-
[show abstract]
[hide abstract]
ABSTRACT: Oxygen isotope compositions of tooth phosphate (δ18Op) were measured in 107 samples defined on the basis of teeth obtained from 375 specimens of extant rodents. These rodents were sampled from pellets collected in Europe from 38°N (Portugal) to 65°N (Finland) with most samples coming from sites located in France and Spain. Large oxygen isotopic variability in δ18Op is observed both at the intra- and inter-species scale within pellets from a given location. This isotopic variability is partly explained by heterochrony in tooth formation related to the short time of mineralization for all rodent species as well as the duration of mineralization that is species-dependent. Consequently, tooth phosphate of rodents records a short seasonal interval in the oxygen isotope compositions of meteoric waters (δ18Omw). In addition, inter-species isotopic variability observed in the same pellets suggests behavioural differences implying distinct isotopic compositions for species living in the same location. At the scale of Europe, a robust linear oxygen isotope fractionation equation was determined for Muroidea between the midrange δ18Op values and δ18Omw values: δ18Op=1.21(±0.20)δ18Omw+24.76(±2.70) with R2=0.79 (n=9; p<0.0001).
Earth and Planetary Science Letters 01/2013; 361:2528-271. · 4.18 Impact Factor
-
Romain Amiot,
Xu Wang,
Zhonghe Zhou,
Xiaolin Wang,
Eric Buffetaut,
Christophe Lécuyer,
Zhongli Ding,
Frédéric Fluteau,
Tsuyoshi Hibino,
Nao Kusuhashi,
Jinyou Mo,
Varavudh Suteethorn,
Yuanqing Wang,
Xing Xu,
Fusong Zhang
[show abstract]
[hide abstract]
ABSTRACT: Early Cretaceous vertebrate assemblages from East Asia and particularly the Jehol Biota of northeastern China flourished during a period of highly debated climatic history. While the unique characters of these continental faunas have been the subject of various speculations about their biogeographic history, little attention has been paid to their possible climatic causes. Here we address this question using the oxygen isotope composition of apatite phosphate (δ ) from various reptile remains recovered from China, Thailand, and Japan. δ values indicate that cold terrestrial climates prevailed at least in this part of Asia during the Barremian-early Albian interval. Estimated mean air temperatures of about 10 ± 4 °C at midlatitudes (∼ 42 °N) correspond to present day cool temperate climatic conditions. Such low temperatures are in agreement with previous reports of cold marine temperatures during this part of the Early Cretaceous, as well as with the widespread occurrence of the temperate fossil wood genus Xenoxylon and the absence of thermophilic reptiles such as crocodilians in northeastern China. The unique character of the Jehol Biota is thus not only the result of its evolutionary and biogeographical history but is also due to rather cold local climatic conditions linked to the paleolatitudinal position of northeastern China and global icehouse climates that prevailed during this part of the Early Cretaceous.
Proceedings of the National Academy of Sciences 03/2011; 108(13):5179-83. · 9.68 Impact Factor
-
Aurélien Bernard,
Christophe Lécuyer,
Peggy Vincent, Romain Amiot,
Nathalie Bardet,
Eric Buffetaut,
Gilles Cuny,
François Fourel,
François Martineau,
Jean-Michel Mazin,
Abel Prieur
[show abstract]
[hide abstract]
ABSTRACT: What the body temperature and thermoregulation processes of extinct vertebrates were are central questions for understanding their ecology and evolution. The thermophysiologic status of the great marine reptiles is still unknown, even though some studies have suggested that thermoregulation may have contributed to their exceptional evolutionary success as apex predators of Mesozoic aquatic ecosystems. We tested the thermal status of ichthyosaurs, plesiosaurs, and mosasaurs by comparing the oxygen isotope compositions of their tooth phosphate to those of coexisting fish. Data distribution reveals that these large marine reptiles were able to maintain a constant and high body temperature in oceanic environments ranging from tropical to cold temperate. Their estimated body temperatures, in the range from 35 degrees +/- 2 degrees C to 39 degrees +/- 2 degrees C, suggest high metabolic rates required for predation and fast swimming over large distances offshore.
Science 06/2010; 328(5984):1379-82. · 31.20 Impact Factor
-
Christophe Lécuyer,
Vincent Balter,
François Martineau,
François Fourel,
Aurélien Bernard, Romain Amiot,
Véronique Gardien,
Olga Otero,
Serge Legendre,
Gérard Panczer,
Laurent Simon,
Rossana Martini
[show abstract]
[hide abstract]
ABSTRACT: The oxygen isotope fractionation between the structural carbonate of inorganically precipitated hydroxyapatite (HAP) and water was determined in the range 10–37 °C. Values of 1000 ln α() are linearly correlated with inverse temperature (K) according to the following equation: 1000 ln α() = 25.19 (±0.53)·T−1 − 56.47 (±1.81) (R2 = 0.998). This fractionation equation has a slightly steeper slope than those already established between calcite and water (
[57] and [28]) even though measured fractionations are of comparable amplitude in the temperature range of these experimental studies. It is consequently observed that the oxygen isotope fractionation between apatite carbonate and phosphate increases from about 7.5‰ up to 9.1‰ with decreasing temperature from 37 °C to 10 °C. A compilation of δ18O values of both phosphate and carbonate from modern mammal teeth and bones confirms that both variables are linearly correlated, despite a significant scattering up to 3.5‰, with a slope close to 1 and an intercept corresponding to a 1000 ln α() value of 8.1‰. This apparent fractionation factor is slightly higher or close to the fractionation factor expected to be in the range 7–8‰ at the body temperature of mammals.
Geochimica et Cosmochimica Acta 04/2010; · 4.26 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The oxygen isotope composition of human phosphatic tissues (delta18OP) has great potential for reconstructing climate and population migration, but this technique has not been applied to early human evolution. To facilitate this application we analyzed delta18OP values of modern human teeth collected at 12 sites located at latitudes ranging from 4 degrees N to 70 degrees N together with the corresponding oxygen composition of tap waters (delta18OW) from these areas. In addition, the delta18O of some raw and boiled foods were determined and simple mass balance calculations were performed to investigate the impact of solid food consumption on the oxygen isotope composition of the total ingested water (drinking water+solid food water). The results, along with those from three, smaller published data sets, can be considered as random estimates of a unique delta18OW/delta18OP linear relationship: delta18OW=1.54(+/-0.09)xdelta18OP-33.72(+/-1.51)(R2=0.87: p [H0:R2=0]=2x10(-19)). The delta18O of cooked food is higher than that of the drinking water. As a consequence, in a modern diet the delta18O of ingested water is +1.05 to 1.2 per thousand higher than that of drinking water in the area. In meat-dominated and cereal-free diets, which may have been the diets of some of our early ancestors, the shift is a little higher and the application of the regression equation would slightly overestimate delta18OW in these cases.
Journal of Human Evolution 09/2008; 55(6):1138-47. · 3.64 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Teeth from the Early Cretaceous Napai Formation of Fusui County, Guangxi Zhuang Autonomous Region (South China), initially described as the sauropterygian Sinopliosaurus fusuiensis, are redescribed as belonging to a spinosaurid theropod closely allied to Siamosaurus suteethorni, from the Early Cretaceous of Thailand. This identification extends to China the geographical range of Asian spinosaurs, previously reported from Thailand and Japan.
Geological Magazine 08/2008; 145(05):745 - 748. · 1.76 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A high-precision, and rapid on-line method for oxygen isotope analysis of silver phosphate is presented. The technique uses high-temperature elemental analyzer (EA)-pyrolysis interfaced in continuous flow (CF) mode to an isotopic ratio mass spectrometer (IRMS). Calibration curves were generated by synthesizing silver phosphate with a 13 per thousand spread in delta(18)O values. Calibration materials were obtained by reacting dissolved potassium dihydrogen phosphate (KH(2)PO(4)) with water samples of various oxygen isotope compositions at 373 K. Validity of the method was tested by comparing the on-line results with those obtained by classical off-line sample preparation and dual inlet isotope measurement. In addition, silver phosphate precipitates were prepared from a collection of biogenic apatites with known delta(18)O values ranging from 12.8 to 29.9 per thousand (V-SMOW). Reproducibility of +/- 0.2 per thousand was obtained by the EA-Py-CF-IRMS method for sample sizes in the range 400-500 microg. Both natural and synthetic samples are remarkably well correlated with conventional (18)O/(16)O determinations. Silver phosphate is a very stable material and easy to degas and, thus, could be considered as a good candidate to become a reference material for the determination of (18)O/(16)O ratios of phosphate by high-temperature pyrolysis.
Journal of Mass Spectrometry 02/2007; 42(1):36-41. · 3.27 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Latitudinal variations in model biogenic apatite delta(18)O values were calculated using fractionation equations of vertebrates and weighted rainfall delta(18)O values along with mean annual air temperatures provided by IAEA-WMO meteorological stations. The reference equation obtained was used to compute a continental temperature gradient for the Late Campanian-Middle Maastrichtian interval by using published and new delta(18)O values of phosphate from vertebrates. Samples are mainly tooth enamel from crocodilians and dinosaurs that lived at paleolatitudes ranging from 83(-9)(+4degreesN) (Alaska) to 32+/-3degreesS (Madagascar). The temperature gradient was less steep (0.4+/-0.1 degreesC/degreeslatitude) than the present-day one (0.6 degreesC/degreeslatitude) with temperatures that decreased from about 30 degreesC near the equator to about -5 degreesC at the poles. Above 30degrees of paleolatitude, air temperatures were higher than at present. The validity of these results is discussed by comparison with climatic criteria inferred from paleontological, palcobotanical and sedimentological data. The latitudinal distribution of oxygen isotope compositions of continental vertebrates is potentially a powerful tool for quantifying Mesozoic terrestrial climates.
Earth and Planetary Science Letters 09/2004; 226(1-2):255-272. · 4.18 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Latitudinal variations in model biogenic apatite δ18O values were calculated using fractionation equations of vertebrates and weighted rainfall δ18O values along with mean annual air temperatures provided by IAEA–WMO meteorological stations. The reference equation obtained was used to compute a continental temperature gradient for the Late Campanian–Middle Maastrichtian interval by using published and new δ18O values of phosphate from vertebrates. Samples are mainly tooth enamel from crocodilians and dinosaurs that lived at paleolatitudes ranging from 83−9+4°N (Alaska) to 32±3°S (Madagascar). The temperature gradient was less steep (0.4±0.1 °C/°latitude) than the present-day one (0.6 °C/°latitude) with temperatures that decreased from about 30 °C near the equator to about −5 °C at the poles. Above 30° of paleolatitude, air temperatures were higher than at present. The validity of these results is discussed by comparison with climatic criteria inferred from paleontological, paleobotanical and sedimentological data. The latitudinal distribution of oxygen isotope compositions of continental vertebrates is potentially a powerful tool for quantifying Mesozoic terrestrial climates.
Earth and Planetary Science Letters 09/2004; 226(1-2):255-272. · 4.18 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Oxygen isotope compositions of phosphate in tooth enamel from large mammals (i.e. horse and red deer) were measured to quantify past mean annual air temperatures and seasonal variations between 145 ka and 33 ka in eastern France. The method is based on interdependent relationships between the δ18O of apatite phosphate, environmental waters and air temperatures. Horse (Equus caballus germanicus) and red deer (Cervus elaphus) remains have δ18O values that range from 14.2‰ to 17.2‰, indicating mean air temperatures between 7°C and 13°C. Oxygen isotope time series obtained from two of the six horse teeth show a sinusoidal-like signal that could have been forced by temperature variations of seasonal origin. Intra-tooth oxygen isotope variations reveal that at 145 ka, winters were colder (− 7 ± 2°C) than at present (3 ± 1°C) while summer temperatures were similar. Winter temperatures mark a well-developed West–East thermal gradient in France of about − 9°C, much stronger than the −4°C difference recorded presently. Negative winter temperatures were likely responsible for the extent and duration of the snow cover, thus limiting the food resources available for large ungulates with repercussions for Neanderthal predators.
Quaternary Research. 75(3):605-613.
-
Romain Amiot,
Xu Wang,
Christophe Lécuyer,
Eric Buffetaut,
Larbi Boudad,
Lionel Cavin,
Zhongli Ding,
Frédéric Fluteau,
Alexander W.A. Kellner,
Haiyan Tong,
Fusong Zhang
[show abstract]
[hide abstract]
ABSTRACT: In order to investigate mid-Cretaceous terrestrial climates of low paleolatitudes, Moroccan, Tunisian and Brazilian vertebrate apatites have been analyzed for their oxygen and carbon isotope compositions of phosphates (δ18Op) and carbonates (δ18Oc, δ13Cc). At each site, coexisting theropod dinosaurs, titanosaurid sauropods, pterosaurs, crocodilians, turtles and fish have distinct δ18Op and δ13Cc values reflecting their ecologies, diets and foraging environments. Oxygen isotope compositions of surface waters (δ18Ow) estimated from turtle and crocodile δ18Op values range from − 5.0 ± 1.0‰ to − 2.4 ± 1.0‰, which do not differ from mean annual rainwater values occurring today under inter-tropical sub-arid to arid climates. High water temperatures ranging from 21 ± 6 °C to 34 ± 2 °C deduced from fish δ18Op values are in agreement with those published for mid-Cretaceous low latitudes. Temporary or seasonal droughts are inferred from high δ18Op values of lungfish teeth, even though lower reptile δ18Op values suggest the use of distinct and most likely larger or regularly renewed bodies of water. Environmental conditions of the studied low latitude regions during the Aptian–Cenomanian interval were somewhat similar to those experienced today under semi-arid to arid tropical or equatorial climates, but with higher mean surface temperatures than present-day ones.
Palaeogeography Palaeoclimatology Palaeoecology 297(2):439-451. · 2.39 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Oxygen isotope compositions of phosphate (δ18Op) were measured in tooth enamel from captive and wild individuals of 8 crocodilian species. A rough linear correlation is observed between the δ18Op of all the studied species and the oxygen isotope composition of ambient water (δ18Ow). Differences in mean air temperature, diet and physiology could contribute significantly to the large scatter of δ18Op values. The combination of these parameters results in a fractionation equation for which the slope (0.82) is lower than that expected (≥ 1) from predictive model equations that assume temperature and diet as fixed parameters. Taking into account large uncertainties, the observed oxygen isotope fractionation between phosphate and ambient water does not statistically differ from that formerly established for aquatic turtles. Case studies show that δ18Op values of fossil crocodile tooth enamel can be used to discriminate between marine and freshwater living environments within a precision of about ± 2‰ only.
Palaeogeography, Palaeoclimatology, Palaeoecology.
-
Romain Amiot
-
Romain Amiot
-
[show abstract]
[hide abstract]
ABSTRACT: Isolated dinosaur teeth recovered from seven localities near Fuxin (western Liaoning Province, northeastern China) are described. They come from sediments belonging to the Shahai and Fuxin formations, considered to be Aptian to Albian in age. Seven taxa have been recognized. They include the oviraptorosaur Incisivosaurus, dromaeosaurid theropods, Euhelopus-like sauropods, as well as indeterminate nodosaurid, ankylosaurid, iguanodontoid and basal neoceratopsian ornithischians. The Shahai and Fuxin dinosaur faunas show the persistence of some Jehol biota taxa such as the highly specialised Incisivosaurus, basal titanosauriform sauropods, basal neoceratopsians and some dromaeosaurids, and the addition of more derived iguanodontoids and ankylosaurians. The persistence of some dinosaurs of the Jehol Biota into the Shahai and Fuxin formations suggests a long term stability of Liaoning terrestrial environments during the Early Cretaceous. Despite sampling bias and the rather small sample that must be taken into account, teeth abundances show a significant compositional difference between the localities of the Shahai and Fuxin formations, neoceratopsian teeth representing one third of dinosaur tooth remains in the Shahai Formation whereas they are totally absent in the Fuxin Formation. Ankylosaur teeth, in contrast, represent 3% of total remains in the Shahai Formation, whereas they seem to be the only herbivorous dinosaurs in the Fuxin Formation with 40% of the total number of teeth (the rest being theropod dinosaur teeth). Although a difference in micro-environmental conditions between Shahai and Fuxin localities may at least partly explain such pattern, the unusual and unbalanced faunal composition of Fuxin localities remains enigmatic and will need further field collecting in order to be clarified.
Journal of Asian Earth Sciences.
-
[show abstract]
[hide abstract]
ABSTRACT: Phosphatic remains of marine vertebrates recovered from five fossil sites of the Pisco Formation ranging from the latest Middle/earliest Late Miocene (Ca 11–13 Ma) to the Early Pliocene (Ca 3.5 Ma) have been analysed for their oxygen isotope compositions (δ18Op). Coexisting seals, dolphins, whales, penguins and sharks from each locality have distinct δ18Op values reflecting ecology and physiology differences, ranging from 18.2‰ to 21.4‰ for marine mammals, from 19.5‰ to 21.5‰ for marine birds and from 20.9‰ to 23.1‰ for sharks. Systematic offsets observed between dolphin teeth and bones as well as between dolphin and whale bones indicate that the fractionation equation established by using data from extant cetaceans may not be directly applicable to Miocene cetaceans in order to estimate water δ18Ow values. Assuming that polar ice-caps were not totally developed during this time interval, marine palaeotemperatures ranging from 13.0 ± 1.3 °C to 17.2 ± 1.3 °C were estimated. Comparison of our results with those obtained in other World's areas suggests that the oxygen isotope ratios of Pisco vertebrates reflect the influence of both global and local events, such as the setting of the Atacama Desert, the cold Humboldt Current or the global phases of ice-cap growth and decay.
Palaeogeography, Palaeoclimatology, Palaeoecology.
-
[show abstract]
[hide abstract]
ABSTRACT: The much debated question of dinosaur thermophysiology has not yet been conclusively solved despite numerous attempts. We used the temperature-dependent oxygen isotope fractionation between vertebrate body water (δ18Obody water) and phosphatic tissues (δ18Op) to compare the thermophysiology of dinosaurs with that of non-dinosaurian ectothermic reptiles. Present-day δ18Op values of vertebrate apatites show that ectotherms have higher δ18Op values than endotherms at high latitudes due to their lower body temperature, and conversely lower δ18Op values than endotherms at low latitudes. Using a data set of 80 new and 49 published δ18Op values, we observed similar and systematic differences in δ18Op values (Δ18O) between four groups of Cretaceous dinosaurs (theropods, sauropods, ornithopods and ceratopsians) and associated fresh water crocodiles and turtles. Expressed in terms of body temperatures (Tb), these Δ18O values indicate that dinosaurs maintained rather constant Tb in the range of endotherms whatever ambient temperatures were. This implies that high metabolic rates were widespread among Cretaceous dinosaurs belonging to widely different taxonomic groups and suggest that endothermy may be a synapomorphy of dinosaurs, or may have been acquired convergently in the studied taxa.
Earth and Planetary Science Letters.
