Publications by authors named "Antonino Briguglio"

17 Publications

  • Page 1 of 1

First fossil-leaf floras from Brunei Darussalam show dipterocarp dominance in Borneo by the Pliocene.

PeerJ 2022 24;10:e12949. Epub 2022 Mar 24.

Lambiase Geoscience, Nokomis, Florida, United States.

The Malay Archipelago is one of the most biodiverse regions on Earth, but it suffers high extinction risks due to severe anthropogenic pressures. Paleobotanical knowledge provides baselines for the conservation of living analogs and improved understanding of vegetation, biogeography, and paleoenvironments through time. The Malesian bioregion is well studied palynologically, but there have been very few investigations of Cenozoic paleobotany (plant macrofossils) in a century or more. We report the first paleobotanical survey of Brunei Darussalam, a sultanate on the north coast of Borneo that still preserves the majority of its extraordinarily diverse, old-growth tropical rainforests. We discovered abundant compression floras dominated by angiosperm leaves at two sites of probable Pliocene age: Berakas Beach, in the Liang Formation, and Kampong Lugu, in an undescribed stratigraphic unit. Both sites also yielded rich palynofloral assemblages from the macrofossil-bearing beds, indicating lowland fern-dominated swamp (Berakas Beach) and mangrove swamp (Kampong Lugu) depositional environments. Fern spores from at least nine families dominate both palynological assemblages, along with abundant fungal and freshwater algal remains, rare marine microplankton, at least four mangrove genera, and a diverse rainforest tree and liana contribution (at least 19 families) with scarce pollen of Dipterocarpaceae, today's dominant regional life form. Compressed leaves and rare reproductive material represent influx to the depocenters from the adjacent coastal rainforests. Although only about 40% of specimens preserve informative details, we can distinguish 23 leaf and two reproductive morphotypes among the two sites. Dipterocarps are by far the most abundant group in both compression assemblages, providing rare, localized evidence for dipterocarp-dominated lowland rainforests in the Malay Archipelago before the Pleistocene. The dipterocarp fossils include winged fruits, at least two species of plicate leaves, and very common leaves. We attribute additional leaf taxa to Rhamnaceae (), Melastomataceae, and Araceae (), all rare or new fossil records for the region. The dipterocarp leaf dominance contrasts sharply with the family's <1% representation in the palynofloras from the same strata. This result directly demonstrates that dipterocarp pollen is prone to strong taphonomic filtering and underscores the importance of macrofossils for quantifying the timing of the dipterocarps' rise to dominance in the region. Our work shows that complex coastal rainforests dominated by dipterocarps, adjacent to swamps and mangroves and otherwise similar to modern ecosystems, have existed in Borneo for at least 4-5 million years. Our findings add historical impetus for the conservation of these gravely imperiled and extremely biodiverse ecosystems.
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http://dx.doi.org/10.7717/peerj.12949DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8958975PMC
March 2022

A predictive model for the ichnological suitability of the Jezero crater, Mars: searching for fossilized traces of life-substrate interactions in the 2020 Rover Mission Landing Site.

PeerJ 2021 23;9:e11784. Epub 2021 Sep 23.

Dipartimento di Scienze della Terra 'Ardito Desio', University of Milan, Milan, Italy.

Ichnofossils, the fossilized products of life-substrate interactions, are among the most abundant biosignatures on Earth and therefore they may provide scientific evidence of potential life that may have existed on Mars. Ichnofossils offer unique advantages in the search for extraterrestrial life, including the fact that they are resilient to processes that obliterate other evidence for past life, such as body fossils, as well as chemical and isotopic biosignatures. The goal of this paper is evaluating the suitability of the Mars 2020 Landing Site for ichnofossils. To this goal, we apply palaeontological predictive modelling, a technique used to forecast the location of fossil sites in uninvestigated areas on Earth. Accordingly, a geographic information system (GIS) of the landing site is developed. Each layer of the GIS maps the suitability for one or more ichnofossil types (bioturbation, bioerosion, biostratification structures) based on an assessment of a single attribute (suitability factor) of the Martian environment. Suitability criteria have been selected among the environmental attributes that control ichnofossil abundance and preservation in 18 reference sites on Earth. The goal of this research is delivered through three predictive maps showing which areas of the Mars 2020 Landing Site are more likely to preserve potential ichnofossils. On the basis of these maps, an ichnological strategy for the Perseverance rover is identified, indicating (1) 10 sites on Mars with high suitability for bioturbation, bioerosion and biostratification ichnofossils, (2) the ichnofossil types, if any, that are more likely to be present at each site, (3) the most efficient observation strategy for detecting eventual ichnofossils. The predictive maps and the ichnological strategy can be easily integrated in the existing plans for the exploration of the Jezero crater, realizing benefits in life-search efficiency and cost-reduction.
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http://dx.doi.org/10.7717/peerj.11784DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8466086PMC
September 2021

Lunar cycles and rainy seasons drive growth and reproduction in nummulitid foraminifera, important producers of carbonate buildups.

Sci Rep 2019 06 4;9(1):8286. Epub 2019 Jun 4.

Institut für Paläontologie, Universität Wien, 1090, Wien, Austria.

Representatives of the foraminifer Nummulites are important in Earth history for timing Cenozoic shallow-water carbonates. Taphonomic complexity explains the construction of carbonate buildups, but reproduction and life span of the constructing individuals are unknown. During the 15-month investigation period, asexually reproduced schizonts and gamonts showed equal proportions in the first half of this period, whereas gamonts predominated in the second half. Oscillations in cell growth are mainly caused by light intensities during chamber construction when minor differences in water depth increase the photosynthetic rate of endosymbiotic diatoms during neap tides. The continuous reproduction rate of N. venosus throughout the year is increased in subtropical calms by higher summer temperatures and the marginal input of inorganic nutrients during rainy seasons. The expected life span of both gamonts and schizonts are 18 months.
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http://dx.doi.org/10.1038/s41598-019-44646-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6547678PMC
June 2019

Morphometric analysis of Eocene nummulitids in western and central Cuba: taxonomy, biostratigraphy and evolutionary trends.

J Syst Palaeontol 2019 13;17(7):557-595. Epub 2018 Apr 13.

Dipartimento di Scienze della, Terra dell'Ambiente e della Vita, Universitá degli Studi di Genova, Corso Europa, 26, I-16132Genova, Italy.

Megalospheric specimens of Nummulitidae from eight localities in western and central Cuba were morphometrically investigated using test characters described by 11 growth-independent and growth-invariant attributes that provide a complete geometric reconstruction of nummulitid equatorial morphology. The species , , and were classified by an agglomerative cluster analysis. Discriminant analysis yielded significant morphological separators between the species such as the backbend angle, marginal radius increase, perimeter ratio and first chamber length. The transition of tightness to laxity of the spiral was an important morphological separator at the generic level, representing a clear general trend coupled with the change in palaeodepth. Based on further discriminant analysis, an increase in proloculus size was detected in from the middle Eocene to early late Eocene, supporting this important evolutionary pattern in many lineages of . Operculinid forms showed an opposite and more weakly pronounced time-dependent trend in the size decrease of the proloculus. In the Cuban localities, occurs from the Lutetian to Priabonian, while is restricted to the Bartonian to Priabonian. The moderately to loosely coiled operculinid taxa and have longer stratigraphical ranges from the middle Eocene to probably the early Oligocene. and show a broader variability in marginal radius increase, and thus probably occupied wider niches than . The latter seems to be restricted to the shelf edge and to the shallowest parts of the upper slope. A possible phylogenetic connection between and is suggested by the closest equatorial morphology of sp. indet. to tightly coiled forms of . Discriminant analysis documents the strongest similarities in perimeter ratio, backbend angle, initial marginal radius and proloculus mean diameter.
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http://dx.doi.org/10.1080/14772019.2018.1446462DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6474738PMC
April 2018

Growth estimation of the larger foraminifer by means of population dynamics.

PeerJ 2019 16;6:e6096. Epub 2019 Jan 16.

Dipartimento di Scienze della terra, dell'ambiente e della vita (DISTAV), Università degli Studi di Genova, Genova, Italy.

In , the flagship species of laboratory investigations of larger benthic foraminifera (LBF) since the 70's, the timing of reproduction, longevity and natural chamber building rates are still understudied. A recently developed method, the natural laboratory (sensu Hohenegger), has been applied on populations from Sesoko Jima, NW Okinawa, Japan. An averaged chamber building rate and longevity of were calculated based on 17 monthly samplings at fixed stations. All samples were collected at 20 and 50 m water depths using SCUBA. Live populations were dried and investigated by microCT. The monthly frequency distributions of chamber numbers and test diameters have been decomposed in normally distributed components. For each month, mean and standard deviations of the components were used to calculate the maximum chamber number and maximum test diameter. Based on these values, the natural chamber building rate (CBR) or diameter increase rate (DIR) could be estimated using the Michaelis-Menten function. CBR and DIR were inverted to estimate the 'birthdate' of all investigated individuals. Based on frequencies of these 'birthdates', main reproduction events could be detected and compared to the reproduction timing of other subtropical and tropical LBF taxa. Furthermore, peaks in reproduction could be linked to monsoon wet seasons (="rainy seasons") and winter rains.
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http://dx.doi.org/10.7717/peerj.6096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339478PMC
January 2019

A new icriodontid conodont cluster with specific mesowear supports an alternative apparatus motion model for Icriodontidae.

J Syst Palaeontol 2018 15;16(11):909-926. Epub 2017 Aug 15.

Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, GadongBE1410, Brunei Darussalam.

Increasing numbers of conodont discoveries with soft tissue preservation, natural assemblages and fused clusters of the hard tissue have strengthened the hypothesis regarding the function and mechanism of the conodont feeding apparatus. Exceptional fossil preservation serves as a solid basis for modern reconstructions of the conodont apparatus illustrating the complex interplay of the single apparatus elements. Reliable published models concern the ozarkodinid apparatus of Pennsylvanian and Early Triassic conodonts. Recognition of microwear and mammal-like occlusion, especially of platform elements belonging to individuals of the genus , allows rotational closure to be interpreted as the crushing mechanism of ozarkodinid platform (P1) elements. Here we describe a new icriodontid conodont cluster of that consists of one pair of icriodontan (I) and 10 pairs of coniform (C1-5) elements, with I elements being preserved in interlocking position. The special kind of element arrangement within the fused cluster provides new insights into icriodontid apparatus reconstruction and notation of elements. However, orientation of coniform elements is limited to a certain degree by possible preservational bias. Four possible apparatus models are introduced and discussed. Recognition of specific wear on denticle tips of one of the icriodontan elements forms the basis for an alternative hypothesis of apparatus motion. Analysis of tip wear suggests a horizontal, slightly elliptical motion of opposed, antagonistically operating I elements. This is supported by similar tip wear from much better preserved, but isolated, elements of Middle Devonian icriodontids. More detailed interpretation of the masticatory movement will allow enhanced understanding of anatomical specifications, diet and palaeobiology of different euconodont groups.
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http://dx.doi.org/10.1080/14772019.2017.1354090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6023268PMC
August 2017

Growth of under natural and laboratory conditions.

Mar Micropaleontol 2016 Jan 15;122:27-43. Epub 2015 Nov 15.

University of Vienna, Department of Palaeontology, Althanstrasse 14, 1090 Vienna, Austria.

The use of micro-computed tomography (μCT) provides a unique opportunity to look inside the shells of larger benthic foraminifera to investigate their structure by measuring linear and volumetric parameters. For this study, gamonts/schizonts and agamonts of the species d'Orbigny were examined by μCT; each single chamber's volume was digitally measured. This approach enables cell growth to be recognised in terms of chamber volume sequence, which progressively increases until reproduction occurs. This sequence represents the ontogeny of the foraminiferal cell and has been used here to investigate controlling factors potentially affecting the process of chamber formation. This is manifested as instantaneous or periodic deviations of the realised chamber volumes derived from modelled growth functions. The results obtained on naturally grown specimens show oscillations in chamber volumes which can be modelled by sums of sinusoidal functions. A set of functions with similar periods in all investigated specimens points to lunar and tidal cycles. To determine whether such cyclic signals are genuine and not the effects of a theoretical model, the same analysis was conducted on specimens held in a closed laboratory facility, as they should not be affected by natural environmental effects. Surprisingly, similar cyclicities were observed in such samples. However, a solely genetic origin of these cycles couldn't be verified either. Therefore, detailed analysis on the phase equality of these growth oscillations have been done. This approach is pivotal for proving that the oscillatory patterns discovered in LBF are indeed genuine signals, and on how chamber growth might be influenced by tidal currents or lunar months.
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http://dx.doi.org/10.1016/j.marmicro.2015.11.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5238945PMC
January 2016

Growth, chamber building rate and reproduction time of (Foraminifera) under natural conditions.

Coral Reefs 2017 4;36(4):1097-1109. Epub 2017 Jul 4.

2Department of Petroleum Geoscience, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong, BE1410 Brunei Darussalam.

We investigated the symbiont-bearing benthic foraminifer to determine the chamber building rate (CBR), test diameter increase rate (DIR), reproduction time and longevity using the 'natural laboratory' approach. This is based on the decomposition of monthly obtained frequency distributions of chamber number and test diameter into normally distributed components. Test measurements were taken using MicroCT. The shift of the mean and standard deviation of component parameters during the 15-month investigation period was used to calculate Michaelis-Menten functions applied to estimate the averaged CBR and DIR under natural conditions. The individual dates of birth were estimated using the inverse averaged CBR and the inverse DIR fitted by the individual chamber number or the individual test diameter at the sampling date. Distributions of frequencies and densities (i.e., frequency divided by sediment weight) based on both CBR and DIR revealed continuous reproduction throughout the year with two peaks, a stronger one in June determined as the onset of the summer generation (generation 1) and a weaker one in November determined as the onset of the winter generation (generation 2). This reproduction scheme explains the presence of small and large specimens in the same sample. Longevity, calculated as the maximum difference in days between the individual's birth date and the sampling date, is approximately 1.5 yr, an estimation obtained by using both CBR and DIR.
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http://dx.doi.org/10.1007/s00338-017-1601-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6959394PMC
July 2017

New results on the hydrodynamic behaviour of fossil Nummulites tests from two nummulite banks from the Bartonian and Priabonian of northern Italy.

Boll Soc Paleontol Ital 2015 Sep;54(2):103-116

Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 103, I-41125 Modena, Italy.

Settling velocities of 58 well-preserved tests of fossil Nummulites were experimentally determined using a settling tube. The tests were collected from the nummulite banks of Pederiva di Grancona (A forms of N. lyelli N. striatus, Middle Eocene) and San Germano dei Berici (A and B forms of N. fabianii, Late Eocene), both in the Berici Mts. (Veneto, northern Italy). The data were compared with estimated settling velocities that the same specimens might have had in life conditions. This was done by reconstructing their densities simulating water-filled condition and, to simulate post-diagenetic effects, under calcite-filled condition. These simulations show that A and B forms, even if they greatly diverge in shape, volume and size, still possess comparable settling velocities, and that each nummulite bank is characterized by specific hydrodynamic parameters. The use of settling velocity as a parameter to quantify the hydrodynamic behaviour of particles in seawater enables estimation of palaeoenvironmental conditions such as depth, substrate and the energy scenario. Such information is useful in obtaining further insights into the genesis of nummulite banks, the autochthony or allochthony of which is still being debated. Our results point to an autochthonous interpretation.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4678592PMC
September 2015

TEST FUSION IN ADULT FORAMINIFERA: A REVIEW WITH NEW OBSERVATIONS OF AN EARLY EOCENE SPECIMEN.

J Foraminifer Res 2014 Jul;44(3):316-324

Institut für Paläontologie, Universität Wien, Althanstrasse 14, A-1090 Vienna, Austria.

In foraminifera, so-called "double tests" usually arise due to abnormal growth originating mainly from twinning, but may also be caused by irregularities in the early chambers and by regeneration after test injury that modifies the direction of growth. A fourth cause of double tests has only rarely been reported: the fusion of the tests of two adult individuals. We studied an early Eocene double test consisting of two adult individuals that fused after an extended period of independent growth. The specimen was studied using computed tomography with micrometric resolution (micro-CT) that allowed bi- and three-dimensional visualization of the internal structure. Before fusion each individual test had 30-36 chambers, which, by comparison with growth rates in recent nummulitids, implies at least three months of independent growth. After fusion, the compound test grew in two spirals that fused after about one whorl and then continued in a single spiral. To fuse their tests, either adult individuals have to be forced to do so or the allorecognition (ability to distinguish between self and another individual) mechanisms must fail. A possible explanation for the merged tests in this study is forced fusion in attached individuals after surviving ingestion and digestion by a metazoan. Alternatively, environmental stress could lead to a failure of allorecognition mechanisms and/or foraminiferal motility. Once fused, subsequent growth seems to be determined mainly by the relative orientation of individual tests. In any case, the frequency in which adult fusion occurs remains unknown.
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http://dx.doi.org/10.2113/gsjfr.44.3.316DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4497801PMC
July 2014

Growth oscillation in larger foraminifera.

Paleobiology 2014 ;40(3):494-509

Department of Palaeontology, University of Vienna, Vienna 1090, Austria.

This work shows the potential for applying three-dimensional biometry to studying cell growth in larger benthic foraminifera. The volume of each test chamber was measured from the three-dimensional model obtained by means of computed tomography. Analyses of cell growth based on the sequence of chamber volumes revealed constant and significant oscillations for all investigated specimens, characterized by periods of approximately 15, 30, 90, and 360 days. Possible explanations for these periods are connected to tides, lunar cycles, and seasonality. The potential to record environmental oscillations or fluctuations during the lifetime of larger foraminifera is pivotal for reconstructing short-term paleoenvironmental variations or for gaining insight into the influence of tides or tidal current on the shallow-water benthic fauna in both recent and fossil environments.
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http://dx.doi.org/10.1666/13051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4497532PMC
January 2014

The basal Lutetian Transgression on the Tethyan shelf of the European craton (Adelholzen beds, Eastern Alps, Germany).

Newsl Stratigr 2013 Oct;46(3):287-301

Naturkunde- und Mammut-Museum Siegsdorf, Auenstraße 2, 83313 Siegsdorf, Germany.

The middle Eocene Adelholzen beds were deposited on the northern part of the Tethyan shelf of the European Plate. In the Eastern Alps, the Wimmern section near Teisendorf (Germany) is the only known outcrop exposing the basal unconformity of this sequence. The outcrop comprises an 8 m thick condensed transgressive shallow marine succession characterized by glauconite-rich weakly consolidated greensand and mudstone containing abundant larger benthic foraminifera. It spans the lower part of calcareous nannoplankton Zone NP15 (Sub-Zones NP15a and lower part of NP15b), planktonic foraminifera Sub-Zone E7b and Zone E8 partim and the upper part of shallow benthic Zone SBZ13. The landward migration of the paleo-shoreline was not an effect of flexural downbending of the European Plate but can be correlated to the major unconformity at the base of eustatic supercycle TA3. The onset of this sea-level rise was in the latest part of Biochron NP14b and almost coincided with the NP14b/NP15a-boundary.
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http://dx.doi.org/10.1127/0078-0421/2013/0035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4510927PMC
October 2013

Middle to Late Eocene paleoenvironmental changes in a marine transgressive sequence from the northern Tethyan margin (Adelholzen, Germany).

Austrian J Earth Sci 2013;106(2):45-72

Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria ; Universität Wien, Institut für Paläontologie, Althanstraße 14, A-1090 Wien, Austria.

The northern Tethyan margin is a key region for determining environmental changes associated with the collision of continental and oceanic tectonic plates and Alpine orogeny. Herein we investigated Middle to Late Eocene neritic to bathyal sediments deposited during an interval of unstable climatic conditions. In order to quantify paleoenvironmental changes, we developed a detailed age model based on biozonations of planktic foraminifera, calcareous nannoplankton, and larger benthic foraminifera. The section at Adelholzen covers the almost complete Lutetian Stage (calcareous nannoplankton zones NP15a-16, planktic foraminifera zones E8-11, shallow benthic (foraminifera) zones SBZ13-15) and large parts of the Priabonian Stage (NP18-20, E14/15), while the intermediate Bartonian Stage (NP17) is completely missing. Foraminiferal, calcareous nannoplankton, and macrofossil assemblages were analyzed for changes in paleo-water depth, mixing and stratification, paleo-primary productivity (pPP), food supply, and bottom water oxygenation. Paleo-water depth estimates range from 50 m (middle neritic, early Lutetian) to nearly 500 m (upper bathyal, late Priabonian). The combination of assemblage composition, planktic and benthic foraminiferal accumulation rates, and derived parameters (carbon-flux to sea floor, pPP) enabled us to identify a series of distinct paleoceanographic events of at least regional significance. Such events are characterized by considerable changes in primary productivity or reduced bottom water ventilation. Calculated pPP-values indicate oligotrophic conditions throughout.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558959PMC
January 2013

PALEOBIOLOGICAL APPLICATIONS OF THREE-DIMENSIONAL BIOMETRY ON LARGER BENTHIC FORAMINIFERA: A NEW ROUTE OF DISCOVERIES.

J Foraminifer Res 2013 Jan;43(1):72-87

University of Miskolc, Institute of Mineralogy and Geology, H-3515 Miskolc-Egyetemváros, Hungary.

Four specimens of larger benthic foraminifera (the Recent and , and the phylogenetically related Paleogene and ) were investigated by X-ray tomography. The resulting three-dimensional measurements enabled a comprehensive, quantitative study of shell morphology to interpret cell growth without specific shell preparation and/or destruction. After segmentation and extraction of all scanned lumina, the following characters were measured on all chambers of each specimen: chamber volume, septal distance, chamber height, and chamber width. The sequence of chamber lumina follows either a logistic function (, ), where the deceleration in growth rate of the latest chambers could mark the onset of reproduction, or it can be modeled by a series of stepwise functions with differing constants (). Variations around the growth model are either periodic, following external cycles, or random as expressed by abrupt deviations. Therefore, they may reflect the response of the cell to environmental changes in terms of cyclic changes (e.g., seasonality) or single events (e.g., predator attack). Correlations between chamber volume and the other chamber parameters show that septal distance always matches the sequence in chamber volume and can therefore be used as a proxy for environmental analyses in both growth models. Chamber height and width often remain constant around their function and rarely deviate drastically to accommodate the needed lumen for retaining test size and shape. Chamber width may vary according to chamber volume in involute specimens, whereas both chamber height and width correlate with volume in those tests following an Archimedean spiral. X-ray-tomography shows particular promise in determining which parameters that can be assessed routinely in two dimensions primarily reflect environmental conditions vs. parameters best used for taxonomic identification and for systematic lineage reconstruction.
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http://dx.doi.org/10.2113/gsjfr.43.1.72DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4497502PMC
January 2013

n. sp. from the upper Chattian of Porto Badisco (southern Apulia, Italy).

Boll Soc Paleontol Ital 2012 Nov;51(3):167-176

Institut für Paläontologie, Universität Wien, Althanstrasse 14, A-1090 Vienna, Austria;

A new species of Rotaliidae, n. sp., is described from the upper Chattian of the Porto Badisco Calcarenites (Salento Peninsula, Southern Italy). The studied specimens are assigned to the foraminiferal genus based on the presence of vertical canals in both the ventral and dorsal side of the test, and an intraseptal canal system that evolves into marginal sutural canals. The new species differs from the type species of the genus, , in having a lower chamber lumen, and smaller dimension.
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http://dx.doi.org/10.4435/BSPI.2012.19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4747143PMC
November 2012

AXIALLY ORIENTED SECTIONS OF NUMMULITIDS: A TOOL TO INTERPRET LARGER BENTHIC FORAMINIFERAL DEPOSITS.

J Foraminifer Res 2012 Apr;42(2):134-142

University of Vienna, Department of Paleontology, Althanstrasse 14, A 1090 Wien, Austria.

The "critical shear velocity" and "settling velocity" of foraminiferal shells are important parameters for determining hydrodynamic conditions during deposition of banks. These can be estimated by determining the size, shape, and density of nummulitid shells examined in axial sections cut perpendicular to the bedding plane. Shell size and shape can be determined directly from the shell diameter and thickness, but density must be calculated indirectly from the thin section. Calculations using the half-tori method approximate shell densities by equalizing the chamber volume of each half whorl, based on the half whorl's lumen area and its center of gravity. Results from this method yield the same lumen volumes produced empirically by micro-computed tomography. The derived hydrodynamic parameters help estimate the minimum flow velocities needed to entrain nummulitid tests and provide a potential tool to account for the nature of their accumulations.
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http://dx.doi.org/10.2113/gsjfr.42.2.134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4496731PMC
April 2012

How to react to shallow water hydrodynamics: The larger benthic foraminifera solution.

Mar Micropaleontol 2011 Nov;81(1-2):63-76

Institut für Paläontologie, Universität Wien, Geozentrum, Althanstrasse 14, 1090 Vienna, Austria.

Symbiont-bearing larger benthic foraminifera inhabit the photic zone to provide their endosymbiotic algae with light. Because of the hydrodynamic conditions of shallow water environments, tests of larger foraminifera can be entrained and transported by water motion. To resist water motion, these foraminifera have to build a test able to avoid transport or have to develop special mechanisms to attach themselves to substrate or to hide their test below sediment grains. For those species which resist transport by the construction of hydrodynamic convenient shapes, the calculation of hydrodynamic parameters of their test defines the energetic input they can resist and therefore the scenario where they can live in. Measuring the density, size and shape of every test, combined with experimental data, helps to define the best mathematical approach for the settling velocity and Reynolds number of every shell. The comparison between water motion at the sediment-water interface and the specimen-specific settling velocity helps to calculate the water depths at which, for a certain test type, transport, deposition and accumulation may occur. The results obtained for the investigated taxa show that the mathematical approach gives reliable results and can discriminate the hydrodynamic behaviour of different shapes. Furthermore, the study of the settling velocities, calculated for all the investigated taxa, shows that several species are capable to resist water motion and therefore they appear to be functionally adapted to the hydrodynamic condition of its specific environment. The same study is not recommended on species which resist water motion by adopting hiding or anchoring strategies to avoid the effect of water motion.
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http://dx.doi.org/10.1016/j.marmicro.2011.07.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4979689PMC
November 2011
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