Isotopic aspects of dinosaur reproduction
Romain Amiot1, Christophe Lécuyer1, Xiaolin Wang2, Xing Xu2, Jinyou Mo3, Zhonghe Zhou2, François Fourel1, Shuo Wang4 and Jean-Michel Mazin1
1CNRS UMR 5276, Université de Lyon and Ecole Normale Supérieure de Lyon, France
2Institute of Vertebrate Paleontology and Paleoanthropology, CAS, China
3Natural History Museum of Guangxi, China
4Beijing Capital Normal University, China
A key factor that constrains the spatial and temporal distribution of land vertebrates is their ecological capability for breeding. Because of their large variation in body size and latitudinal distribution, non-avian dinosaurs must have developed various strategies to ensure successful reproduction, such as the selection of optimal egg-laying environment, time period, and egg-brooding strategy to keep incubation temperature at an ideal range. In order to investigate this latter aspect, incubation temperature of oviraptorosaur embryos have been estimated using the recently updated phosphate-water temperature scale, applied here to calculate the temperature at which embryo apatite precipitates from egg fluids. Whereas the apatite d18Op value can be measured directly from preserved embryo bones, the egg fluids d18Oew value can be estimated from the oxygen isotope composition of eggshell calcite by applying the fractionation factors determined between eggshell calcite and egg fluids of extant birds. Using these relationships, the oxygen isotope composition of three oviraptorosaur eggshell calcites and their embryo apatite have been measured. These fossil eggs have been recovered from the Late Cretaceous Nanxiong Formation of China. Calculated embryo incubation temperature lies within the 33-40°C range, which is likely above environmental temperatures at that time and consistent with brooding behaviour.
Deep-sea barnacle shell: geochemical signal and microstructure
Ana-Voica Bojar1 and Hans-Peter Bojar2
1University of Salzburg, Austria
2Universalmuseum Joanneum, Austria
One of the largest hydrothermal fields of the Manus Spreading Center, Papua New Guinea is Hydrothermal Field 1 (Vienna Woods). The heterogeneous fauna collected at this site consists of gastropods, barnacles, bythograeid crabs, bresiliid shrimps, vestimentiferans and sea anemones. Barnacles are crustaceans adapted to a sessile existence and that cement to substrates by proteins. Less than 2% of barnacle species are found at depths between 100 m and 2,500 m, most inhabiting shallow marine environments. In the present study, we have investigated shell microstructure in addition to minor elements (Mg, Na, S, Sr) and stable isotope distributions of barnacles collected at depths of 2,500 m from the Vienna Woods hydrothermal field. Stable isotopes as well as the elemental composition of Eochionelasmus ohtai manusensis were retrieved along profiles perpendicular to growth lines. Preliminary data indicate that within one shell, oxygen isotope values show variations of up to 0.6‰. According to calculated temperatures, Echionelasmus populated sites with temperatures between 2°C and 5°C, in agreement with the habitat from the North Fiji and Lau Basins, where temperatures of max. 6°C are documented for the environment of Echionelasmus. Calculated and measured temperatures indicate input of hydrothermal fluid, with barnacles occupying a niche in a marginal position with respect to active vents.
Carnivoran resource and habitat use in the context of a Late Miocene faunal turnover episode
Laura Domingo1,3, M. Soledad Domingo2, Paul L. Koch3, Jorge Morales4 and M. Teresa Alberdi4
1Geosciences Institute, Complutense University of Madrid, Spain
2Complutense University of Madrid, Spain
3University of California, Santa Cruz, USA
4Spanish National Research Council, Madrid, Spain
We investigate resource and habitat use by apex predators through stable isotope analysis on two Spanish Late Miocene localities: Los Valles de Fuentidueña (~9.6 Ma, LVF) and Cerro de los Batallones (~9.1 Ma, BAT). The temporal window represented by LVF and BAT was crucial in the shaping of the current Iberian mammalian structure. It corresponds to the initial stages of a faunal turnover episode and regional environmental change at ~9.5–8.5 Ma (Vallesian–Turolian transition) associated with an increase in the seasonality of precipitation. Herbivore and carnivore d13C and d18O values do not indicate significant changes in either the vegetation cover or the hydrological regime during the time lapse represented between LVF and BAT. From the standpoint of predator–prey interactions, LVF and BAT large active carnivores encountered high levels of interspecific competition, although some genera, such as the amphicyonid Magericyon and the hyaenid Lycyaena, seemed to avoid competition by taking prey from more open habitats. We propose that apex predator sympatry may have been favoured if a low seasonality of precipitation, as inferred for the onset of the Vallesian–Turolian turnover event, promoted high levels of primary productivity with a direct impact on biomass availability at different trophic levels.
Non-traditional isotopic approaches to study the physiology of biomineralizing organisms
Robert A. Eagle
University of California, Los Angeles, USA
Recent research has focused on non-traditional isotope systems as tracers of the physiology of biomineralizing organisms. In particular, isotopic ordering in fossil vertebrate biominerals can function as an indicator of body temperatures or taphonomy. In modern teeth and in eggshells, 13C-18O bond abundance in the carbonate moiety reflects body temperature of the organism. The technique therefore has the potential to unlock information on the body temperature and physiology of extinct vertebrates and of palaeoenvironments, but in some fossil taxa and localities, this isotopic signal has been altered during diagenesis. Another area of recent research uses boron isotope (d11B) measurements to reveal aspects of the biology of marine calcifying organisms. Traditionally used as a palaeooceanographic proxy for ocean pH, d11B in the carbonate shells or skeletons of diverse cultured modern marine organisms records information on their ability to modify their internal pH and buffer it with respect to seawater across a range of atmospheric CO2 concentrations. In some taxa, biological control over internal pH may compromise the use of d11B as a palaeo-ocean pH proxy. Conversely, comparative measurements of d11B in co-occurring marine organisms may yield information on both ocean pH and physiology.
Isotope perspectives in vertebrate palaeobiology
Jeremy E. Martin, Théo Tacail and Vincent Balter
CNRS UMR 5276, Université de Lyon and Ecole Normale Supérieure de Lyon, France
The recent development of multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS), notably in the disciplines of Earth sciences, now allows the measurement of precise isotope ratios, even under low concentration. Non-traditional isotope systems, such as alkaline earth (Ca, Mg) and transition (Cu, Fe, Zn) metals, are now being measured in a variety of biological tissues, including bones and teeth. Although our understanding of the environmental and biological mechanisms behind the fractionation of such elements is still in its infancy, some of these isotopes are suspected to fractionate along the food chain as has been reported in the literature for Ca, Mg and Zn. Other geochemical methods, such as concentration analyses, permit a prior assessment of diagenesis in the fossils to be analysed and such approaches allow us to recognize that, in some circumstances, not only enamel but also dentine or bone can preserve its original biogenic composition. The aims here are to review current knowledge surrounding these isotopic tools, to address their potential preservation in biological apatite, to provide the palaeobiologist with a guide to the different toolkits available, and to discuss their potential applications in vertebrate palaeobiology.
The foraging ecology of pterosaurs - implications from stable isotope analysis
Thomas Tütken1 and David W. E. Hone2
1University of Mainz, Germany
2Queen Mary University of London, UK
Means of testing the available hypotheses for the diet of many pterosaurs have proved elusive. While there is good evidence that many pterosaurs were piscivores, the location of the fossil remains of numerous species leaves open the question as to whether they fed in primarily marine or terrestrial settings. Here, using stable isotope analysis of skeletal bioapatite, we examine the potential ecological habits of 18 pterosaur taxa from more than seven different families, covering a broad spectrum of hypothesized diets as evidenced in Mesozoic marine and terrestrial deposits. Based upon the carbon and oxygen isotope compositions of both tooth and bone samples relative to the surrounding matrix, the food and water sources used by these flying reptiles are inferred and compared with existing feeding hypotheses. In general, the large range of oxygen and carbon isotope compositions indicate the consumption of water and food from isotopically distinct sources ranging from freshwater to marine settings. The stable isotope data will be discussed in the context of those from modern-day birds and reptiles with aquatic and terrestrial feeding habits to assess the foraging ecology of pterosaurs.
Reconstructing Ordovician (Floian) conodont ecology and Laurentian seawater temperatures using oxygen isotopes
James R. Wheeley1, Phillip E. Jardine2, Robert J. Raine3, Ian Boomer1 and M. Paul Smith4
1University of Birmingham, UK
2Open University, UK
3British Geological Survey, UK
4Oxford University Museum of Natural History, UK
Conodont d18O is increasingly used throughout the Palaeozoic–Triassic to reconstruct seawater temperatures, especially low–mid latitude temporal changes. Much less attention has been paid to d18O variation for time-slices across palaeoenvironments or within sample assemblages. Furthermore, there have been few isotopic tests of conodont ecological models based on biogeographic and bio- and lithofacies distributions. Here we present the first test of the ecological model for Ordovician conodonts based on analysis and interpretation of d18O values from a Lower Ordovician (Floian) shelf edge–slope assemblage of the Shallow Bay Formation, Cow Head Group, western Newfoundland. Nine taxa yield a 1.7–1.8‰ intra-sample variability based on mixed tissue and white matter-only analyses. This d18O variability is equivalent to a ~8°C range. Fitting linear mixed models to the dataset demonstrates significant differences between the d18O of some species, in both mixed and single histology analyses, supporting the interpretation that an isotopic and temperature gradient is preserved. By combining knowledge of conodont distributions in host rocks and geological setting with conodont d18O, an integrated palaeoecological and palaeoceanographic model is proposed, with species inhabiting a range of bathymetries (epipelagic–mesopelagic) across the shelf–shelf-edge–slope palaeoenvironment. This model supports the depth stratification ecology for conodonts and their pelagic mode of life. These findings highlight the risk of using single species d18O as representative of time-slice seawater temperatures and promote isotopic ecological analysis for temporal d18O studies.