Herbivore Tooth Research Articles

Reply to the comment on “Implications of diagenesis for the isotopic analysis of Upper Miocene large mammalian herbivore tooth enamel from Chad” by L. Jacques, N. Ogle, I. Moussa, R. Kalin, P. Vignaud, M. Brunet and H. Bocherens [Palaeogeography, Palaeoclimatology, Palaeoecology 266 (2008) 200–210

n their comment to our recent paper (Jacques et al., 2008), Zazzo et al. (2009-this issue) provide a correction regarding some technical features of one of the isotopic mass spectrometers used in our comparative study. It appears that the system used to purify CO2 in Saskatoon was a dual inlet (DI) and not a continuous flow (CF) as mistakenly stated. As this system was considered as reliable as the other CF used in the comparative study, Zazzo et al. (2009-this issue) infer that the isotopic ratios previously measured on heavily contaminated material from a late Miocene Chadian site, Toros Menalla (TM), with another DI are reliable as well. Our reply will re-evaluate the comparison between CF and DI systems in the light of the correction for the system used in Saskatoon, and discuss the claim that previous isotopic measurements made on Chadian material reflect biogenic signatures and were not affected by oxide contamination.

Comment on “Implications of diagenesis for the isotopic analysis of Upper Miocene large mammalian herbivore tooth enamel from Chad” by L. Jacques, N. Ogle, I. Moussa, R. Kalin, P. Vignaud, M. Brunet and H. Bocherens [Palaeogeography, Palaeoclimatology, Palaeoecology 266 (2008) 200–210

Comment on “Implications of diagenesis for the isotopic analysis of Upper Miocene large mammalian herbivore tooth enamel from Chad” by L. Jacques, N. Ogle, I. Moussa, R. Kalin, P. Vignaud, M. Brunet and H. Bocherens [Palaeogeography, Palaeoclimatology, Palaeoecology 266 (2008) 200–210

Multiproxy reconstruction of the palaeoclimate and palaeoenvironment of the Middle Miocene Somosaguas site (Madrid, Spain) using herbivore dental enamel

Profound palaeoclimatic changes took place during the Middle Miocene. The Miocene Climatic Optimum (∼ 20 to 14–13.5 Ma) was followed by a sudden (∼ 200 ka) decrease in temperature and an increase in aridity around the world as a consequence of the reestablishment of the ice cap in Antarctica. Somosaguas palaeontological site (Madrid Basin, Spain) has provided a rich record of mammal remains coincident with this global event (Middle Miocene Biozone E, 14.1–13.8 Ma). It contains four fossiliferous levels (T1, T3-1, T3-2 and T3-3, with T1 being the oldest) that span an estimated time of ∼ 105–125 ka. Scanning Electron Microscope (SEM) and Rare Earth Element (REE) analyses performed on herbivore tooth enamel ( Gomphotherium angustidens, Anchitherium cf . A. cursor, Conohyus simorrensis, Prosantorhinus douvillei and ruminants) indicate that diagenetic processes have not been intense enough as to obscure the original geochemical signal. Stable isotope ( δ 18O CO3, δ 13C CO3 and δ 18O PO4) analyses have been measured on the herbivore tooth enamel across these levels with the aim of determining to what extent the global cooling and aridity pattern is recorded at this site. A decrease in δ 18O CO3 and δ 18O PO4 has been detected from T1 to T3-3 and T3-1 to T3-3 respectively indicating a progressive drop of about 6 °C (from around 18 °C to 12 °C) in mean annual temperatures within T3. Tooth enamel δ 13C values experience an increase from T3-1 to T3-3 suggesting an increase in aridity. Ba/Ca analyses have also been performed on the tooth enamel in order to detect changes in the palaeoecology of the studied taxa. This ratio allows the establishment of particular feeding patterns such as a more browsing habit in the case of Gomphotherium angustidens compared to Anchitherium cf . A. cursor as suggested by higher Ba/Ca values in the latter. Trace elements do not support any significant change across the succession in the dietary behaviour of the species analyzed, despite the stable isotopes evidence of an important palaeoclimatic shift from T1 to T3-3.

Implications of diagenesis for the isotopic analysis of Upper Miocene large mammalian herbivore tooth enamel from Chad

High resolution chemical and textural investigation of Upper Miocene mammalian tooth enamel from Chad using electron microprobe and scanning electron microscope techniques provide direct evidence of extensive diagenetic alteration when compared with some modern and contemporaneous fossil specimens. Chemical and textural changes in Chadian fossil enamel during fossilization include large amounts of secondary Fe, Si, Mn, and Al-bearing oxides – both as coarse precipitation in cracks and permeating the apatite – high fluorine contamination (i.e., apatite alteration), Ca, P, Cl, Na and Mg depletion, and sulphur contamination. Such diagenetic contamination significantly affects the oxygen and carbon isotope analysis of carbonate in apatite, altering the δ 18O and δ 13C biogenic signals towards more positive values. Isotopic alteration is however greater for oxygen than for carbon. Indeed, isotopic analysis of the heavily oxide and S-contaminated Chadian fossil tooth enamel samples on a classical Dual Inlet-MultiPrep system versus three Continuous Flow-IRMS mass spectrometers show great differences in both the δ 18O and δ 13C values. While the MultiPrep-Dual Inlet approach provides carbon and oxygen isotopic results that are indubitably altered and generally inconsistent with any biological values, isotopic analysis on Continuous Flow systems – which automatically filter out contaminating gases – allow to attain or at least greatly approach primary isotopic signals. Some of the Chadian fossil enamel samples analysed in this work come from the very important Upper Miocene TM266 fossil locality that yielded Sahelanthropus tchadensis a.k.a. “Toumaï”, the oldest member of the hominid clade known so far. At this site, as in others, a few or no other environmental proxies than isotopic analysis of biomaterials are available for palaeoenvironmental and palaeoecological reconstructions. Therefore, to obtain reliable environmental information from the time of this ancient Hominid, recovering uncontaminated biogenic isotopic signals is crucial and from these results it is now technically possible.

Stable isotopic variations in modern herbivore tooth enamel, plants and water on the Tibetan Plateau: Implications for paleoclimate and paleoelevation reconstructions

Stable isotope analyses of fossil teeth and other authigenic minerals have been used to reconstruct the paleoenvironment and paleoelevation of the Tibetan Plateau. The accuracy of such reconstructions is limited by the lack of a comprehensive modern comparative database from the region. We analyzed the carbon and oxygen isotopic compositions ( δ 13C and δ 18O values) of tooth enamel from modern herbivores, the δ 13C values of grasses and the δ 18O values of water samples collected from various elevations within the Tibetan Plateau to examine their relationships with modern environment/elevation. The δ 13C values of enamel samples from horses, yaks and goats display a narrow range of variation, with a mean of − 10.7 ± 1.4‰ ( n = 301), indicating that these modern herbivores were feeding predominantly on C3 plants, consistent with the current dominance of C3 vegetation in the region. Some of the samples have δ 13C values between − 7.3 and − 10‰. Although these higher δ 13C values could suggest consumption of some C4 plants by the animals, the lack of significant seasonal δ 13C variations within individual teeth indicates that these higher enamel δ 13C values are due to consumption of C3 plants experiencing water stress and/or some CAM plants rather than C4 plants. Our data show that the conservative “cut-off” δ 13C value for a pure C3 diet within the Tibetan Plateau should be − 8‰ for modern herbivores and − 7‰ (or even − 6.5‰) for fossils if the region was as arid in the past as today. In contrast to the small intra-tooth δ 13C variations within individual teeth, serial enamel samples display large intra-tooth δ 18O variations, reflecting seasonal variations in the δ 18O of meteoric water. The mean δ 18O values of tooth enamel from yaks and horses show a strong correlation with water δ 18O values, confirming that the δ 18O of tooth enamel from obligate drinker generally tracks the δ 18O of meteoric water. Unfortunately, elevation alone cannot explain most of the variance in the δ 18O of precipitation and tooth enamel, suggesting that quantitative reconstruction of the paleoelevation of the Tibetan Plateau using re-constructed δ 18O values of paleo-meteoric water from fossil enamel or other oxygen-bearing minerals is not warranted. For a given environment, horses have the lowest enamel– δ 18O values while goats display the highest enamel– δ 18O values among the species studied. The large inter-species δ 18O variations are likely due to differences in physiology and diet/drinking behavior of the animals. This underscores the importance of species-specific studies when interpreting δ 18O data of fossil mammalian teeth in a stratigraphic sequence as a record of paleoclimate changes.

An assessment of the archaeological applicability of faunal ageing methods based on dental wear

AbstractMortality profiles are central to our reconstructions of past animal hunting and herding strategies. This article considers five different ageing methods based on the progressive wear of hypsodont herbivore teeth. The Quadratic Crown Height Method and the Linear Crown Height Method are based on tooth crown height. The Grant and both Payne methods are based on occlusal wear patterns. Statistical correlations and mortality profiles constructed using caprine teeth from the Anatolian Neolithic site of Çatalhöyük are used to assess the archaeological utility of each method. All of the methods are affected by uncertainties about inter‐ and intrapopulation variation in rates of wear, and by issues surrounding the degree of fragmentation in an assemblage. The crown height methods are biased against younger age classes. The occlusal wear‐based methods suffer less from inherent age‐related biases, but have significant and potentially biasing problems related to fragmentation. The degree of fragmentation in an assemblage determines which method is most appropriate for use. Comparisons of dental wear‐based mortality profiles across assemblages or sites should be treated with considerable caution, unless the same method was used on all assemblages. Copyright © 2008 John Wiley & Sons, Ltd.

Vegetational ecotype of the Gyirong Basin in Tibet, China and its response in stable carbon isotopes of mammal tooth enamel

Carbon isotope analysis of modern herbaceous plants in the Gyirong Basin (Tibet, China) indicates that although C3 plants are dominant, C4 plants rarely comprise of the vegetation in the area at 4000 m above sea level. The C4 plants discovered in the Gyirong Basin areSalsola nepalensis of Chenopodiaceae andPennisetum flaccidum of Gramineae, affirming that C4 plants affected by high solar gain can be distributed at high altitude, which supports the opinion that some C4 plants can exist in areas of high elevation. Carbon isotope analysis of herbivore tooth enamel from the Gyirong Basin indicates that carbon isotopes of structural carbonate in biogenic apatite at high altitude still keep a stable enrichment relationship with those of plants in their diet. Carbon isotopes in tooth enamel are therefore an accurate proxy for vegetation ecotypes and should reflect climatic and environmental features.

Middle Pleistocene climate and habitat change at Zhoukoudian, China, from the carbon and oxygen isotopic record from herbivore tooth enamel

The Pleistocene deposits at Zhoukoudian, often referred to as the “Peking Man” site, contain dental remains from a diverse group of herbivores, including Equus sanmeniensis, Cervus elaphus, Cervus nippon, Megaloceros pachyosteus, Sus lydekkeri, and Dicerorhinus choukoutienensis. The carbon and oxygen isotopic compositions of structural carbonate within the enamel of these teeth are used to reconstruct the paleodiet and paleoenvironment of the mammals. The δ 13C values of enamel from Zhoukoudian range from −2.3‰ to −13.0‰, indicating that these mammals consumed between ∼25% and 100% C 3 plants. The presence of significant amounts of C 4 plants in the diets of some herbivore species indicates that at the onset of the Middle Pleistocene local habitats included mixed C 3/C 4 vegetation. By approximately 470,000 yr ago, C 3 plants dominated the diets of herbivores studied, suggesting that the abundance of C 4 flora had decreased in the area. For all deer analyzed in this study, the values of δ 13C and δ 18O decrease substantially from about 720,000 to 470,000 yr ago. This trend may be due to a strengthening of the winter monsoon during the Middle Pleistocene.

Modern calibration of phytolith carbon isotope signatures for C3/C4 paleograssland reconstruction

The carbon isotope signature of fossil phytoliths (silica bodies produced in abundance in the tissue of grasses) presents a promising tool for reconstructing the biogeography of C3 and C4 grasses during the Neogene. Previously applied isotopic techniques, such as the carbon isotope signatures of soil carbonate, herbivore tooth enamel, and leaf-waxes, are limited in that they cannot distinguish between C3 grasses and C3 shrubs/trees. As a result, these records do not provide any information on the relative dominance of C3 vs. C4 grasses. Phytolith carbon isotope ratios, on the other hand, have the potential to provide a direct record of the photosynthetic pathway (C3 or C4) of grasses specifically. Because this technique is still in its infancy, several modern calibration issues remain and are examined here through the presentation of some new data and the synthesis of existing published data on the δ13C values of phytoliths from modern grasses and soils. First, fresh phytoliths extracted directly from grasses exhibit depleted isotopic values relative to the source plant and phytoliths from C4 grasses are more depleted than phytoliths from C3 grasses. This difference in depletion is most likely the result of lipids present within phytoliths, which are also generally more depleted in C4 plants than C3 plants relative to whole plant values. Second, phytolith assemblages from modern soils do not share the same degree of isotopic depletion or compression as fresh phytoliths. This suggests that soil phytolith assemblage δ13C is affected by pedogenic or taphonomic processes. The weight of current evidence suggests that pedogenic alteration is less of a concern, while selective preservation (taphonomic bias) may play an important role. Even so, comparison of the δ13C values of phytolith assemblages with δ13C values of soil organic matter (SOM) from modern soils indicates that phytoliths can record the C3/C4 contribution to the soil. It appears that phytoliths retain a longer-term, smoothed record in contrast to the more rapid turnover of SOM pools that can be influenced by even recent land-use changes. Third, the interpretation of fossil phytolith δ13C in terms of proportion of C3 and C4 grasses requires isotopic end-member values. End-members from fresh phytoliths cannot be used because they fail to capture the range of soil phytolith assemblage data. Comparison of soil phytolith δ13C values with SOM δ13C yields empirically derived end-member values that take into account any taphonomic effects. These end-members (C3=−26.8‰, C4=−15.3‰) capture the range of observed values for soil and paleosol phytolith δ13C values spanning the last 650,000 years. The modern calibration work presented here provides the necessary groundwork for applying this technique to paleoecological reconstructions of Neogene grasslands.

Modern calibration of phytolith carbon isotope signatures for C 3/C 4 paleograssland reconstruction

The carbon isotope signature of fossil phytoliths (silica bodies produced in abundance in the tissue of grasses) presents a promising tool for reconstructing the biogeography of C 3 and C 4 grasses during the Neogene. Previously applied isotopic techniques, such as the carbon isotope signatures of soil carbonate, herbivore tooth enamel, and leaf-waxes, are limited in that they cannot distinguish between C 3 grasses and C 3 shrubs/trees. As a result, these records do not provide any information on the relative dominance of C 3 vs. C 4 grasses. Phytolith carbon isotope ratios, on the other hand, have the potential to provide a direct record of the photosynthetic pathway (C 3 or C 4) of grasses specifically. Because this technique is still in its infancy, several modern calibration issues remain and are examined here through the presentation of some new data and the synthesis of existing published data on the δ 13C values of phytoliths from modern grasses and soils. First, fresh phytoliths extracted directly from grasses exhibit depleted isotopic values relative to the source plant and phytoliths from C 4 grasses are more depleted than phytoliths from C 3 grasses. This difference in depletion is most likely the result of lipids present within phytoliths, which are also generally more depleted in C 4 plants than C 3 plants relative to whole plant values. Second, phytolith assemblages from modern soils do not share the same degree of isotopic depletion or compression as fresh phytoliths. This suggests that soil phytolith assemblage δ 13C is affected by pedogenic or taphonomic processes. The weight of current evidence suggests that pedogenic alteration is less of a concern, while selective preservation (taphonomic bias) may play an important role. Even so, comparison of the δ 13C values of phytolith assemblages with δ 13C values of soil organic matter (SOM) from modern soils indicates that phytoliths can record the C 3/C 4 contribution to the soil. It appears that phytoliths retain a longer-term, smoothed record in contrast to the more rapid turnover of SOM pools that can be influenced by even recent land-use changes. Third, the interpretation of fossil phytolith δ 13C in terms of proportion of C 3 and C 4 grasses requires isotopic end-member values. End-members from fresh phytoliths cannot be used because they fail to capture the range of soil phytolith assemblage data. Comparison of soil phytolith δ 13C values with SOM δ 13C yields empirically derived end-member values that take into account any taphonomic effects. These end-members (C 3=−26.8‰, C 4=−15.3‰) capture the range of observed values for soil and paleosol phytolith δ 13C values spanning the last 650,000 years. The modern calibration work presented here provides the necessary groundwork for applying this technique to paleoecological reconstructions of Neogene grasslands.

ESR dating and the human evolution: contribution to the chronology of the earliest humans in Europe

In the last 20 years, the electron spin resonance (ESR) dating method has allowed the establishment of a chronological time frame over most of the history of human evolution. Despite many difficulties found for ESR dating of bones and carbonates, tooth enamel dated by ESR has been proven as a reliable method in its application to fossil teeth and quartz. Both of the latter materials have allowed dating of Early and Middle Pleistocene sites which are not datable using other methods such as the Argon–Argon method. In particular, recent discoveries of human remains in western Europe have been proposed to be sites of the earliest arrival of humans there, and have been dated to the Early Pleistocene by ESR using quartz and tooth enamel. Combined ESR and U-series dating of fossil herbivore teeth are the only means of dating layers from which such ancient remains have been recovered in western Europe. Good examples are the sites of Atapuerca Gran Dolina, Spain and Visogliano, Italy which have been dated using tooth enamel. When no bones and teeth can be found in prehistoric sites, ESR dating on quartz extracted from sediments has been used to date sites whose ages range over the entire Quaternary period. We present here two examples that occur in fluvial terraces of the river Creuse, France and at Monte Poggiolo site, Italy, where several artefacts of an archaic pebble industry have been recovered.

Cenozoic Mammalian Herbivores From the Americas: Reconstructing Ancient Diets and Terrestrial Communities

▪ Abstract Herbivory first evolved in terrestrial mammals during the late Cretaceous, ∼100 million years ago (Mya). Of the ∼35 ordinal-level clades of extinct or extant eutherian mammals from the New World, ∼24 have been adapted to herbivory in one form or another. Dental adaptations for specialized terrestrial browsing are first recognized during the early Cenozoic (Paleocene-Eocene). Mammalian herbivores adapted for grazing did not become widespread in the New World until the middle Cenozoic; it seems that this adaptation and the spread of grasslands occurred during the late Oligocene (30 Mya) in South America ∼10 million years earlier than in North America (20 Mya). Carbon isotopic evidence from fossil herbivore teeth indicates that C3 plants predominated until the late Miocene (∼8 Mya). Thereafter, C3 and C4 terrestrial communities diversified. Late Pleistocene extinctions ∼10,000 years ago decimated the diversity of mammalian herbivores, particularly those of larger body size.

Evolution of the grazing niche in Pleistocene mammals from Florida: evidence from stable isotopes

Previous isotopic studies of herbivorous mammals suggested that the dispersal of the grazing mammals, Mammuthus and Bison resulted in the endemic grazers incorporating more browse into their diets. In order to test this hypothesis, we analyzed 84 bulk enamel samples from six co-occurring genera from the Pleistocene of Florida to determine their carbon isotopic composition. We also analyzed 145 samples taken from along the growth axis of the tooth (serial sampling) from 12 specimens of three co-occurring genera in order to investigate seasonal resource partitioning. Our results suggest that: 1. There were no inter-generic or intra-generic differences in feeding strategy for Equus, Bison, and Mammuthus throughout the Pleistocene of Florida. 2. Significant isotopic differences observed in the feeding strategy of Hemiauchenia and Platygonus are due to floral shifts or to interactions with other grazers in Florida. 3. The three late Pleistocene sympatric grazers displayed similar seasonal carbon isotopic variations, suggesting either the lack of forage specificity or abundant resources making forage partitioning unneccessary. 4. Because these organisms did coexist, niche partitioning must have occurred by some aspect not discernible through analyzing stable carbon and oxygen isotopes. Stable isotopic analysis of herbivore tooth enamel allows for the quantitative understanding of specific paleoecological interactions among ancient animals. Further analysis of seasonal-scale changes of ancient ecosystems will bring us closer to the scale of understanding seen in present-day ecosystems.

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

ABSTRACTCarbon 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.

Variability in oxygen isotope compositions of herbivore teeth: reflections of seasonality or developmental physiology?

Oxygen isotope compositions of herbivore tooth enamel from two areas in Kenya were measured using a laser fluorination approach. Isotope heterogeneity was found within four sets of teeth in the jaws of different individuals (∼2‰), as well as within individual teeth. The rear molar (M3) of a zebra shows a 1.4‰ variability, whereas, the middle and rear molars (M2 and M3) of a gazelle show variations of 1.7 to 2.9‰. The front molar (M1) of a gazelle is relatively homogeneous (∼0.25‰). Compositional heterogeneities are spatially correlated, and comparison to theoretical models suggests that they largely reflect different times of tooth growth coupled with seasonal changes in forage composition, rather than developmental physiology. Spatially-specific enamel analysis combined with knowledge of genus-specific diet, water turnover, and physiology allows paleoclimate seasonality to be assessed.

Late Pleistocene C4Plant Dominance and Summer Rainfall in the Southwestern United States from Isotopic Study of Herbivore Teeth

Patterns of climate and C4plant abundance in the southwestern United States during the last glaciation were evaluated from isotopic study of herbivore tooth enamel. Enamel δ13C values revealed a substantial eastward increase in C4plant consumption forMammuthusspp.,Bisonspp.,Equusspp., andCamelopsspp. The δ13C values were greatest inBisonspp. (−6.9 to +1.7‰) andMammuthusspp. (−9.0 to +0.3‰), and in some locales indicated C4-dominated grazing. The δ13C values of Antilocaprids were lowest among taxa (−12.5 to −7.9‰) and indicated C3feeding at all sites. On the basis of modern correlations between climate and C4grass abundance, the enamel data imply significant summer rain in parts of southern Arizona and New Mexico throughout the last glaciation. Enamel δ18O values range from +19.0 to +31.0‰ and generally increase to the east. This pattern could point to a tropical or subtropical source of summer rainfall. At a synoptic scale, the isotope data indicate that interactions of seasonal moisture, temperature, and lowered atmospheric pCO2determined glacial-age C4abundance patterns.

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 delta 13C and delta 18O. The delta 18O 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 delta 18O of tooth enamel indicates differences in water sources between some of the mammals. The delta 13C values of tooth enamel ranged from -8.6(-)-13.0/1000 which is compatible with a pure C3 diet, though the possibility of a small C4 fraction 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 C4 grasses. This study does not preclude the presence of C3 grasses at Fort Ternan; it is possible that C3 grasses could have had a wider geographic range if atmospheric CO2 levels were higher than the present values.

Herbivore tooth oxygen isotope compositions: Effects of diet and physiology

The applicability of rapid and precise laser probe analysis of tooth enamel for δ 18O has been verified, and the method has been applied to different modern herbivores in East Africa. Sampling and pretreatment procedures involve initial bleaching and grinding of enamel to <75 μm, and elimination of adsorbed water and organic compounds with BrF 5. Typical analytical reproducibilities for 0.5–2 mg samples are ±0.08‰ (± 1σ). Chemical and spectroscopic characterization of pretreated but unanalyzed samples show no alteration compared to fresh enamel. Solid reaction products are nearly pure CaF 2 with little evidence for residual O 2. Because laser probe fluorination extracts oxygen from all sites in the apatite structure (phosphate, structural carbonate, and hydroxyl), only unaltered tooth enamel (>95% apatite) can be analyzed reliably. Different East African herbivores exhibit previously unsuspected compositional differences. Average enamel δ 18O values (V-SMOW) are approximately: 25‰ (goat), 27‰ (oryx), 28‰ (dikdik and zebra), 29‰ (topi), 30‰ (gerenuk), and 32‰ (gazelle). These compositions differ from generalized theoretical models, but are broadly consistent with expected isotope effects associated with differences in how much each animal (a) drinks, (b) eats C3 vs. C4 plants, and (c) pants vs. sweats. Consideration of diet, water turnover, and animal physiology will allow the most accurate interpretation of ancient teeth and targeting of environmentally-sensitive animals in paleoclimate studies.

A 16-Ma record of paleodiet using carbon and oxygen isotopes in fossil teeth from Pakistan

The Siwalik Sequence of northern Pakistan contains a 16-Ma record of paleosol carbonate and fossil teeth from which a record of paleovegetation can potentially be reconstructed and compared. The carbon isotopic composition of paleosol carbonate and organic matter from Siwalik strata reflects a major paleoecological change on the floodplains of major rivers beginning ∼ 7.3 Ma ago. By 6 Ma C 3-dominated plant communities, probably composed of mostly trees and shrubs, were displaced by nearly continuous C 4 grassland. We find that the carbon isotopic ratios in herbivore tooth enamel reflect this dramatic ecologic shift. Carbonate in enamel older than 7 Ma averages −11‰ in δ 13C PDB, consistent with a largely C 3 diet. Enamel from the Plio-Pleistocene averages +1.9‰ in δ 13C, similar to the value displayed by modern C 4 grazers. Analysis of post-burial carbonate cements, and the concordance with isotopic evidence from paleosols argues strongly against major isotopic alteration of the enamel, while coexisting bone may have been altered early in burial. This study confirms that enamel apatite is useful for paleodietary reconstruction much further back in the geologic record than was previously thought.

A 16-Ma record of paleodiet using carbon and oxygen isotopes in fossil teeth from Pakistan

The Siwalik Sequence of northern Pakistan contains a 16-Ma record of paleosol carbonate and fossil teeth from which a record of paleovegetation can potentially be reconstructed and compared. The carbon isotopic composition of paleosol carbonate and organic matter from Siwalik strata reflects a major paleoecological change on the floodplains of major rivers beginning7.3 Ma ago. By 6 Ma C 3-dominated plant communities, probably composed of mostly trees and shrubs, were displaced by nearly continuous C 4 grassland. We find that the carbon isotopic ratios in herbivore tooth enamel reflect this dramatic ecologic shift. Carbonate in enamel older than 7 Ma averages −11‰ in δ 13C PDB, consistent with a largely C 3 diet. Enamel from the Plio-PIeistocene averages +1.9‰ in δ 13C, similar to the value displayed by modern C 4 grazers. Analysis of post-burial carbonate cements, and the concordance with isotopic evidence from paleosols argues strongly against major isotopic alteration of the enamel, while coexisting bone may have been altered early in burial. This study confirms that enamel apatite is useful for paleodietary reconstruction much further back in the geologic record than was previously thought.