bluuebunny/crossref_metadata_2025 huggingface dataset:
Pliocene scallop growth lines: potential for environmental reconstruction and population dynamics
Authors: Clark George R. , Archer Allen W.
Published: January 2018

Prominent growth ridges on the shell of the modern scallop Pecten diegensis are known to form with a daily periodicity. Pecten stearnsii, its direct ancestor, has the same growth ridges and would be expected to form them at the same rate.

Pecten stearnsii specimens collected from the Pliocene Imperial Formation near San Filipe, Baja California, Mexico, have repetitive variations in the spacing of their growth ridges. Harmonic analysis of these variations found three tidal periodicities to be present, tropic (13.7 days), synodic (14.8 days), and anomalistic (27.6 days). This observation also served to confirm the daily nature of the growth ridges.

Tidal patterns at various locations within the present-day Gulf of California are dominated to various degrees by synodic and tropic periodicities. Comparisons of the growth-line records to modern tidal records by cross-correlation found a good match with a tidal station south of the collecting site, where the tropic periodicity dominates but the synodic periodicity is still important.

An important aspect of this match is that a graph of cross-correlations at all possible overlaps shows a cycle of good correlations, with a period of six months between peaks. As this is a reflection of the resonance between tropic and synodic periodicities, the peaks would occur at the same times of year in the Pliocene as today. This makes it possible to relate each specimen's growth record to the calendar, although two alternate interpretations, six months apart, would exist.

Two possible relationships would be of interest. First, if all the specimens had died at the same time of year it could mean a catastrophe, such as a severe storm. This was not the case, which is in itself a useful observation. Second, if all the specimens began their growth line record at the same time of year, it would suggest specific seasons for spawning and for spatfall. Here the evidence was more supportive; most specimens began forming growth ridges in either late March or late September, with perhaps a month's growth prior to the first growth ridge.

If isotopic paleotemperature analysis can be applied to these shells, or to others with similar characteristics, new levels of resolution in both environmental reconstruction and paleopopulation analysis may be achieved.
Evolution, dispersal and habitat preference of deep-sea trace fossils
Authors: Crimes T. Peter
Published: January 2018

Cambrian deep-sea sediments have yielded few trace fossils. The first moderately diverse suite is found in an Arenig flysch sequence in Eire. There followed a gradual increase in diversity and abundance of trace fossils in deep-sea niches in the Palaeozoic and early Mesozoic. A major burst of behaviourial evolution appears to have taken place during the Cretaceous and, from then through the Tertiary, high levels of trace fossil abundance and diversity were maintained. This is confirmed by recent work on Miocene deep-sea sequences and from a superbly preserved, diverse, ichnofauna recently discovered in strata of Oligocene and Miocene age in the Makran Range of Iran.

In the past, it has been inferred that there was a gradual improvement in behavioral programming in deep-sea traces, with a trend towards economy of effort and perfection. However, Lower Palaeozoic deep water traces show careful, complex, behavioral programming which was to change little through the rest of the Phanerozoic.

Within the deep-sea, there are, however, significant variations in the ichnospectrum in different niches. For example, the inner parts of seep-sea sand fans, particularly the channelled areas, have a mixture of “deep” and “shallow” water traces, whereas the outer fan normally has only deep water forms.
Biostratinomy of Recent intertidal bivalves at False Bay, San Juan Island, Washington, U.S.A.
Authors: Dent Steven R. , Uhen Mark
Published: January 2018

The importance of hydrologic processes in determining where and how a shell will be deposited is widely acknowledged, but few actualistic studies of these processes have been conducted. Additional knowledge of how the hydrologic regime influences the post-mortem distribution, orientation, and burial of modern shells can provide valuable paleoecological insights.

For the purposes of biostratinomy, single and articulated shells of Macoma nasuta and Clinocardium sp. were studied in False Bay, a semicircular inlet located on the west coast of San Juan Island, WA. Dead shells of these species were the most numerous and conspicuous skeletal elements present on the tidal flats. Transects were used to quantify the valves' natural distribution, orientation and depth of burial. Shell concentrations were significantly greater toward shore and decreased toward the center of the bay. The majority of these valves were articulated (56.4%) and oriented in the convex-up attitude (71.7%).

Tides and waves were the bay's dominant hydrologic forces. Spring low tides (maximum range of -0.8 m to 2.6 m) leave most of the bay subaerially exposed. During periods of immersion, waves from the Straits of Juan de Fuca underwent refraction, diffraction, and shoaling as they moved into False Bay. This influence was evidenced in the concentric sand bars which average 100 m long, 20 m wide and 0.5 m high. Painted and numbered valves were used to determine the effects of waves and tides. Shells were place in m2 areas both in a tidal channel and on a sand bar at low tide and then left for 1–2 tidal cycles. Recovery rates of shells ranged from 76.7% to 93.3%. Regardless of initial attitude, the majority were found in a convex-up attitude; convex-up valves remained in that orientation (89.8% – 97.7%) while those initially convex-down were reoriented to the convex-up position (75% – 86%). These findings confirmed that the convex-up position is the most hydrodynamically stable.

The most interesting aspect of this study was the nature of valve transport. Valves placed in the tidal channel moved less than one meter while those on the sand bar showed a strong bimodal distribution: shells moved either less than 2 m or distances ranging from 10 to greater than 119 m. The long range transport was unexpected; it was caused by the flotation, under calm meteorological conditions, of subaerially exposed convex-down shells on the incoming tide. This mode of transport moved the valves considerably greater distances than either saltation or traction in bedload. Shell flotation was not correlated to valve size, handedness, nor species.
Higher taxa in the fossil record and the recognition of evolutionary events: patterns vs. processes
Authors: Fastovsky David E. , Sheehan Peter M.
Published: January 2018

The fossil record is commonly (but not universally) invoked as an historical record with which to test evolutionary scenarios. The process by which this takes place involves the recognition of patterns of taxa in a temporal framework. The patterns are in turn interpreted as the result of some evolutionary mechanism. We submit that if the fossil record is to be a tool in evolutionary studies, the use of appropriately-defined higher taxa can be consistent with the objective of recognizing patterns from which evolutionary events can be inferred.

We implemented a study to monitor the ecological diversity of “families” of dinosaurs through the last 2.2 million years of the Cretaceous in the terrestrial sediments of the Hell Creek Formation in eastern Montana. We concluded, using the Shannon index and rarefaction as monitors, that at the “family” level, the ecological diversity of dinosaurs remained constant.

We suspect that the taxa we designated as “families” did not branch ancestrally at equivalent points in their respective phylogenies. Nevertheless, each is a monophyletic group, established and united by synapomorphies. We therefore measured and tracked the relative proportions of monophyletic groups through sequential time slices of the latest Cretaceous. We interpreted this as a measure of ecological diversity.

The phylogenetic methods that were used to define the extinct “families” in our study are epistemologically indistinguishable from methods that are used to establish monophyletic fossil groups at any taxonomic level, including the lowest levels. Why should special significance be attributed to a taxonomic level (i.e., species) that is obtained by means no different from those used to obtain the other levels?

Use of the fossil record in evolutionary reconstruction requires the recognition of patterns, and the attribution of evolutionary mechanisms to those patterns. It is unlikely that selection acts on units other than populations which arguably, are not even taxa. Recognition of historical patterns rather than causality or process, therefore, may be the unique province of the stratigraphic record.
Neogene Siwalik mammalian lineages: species longevities, rates of change, and modes of speciation
Authors: Flynn Lawrence J. , Barry John C. , Morgan Michele E. , Pilbeam David , Jacobs Louis L. , Lindsay Everett H.
Published: January 2018

The Siwalik sequence, particularly the interval from 18 to 7 Ma, provides one of the few terrestrial data sets that allows direct measurement of temporal durations of mammalian species. Its data are drawn from a single biogeographic subprovince and superposed collections likely represent successive samples of single lineages. Observed temporal ranges underestimate total species longevities if (1) species existed in other biogeographic provinces before or after the temporal ranges recorded in the Siwaliks, or (2) the fossil record inadequately samples species durations in the Siwalik subprovince. Some data, notably from Afghanistan, China, and Thailand, bear on the first variable. The second can be controlled by considering data quality, in this case the temporal distribution of good data sets, to assess the scale of accuracy available for defining range endpoints. In general, range endpoints can be estimated to the nearest 0.1 million years.

The diverse Rodentia give a mean species longevity of 2.2 million years for the Miocene Siwaliks. This includes single records, but of course ignores unretrieved rare or short-lived taxa. The diverse Artiodactyla yield 3.1 million years. The difference may reflect greater body size and longer generation time; large Perissodactyla and Proboscidea have longer temporal ranges. Carnivorous mammals also show about 3 million year durations. Given these data, the average longevity for Sivapithecus species (1.6 million years) is modest. The deposits of the Clarks Fork Basin, Wyoming, offer a Paleogene data set comparable to that of the Neogene Siwaliks. Paleocene-Eocene mammals of North America yield shorter longevities (most less than one million years).

Extinction is the dominant mode of species termination for Siwalik mammals. Most taxa originated by immigration (as at about 13.5 Ma) or abrupt speciation. There are some cases for insitu transformation of lineages, for example in the genera Punjabemys, Antemus, Percrocuta, Dorcatherium, Giraffokeryx, and Selenoportax. The rodent Kanisamys shows a rate of increase in tooth size of 0.5 darwins. This overall rate is moderate by Paleogene standards, but includes an interval of more rapid change between 9.0 and 8.5 Ma.
The Oxford Clay: a paleontological laboratory
Authors: Hudson John D.
Published: January 2018

The Lower Oxford Clay, a marine formation of Middle Jurassic (Callovian) age exposed in central and southern England, merits the attention of paleontologists and geochemists for several reasons. It was the subject of a classic of biostratigraphic and evolutionary paleontology by Brinkmann on the ammonites; sexual dimorphism and bioprovinciality in the same group has since been intensively studied by Callomon and others. Its exploitation by the brick industry has enabled the assembly of one of the most extensive collections of marine vertebrates by the Leeds brothers and later workers; these include the world's largest ever fish, and superbly preserved ichthyosaurs, plesiosaurs and crocodiles now dispersed to museums throughout Europe and beyond. Dinosaurs, while rare, are also diverse. The benthic fauna is dominated by abundant but not diverse molluscs, believed tolerant of soupy bottom conditions and periodic dysoxia. Coccoliths and dinoflagellates represent the phytoplankton. Aragonite, calcite and phosphate biominerals are excellently preserved. In our main study area burial did not exceed 500m.; organic matter is immature. Early diagenesis resulted in the formation of carbonate concretions that preserve original sediment fabrics elsewhere destroyed by compaction; later diagenesis brought about further mineralogical changes.

Work since the 1970's has resulted in much improved understanding of the Lower Oxford Clay biota and its trophic relationships. It is useful to compare it to the more calcareous Middle and Upper Oxford Clay. The biostratigraphy is extremely well-known. The well-preserved fossils invite microstructural and geochemical studies. Economic concerns add impetus to the study of actual or potential hydrocarbon source rocks. Yet the Lower Oxford Clay is full of enigmas and questions still. It looks quiet-water but has many diastems, not all recognizable by classic criteria like shell beds. The fossil preservation might imply a high sediment delivery rate, but the sediment accumulation rate is low. It is organic-rich, but not anoxic. Where did the enigmatic ‘pendent’ bivalves live? Whence the nutrients to support the rich biota? To what extent do organic compounds survive from the primary producers, or does heterotrophic reworking dominate? Can we refine or quantify trophic relationships? We should also be able to use our ‘laboratory’ for experiments of wider significance for paleotemperatures or paleo-CO2 levels.

In the Oxford Clay group of papers we attempt to summarize where traditional paleoecological analysis has led us to so far, and to show how the new approaches made possible by advances in isotopic and biomolecular paleontology can revise and refine our ideas, solve old problems and, no doubt, raise new ones. We believe our collaborative approach has much to offer for paleontologists and geochemists, as also exemplified by the other contributions to the symposium.
Organic stratigraphy and its applications with examples from the North American Western Interior and Antarctica
Authors: Jacobson Stephen R. , Askin Rosemary A.
Published: January 2018

Both insoluble (particulate) and soluble (molecular) sedimentary organic matter carry signatures of physical, chemical, and biological processes. These signatures may reflect (a) primary age-diagnostic, organism-specific, and environmentally-sensitive processes; (b) secondary factors related to mode of transportation, deposition, and preservation; and (c) tertiary agents that indicate post-burial alteration of the organic matter. Application of any or all organic matter data recorded in rocks can be used to solve geologic problems.

Organic stratigraphy may be applied to hydrocarbon exploration. Our example uses both particulate and molecular data to reconstruct the age relations of Cretaceous-Lower Tertiary sediments in Wyoming, to determine the age of thrust fault motion, and to demonstrate constraints on the timing of upward petroleum migration to available trapped reservoirs.

Another perspective helps establish chronostratigraphic frameworks for correlations of global sea-level change. Our example from Antarctic sediments that span the Cretaceous-Tertiary boundary reflects perturbations in relative sea-level and the consequential changes in the distribution of organic particulates from marine and terrestrial regimes. These data can be compared to age-equivalent data from other parts of the world, and test global sea-level change.

Both of these applications demonstrate the versatility of organic matter in solving geologic problems. Data from contemporaneous land plants, freshwater and marine organic-walled micro-organisms provide clues on their lifestyle and subsequent afterlife alteration. Organic stratigraphy represents a long anticipated integration of several paleontological disciplines. It combines aspects of palynology, organic geochemistry, paleobotany, and coal petrography into a coherent science, with an enhanced capability to provide significant applications in the future.
Permian Triassic geologic evolution in the southern Kitakami Belt, Japan
Authors: Kamada Kotaro
Published: January 2018

Before opening of the Japan Sea, the Japanese islands were attached to the eastern margin of the Asian continent. The Southern Kitakami Belt is regarded as a micro-continent in an accretional complex of the islands, that accreted before the Early Cretaceous. But its tectonic setting and location between the belt and the Asian continent is still an unresolved argument.

Permo-Triassic sequences in the Southern Kitakami Belt are composed of shallow to off-shore deposits. These deposits are composed of clastics, carbonates with volcaniclastics. But there was no volcanic activity in the belt in the Middle to Late Permian. From the viewpoint of the sedimentary character and history, the Middle Permian to Middle Triassic sequences differ from their previous and their following successions in the belt. And the sedimentary basin of Middle Permian to Middle Triassic was bounded by transform faults. Magmatic arc was replaced by passive margin as hinterland of the Southern Kitakami Belt during the Middle Permian to Middle Triassic. It means that the sedimentary basin moved from the margin of Yangtze Platform to Sino-Korean Platform at that time.
Demise of the middle Paleozoic crinoid fauna: gradual or mass extinction?
Authors: Kammer Thomas W. , Ausich William I.
Published: January 2018

There are essentially three major crinoid faunas of the Paleozoic: 1) the lower Paleozoic (Ordovician) fauna dominated by disparids and diplobathrid camerates; 2) the middle Paleozoic (Silurian-middle Mississippian) fauna dominated by monobathrid camerates, cladids, and flexibles; and 3) the upper Paleozoic (middle Mississippian-Permian) fauna dominated by cladids. Change from the middle Paleozoic fauna to the late Paleozoic fauna, at or near the Osagean-Meramecian boundary, was characterized by Laudon (1948) as “one of the most remarkable faunal breaks in the entire Paleozoic era”. The monobathrids that had reached their zenith in the Osagean (Tournaisian-Visean) became a very minor component of late Paleozoic faunas. Conventional thinking has implied that a mass extinction of crinoids occurred at the Osagean-Meramecian boundary.

We have biostratigraphically subdivided the late Osagean and early Meramecian into four zones (times A-D, oldest to youngest, all within the Gnathodustexanus zone) in order to study the origination and extinction of all crinoid species during the changeover from the middle to upper Paleozoic faunas. Rather than a mass extinction, a monotonic turnover of species fits a pattern of gradual extinction as extinctions outpaced originations. Data are based on 216 species (taxonomically updated) from 69 localities and are as follows:

The pattern of originations and extinctions for monobathrids is very similar to the pattern for all crinoid species.

The above data have maximum diversity during Time B of the late Osagean followed by declining diversity in times C and D into the early Meramecian. Late Meramecian crinoid faunas (after time D) were less diverse with a maximum of about 45 species. The gradual decline of crinoids across the Osagean-Meramecian boundary cannot be explained as sampling bias (Signor-Lipps effect), because ranges of crinoids thought to be extinct at the boundary are extended into the early Meramecian as well as disappearing at various tinles prior to the boundary.

The decline in diversity and the monotonic turnover of species are hypothesized to be the result of habitat reduction as the Eastern Interior Basin of North America was gradually infilled with clastic sediments at the end of the Acadian Orogeny. Most notable in this regard was the smothering of the Keokuk Limestone carbonate bank. Changes in sea level also contributed to habitat reduction. Lowering of sea level at the end of the Osagean caused restriction of open marine environments. A transgression in the early Meramecian was followed by shoaling and restriction during deposition of the late Meramecian Salem and St. Louis limestones.
Pseudoplankton: hitch-hikers through time or stuck in the mud?
Authors: Kauffman Erle G. , Meyer Christian A. , Villamil Tomás , Harries Peter J.
Published: January 2018

Pseudoplanktic life modes have typically been invoked to explain the presence of abundant fossils belonging to normally low-oxygen intolerant taxa within oxygen-deficient black shales facies (e.g., bivalves, crinoids, barnacles, serpulid worms, brachiopods, gastropods, bryozoans, foraminifers, corals, hydrozoans, and sponges). The same explanation has been used for exceptional paleobiogeographic distribution of benthic species. However, detailed paleoecologic, population, and taphonomic analyses of numerous black-shale biotas in conjunction with recently published models for oxygen-deficient basins suggests that this hypothesis is no longer required to explain the distribution of these taxa in supposedly non-viable habitats. Actual examples that could be interpreted as evidence for pseudoplanktic life habit (i.e., colonization on both sides of ammonites) are very rare. For example, less than 2% of the encrusted ammonites (N = 1240) in the Jurassic Posidonienschiefer show pseudoplanktic colonization patterns. These could be interpreted as flipped specimens within the benthic zone. The remainder are stable “shell-island” substrates with ammonites (and large bivalve shells) colonized on one side only. Most logs believed to be colonized on the lower surface by bivalves and/or crinoids in floating position actually have evidence for benthic encrustation on the tops and sides of the logs, and have obvious current shadows of dead shells.

The data show that: 1) the abundance of these taxa greatly exceeds the expectations of pseudoplanktic rain as well as the number of potential hosts; 2) they commonly occur as short-term event communities rather than as the normal populations expected of continuous pseudoplanktic rain; 3) specimens are commonly found in epibenthic life position; 4) their occurrence patterns show strong facies control usually reflecting benthic oxygen gradients; 5) many preserve a large prodissoconch or protoconch suggesting a long-term planktotrophic larval stage. Most of these “pseudoplanktic” groups appear to have had a benthic life habit.

Moreover, most oxygen-deficient environments disappeared by the end of the Cretaceous along with some of the dominant pseudoplanktic taxa. Drifting logs and seaweeds are common today, but generally lack specific “pseudoplanktic” faunas, with the exception of boring bivalves, gooseneck barnacles, serpulid worms, and bryozoans. Epibenthic bivalves and crinoids are very rare to absent on potential “pseudoplanktic” hosts in modern seas, yet are the main groups of organisms designated as pseudoplankton in the fossil record.
Ontogenetic and evolutionary patterns of septal neck transformation in the Ammonoidea
Authors: Landman Neil H. , Tanabe Kazushige , Weitschat Wolfgang , Mapes Royal H.
Published: January 2018

Four types of septal necks are present in the Ammonoidea: (1) retrochoanitic (entirely projected adapically), (2) modified retrochoanitic (projected adorally or both adorally and adapically on the dorsal side and adapically on the ventral side), (3) amphichoanitic (projected both adorally and adapically), and (4) prochoanitic (entirely projected adorally). Each septal neck is continuous with the rest of the septum and consists primarily of a nacreous layer. A spherulitic-prismatic deposit called the auxiliary deposit commonly appears on the adoral side of the septal neck and covers the inner surface of the nacreous layer. Another spherulitic-prismatic deposit (cuff) may also occur on the adapical side of prochoanitic necks. In all of the Paleozoic suborders except Goniatitina (Prolecanitina, Bactritina, Anarcestina, Agoniatitina, Clymeniina, Gonioclymeniina and Tornoceratina), type 1 necks are present throughout ontogeny (1→1). In the Goniatitina as well as in the Ceratitina, type 1 necks either persist throughout ontogeny (1→1) or develop into type 2 necks (1→2). In the Phylloceratina, type 1 necks are present in early to middle ontogeny, later developing into type 3 necks (1→3). In the Lytoceratina, type 1 necks are only present in very early ontogeny and are immediately replaced by type 4 necks (1→4). In the Ancyloceratina and Ammonitina (with few exceptions), only type 4 necks occur (4→4). Type 1 necks evidently represent the primitive condition. Variation among suborders in the ontogenetic timing of the transformation from the primitive condition to one of the three more derived conditions may be the result of heterochronic processes such as acceleration or predisplacement. However, the pattern of septal neck transformation within suborders is more or less stable and was probably established at the time each suborder originated.
Morphometric studies of radiolarian evolution
Authors: Lazarus Dave
Published: January 2018

Radiolarians are the most diverse of the 4 major fossil forming plankton groups, with several hundred living species, and an equally diverse range of biologic specializations for planktonic existence. Studies of radiolarian evolution are mostly from the Cenozoic, where the opaline silica skeletons of radiolarians are well preserved in most areas of the world's oceans. Cenozoic radiolarian skeletons are mostly too small (50-150 μm) and delicate to easily manipulate individually. Washed sieved skeletons are strewn at random orientations onto glass microslides and viewed in transmitted light. At the required magnifications, most skeletons cannot be viewed in their entirety within a single focus-plane. Many (perhaps the majority) of taxonomic characters in radiolarians are not visible in the skeleton outline, but are internal. These characteristics make normal image analysis techniques more difficult to employ. Computer assisted manual digitizers (one version working in 3 dimensions) have sometimes been used to measure skeletons. Distance, angle, area, and shape outline measurements have all been used to quantify radiolarian morphology.

Radiolarian skeletal growth is determinate, and relatively little ontogenetic or within-population allometric variation is seen. Geographic variation in radiolarian species morphology is common, but little studied. Perhaps due to the effort involved, most ordinary taxonomic work does not employ morphometric data: its use has largely been in species-level evolutionary studies. Phyletic trends in size, shape, and in other characters have long been used to delineate stratigraphically useful chronospecies, and some of these anagenetic series have been morphometrically measured. Cladogenesis has also been morphometrically quantified in a few cases. Most studies of both cladogenesis and anagenetic evolution have documented gradual rates of morphologic change.

Integrated studies of paleogeographic variation and temporal change are still needed, as is better information on modern radiolarian biology. Much more efficient measurement tools are also needed, to handle the very large number of specimens required by integrated studies.
Late Triassic succession of North American halobiid bivalves and their circum-Pacific correlation
Authors: McRoberts Christopher A.
Published: January 2018

The thin-shelled pteriid bivalve Halobia is widely distributed in Upper Triassic (Carnian-mid Norian) marine strata throughout the circum-Pacific region with significant occurrences along the western and arctic margin of North America, northeast Russia, China, Japan, Indochina, islands of the western Pacific, and New Zealand. Halobiids are commonly associated with deep water, black shale facies typically devoid of macrobenthos. This facies occurrence and a thin-shelled, flat-valved morphology suggests an autecology (possibly pseudoplanktic) in contrast to modern benthic pteriids. High speciation and extinction rates of halobiids not only provide an excellent means for dating rocks lacking ammonoids, but they give an independent view of rapidly evolving lineages during Carnian-Norian time.

A composite halobiid succession with nearly complete coverage from the earliest Carnian through the late mid Norian is constructed from numerous North American sequences and localities with ammonoid control. Although differences in nomenclature rather then endemism make correlation of the North American succession with other circum-Pacific regions difficult, similar (and quite possibly homologous) morphologies allow limited correlation between these regions. The early Carnian is typified by H. zitteli, which occurs in predominantly boreal strata of Canada and Siberia. By later Carnian time, a variety of similar morphotypes (probably conspecific) belonging to subspecies of H. superba, H. radiata, and several other species are known throughout the circum-Pacific. The earliest Norian Kerri ammonoid zone is recognized by the first appearance of H. beyrichi in North America, and H. styriaca in Asia. In North America and the rest of the circum-Pacific, the latter part of the early Norian is marked by a rapid diversification of forms, including H. cordillerana and H. fallax. By late mid Norian time diversity reached a maximum 5 species. The mid Norian species H. fallax, H. halorica, and H. plicosa are particularly wide-spread; they occur throughout the circum-Pacific where they coexisted with the earliest Monotis. As in the Alpine-Mediterranean region, the remaining halobiids went extinct by the end of the mid Norian.

Halobiid speciation and extinction rates exceed other Late Triassic macrofauna except ammonoids. The average North American species duration is fewer than three ammonoid zones (ca. 2.5 MY). The late early Norian is a period of pronounced diversification, whereas the middle early Norian and late middle Norian are times of accelerated extinctions. Instead of catastrophic extinction at the Carnian-Norian boundary, North American halobiids exhibit complex taxonomic turnover. Similar diversity patterns are recognizable in other circum-Pacific halobiid sequences.
Did shell layers negatively affect Ordovician soft-bodied infauna?
Authors: Miller Molly F. , Davies David J.
Published: January 2018

What is the relationship, if any, between soft-bodied infaunal animals and shell accumulations? Do shell layers negatively affect infaunal animals and have they in the past? To determine whether this type of taphonomic inhibition may have operated in Ordovician infaunal communities, we evaluated extent of burrow penetration of shell-rich layers in shallow-water limestones of the Lebanon Formation, central Tennessee. Most of the analyzed shell layers, which are a few mm to 15 cm thick, are not cut by burrows. No burrows occur in shell layers in slabs containing 67% of the total area examined (5500 cm2), although burrows are common above and below the shell-rich layers.

Most of the few shell-rich layers that are burrowed occur in wackestones in which skeletal fragements are arranged in a loose/dispersed fabric (Kidwell and Holland, 1991). Where burrow diameter is greater (1 cm) than maximum dimension of most shell fragments (2-4 mm), shells outline the burrow, suggesting that the animal pushed them aside during burrow construction. Where burrow diameter is less (2-3 mm) than length of shell fragments (0.5–2 cm), the burrows occur between the fragments, which show no signs of biogenic reorientation. In the single case where grainstone consisting of densely packed skeletal fragments (3–5 mm in longest dimension) is penetrated, burrow diameter (1 cm) exceeds fragment size.

Shell layers penetrated by burrows originated variably as storm deposits, current winnowed accumulations, and dense shell pavements. No layers with vertically imbricated shells are burrowed; they probably were deposited in a high energy environment inimical to burrowers. With this exception there is little evidence that mode of origin of shell bed exerts strong control over subsequent penetration by burrowers.

Although limited, these data suggest that Ordovician soft-bodied infaunal animals avoided burrowing through shell-rich layers. Those shell layers that were penetrated are loosely packed. Characteristically, in burrow-penetrated shell layers the ratio of fragment size: burrow size is either very low (animal pushed fragments aside) or very high (animal moved between shell fragments). Thus, abundance and character of shell-rich layers may have been an important factor controlling the composition and structure of Ordovician infaunal communities.
Origin and early evolution of Aves: dinosaurs, ancient birds, and mtDNA sequences
Authors: Sereno Paul C.
Published: January 2018

Recently a general cladistic framework for early avian evolution has emerged. Postcranial modifications in the wrist joint and elsewhere firmly establish birds as a diversified subgroup of maniraptoran theropods. And the best known Mesozoic avians–Archaeopteryx and Late Cretaceous Hesperornis and Ichthyornis –have been positioned as successive sister taxa to living birds. Within this framework, however, several basic phylogenetic questions need to be addressed: (1) Which maniraptorans are most closely related to birds? (2) How was the modern avian skeleton built during the first third of avian history, between Archaeopteryx and Late Cretaceous Hesperornis and Ichthyornis? (3) And what are the relationships between the major groups of living birds?

Avian origins. Synapomorphies listed by Ostrom and others to unite birds and other theropods typically apply to all maniraptorans or higher-level theropod clades, leaving unsettled the question of which maniraptorans constitute the immediate outgroups to birds. Deinonychosauria is confirmed as the sister-group to Aves, based principally on synapomorphies of the pectoral and pelvic girdles. In contrast to some previous suggestions, this study supports monophyly of Deinonychosauria (uniting dromaeosaurids and troodontids), with a single origin of the hyper-extendable, raptorial digit II of the pes.

Sinornis and the evolution of powered flight and perching. Archaeopteryx lacks the profound modifications of the avian skeleton that characterize Ichthyornis and modern birds. Recent discovery of Lower Cretaceous birds has brought to light important intermediate stages in the transformation of the avian skeleton. Sparrow-sized Sinornis, discovered in Lower Cretaceous lake deposits in China, exhibits features that are associated with sustained powered flight; the laterally directed glenoid and V-shaped ulnare suggest that the wing was capable of tight flexion during flight. Features unrelated to the flight apparatus, in contrast, have not been altered; the skull is toothed, the manal digits are flexible and clawed, and gastralia are present beneath the rib cage.

Higher-level relationships among living birds. The deep branching history of living birds occurred before the end of the Cretaceous and can be reconstructed from anatomical and genetic evidence in living birds. DNA sequences have been obtained from the mitochondrial cytochrome b gene in a variety of living birds. These data are consistent with a basal split between palaeognaths and neognaths and support the basal position of galliforms and anseriforms among neognaths. Piciforms appear to be closely related to passeriforms, and Corvida does not appear to be monophyletic, in contrast to recent DNA-DNA hybridization results.
Tempo and mode in deep-sea benthic ecology: punctuated equilibrium revisited
Authors: Smith Craig R.
Published: January 2018

The deep-sea floor is traditionally perceived as a remote and deliberate environment; a habitat where a gentle rain of detrital food particles and sluggish bottom currents force biological processes to proceed at slow, steady rates. In this view, benthic community structure is controlled by equilibrium processes, such as extreme levels of habitat partitioning (e.g., “grain matching”) made possible by remarkable ecosystem stability. A number of recent discoveries indicate, however, that the deep-sea floor may be neither remote nor deliberate. Pulses of food and kinetic energy rapidly reach the seafloor from the dynamic upper ocean, and endogenous disturbances may be surprisingly frequent and intense. The biological processes driven by these events can be highly variable in space and time, exhibiting disequilibrium dynamics. I briefly review three types of events (large food falls, pulses of phytodetritus, and biogenic mound building) that “punctuate” the apparent “equilibrium” of the deep-sea floor, and describe how these events may change patterns of macrofaunal feeding, growth, recruitment and/or competitive exclusion. I then discuss how these changes may affect processes of paleoecological significance, including (1) the dispersal and evolution of chemosynthetic communities, (2) mechanisms and rates of trace production/destruction, and (3) maintenance of macrofaunal diversity at the ocean floor.
Preservation of bone proteins and DNA in an ancient fish called ‘Wanda’
Authors: Stathoplos Linda , Tuross Noreen
Published: January 2018

Skeletal fish remains, including several vertebrae (Teleostei incertae sedis), were recovered from the core catcher section (subbottom depth, 10.5 m) of a piston core taken in the Gulf of California (28° 00.34’ N, 111° 31.32’ W; 460 m water depth). Bottom water temperatures in this area are typically less than 10°. Bone material retained original crystal morphology as well as a chemical composition consistent with hydroxyapatite. Insoluble collagen from one small bone fragment, extracted by decalcification in EDTA, was AMS radiocarbon dated at 28,070 ± 310 years b.p. (TO#2190).

Proteins from ancient fish bone fragments were partitioned by sequential extraction into two soluble fractions, non-mineral-associated and mineral-associated, and an insoluble fraction. The amino acid compositions of these extracts were compared to modern fish bone extracts. Soluble fossil fish bone extracts were enriched in collagen, consistent with peptide bond cleavage in this molecule and retention of degradation products by the mineral matrix, as observed previously in other ancient bones.

Three non-collagenous bone cell-produced proteins, osteocalcin, osteonectin, and bone sialoprotein, were identified immunochemically by ELISA (enzyme-linked immunosorbent assay) in the mineral-associated fraction from these ancient fish bones. The serum protein albumin was also identified immunochemically, suggesting that hydroxyapatite binding may enhance preservation of biomolecules in the fossil record. DNA, another molecule that binds to hydroxyapatite, was also observed in the mineral-associated ancient fish extract. The DNA showed signs of both in situ cleavage and complexing to an autofluorescent component that has been observed in other ancient specimens. Thus, the continuous presence of water does not by itself preclude preservation of non-collagenous proteins, insoluble collagen, or DNA in bone for tens of thousands of years. Anoxia and low temperatures afforded by burial in this basin slow molecular decay.

Small animals are underrepresented in the vertebrate terrestrial fossil record primarily due to differential preservation of skeletal material. Oceanic sediments provide an underexploited source of small vertebrate remains containing molecular as well as morphological information with chronometric and systematic utility.
Late cenozoic land mammals and interamerican environments
Authors: Webb S. David , Rancy Alceu
Published: January 2018

Because Late Cenozoic land life in the Americas is best represented in temperate latitudes, it has long been standard practice for paleontologists to infer the history of the Great American Interchange from the classic mammalian sequences in western United States and in Argentina. In this record it is also clear that interchange genera in South America (ultimately of northern origin) make up about half of the modern land-mammal fauna, in contrast with a very limited success on the part of the reciprocal cohort of interchange genera.

On the other hand, tropical biologists at least since the days of A. R. Wallace have known that the Amazon Basin was a very rich center of tropical diversity and that this Neotropical richness had spread northward at least to the latitude of Oaxaca and Veracruz in Mexico. Thus, mammalian paleontologists claim a victory for north temperate forces spreading south, whereas much of the modern biota seems to register a countervailing victory for south tropical forces spreading north.

Current paleontological research in tropical latitudes, especially in the western Amazon Basin, indicates the manner in which these two different views of interamerican biotic movements can be reconciled. In effect both views are true, because they represent alternating modes of interamerican interchange. Perhaps simplistically, we recognize a “glacial arid phase” and an “interglacial humid phase”. During the former phases savanna habitats predominated even at tropical latitudes, as the western Amazonian records of the late Pleistocene strongly indicate. Because the source area in the temperate north was six times as large as that in the south, the great success of northern land mammal groups is explained. On the other hand, during interglacial humid phases, the principal biotic movement was from the vast Amazonian rainforest reservoir through the tropical latitudes of Mesoamerica. We review some of the new evidence of land mammals from tropical America in the late Pleistocene.
Characteristic taphanomic morphologies in fossil soft-tissues and their reproduction in actualistic necrolytic experiments
Authors: Wilby Phil R.
Published: January 2018

Soft-tissues replaced by hydroxyapatite are exceedingly abundant in fossil fish from the Santana Formation (Lower Cretaceous) of Ceara, NE Brasil. A number of tissues are often phosphatized within an individual specimen and may include portions of the alimentary tract, skeletal muscle, dermis, gill apparatus and ovaries. The level of structural detail displayed by these tissues varies considerably between individual fish but is relatively constant within any single specimen. In some, sub-cellular resolution is the norm, whilst in others only gross morphological detail is preserved.

Frequently, certain tissues such as gill filaments and their secondary lamellae; epithelial cells of the gut wall; and, striated muscle fibres, preserve a number of different morphologies. In the latter for example, a continuum exists between homogeneously mineralized fibres which are almost indistinguishable from living muscle, and muscle which is disrupted by exceptionally well developed and irregularly spaced banding. In the same specimens, both the sarcolema and cell nucleii may display varying degrees of distortion. These characteristic morphologies reflect the gradual loss of structural integrity accompanying a period of post-mortem decay prior to and/or during permineralization.

High resolution TEM and SEM studies of structures produced at progressive stages of soft-tissue decay in modern fish, confirm the necrolytic origin of these morphologies. The timing of their appearance under specified conditions is remarkably reproducible. Certain parameters such as the ambient water temperature and salinity appear to have considerable influence over the rapidity of decay, whereas others, including the levels of oxygen and the presence of an established bacterial community have less, especially over short periods.

By cross-referencing certain taphanomically produced structures, estimates of both the timing of phosphatization and the likely bottom water conditions of the Santana Formation “lagoon” may be made.
Evolutionary trends and facial control of Chitinozoa
Authors: Zaslavskaya N.
Published: January 2018

Chitinozoa is an organic world group, the nature of which is not yet known. However, Chitinozoa is a uniform natural group of the organic world with a definite stratigraphical position (O-D). I suggest to use solely peridermal structures to specify evolutional trends of Chitinozoa.

1. The change of carinae that forms the morphological succession Cyathochitina calix-C. campanulaeformis-C. kuckersiana. This succession of species encompasses the early-middle Ordovician interval.

2. The change in the structure of longitudinal ridges that features the evolutionary succession Hercochitina repsinata-H. lindsaensis-H. crickmay at the middle-late Ordovician interval of the south part of Ontario.

3. The change in the ultrastructure of peridermal tissue. It shows well through the structure of appendices in the succession Ancyrochitina ancyrea-A. alveolata-A. siberica, llandovery-wenlock of the Siberian platform and ludlowpridoli of Europe and North America.

The points of peridermal appendix structure might be used for facial analysis. So, basal appendices change from simple branchwise up to complex anastomosis and loop-like during the change of the surrounding from shallow-water shelf up to a deep-water one, forming the morphology succession Ancyrochitina-Clathrochitina. Thus, evolutional trends of Chitinozoa and facial analysis might be based on a detailed study of peridermal structure morphology.
A Better Way to Probe Peat
Authors: Witman Sarah
Published: January 2018

Florida scientists use ground-penetrating radar to image underground carbon stores in the Disney Wilderness Preserve.
Influence of c-Src on hypoxic resistance to paclitaxel in human ovarian cancer cells and reversal of FV-429
Authors: Guo Qinglong , Lu Lu , Liao Yan , Wang Xiaoping , Zhang Yi , Liu Yicheng , Huang Shaoliang , Sun Haopeng , Li Zhiyu , Zhao Li
Published: January 2018

SRC family kinase was documented to have vital roles in adjusting cancer cell malignant behaviors. To date, the role of c-Src, a member of SRC family kinase, in resistance to paclitaxel in human ovarian cancer cells under hypoxia has not been investigated. In the present study, we discovered that hypoxic environment suppressed paclitaxel-induced G2/M phase arrest and blockade of c-Src improved ovarian cancer cells’ sensitivity to paclitaxel. FV-429, a derivative of natural flavonoid wogonin, could suppress gene expression and activation of c-Src, followed by deteriorated Stat3 nuclear translocation and its binding to HIF-1α, resulting in paclitaxel resistance reversal through G2/M arrest potentiation. Our study demonstrated that c-Src contributed to hypoxic microenvironment-rendered paclitaxel resistance in human epithelial ovarian cancer cells by G2/M phase arrest deterioration, and through c-Src suppression, FV-429 was capable of reversing the resistance by blocking c-Src/Stat3/HIF-1α pathway.