pliocene temperature changes has been determined in only a few climate proxy records. Our study contrasts paleoceanographic conditions at 3 Ma, an extremely warm period in many areas, with conditions 2.4 Ma, a much cooler interval, in equator-to-pole transects for the North Atlantic and the North Pacific Oceans. By using microfaunal data (ostracodes from ocean margin environments and planktic foraminifers from deep sea cores), quantitative factor analytic and modern analog dissimilarity coefficient analyses were carried out on faunas from the following sections.Our studies lead to the following conclusions: (1) Equator-to-pole thermal gradients in the oceans at 3.0 Ma were not as steep as they are today, but thermal gradients at 2.4 Ma were steeper than those today; (2)At 3 Ma middle to high latitudes were substantially warmer than today, but tropical regions were about the same; (3)Substantial cooling occurred in middle and high latitudes in the western North Pacific Ocean and the western North Atlantic between 3 Ma and 2.4 Ma; (4)Ocean water temperatures off the southeastern U.S. remained the same or cooled only slightly between 3 Ma and 2.4 Ma. Our results support the hypothesis that ocean circulation changes, probably resulting from the closure of near surface water by the Isthmus of Panama, had significant impact on equator-to-pole heat transport and global climate between about 3 and 2.4 Ma. They also argue against the hypothesis that climatically induced ocean temperature changes were directly linked to a major marine extinction in the southwestern North Atlantic and Caribbean.
IGCP 272 - Late Palaeozoic and Early Mesozoic circum-Pacific events and their global correlation
Authors: Dickins J. M. 
Published: January 2018

IGCP 203 - Permo-Triassic events of eastern Tethys and their intercontinental correlation - focussed on the Permian-Triassic boundary sequences and in particular there was a consensus that the distinctive biological changes were associated with strong sea-level and tectonic change, strong volcanic activity and a harsh climate. These factors were connected with an important change in the environment and with the exception perhaps of the climate, reflected deep-seated changes within the earth. The project also resulted in improving the physical understanding of the sequences and their biostratigraphy and correlation.IGCP 272 was developed, and was approved in 1988, to apply these results to understanding the Late Palaeozoic and Early Mesozoic and was focussed on the Pacific as integration around this region seemed to offer especially fruitful possibilities.Working group meetings up to the end of 1991 have been held in Australia (Newcastle and Hobart), New Zealand (Dunedin), South America (Sao Paulo and Buenos Aires) and North America (Washington). Meetings are planned in North America, Japan, Eastern Siberia or Thailand and western Europe (France-Spain-Austria).Special cooperation has developed with the Carboniferous, Permian and Triassic Subcommissions of IUGS and with IGCP 214 - Global Bio-events. Using the more exact time correlations developed it has now been possible to show that major geological and biological events (of different levels of significance) are associated with major boundaries already recognized in the World Standard Stratigraphical Time Scale. These comprise the Carboniferous-Permian, the mid-Permian (twofold subdivision, the Permian-Triassic (already recognized in earlier work), the Lower-Middle and Middle-Upper Triassic and the Triassic-Jurassic boundaries.A special achievement of the project has been to show the similar significance of the Midian-Dzhulfian boundary within the Upper Permian but corresponding closely to the traditional Lower-Upper Permian of China and the Middle-Upper Permian of Japan.Although there are also other events at levels which have not been investigated by the project, those outlined all seem to reflect important changes within the earth.