Stable isotope analysis of middle Miocene mammals from the Siwalik sub-Group of Pakistan

MUHAMMAD TAHIR WASEEM, ABDUL MAJID KHAN, JAY QUADE, ANTHONY KRUPA, DAVID L. DETTMAN, AMTUR RAFEH, and RANA MANZOOR AHMAD

Waseem, M.T., Khan, A.M., Quade, J., Krupa, A., Dettman, D.L., Rafeh, A., and Ahmad, R.M. 2021. Stable isotope analysis of middle Miocene mammals from the Siwalik sub-Group of Pakistan. Acta Palaeontologica Polonica 66 (Supplement to 3): 123–132.

Stable isotope analysis is pivotal for investigating the paleodiet and paleoecology of past mammals. In this paper, we ana­lyzed thirty fossil enamel samples belonging to the families Suidae, Rhinocerotidae, and Deinotheriidae for ­δ13Cenamel and δ18Oenamel composition to investigate paleodiet and paleoecology of middle Miocene mammals of the Siwalik sub-Group of Pakistan. The three mammalian groups, when combined together, yielded an average δ13Cenamel value of -12.2 ± 2‰, indicating a pure to nearly pure C3 diet. Suids show slightly higher δ13Cenamel values of -11.2 ± 1.4‰ when compared to rhinocerotids and deinotheres (-12.3 ± 0.8‰ and -12.5 ± 1.3‰, respectively), which could be explained by selective foraging on new leaf shoots or feeding from open spaces. Alternatively, the differences in δ13Cenamel could be due to different digestive physiologies and different enamel-diet enrichment factors. Members of all three families showed significant differences in δ18Oenamel values, where suids yielded higher δ18O values of -8.2 ± 1.2‰ compared to rhinocerotids and deinotheres (-11.4 ± 1.8‰ and -10.4 ± 1.7‰, respectively). Based upon these results, we assume that these mammals inhabited subtropical forests similar that of mid-Miocene of the Siwalik Group, India and Nepal. The modern analogues of such vegetation system are present in East and South of Myanmar, Nepal, and Malaya where precipitation is enough to support evergreen C3 forests. By contrast, today’s floodplain environments in Pakistan are dominated by C4 grasses, and C3 vegetation is only present in non-floodplain settings.

Key words: Mammalia, paleoclimate, paleodiet, Miocene, Chinji Formation, Pakistan.

Muhammad Tahir Waseem [tahirmuhammad1213@gmail.com], Abdul Majid Khan [majid.zool@pu.edu.pk] (corresponding author), and Amtur Rafeh [amturrafeh@gmail.com], Department of Zoology, University of the Punjab, Lahore 54590, Pakistan.

Jay Quade [quadej@email.arizona.edu], Anthony Krupa [akrupa@email.arizona.edu], and David L. Dettman [dettman­ @email.arizona.edu], Department of Geosciences, University of Arizona, Tucson AZ 85721, USA.

Rana Manzoor Ahmad [manzoor.zoology@uo.edu.pk], Department of Zoology, University of Okara, Punjab 56300, Pakistan.

Received 28 June 2020, accepted 23 October 2020, available online 24 May 2021.

Copyright © 2021 M.T. Waseem et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (for details please see http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Introduction

The temporal and spatial records of climate archived in thick Neogene and Quaternary continental deposits in northern Pakistan provide an exceptional opportunity to explore the patterns of evolution and adaptation of mammals over the time span of million years (Badgley et al. 2008; Morgan et al. 2009; Patnaik et al. 2019). Stable isotope (SI) analysis of carbon and oxygen of enamel from mammals, both expressed in the familiar delta (δ) notation in per mil (‰) according to V-PDB (Vienna Pee Dee Belemnite) standards, allow us to reconstruct the past diets (δ13Cdiets) and paleoenvironmental meteoric water (δ18Omw), which in turn reflect paleovegetation and paleoclimate during the Neogene and Quaternary (Quade et al. 1992, 1995a, b; Cerling et al. 1997a, 2015; White et al. 2009; Sanyal et al. 2005, 2010; Uno et al. 2011; Ben-David and Flaherty 2012; Khan et al. 2020; Waseem et al. 2020a). The Siwalik sub-Group of northern Pakistan contains a high-resolution fossil record spanning the Neogene time period (Quade et al. 1989; Barry et al. 2002, 2013; Dennell et al. 2006; Flynn et al. 2016; Fig. 1). Morgan et al. (1994), Uno et al. (2011), and Hynek et al. (2012) interpreted elevated δ13C values in fossil herbivore enamel (δ13Cenamel) to reflect a component of C4 vegetation in the mid-Miocene (~11–10 Ma) across several continents. However, the major C4 radiation in the Siwalik sub-Group has been documented to occur after ~10 Ma (Barry et al. 1982, 2002; Quade et al. 1995a, b; Morgan et al. 2009). In this study, we explore the isotopic composition of enamel from three families of large herbivores to reconstruct paleoenvironments and check for evidence of C4 dietary intake in the middle Miocene (14.2–11.2 Ma) of the Siwalik sub-Group of Pakistan. Enamel was selected for the analysis due to its high resistance to diagenesis and large crystal size and low porosity, which makes it the best material for paleodietary reconstruction in ancient ecosystems (Quade et al. 1992; Kohn et al. 1996, 2002; Kohn and Cerling 2002).

There are three metabolic pathways through which carbon is incorporated in the plants. Trees, nearly all shrubs, forbs, ferns, sedges, and most non-tropical or high altitude grasses utilize the C3 pathway of photosynthesis in which δ13Cdiet ranges from -34 to -22‰ (Koch 1998; Pérez-Crespo et al. 2017), and average around -28.2 ± 6‰ under the present δ13CCO2 = -8‰, or -6.7‰, pre-industrially (Kohn 2010). The C4 pathway is found in most of the warm region-grasses and some sedges with a range of δ13Cdiet values from -14 to -10‰ (Cerling 1999). The abundance of C3/C4 vegetation in an ecosystem is governed by many factors, including the mean annual temperature (MAT), mean annual precipitation (MAP), and partial pressure of carbon dioxide in the atmosphere (pCO2) (Kohn 2010; Waseem et al. 2020b). The comparatively cooler areas (MAT <25°C) with precipitation higher than 1–2 m/year show a dominance of C3 vegetation while warmer areas (MAT >25°C) with drier conditions (MAP <1–2 m/year) show a dominance of C4 grasses (Nelson 2007). Furthermore, the C4 pathway can work efficiently under lower pCO2 and lower humidity levels compared to C3 pathway (Medrano and Flexas 2000; Bellasio et al. 2018) due to the fact that carbon is fixed twice in C4 pathway as compared to C3 pathway (Kohn and Cerling 2002). The δ13C values of plants are governed by other factors such as low light intensity, saline soil, water availability, and local microhabitat conditions (Ehleringer et al. 1987; Codron et al. 2005; Bibi 2007).

These averages and ranges in δ13C value for modern plants were ~1.3‰ higher during the middle Miocene in fossil C3 and C4 plants, due largely to the effect of fossil fuel burning in decreasing δ13CCO2 of the atmosphere (see Tipple et al. 2010). Thus, we use the δ13CCO2 (-5.2‰) as in Tipple et al. (2010) for pre-10 Ma time span. The third photosynthetic pathway, crassulacean acid metabolism (CAM), is found in succulent plants which are mostly present in deserts or epiphytic plants in closed forests (Passey et al. 2005; Andrade et al. 2007) and were probably negligible in the Siwaliks.

Upon feeding on plants, the carbon is incorporated in the herbivores tooth enamel during the period of tooth formation. When carbon isotopes are incorporated in the enamel of herbivores, δ13Cenamel values are fractionated by an enrichment factor (eenamel-diet):

eenamel-diet = (aenamel-diet - 1) × 1000 (1), where: a enamel-diet = (denamel + 1000)/(ddiet + 1000)

Thus, middle Miocene animals consuming C3 vegetation outside of rainforests and deserts with δ13Cdiet values from -28.1 to -23.1‰ should show δ13Cenamel values ranging from about -14 to -9‰, whereas middle Miocene animals feeding on C4 vegetation should show δ13Cenamel values ranging from ~-2 to ~+2‰. The values between ~-9 to ~-2‰ are considered to reflect mixed feeding on C3/C4 vegetation (MacFadden and Cerling 1996). In this study, we assume that δ13Cenamel values ≤-16.1‰ denote browsing under closed-canopy forests, -16 to -14‰ for sub-canopy browsing, -14 to -12‰ for browsing in forests, and -12 to -8‰ for browsing in woodlands (Cerling and Harris 1999; Domingo et al. 2012). The δ13Cenamel between -8 to -3‰ will be considered as mixed feeding on C3/C4 vegetation while values >-2‰ can be interpreted as grazing on dominantly C4 grasses (Cerling et al. 1997a, b, 2004; Kohn 2010). However, eenamel-diet does not solely depend upon one factor. Tejada-Lara et al. (2018) argue that a single value of eenamel-diet of ~14.1‰ does not account for all the mammals from monkeys to elephants by overlooking the other metabolic and physiological effect on carbon fractionation. For example, different mammals show different eenamel-diet depending on body mass and digestive physiology (Tejada-Lara et al. 2018). Combining all factors, we assume an average eenamel-diet of ~+14.1‰ for large-bodied rhinocerotids and deinotheres and ~+13.1‰ for suids according to Codron et al. (2011) and Tejada-Lara et al. (2018).

Oxygen enters an animal’s body in three main ways: (i) from drinking water, (ii) water derived from food, and (iii) inhalation, and leaves the body through sweat, exhalation, and urination (Sponheimer and Lee-Thorp 1999; Koch 2007; Sánchez 2005; Blumenthal et al. 2017, 2018). Of these sources, the majority of oxygen isotopes incorporated into enamel are from drinking water and diet, and δ18O values of local meteoric water (δ18Omw) are affected by environmental temperature, amount of precipitation, latitude, and altitude (Dansgaard 1964). The general trend of δ18Oenamel values is set by the ecology as the animals living under closed habitat and in humid conditions (forests) tend to show lower ­δ18Oenamel values compared to the animals living in open and arid (savannah or grasslands) areas (Feranec and MacFadden 2006). Levin et al. (2006) categorized the animals under two broad categories on the basis of their physiology and beha­vior. Evaporation sensitive (ES) taxa tend to obtain most of their water from their diet (leafy plants) and generally are ruminants (δ18O values of their enamel is correlated to the evaporation of leaf water), whereas evaporation insensitive (EI) taxa are mostly non-ruminants that depend on surface water for their body water requirements (δ18Oenamel is correlated to local drinking water sources). In this study, all the families sampled can be categorized as EI taxa on the basis of the physiology of the modern analogues, providing better insights into the δ18O value of palaeo-precipitation (Levin et al. 2006; Blumenthal et al. 2017; Faith 2018).

The fossil fauna of Chinji Formation includes Rhino­cerotidae, Suidae, Tragulidae, Bovidae, Giraffidae, Deino­theriidae, Gomphotheriidae, and other taxa including Homi­nidae, Rodentia, and Carnivora (Pilgrim 1937; Khan et al. 2013; Barry et al. 2013; Flynn et al. 2016). We focus here on the paleodiets, paleoenvironments, and niche partitioning among Rhinocerotidae, Suidae, and Deinotheriidae from the middle Miocene of northern Pakistan. We selected these three EI taxa over non-EI taxa as δ18Oenamel value of EI taxa is correlated to their water source (Faith 2011, 2018). Furthermore, we selected one specialized browser (deinotheres), one taxon (i.e., Hyotherium pilgrimi) which disappeared from the Siwalik record during the late Miocene, and one taxon (rhinocerotid, Chilotherium intermedium) which shifted towards a C4 diet during the late Miocene (Badgley et al. 2008; Morgan et al. 2009) to evaluate whether these taxa ate C3 or C4 plants during the middle Miocene time span in the Siwalik sub-Group of Pakistan.

The rhinocerotid, Chilotherium intermedium, was widespread in the Siwalik sub-Group of India and Pakistan, and existed up to the late Miocene (~7 Ma) in China. This species is characterized by low-crowned cheek teeth (brachydonty) with thin enamel folding and less complexity, indicating a diet composed of soft and less-gritty vegetation, preferably leaves of plants and trees (Khan 2009). C. intermedium was comparatively smaller (height 1.5 m and weight 1–2 tons) than modern black rhinos (Diceros bicornis) (height up to 1.8 m and weight up to 2.2 tons) (Decher 1999; Deng 2005).

Deinotherium pentapotamiae and D. indicum (Deino­theriidae) (body weight up to 11 tons and height up to 5 m, Larramendi 2016) was widespread in the Siwalik Group and contemporaneous African sites for most of the middle Miocene, and it persisted as late as ~9 Ma in the Indian sub-continental region (Sarwar 1977). Two hooked shaped lower tusks were present in the species of Deinotherium with a flat skull, unlike other proboscideans, along with low-crowned teeth, indicating a browsing diet (Sarwar 1977; Shoshani and Tassy 2005).

Hyotherium pilgrimi (Suidae) was a species with bunodont (rounded cusps) and brachyodont cheek teeth which existed during the middle Miocene time span in the Siwaliks. It had a range of body weight from 150–200 kg and height up to 1.1 m (Sorkin 2008). The mesowear and morphological studies (low hypsodonty index of 1.1, simple bunodont dentition with thick enamel) show that this species browsed on leaves and fruits (Barry et al. 2002; Tariq 2010; Aslam 2018). In general, all the middle Miocene mammals of the Siwalik sub-Group of Pakistan show morphological characters indicating browsing diets in forests and woodland settings, like their Indian counterparts (Patnaik et al. 2019).

Institutional abbreviations.—EB, Environmental Biology Laboratory, Institute of Zoology, University of the Punjab, Lahore, Pakistan.

Other abbreviations.—CAM, crassulacean acid meta­bo­lism; EI, evaporation insensitive; ES, evaporation sensitive; MAP, mean annual precipitation; MAT, mean annual temperature; SI, stable isotopes; V-PDB, Vienna Pee Dee Belemnite.

Geological setting

The middle Miocene is represented by the Chinji Formation in the Siwalik sub-Group of Pakistan (Fig. 1), which spans 14.2–11.2 Ma (Barry et al. 2002). The thickness and near-continuous deposition of the strata have permitted the development of a robust chronostratigraphic framework for the Chinji Formation on the basis of paleomagnetic dating. The samples for this study were collected from the Chinji-Nagri and Dhok Bun Ameer Khatoon sections (Fig. 1). The Chinji-Nagri section (Fig. 1B, C) is present in Chakwal District, Punjab (32°39´N, 72°22´E), whereas the Dhok Bun Ameer Khatoon section (DBAK) (Fig. 1B, D) is located 50 km north of Chinji Village (32°47´N, 72°55´E). The boundary between Chinji and Nagri formations can be placed at 11.2 Ma (Fig. 1A), between magnetic zones C5r.3r and C5n.3n (Johnson et al. 1982, calibrated according to Gradstein et al. 2012). The lower boundary of the Chinji Formation with the underlying Kamlial Formation (Fig. 1A) can be placed between C5ACr and C5ADn at 14.2 Ma (Channell et al. 2013). Siltstone and sandstone deposited in an overall fluvial environment dominate the general lithology of the Siwalik sub-Group sediments. Most of the samples come from reddish to gray mudstone (Fig. 1C, D) marginal to large-river paleochannels. The ages are assigned as the mid points following Barry et al. (2002).

Material and methods

For SI analysis, thirty samples from three mammalian families were selected across the middle Miocene of the Siwalik sub-Group of Pakistan. The samples were identified to the species level and further processed for SI analysis. Statistical analysis was conducted using Statistical Package for Social Studies (SPSS) version 20.0.

For the extraction of enamel, a rotary dental drill with carbide burrs was used. Around 15–20 mg of enamel was extracted from each tooth (only molars and premolars were included). Enamel was extracted along one single transect from cervix to crown apex (longitudinal) from buccal surface of upper teeth and lingual surface of lower teeth.

Powdered enamel was further pre-treated with 10 ml of 2% NaOCl for one hour to remove organic matter and the solution was decanted and rinsed with distilled water three times. The samples were than treated with 10 ml of 0.1% acetic acid for 1 hour to remove exogenous carbonates and rinsed with water (Nelson 2007). Samples were then oven dried before isotope analysis (Koch et al. 1997).

δ18Oenamel and δ13Cenamel values were measured at the Uni­versity of Arizona, USA, using an automated carbonate preparation device (KIEL-III) coupled to a gas-ratio mass spectrometer (Finnigan MAT 252). Powdered samples were reacted with dehydrated phosphoric acid under vacuum at 70°C. The isotope ratio measurement is calibrated based on repeated measurements of NBS-19 and NBS-18, and precision is 0.11‰ for δ18O (V-PDB) and 0.08‰ for δ13C (V-PDB).

Results

Stable Carbon Isotopes.—The average δ13Cenamel across all the families was found to be -12.2 ± 2.2‰. The Suidae, Rhinocerotidae, and Deinotheriidae returned average values of δ13Cenamel of -11.2 ± 1.4‰ (n = 10), -12.3 ± 0.8‰ (n = 10), and -12.5 ± 1.3‰ (n = 10), respectively (Table 1). Normality tests indicate that data were normally distributed. One-way ANOVA along with the post-hoc (Tukey’s HSD) test show no significant differences in δ13C values between Rhinocerotidae and Deinotheriidae (p = 0.061), whereas Suidae showed significant differences compared to Deinotheriidae (p = 0.039) and Rhinocerotidae (p = 0.041).

Stable Oxygen Isotopes.—The average δ18Oenamel (V-PDB) across all the families was -9.9 ± 3‰, wherein Suidae, Rhinocerotidae, and Deinotheriidae yiel­ded average values for δ18Oenamel of -8.2 ± 1.2‰ (n = 10), -11.4 ± 1.8‰ (n = 10), and -10.4 ± 1.7‰ (n = 10), respectively (Table 1). The data were normally distributed. One-way ANOVA along with post-hoc test indicated that the δ18Oenamel of suids is significantly different from the δ18Oenamel of rhinos and deinotheres (p = 0.041) (Table 1, Fig. 2).

Discussion

The average δ13Cenamel value of middle Miocene mammals (-12.2 ± 2‰) in our data overall indicates a diet composed of C3 vegetation, which was likely present in the form of forests and woodlands (Kohn and Cerling 2002; Kohn 2010). Patnaik et al. (2019) report the range of δ13Cenamel for large herbivores from -13.9 to -11.6‰ for middle Miocene Siwalik sub-Group of India, which matches our results. The lowest δ13Cenamel value in our results (-13.9‰) was recorded at ~13 Ma interval, whereas the highest value (-9.6‰) was recorded at ~12 Ma (Fig. 2, Table 1). This shows that the lower Chinji Formation was dominated by C3 vegetation, likely present in the form of forestland, whereas the upper Chinji was dominated by C3 open woodlands (Kohn and Cerling 2002; Kohn 2010). Thus, vegetation and habitat appear to have changed towards more open ecological settings in the upper Chinji Formation. The shift to open woodland is also apparent in the suid δ13Cenamel results, which return an estimate for suid diet of -22.7‰, assuming eenamel-diet = +13.1‰. (Kohn 2010; Cerling et al. 2015; Table 1). Moreover, the possibility of consumption of C3 grasses cannot be ruled out as extant suids in eastern Africa also consume C3 grasses but show a low-crowned dental morphology (Harris and Cerling 2002; Souron 2017).

These findings are supported by evidence presented in Quade and Cerling (1995), who reported δ13Cpaleosol carbonate values from Kamlial and Chinji formations ranging from -12.9 to -9.5‰, indicating a forestland and woodland environment. Further afield, Quade et al. (1995b) from Pasalar, Turkey, and Uno et al. (2016) from eastern Africa report the δ13C values from paleosol and ungulate enamel, respectively. Both studies report a dominance of C3 vegetation with very little or no C4 vegetation during the middle Miocene time span.

The higher δ13Cenamel values in suids compared to rhinocerotids and deinotheres indicate that this family preferred more open areas for their feeding or browsed on a leafy vegetation. Tariq (2010) reports a frugivorous component to diets in suids on the basis of mesowear analysis. The mesowear analysis coupled with the morphological features of suid teeth (bunodont teeth with thick enamel) is in agreement with the hypothesis, based upon our δ13Cenamel data, that suids of middle Miocene utilized C3 plants in open habitats, including fruits, as their dietary resource and inhabited relatively more open areas (Tariq 2010; Aslam 2018; Waseem et al. 2020b).

On the basis of average δ13Cenamel and δ18Oenamel values, we may hypothesize that middle Miocene climate was sub-humid and animals drank from shaded water holes or rivers (Sanyal et al. 2010; Tada et al. 2016). If we use the equation for MAP calculation on the basis of δ13Cdiet following Kohn (2010), we can say that in middle Miocene of the Siwalik sub-Group of Pakistan MAP was lower than ~700 mm/year (see Kohn 2010: fig. 3). The average value of δ18Oenamel (-9.9 ± 3‰) of all non-ruminant taxa is low, indicating sub-humid conditions (Fig. 2B) during the middle Miocene time span in the Siwalik sub-Group of Pakistan, which is consistent with Indian contemporaneous sites (Patnaik et al. 2019). The low δ18Oenamel values also probably indicate that in the middle Miocene, animals drank from relatively unevaporated water holes or rivers.

The δ18Oenamel and δ13Cenamel values increase gradually from ~14 Ma to ~11 Ma (Fig. 2A, B), culminating in more open environments supporting a woodland or perhaps minor C4 vegetation (0–18% cover). However, the Hyotherium pilgrimi samples show higher δ13Cenamel values in our data which may also imply that this response may be species specific. Even if we consider the values as species specific, the open ecology towards the end of middle Miocene is still supported as we consider that the studied suid species occupied more open areas similar to the late Miocene suids. However, suids in the late Miocene showed feeding in both open and closed environments (Nelson 2005, 2007).

Niche partitioning among middle Miocene mammals

The studied middle Miocene mammals show some degree of niche partitioning (Fig. 3). The deinotheres and rhinocerotids from middle Miocene of Indian Siwaliks show an average δ13Cenamel values of -12.5‰ and -12.8‰, respectively, very close to the ranges in our results for these taxa (Patnaik et al. 2019), pointing to overall similar ecological and die­tary preferences. The suids (average δ13Cenamel = -11.2 ± 1.4‰) inhabited a woodland/forestland setting where they fed on C3 vegetation consisting of plants, including fruits. They may have drunk from less shaded water holes as represented by their elevated δ18Oenamel values (-8.1‰) compared to the other middle Miocene taxa (Fig. 2B, C). The rhinocerotids and deinotheres show similarly low (p >0.05) δ13C values (-12.2‰ and -12.4‰, respectively), indicating that both families inhabited a forestland setting and browsed from understory vegetation (Fig. 2A, C), as reported by Patnaik et al. (2019) for contemporaneous Indian sites. However, the δ18Oenamel values significantly differ between these two families (-11.3 ± 1.8‰ and -10.4 ± 1.7‰; Fig. 2B). Heissig (1972, 2003) reports that middle Miocene rhinocerotids of Pakistan preferred a habitat close to water bodies and Biasatti et al. (2018) report the same behavior for middle Miocene rhinocerotids of China. Thus, we may assume that middle Miocene rhinocerotids lived in habitats close to water, resulting in the lowest δ18Oenamel values among all the middle Miocene taxa analyzed in this study. Deinotheres preferred a forested habitat where they had access to water but they did not live very close to the water bodies like rhinocerotids as indicated by the δ18Oenamel values (Fig. 3).

Conclusions

We analyzed thirty specimens belonging to three families of middle Miocene Siwalik sub-Group of Pakistan. On the basis of our results, we conclude that these middle Miocene species inhabited dense forests and woodlands where they fed on the C3 vegetation and drank from shaded water resources like ponds or rivers which were frequently refilled by precipitation (Fig. 3). We did not find clear evidence of significant C4 vegetation in their diet. The δ18Oenamel results reveal that the environment was more humid at ~14 Ma and became less humid towards the upper Chinji Formation (12–11.2 Ma). In general, the middle Miocene Siwaliks of Pakistan were dominated by forests and woodlands with precipitation supporting a more evergreen ecology as in the middle Miocene of eastern Africa, India, and Nepal and present-day vegetation of Myanmar (Quade et al. 1995a, b; Uno et al. 2016).

Acknowledgements

The authors are thankful to Antoine Souron (University of Bordeaux, France) and anonymous reviewers for their constructive commentary and very helpful comments which enhanced the quality of the manuscript. This work has been supported by the Higher Education Commission indigenous fellowship to MTW for Ph.D. studies vide pin no. 315-28107-2BS3-243. We also acknowledge the support in sample analysis from Desert Laboratory, University of Arizona, Tucson, USA.

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Acta Palaeontol. Pol. 66 (Supplement to 3): 123–132, 2021

https://doi.org/10.4202/app.00788.2020