Seasonality and Paleoecology of the Late Cretaceous Multi-Taxa Vertebrate Assemblage of “Lo Hueco” (Central Eastern Spain)

Isotopic studies of multi-taxa terrestrial vertebrate assemblages allow determination of paleoclimatic and paleoecological aspects on account of the different information supplied by each taxon. The late Campanian-early Maastrichtian “Lo Hueco” Fossil-Lagerstätte (central eastern Spain), located at a subtropical paleolatitude of ~31°N, constitutes an ideal setting to carry out this task due to its abundant and diverse vertebrate assemblage. Local δ¹⁸O_PO4 values estimated from δ¹⁸O_PO4 values of theropods, sauropods, crocodyliforms, and turtles are close to δ¹⁸O_H2O values observed at modern subtropical latitudes. Theropod δ¹⁸O_H2O values are lower than those shown by crocodyliforms and turtles, indicating that terrestrial endothermic taxa record δ¹⁸O_H2O values throughout the year, whereas semiaquatic ectothermic taxa δ¹⁸O_H2O values represent local meteoric waters over a shorter time period when conditions are favorable for bioapatite synthesis (warm season). Temperatures calculated by combining theropod, crocodyliform, and turtle δ¹⁸O_H2O values and gar δ¹⁸O_PO4 have enabled us to estimate seasonal variability as the difference between mean annual temperature (MAT, yielded by theropods) and temperature of the warmest months (TWMs, provided by crocodyliforms and turtles). ΔTWMs-MAT value does not point to a significantly different seasonal thermal variability when compared to modern coastal subtropical meteorological stations and Late Cretaceous rudists from eastern Tethys. Bioapatite and bulk organic matter δ¹³C values point to a C₃ environment in the “Lo Hueco” area. The estimated fractionation between sauropod enamel and diet is ~15‰. While waiting for paleoecological information yielded by the ongoing morphological study of the “Lo Hueco” crocodyliforms, δ¹³C and δ¹⁸O_CO3 results point to incorporation of food items with brackish influence, but preferential ingestion of freshwater. “Lo Hueco” turtles showed the lowest δ¹³C and δ¹⁸O_CO3 values of the vertebrate assemblage, likely indicating a diet based on a mixture of aquatic and terrestrial C₃ vegetation and/or invertebrates and ingestion of freshwater.     

Pronghorn (Antilocapra americana) enamel phosphate δ18O values reflect climate seasonality: Implications for paleoclimate reconstruction

Stable oxygen isotope (δ¹⁸O) compositions from vertebrate tooth enamel are widely used as biogeochemical proxies for paleoclimate. However, the utility of enamel oxygen isotope values for environmental reconstruction varies among species. Herein, we evaluate the use of stable oxygen isotope compositions from pronghorn (Antilocapra americana Gray, 1866) enamel for reconstructing paleoclimate seasonality, an elusive but important parameter for understanding past ecosystems. We serially sampled the lower third molars of recent adult pronghorn from Wyoming for δ¹⁸O in phosphate (δ¹⁸O_PO4) and compared patterns to interpolated and measured yearly variation in environmental waters as well as from sagebrush leaves, lakes, and rivers (δ¹⁸O_w). As expected, the oxygen isotope compositions of phosphate from pronghorn enamel are enriched in ¹⁸O relative to environmental waters. For a more direct comparison, we converted δ¹⁸O_w values into expected δ¹⁸O_PO4* values (δ¹⁸O_W‐_PO4*). Pronghorn δ¹⁸O_PO4 values from tooth enamel record nearly the full amplitude of seasonal variation from Wyoming δ¹⁸O_W‐PO4* values. Furthermore, pronghorn enamel δ¹⁸O_PO4 values are more similar to modeled δ¹⁸O_W‐PO4* values from plant leaf waters than meteoric waters, suggesting that they obtain much of their water from evaporated plant waters. Collectively, our findings establish that seasonality in source water is reliably reflected in pronghorn enamel, providing the basis for exploring changes in the amplitude of seasonality of ancient climates. As a preliminary test, we sampled historical pronghorn specimens (1720 ± 100 AD), which show a mean decrease (a shift to lower values) of 1–2‰ in δ¹⁸O_PO4 compared to the modern specimens. They also exhibit an increase in the δ¹⁸O amplitude, representing an increase in seasonality. We suggest that the cooler mean annual and summer temperatures typical of the 18th century, as well as enhanced periods of drought, drove differences among the modern and historical pronghorn, further establishing pronghorn enamel as excellent sources of paleoclimate proxy data.     

Oxygen and Carbon Isotope Variations in a Modern Rodent Community – Implications for Palaeoenvironmental Reconstructions

Background

The oxygen (δ¹⁸O) and carbon (δ¹³C) isotope compositions of bioapatite from skeletal remains of fossil mammals are well-established proxies for the reconstruction of palaeoenvironmental and palaeoclimatic conditions. Stable isotope studies of modern analogues are an important prerequisite for such reconstructions from fossil mammal remains. While numerous studies have investigated modern large- and medium-sized mammals, comparable studies are rare for small mammals. Due to their high abundance in terrestrial ecosystems, short life spans and small habitat size, small mammals are good recorders of local environments.

Methodology/Findings

The δ¹⁸O and δ¹³C values of teeth and bones of seven sympatric modern rodent species collected from owl pellets at a single locality were measured, and the inter-specific, intra-specific and intra-individual variations were evaluated. Minimum sample sizes to obtain reproducible population δ¹⁸O means within one standard deviation were determined. These parameters are comparable to existing data from large mammals. Additionally, the fractionation between coexisting carbonate (δ¹⁸O_CO3) and phosphate (δ¹⁸O_PO4) in rodent bioapatite was determined, and δ¹⁸O values were compared to existing calibration equations between the δ¹⁸O of rodent bioapatite and local surface water (δ¹⁸O_LW). Specific calibration equations between δ¹⁸O_PO4 and δ¹⁸O_LW may be applicable on a taxonomic level higher than the species. However, a significant bias can occur when bone-based equations are applied to tooth-data and vice versa, which is due to differences in skeletal tissue formation times. δ¹³C values reflect the rodents’ diet and agree well with field observations of their nutritional behaviour.

Conclusions/Significance

Rodents have a high potential for the reconstruction of palaeoenvironmental conditions by means of bioapatite δ¹⁸O and δ¹³C analysis. No significant disadvantages compared to larger mammals were observed. However, for refined palaeoenvironmental reconstructions a better understanding of stable isotope signatures in modern analogous communities and potential biases due to seasonality effects, population dynamics and tissue formation rates is necessary.     

Records of palaeo‐seawater condition from oxygen‐isotope profiles of early Pleistocene fossil molluscs from the Seoguipo Formation (Korea)

Kim, J.K., Khim, B.‐K., Woo, K.S., & Yoon, S.H. 2009: Records of palaeo‐seawater condition from oxygen‐isotope profiles of early Pleistocene fossil molluscs from the Seoguipo Formation (Korea). Lethaia, Vol. 43, pp. 170–181. High‐resolution δ¹⁸O profiles of early Pleistocene fossil molluscs (Mizuhopecten tokyoensis hokurikuensis) from the shallow‐marine sedimentary Seoguipo Formation (Korea) were found to exhibit distinct annual cycles identified by their unique seasonality (δ¹⁸O amplitude). A direct comparison of fossil δ¹⁸O profiles with that of living shells (Amusium japonicum japonicumi) indicated that the palaeoseawater conditions differed from present‐day seawater. Specifically, the positive δ¹⁸O shift in the isotope profile of the fossil specimens relative to that of the living mollusc shell reflected that palaeotemperature was lower than that today. However, a comparison of the coldest palaeotemperatures (determined from the heaviest δ¹⁸O values of fossil shells), with the present‐day winter temperatures indicates that temperature variation alone cannot account for the entire positive δ¹⁸O offset. These findings indicate that variation in the seawater δ¹⁸O_w values plays a dominant role in the biogenic carbonate precipitation of fossils. Thus, the fossil shells obtained from stratigraphic units suggest different palaeoenvironmental conditions, including lower temperatures and ¹⁸O‐enriched glacial seawater, when compared with the present‐day conditions. The Seoguipo Formation records at least five cycles of relative sea‐level fluctuations, with changes in fossil δ¹⁸O amplitudes separated by sequence boundaries likely to reflect variations of unique palaeoseawater condition, although the oxygen‐isotope profile of fossil molluscs appears to provide a snap‐shot of the palaeoclimatic signature. □Early Pleistocene, mollusc fossils, oxygen isotope, palaeoenvironment, seawater temperature.     

Oxygen-18 Content of Atmospheric Oxygen Does Not Affect the Oxygen Isotope Relationship between Environmental Water and Cellulose in a Submerged Aquatic Plant, Egeria densa Planch

We determined that the oxygen isotopic composition of cellulose synthesized by a submerged plant, Egeria densa Planch., is related to the isotopic composition of environmental water by a linear function, δ¹⁸O cellulose = 0.48 δ¹⁸O water + 24.1%‰. The observation of a slope of less than 1 indicates that a portion of cellulose oxygen is derived from an isotopically constant source other than water. We tested whether this source might be molecular oxygen by growing plants in the presence of high concentrations of ¹⁸O in the form of O₂ bubbled into the bottom of an aquarium. Cellulose synthesized during this experiment did not have significantly different oxygen isotope ratios than that synthesized by control plants exposed to O₂ of normal ¹⁸O abundance. We propose that oxygen in organic matter recycled from senescent portions of the plant is incorporated into cellulose. Our findings indicate that paleoclimatic models linking the oxygen isotope composition of environmental water to cellulose from fossil plants will have to be modified to account for contributions of oxygen from this or other sources besides water.     

Spectroscopic investigations of Er(3+) :CdO-Bi(2) O(3) -B(2) O(3) glasses

This article reports on the optical properties of Er³⁺ ions doped CdO–Bi₂O₃–B₂O₃ (CdBiB) glasses. The materials were characterized by optical absorption and emission spectra. By using Judd–Ofelt theory, the intensity parameters Ω_λ (λ = 2, 4, 6) and also oscillatory strengths were calculated from the absorption spectra. The results were used to compute the radiative properties of Er³⁺:CdBiB glasses. The concentration quenching and energy transfer from Yb³⁺–Er³⁺ were explained. The stimulated emission cross‐section, full width at half maximum (FWHM) and FWHM × values are also calculated for all the Er³⁺:CdBiB glasses. Copyright © 2011 John Wiley & Sons, Ltd.     

Carbon isotopic abundances in Mesozoic and Cenozoic fossil plants: Palaeoecological implications

Carbon isotopic abundances have been measured for more than one hundred samples of fossil plants ranging in age from middle Triassic to late Tertiary. Most of the plant fossils were identified at the specific or generic level and were selected as representing a variety of continental environments, including xeric and humid habitats. Material analysed included numerous fragments of flowers, seeds, fruits, leaves and wood, as well as a single amorphous lignite sample. The analyses performed for the plant fragments indicate relatively constant isotopic compositions during this time interval, with plant δ¹³C values ranging between -28 and -20%. These values are within the range for living terrestrial plants with C₃, photosynthesis, although values more positive than -23% are rare in C₃ plants and typically found in plants growing under environmental stress. Lower δ¹³C values might have been expected owing to the much higher CO₂, levels of the Cretaceous atmosphere that have been inferred from marine carbonates. No fossils with values indicating C₄, photosynthesis were discovered. Fossil plants from inferred mesic environments showed δ¹³C values ranging between -26.7 and -24.1%. Highest δ¹³C values in angiosperms (up to -20.1%) were measured for Late Cretaceous combretaceous flowers from Portugal. Some cheirolepidiaceous conifers from the Early Cretaceous also showed high δ¹³C values. Values measured for Pseudofrenelopsis varians and Glenrosa taxensis were -21.9%, and values of gymnosperm wood, probably of cheirolepidiaceous affinity, were -19.0%. These high values are in accordance with inferred ecological conditions for the fossil plants. They may suggest a tendency for C₄,-like photosynthesis, although the data are equivocal. Higher values (-17.3%) clearly falling outside the C₃, range were, however, obtained from a single lignite fragment of Late Cretaceous (Maastrichtian) age. The nature of this plant fragment is unknown, but the result suggests that C₄-like photosynthesis was present at least in some latest Cretaceous vegetation. A hadrosaurian dinosaur with well-preserved collagen-like organic matter from the same deposit showed δ¹³C values around-16%, which also suggests the presence of CAM or even C₄ plants in the latest Cretaceous. □Carbon isotopic abundances, δ¹³C values, dinosaurs, plants, photosynthetic pathways, Mesozoic.     

Dietary and environmental reconstruction with stable isotope analyses of herbivore tooth enamel from the Miocene locality of Fort Ternan, Kenya

Tooth enamel of nine Middle Miocene mammalian herbivores from Fort Ternan, Kenya, was analyzed for δ¹³C and δ¹⁸O. The δ¹⁸O values of the tooth enamel compared with pedogenic and diagenetic carbonate confirm the use of stable isotope analysis of fossil tooth enamel as a paleoenvironmental indicator. Furthermore, the δ¹⁸O of tooth enamel indicates differences in water sources between some of the mammals. The δ¹³C values of tooth enamel ranged from −8·6–−13·0‰ which is compatible with a pure C₃diet, though the possibility of a small C₄fraction in the diet of a few of the specimens sampled is not precluded. The carbon isotopic data do not support environmental reconstructions of a Serengeti-typed wooded grassland with a significant proportion of C₄grasses. This study does not preclude the presence of C₃grasses at Fort Ternan; it is possible that C₃grasses could have had a wider geographic range if atmospheric CO₂levels were higher than the present values.     

Ancient latitudinal gradients of C3/C4 grasses interpreted from stable isotopes of New World Pleistocene horse (Equus) teeth

Carbon and oxygen isotopic data are reported from 116 Pleistocene Equus teeth from sixty-six localities in the New World ranging from 68°N (Alaska, Canada) to 35°S (Argentina). Equus species have been predominantly grazers, and as such, carbon isotopic values of their tooth enamel provide evidence of the Pleistocene distribution of C₃ and C₄ grasses. The carbon data presented here indicate a gradient (δ¹³C range of 10 parts/mil) in the relative proportion of C₃ and C₄ grasses between high latitude and equatorial Equus samples. The largest amount of change from C₃ to C₄ grasses during the Pleistocene occurred in the mid-latitudes between about 30 to 40°. The oxygen data, which vary proportionately with temperature, indicate a latitudinal gradient (δ¹⁸O range of 20 parts/mil) between high-latitude and equatorial Equus samples. The basic pattern of latitudinal gradients of C₃/C₄ grass distribution and temperature as interpreted from these Pleistocene data is similar to the modern-day. The use of stable isotopes of fossil herbivore teeth represents a new means to interpret Pleistocene climates and terrestrial ecology.     

Synthesis of Chlorodideoxynucleosides Using Tris(2,4,6-tribromophenoxy)-dichlorophosphorane (BDCP)

Abstract

5′-Chloro-5′-deoxy-N,3′-O-dibenzoylthymidine (3a), 5′-chloro-5′-deoxy-N⁴, 3′-O-dibenzoyldeoxycytidine(3b), 5′-chloro-5′-deoxy-N⁶,3′-O-dibenzoyldeoxyadenosine(3c), N-benzoyl-1-(3-chloro-2,3-dideoxy-5-O-trityl-ß-D-xylofuranosyl)thymine (5a) and N⁶-benzoyl-9-(3-chloro-2,3-dideoxy-5-O-trityl-ß-D-xylofuranosyl)adenine (5b) have been synthesized in very high yields using a new efficient reagent, tris(2,4,6-tribrom-ophenoxy)dichlorophosphorane (BDCP). The reaction time was greatly reduced to 5–8 min. NOE data suggested an inversion of configuration at C₃-position and thus an SN2 mechanism has been proposed for the chlorination reaction.

     

Stable Isotope Signatures of Middle Palaeozoic Ahermatypic Rugose Corals – Deciphering Secondary Alteration,Vital Fractionation Effects,and Palaeoecological Implications

This study investigates stable isotope signatures of five species of Silurian and Devonian deep-water, ahermatypic rugose corals, providing new insights into isotopic fractionation effects exhibited by Palaeozoic rugosans, and possible role of diagenetic processes in modifying their original isotopic signals. To minimize the influence of intraskeletal cements on the observed signatures, the analysed specimens included unusual species either devoid of large intraskeletal open spaces (''button corals'': Microcyclus, Palaeocyclus), or typified by particularly thick corallite walls (Calceola). The corals were collected at four localities in the Holy Cross Mountains (Poland), Mader Basin (Morocco) and on Gotland (Sweden), representing distinct diagenetic histories and different styles of diagenetic alteration. To evaluate the resistance of the corallites to diagenesis, we applied various microscopic and trace element preservation tests. Distinct differences between isotopic compositions of the least-altered and most-altered skeleton portions emphasise a critical role of material selection for geochemical studies of Palaeozoic corals. The least-altered parts of the specimens show marine or near-marine stable isotope signals and lack positive correlation between δ¹³C and δ¹⁸O. In terms of isotopic fractionation mechanisms, Palaeozoic rugosans must have differed considerably from modern deep-water scleractinians, typified by significant depletion in both ¹⁸O and ¹³C, and pronounced δ¹³C-δ¹⁸O co-variance. The fractionation effects exhibited by rugosans seem similar rather to the minor isotopic effects typical of modern non-scleractinian corals (octocorals and hydrocorals). The results of the present study add to growing evidence for significant differences between Scleractinia and Rugosa, and agree with recent studies indicating that calcification mechanisms developed independently in these two groups of cnidarians. Consequently, particular caution is needed in using scleractinians as analogues in isotopic studies of extinct coral lineages. Answering some of the pertinent palaeoecological questions, such as that of the possibility of photosymbiosis in Palaeozoic corals, may not be possible based on stable isotope data.     

Bis(undecatungstogermanate) lanthanates of potassium

The K₁₃[Ln(GeW₁₁O₃₉)₂]·nH₂O (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Tm, Yb) have been prepared. Some properties of these compounds have been studied. The change of main bands in their IR spectra with reference to α-GeW₁₂O₄₀⁴⁻ is discussed. v_as (W---O_d) is shifted toward low wavenumber and v_as (W---O_b---W), δ(O---Ge---O) each appear as two distinct bands. X-ray powder diffraction shows that the molecular symmetry of K₁₃[Ln(GeW₁₁O₃₉)₂] is lower than that of α-K₈(GeW₁₁O₃₉). XPS determinations reveals that the Ln---O bond has coordination character and that the shifts of W_4f and O_ls are between K₁₃Ln (GeW₁₁O₃₉₂ and α-H₄(GeW₁₂O₄₀). Magnetic measurement confirms that the lanthanide elements are +3 valent in this complexes and the magnetic moments are very close to the values found by Van Vleck.     

Carbon and oxygen isotopic disequilibria of recent deep-sea benthic foraminifera

The carbon and oxygen isotopic compositions of 149 samples of benthic foraminifera from deep-sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water. Uvigerina, Pyrgo murrhina, and Oridorsalis tener are the closest to ¹⁸O equilibrium (with average deviations about −0.4‰), while Planulina wuellerstorfi and P. murrhina are the closest to ¹³C equilibrium (with average deviations about −1‰). P. wuellerstorfi shows the most systematic relationship between δ ¹³C and bottom water apparent oxygen utilization. The intraspecific variabilities in δ ¹⁸O and δ ¹³C suggest that estimates of bottom water paleotemperatures can be made to a precision of ± 0.7°C, while estimates of past apparent oxygen utilization (AOU) can be made to ± 35 μmol/kg. Based on intraspecific comparisons of the Recent samples with fossils, no temporal changes in the degree of either ¹⁸O or ¹³C disequilibrium have been detected for Planulina wuellerstorfi, Uvigerina, Oridorsalis tener and Globocassidulina subglobosa.     

Fossil human remains from Bolomor Cave (Valencia, Spain)

Systematic excavations carried out since 1989 at Bolomor Cave have led to the recovery of four Pleistocene human fossil remains, consisting of a fibular fragment, two isolated teeth, and a nearly complete adult parietal bone. All of these specimens date to the late Middle and early Late Pleistocene (MIS 7-5e). The fibular fragment shows thick cortical bone, an archaic feature found in non-modern (i.e. non-Homo sapiens) members of the genus Homo. Among the dental remains, the lack of a midtrigonid crest in the M₁ represents a departure from the morphology reported for the majority of Neandertal specimens, while the large dimensions and pronounced shoveling of the marginal ridges in the C¹ are similar to other European Middle and late Pleistocene fossils. The parietal bone is very thick, with dimensions that generally fall above Neandertal fossils and resemble more closely the Middle Pleistocene Atapuerca (SH) adult specimens. Based on the presence of archaic features, all the fossils from Bolomor are attributed to the Neandertal evolutionary lineage.     

Fossil remains of Macaca sylvanus florentina (Cocchi, 1872) (Primates, Cercopithecidae) from the Early Pleistocene of Quibas (Murcia, Spain)

The macaque material from the Early Pleistocene site of Quibas (Albanilla, Murcia, Spain), including dentognathic remains, isolated teeth and some postcranial bone fragments, is described. Both metrically and morphologically, this sample must be attributed to Macaca sylvanus (the Barbary macaque). This species is currently distributed through North Africa and Gibraltar, but was much more widely distributed during the Plio-Pleistocene, being represented by several European fossil subspecies. Metrical comparisons of dental size and proportions between extant M. s. sylvanus and fossil Macaca sylvanus florentina from the type locality and other Italian sites are undertaken, in order to classify the remains from Quibas at the subspecies level. The results show that the Quibas sample not only fits the range of variation of M. s. florentina from the type locality, but also differs from the extant Barbary macaque condition in several regards. This permits us to formally attribute the material from Quibas to M. s. florentina. The material described in this paper therefore significantly improves the knowledge of this fossil taxon, particularly regarding the upper dentition, and further confirms the taxonomic distinctiveness of this extinct taxon at the subspecies rank. Taken as a whole, M. s. florentina largely overlaps in dental dimensions with M. s. sylvanus, but differs from the latter by displaying (on average): (1) absolutely longer upper molars (especially M¹ and M³); (2) relatively wider upper molars (especially M¹ and M²); (3) longer M³ as compared with the M²; (4) absolutely longer M₁ and M₃; and (5) relatively narrower M₃.     

Synthesis and magnetic properties of bis(μ-hydroxo)bis[(2,2 ′-bipyridyl)copper(II)] squarate. Crystal structure of bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] squarate tetrahydrate

The compound [Cu₂(bipy)₂(OH)₂](C₄O₄)·5.5H₂O, where bipy and C₄O₄²⁻ correspond to 2,2′-bipyridyl and squarate (dianion of 3,4-dihydroxy-3-cyclo- butene-1,3-dione) respectively, has been synthesized. Its magnetic properties have been investigated in the 2–300 K temperature range. The ground state is a spin-triplet state, with a singlet-triplet separation of 145 cm⁻¹. The EPR powder spectrum confirms the nature of the ground state.Well-formed single crystals of the tetrahydrate, [Cu₂(bipy)₂(OH)₂](C₄O₄)·4H₂O, were grown from aqueous solutions and characterized by X-ray diffraction. The system is triclinic, space group P , with a = 9.022(2), b = 9.040(2), c = 8.409(2) Å, α = 103.51(2), β = 103.42(3), γ = 103.37(2)°, V = 642.9(3) ų, Z = 1, D_x = 1.699 g cm⁻³, μ(Mo Kα) = 17.208 cm⁻¹, F(000) = 336 and T= 295 K. A total of 2251 data were collected over the range 1θ25°; of these, 1993 (independent and with I3σ(I)) were used in the structural analysis. The final R and R_w residuals were 0.034 and 0.038 respectively. The structure contains squarato-O¹, O³-bridged bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] units forming zigzag one-dimensional chains. Each copper atom is in a square-pyramidal environment with the two nitrogen atoms of 2,2′-bipyridyl and the two oxygen atoms of the hydroxo groups building the basal plane and another oxygen atom of the squarate lying in the apical position.The magnetic properties are discussed in the light of spectral and structural data and compared with the reported ones for other bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] complexes.     

Dentine oxygen isotopes (δ18O) as a proxy for odontocete distributions and movements

Spatial variation in marine oxygen isotope ratios (δ¹⁸O) resulting from differential evaporation rates and precipitation inputs is potentially useful for characterizing marine mammal distributions and tracking movements across δ¹⁸O gradients. Dentine hydroxyapatite contains carbonate and phosphate that precipitate in oxygen isotopic equilibrium with body water, which in odontocetes closely tracks the isotopic composition of ambient water. To test whether dentine oxygen isotope composition reliably records that of ambient water and can therefore serve as a proxy for odontocete distribution and movement patterns, we measured δ¹⁸O values of dentine structural carbonate (δ¹⁸O_SC) and phosphate (δ¹⁸O_P) of seven odontocete species (n = 55 individuals) from regional marine water bodies spanning a surface water δ¹⁸O range of several per mil. Mean dentine δ¹⁸O_SC (range +21.2 to +25.5‰ VSMOW) and δ¹⁸O_P (+16.7 to +20.3‰) values were strongly correlated with marine surface water δ¹⁸O values, with lower dentine δ¹⁸O_SC and δ¹⁸O_P values in high‐latitude regions (Arctic and Eastern North Pacific) and higher values in the Gulf of California, Gulf of Mexico, and Mediterranean Sea. Correlations between dentine δ¹⁸O_SC and δ¹⁸O_P values with marine surface water δ¹⁸O values indicate that sequential δ¹⁸O measurements along dentine, which grows incrementally and archives intra‐ and interannual isotopic composition over the lifetime of the animal, would be useful for characterizing residency within and movements among water bodies with strong δ¹⁸O gradients, particularly between polar and lower latitudes, or between oceans and marginal basins.     

Effects of charring on the carbon isotopic composition of grass (Poaceae) epidermis

Charred modern grass epidermis preserves the carbon isotopic composition of the parent plant photosynthetic pathway. Fifty-nine modern grasses and sedges were collected in lowland western Uganda. All charred epidermal samples from C₄ grasses or sedges preserve a carbon isotopic value within the range typical for C₄ plants (−17 to −10‰), and charred epidermal fragments from C₃ plants have carbon isotopic values between −30 and −26‰. The process of charring results in a slightly enriched carbon isotopic signature (−11.9‰ mean charred value as compared to −12.8‰ mean unaltered grass tissue value). δ¹³C measurements of replicate samples from the same plant vary within 1–2‰, yet all values for the same plant stay within the expected values for the photosynthetic pathway of the plant. δ¹³C measurements on >180-μm charred grass epidermal fragments extracted from surface sediment samples from three lakes on the lowland western Ugandan landscape confirm the predominant lowland C₄ grass input (δ¹³C=−16 to −19‰). These results demonstrate the utility of using carbon isotopic analysis of charred grass epidermis to reconstruct C₃ vs. C₄ grassland assemblages on the landscape. Furthermore, such downcore δ¹³C profiles can be used to highlight key zones of C₃ vs. C₄ grass change for which taxonomic analysis of fossil grass epidermis could provide more detailed information regarding grassland community composition.     

DESCRIPTION OF A NEW FOSSIL GENUS AND SPECIES HUAXIASCIOPHILITES JINGXIENSIS (DIPTERA: MESOSCIOPHILIDAE) FROM EARLY CRETACEOUS JINGXI BASIN OF BEIJING,CHINA*

Abstract A new fossil genus and species of the family Mesosciophilidae, Huaxiasciophilites jingxiensis gen. et sp. nov. is described. The fossils of the new genus and species were collected from the Early Cretaceous Lushangfen Formation (K⁴₁ 1) of Jingxi basin of Beijing China. The new genus is established based on the following characters: that Sc short, not exceed the forking of R and Rs, with branches; r‐m longer than basal part of Rs; Rs very thick and undee; and radial cell very short. The phylogenetic tree of Mesosciophilidae superimposed on the geological time scale was also analyzed. The holotype is deposited in the Beijing Forestry University.     

On the controls of leaf-water oxygen isotope ratios in the atmospheric Crassulacean acid metabolism epiphyte Tillandsia usneoides

Previous theoretical work showed that leaf-water isotope ratio (δ¹⁸O_L) of Crassulacean acid metabolism epiphytes was controlled by the δ¹⁸O of atmospheric water vapor (δ¹⁸O_a), and observed δ¹⁸O_L could be explained by both a non-steady-state model and a “maximum enrichment” steady-state model (δ¹⁸O_L-M), the latter requiring only δ¹⁸O_a and relative humidity (h) as inputs. δ¹⁸O_L, therefore, should contain an extractable record of δ¹⁸O_a. Previous empirical work supported this hypothesis but raised many questions. How does changing δ¹⁸O_a and h affect δ¹⁸O_L? Do hygroscopic trichomes affect observed δ¹⁸O_L? Are observations of changes in water content required for the prediction of δ¹⁸O_L? Does the leaf need to be at full isotopic steady state for observed δ¹⁸O_L to equal δ¹⁸O_L-M? These questions were examined with a climate-controlled experimental system capable of holding δ¹⁸O_a constant for several weeks. Water adsorbed to trichomes required a correction ranging from 0.5‰ to 1‰. δ¹⁸O_L could be predicted using constant values of water content and even total conductance. Tissue rehydration caused a transitory change in δ¹⁸O_L, but the consequent increase in total conductance led to a tighter coupling with δ¹⁸O_a. The non-steady-state leaf water models explained observed δ¹⁸O_L (y = 0.93*x − 0.07; r² = 0.98) over a wide range of δ¹⁸O_a and h. Predictions of δ¹⁸O_L-M agreed with observations of δ¹⁸O_L (y = 0.87*x − 0.99; r² = 0.92), and when h > 0.9, the leaf did not need to be at isotopic steady state for the δ¹⁸O_L-M model to predict δ¹⁸O_L in the Crassulacean acid metabolism epiphyte Tillandsia usneoides.Tropical and subtropical epiphytic higher plants have long been a curiosity to plant physiologists because of the multiple and unique constraints on physiology that the epiphytic lifeform represents (Mez, 1904; Benzing, 1970; Medina and Troughton, 1974). While the competition for light has no doubt led the plants to the tree tops, the concomitant loss of roots effectively removed the plants from an environment of abundant rainfall to one of arid conditions (Griffiths et al., 1986; Smith et al., 1986a; Winter and Smith, 1996). In a sense, the plants shifted biomes by immigrating vertically instead of horizontally. This shift led to morphological adaptations like the development of modified leaf hairs to absorb water and the formation of tanks via the overlapping of leaf bases as well as physiological adaptations such as maintaining high leaf osmotic potential and, perhaps most notably, the evolution of the CO₂-concentrating mechanism known as Crassulacean acid metabolism (CAM) photosynthesis (Medina and Troughton, 1974; Benzing et al., 1976; Griffiths and Smith, 1983; Smith et al., 1986b; Martin and Schmitt, 1989; Martin et al., 2004; Ohrui et al., 2007). This unique physiology of tropical and subtropical CAM epiphytes also presents an intriguing contrast to the general way we view oxygen isotope ratios (δ¹⁸O) in plant water and organic material (Helliker and Griffiths, 2007; Helliker and Noone, 2009).The enrichment of ¹⁸O in leaf water during plant transpiration leads to a suite of physiology-based tracers that inform us of current and past plant-environment interactions. Leaf water δ¹⁸O (δ¹⁸O_L) labels CO₂ and allows for partitioning of the gross components of net CO₂ flux from ecosystem to regional scales (Yakir and Wang, 1996; Ciais et al., 1997; Styles et al., 2002; Cuntz et al., 2003; Ogee et al., 2004; Helliker et al., 2005). The production of isotopically distinct O₂ by photosynthesis allows for global-scale estimates of productivity over millennia (Guy et al., 1993; Luz et al., 1999; Hoffmann et al., 2004). The isotopic record of δ¹⁸O_L in leaf and tree ring cellulose allows for the reconstruction of growth environment and/or physiological responses to that growth environment (Epstein et al., 1977; Anderson et al., 1998; Switsur and Waterhouse, 1998; Barbour and Farquhar, 2000; Barbour et al., 2000; Roden and Ehleringer, 2000; Ferrio and Voltas, 2005; Poussart and Schrag, 2005; Helliker and Richter, 2008). Much of the error associated with the above δ¹⁸O applications could be decreased with better estimates of the isotope ratio of atmospheric water vapor (δ¹⁸O_a), a primary control on leaf-water ¹⁸O enrichment (Farquhar and Cernusak, 2005; Helliker and Griffiths, 2007), and the study of δ¹⁸O_L in CAM epiphytes may offer better estimates of δ¹⁸O_a through time and space (Helliker and Griffiths, 2007).The epiphyte, and specifically the CAM vascular epiphyte, offers an extreme in the way δ¹⁸O in plant water and organic material is viewed. For most vascular plants, δ¹⁸O_L is controlled by a balance of soil water δ¹⁸O and δ¹⁸O_a; soil water comes into the leaves via the root system, and atmospheric vapor diffuses into the leaf through open stomata. The balance of the two water sources is determined by relative humidity (h): if h is high, then δ¹⁸O_L is controlled proportionally more by δ¹⁸O_a; if h is unity, then δ¹⁸O_L is at equilibrium with δ¹⁸O_a. If these plants happen to lose water during a humid night, then leaf water exchange can lead to control by, and possibly equilibrium with, δ¹⁸O_a (Lai et al., 2008). Typically, the dramatic increase of transpiration during the daytime moves the δ¹⁸O_L away from equilibrium with δ¹⁸O_a. Hence, the nocturnal movement of δ¹⁸O_L toward equilibrium with δ¹⁸O_a in most vascular plants is not likely recorded in plant organic material and is only important to the isotopic composition of CO₂ during nocturnal respiration (Cernusak et al., 2004). In the CAM epiphyte, rainwater and dewfall rehydrate epiphyte tissue, and due to stomata being open at night, when h is near unity, rehydration water is quickly exchanged with atmospheric water vapor. This leads to the situation, hypothesized by Helliker and Griffiths (2007), where rainfall and dewfall (which are in equilibrium with δ¹⁸O_a; Gat, 1996) control tissue water status, and the δ¹⁸O of this tissue water is continuously controlled by δ¹⁸O_a through subsequent nocturnal vapor exchange. Because stomata are typically closed during the day, organic material synthesized by the photosynthetic carbon reduction cycle should obtain the δ¹⁸O signature of δ¹⁸O_a-controlled leaf water (Helliker and Griffiths, 2007). It is this situation that yields new applications for δ¹⁸O that are unique to epiphytes: the reconstruction of physiological responses to the epiphytic growth habit (Reyes-Garcia et al., 2008) and the reconstruction of δ¹⁸O_a (Helliker and Griffiths, 2007). It was recently shown through empirical and theoretical work that lichen thalli obtain equilibrium with δ¹⁸O_a even under nonsaturating conditions (Hartard et al., 2009). The lichen system of equilibrium with δ¹⁸O_a represents an important contrast to that of CAM epiphytes, and this is discussed later. The theoretical work presented by Hartard et al. (2009), however, is extremely helpful for the interpretation of isotopic signals in CAM epiphytes.Helliker and Griffiths (2007) developed the theoretical underpinnings for δ¹⁸O_a as a control on CAM epiphyte δ¹⁸O_L. They extended the thoughts of Farquhar and Cernusak (2005) to show that at the high nocturnal h experienced by CAM epiphytes, gross exchange fluxes of water vapor into the leaf from the atmosphere can be several times the transpirational flux out of the leaf. Model simulations showed that constant environmental conditions and continuous water loss led to an isotopic steady state where both δ¹⁸O_L and transpired water (δ¹⁸O_E) converged to a single isotopic value controlled by the exchange of δ¹⁸O_a and described by the following “maximum enrichment” equation (Farquhar and Gan, 2003; Helliker and Griffiths, 2007; Hartard et al., 2009):where the steady-state δ¹⁸O_L (R_L) is determined solely by δ¹⁸O_a (R_a), h, the temperature-dependent equilibrium fractionation factor α*, and the balance of the ratio of diffusivities of light to heavy water molecules through the stomata and through the leaf boundary layer, α^K (Flanagan et al., 1991; Farquhar and Lloyd, 1993; Farquhar and Cernusak, 2005). The non-steady-state analytical solution for δ¹⁸O_L developed by Hartard et al. (2009; Eq. 6 in “Materials and Methods,” hereafter referred to as the Hartard-Cuntz solution) clearly demonstrates that, through time in the nonsteady state, δ¹⁸O_L is continuously moving toward the value of R_l-M (δ¹⁸O_l-M). In a similar manner, the simulations of Helliker and Griffiths (2007) suggested that even at values of nocturnal h of 0.8, which is low for a CAM epiphyte (Garth, 1964; Smith et al., 1986b), δ¹⁸O_L was controlled almost entirely by the isotope ratio of atmospheric water vapor and the maximum enrichment equation above would ultimately predict δ¹⁸O_L. The simulations also showed that the approach to steady state was faster and occurred through less water loss as h increased. In general, their simulations showed that δ¹⁸O_L approached the steady-state value, or δ¹⁸O_l-M, much faster than δ¹⁸O_E, and this yields an important prediction that is tested by our study: the leaf does not need to be at full isotopic steady state for δ¹⁸O_L to be at or near the steady-state, maximum enrichment value (δ¹⁸O_l-M).There are many unresolved questions as to the agreement between models and observations that underpin the efficacy of using δ¹⁸O_L to reconstruct δ¹⁸O_a. The empirical work of Helliker and Griffiths (2007) did show support for the modeling exercises, but only over a narrow range of conditions. Their experimental setup was limited, as it was developed to demonstrate a preliminary proof of concept. Also, the invariably high h and noisy δ¹⁸O_a (±1.2‰) of Helliker and Griffiths (2007) could lead one to erroneously conclude that δ¹⁸O_L was in direct equilibrium with δ¹⁸O_a even when h was less than unity, which should not be the case. The primary controls of CAM epiphyte δ¹⁸O_L are h and δ¹⁸O_a, and the manner in which changes in δ¹⁸O_a and h affect δ¹⁸O_L through time must be assessed. Like many CAM epiphytes, the study species Tillandsia usneoides has a heavy covering of hygroscopic trichomes. While the water adsorbed to these trichomes does not lead to water uptake by living cells at subsaturating conditions (Martin and Schmitt, 1989), the water is inevitably sampled and extracted for δ¹⁸O_L determination. Hence, the isotopic offset caused by these trichomes must be determined. Total plant conductance to water loss (g_tot; stomatal and boundary layer conductance) controls the rate of exchange of tissue water with water vapor and the relative water content (RWC) of the plant. Therefore, the effect of changes in RWC on δ¹⁸O_L, through both water loss and rehydration, must be determined. Previous work has shown that changes in water volume are not important to predictions of δ¹⁸O_L (Cernusak et al., 2002; Cuntz et al., 2007), and a similar finding in CAM epiphytes could greatly simplify our interpretation of observed δ¹⁸O_L. In summary, the goal of this study was to construct controlled-environment experiments to assess how well observed δ¹⁸O_L could be predicted over a range of conditions through both steady-state and non-steady-state approaches of Helliker and Griffiths (2007) and Hartard et al. (2009).