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The spread of grasslands in the Miocene and of C4 grasses in the late Miocene-Pliocene represents a major development in terrestrial plant evolution that affected the climate system and faunal evolution. The macrofossil record of grasses is sparse, likely due to the limited preservation potential of grasses. Diagnosis of the C3 or C4 photosynthetic pathway depends on preservation of both cellular structures and organic carbon for isotope analysis. Here we analyze the anatomical and isotopic composition of newly-collected grass fossils from the Dove Spring Formation, Red Rock Canyon State Park, California, USA, located in the El Paso Basin on the western side of the Basin and Range Province, a site previously identified as one of the earliest known C4 grass fossil bearing localities. We analyzed the anatomical and geochemical characteristics of these new grass fossils dated to 12.01–12.15 Ma. The fossils analyzed in this study include grass shoots and in cross-section display anatomy indicative of the C3 photosynthetic pathway. We isolated organic carbon from the stem fossils and determined the carbon isotopic composition to be − 24.8 ± 0.5‰. Together, the anatomical and geochemical analyses confirm that these plants used the C3 photosynthetic pathway. Our findings are consistent with dietary evidence based on tooth enamel from grazing mammals of available C3 resources in the same sections. These newly reported Miocene-age C3 grass fossils contribute to a sparse macrofossil record of grass evolution. Overall, paleoecological reconstructions at this site indicate more humid conditions during the Miocene compared to the modern Mojave Desert with C3 grasses and diverse grazing mammals.

The stable carbon isotope ratios of tooth enamel from 89 herbivores from the Dove Spring Formation (DSF) of the El Paso Basin, western Mojave Desert, California, were analyzed to determine if C4plants may have been present in the late Miocene of southern California. Taxa analyzed include antilocaprids, castorids, camelids, equids, gomphotheriids, merycoidodontids, and rhinocerotids. The atmospheric CO2-δ13C value has varied significantly in the geologic past, leading to changes in the δ13C values of plants and tooth enamel. The estimated δ13C value of atmospheric CO2in the middle to late Miocene is −5.8±0.2‰, making the pure C3diet cutoff value higher than the modern by ~2‰. Given this, much of the evidence of an early spread of C4, which inappropriately uses the modern C3diet cutoff value, may be a false signal from water-stressed C3plants and the amount of C4biomass in the geologic past may have been over-estimated. The enamel-δ13C values of all taxa sampled are −10.1±1.1‰ (n=89). Accounting for the changes in the δ13C values of atmospheric CO2, enamel-δ13C values from the DSF indicate that herbivores from that area had C3diets and lived in an environment dominated by C3plants. Serial enamel isotope data from the DSF revealed negligible intra-tooth variations in the δ13C values, confirming that these herbivores consumed C3plants year-round. If the C4photosynthetic pathway did spread to southern California prior to the rapid, global rise in C4in the late Miocene, the taxa sampled did not incorporate C4biomass into their diets. The results of the stable carbon isotope analysis, along with the evidence from the rock record and the life habits of the fossil taxa present, indicate that the El Paso Basin consisted of diverse habitats including C3grasslands, wooded C3grasslands, and riparian forests.

DeSantis et al. respond to the concerns raised by Van Valkenburgh et al. on their original study.

Author(s): Fox, Nathaniel S.; Takeuchi, Gary T.; Farrell, Aisling B.; Blois, Jessica L. | Abstract: Leporid remains are common in Quaternary fossil assemblages and are useful paleoenvironmental indicators. Identifying leporid fossils to species is challenging, though previous work has shown that identifications are more feasible if fossils can be narrowed down to a subset of potential species occurring across limited spatial scales. We sampled 120 adult and nine juvenile dentaries of six extant western North American species (Lepus americanus, L. californicus, L. townsendii, Sylvilagus audubonii, S. bachmani, and S. nuttallii) to establish useful characters for genus and species-level identification of late Quaternary leporid fossils in California. Most individuals can be differentiated from individuals of other species using a combination of lower third premolar enamel folding patterns and dental measurements. However, it is difficult to discriminate dental elements among L. californicus and L. townsendii and elements of S. nuttallii from S. audubonii, S. bachmani, and L. americanus. Here we present criteria for differentiating western leporid dental remains, apply the criteria to identify specimens recovered from several late Quaternary fossil deposits at Rancho La Brea (RLB), California, collectively known as Project 23, and reconstruct changes in relative fossil leporid abundances there. Using our criteria, we identified two extant species, S. audubonii and S. bachmani, among the Project 23 fossils. In addition to relative abundance changes across several RLB deposits, S. audubonii and S. bachmani generally become larger through time, possibly in response to local environmental changes. Establishing region-specific identification criteria as done here may prove useful for discerning morphologically similar species at prehistoric sites elsewhere.

We radiocarbon dated the domestic dog found associated with La Brea Woman at the Rancho La Brea tar pits (Los Angeles, CA) to determine the validity of this human–dog connection. The domestic dog yielded a radiocarbon age of 3125 ± 25 14C yr BP (3250–3400 cal yr BP) and La Brea Woman had a re-dated age of 9080 ± 15 14C yr BP (10,220–10,250 cal yr BP). This ∼7000-year offset dispels the hypothesis this was an intentional and ceremonial human–dog burial.

Due to its lofty height, the Tibetan Plateau features some of the harshest environments in the world with extreme coldness, low oxygen, high UV radiation, and in places, severe aridity. These harsh environments have served as the main driver of vertebrate evolution during the Cenozoic that produced a low productivity, low diversity, high endemicity community — environmental forcing seems to be a dominant mechanism for mammalian evolution in marginal habitats. Mammals have acquired special adaptations for thermal insulation, oxygen transport, DNA damage repair, and others. While broadly similar to faunal assemblages in North China and Central Asia, Tibetan faunas often show initiation of cold-adapted lineages that predate Ice Age megafauna. Our “out of Tibet” hypothesis thus postulates that cold-tolerant species in Pliocene high Tibet were pre-adapted to conditions that were to become widespread during the subsequent Pleistocene Ice Age and Tibet had thus become a cradle for Ice Age megafauna. The best examples of the “out of Tibet” scenario include the Tibetan woolly rhinoceros (Coelodonta thibetana), Tibetan bharal (Pseudois), Asian hunting dog (Sinicuon), and ancestral snow leopard (Panthera blytheae). Our “Third Pole to North Pole” linkage of an extinct Pliocene Tibetan fox, Vulpes qiuzhudingi, with the late Pleistocene and extant arctic fox, Vulpes lagopus, is a subset of the “out of Tibet” hypothesis. One of the iconic Tibetan mammals, the endemic Tibetan antelope (Pantholops) has the longest residence in Tibet going back to the late Miocene, suggesting a long history of perfecting its adaptations to cold environments. Stable carbon and oxygen isotope analyses of fossils from the Tibetan Plateau reveal significant spatial and temporal variations in the evolution of herbivores' diets and environments during the late Cenozoic. The diets of modern Tibetan herbivores consist primarily of C3 plants, reflecting the present-day C3 dominance in high-elevation cold habitats. The available carbon isotope data, however, show that warm-climate C4 grasses were a significant dietary component of ancient herbivores in the Gyirong Basin (central Himalayas) in the late Miocene and in Shangri-La (southeastern Tibetan Plateau) in the Pliocene, and likely in the Qaidam Basin (NE Tibetan Plateau) from late Miocene to early Pliocene and in Kunlun Pass Basin (northeastern Tibetan Plateau) in the Pliocene. This suggests that C4 grasses spread into the Tibetan Plateau in the late Miocene and had persisted in some places to early Pleistocene, but have since disappeared or become insignificant in the region. The retreat of C4 grasses from the Tibetan Plateau is most likely driven by decreases in local temperatures to below the cross-over temperature unfavorable to C4 grasses, as a result of tectonic uplift and/or global climate change. The available isotope data also show that high-elevation cold climatic conditions that favor C3 over C4 grasses arrived earlier in southwestern Tibetan Plateau than in southeastern and northeastern parts of the plateau. This would imply that the Tibetan Plateau had not uniformly reached its present height as recent as early Pleistocene. Future research should focus on determining intra-regional patterns of ecological and climatic changes in order to tease apart the effects of tectonic uplift and global climate change on local and regional environmental changes and to better understand the linkage between tectonics and climatic and biotic changes.

Summary The fossils preserved in the Rancho La Brea “tar” seeps in southern California span the past ∼50,000 years and provide a rare opportunity to assess the ecology of predators (e.g., the American lion, sabertooth cats, cougars, dire wolves, gray wolves, and coyotes), including clarifying the causes and consequences of the terminal Pleistocene extinction event. Here, a multi-proxy approach elucidates dietary responses of carnivorans to changing climates and megafaunal extinctions. Using sample sizes that are unavailable anywhere else in the world, including hundreds of carnivoran and herbivore specimens, we clarify the paleobiology of the extinct sabertooth cats and dire wolves—overturning the idea that they heavily competed for similar prey. Canids (especially the dire wolf) consumed prey from more open environments than felids, demonstrating minimal competition for prey throughout the latest Pleistocene and largely irrespective of changing climates, including just prior to their extinction. Coyotes experienced a dramatic shift in dietary behavior toward increased carcass utilization and the consumption of forest resources (prey and/or plant resources) after the terminal Pleistocene megafaunal extinction. Extant predators’ ability to effectively hunt smaller prey and/or utilize carcasses may have been a key to their survival, especially after a significant reduction in megafaunal prey resources. Collectively, these data suggest that dietary niches of carnivorans are not always static and can instead be substantially affected by the removal of top predators and abundant prey resources.

article i nfo The Pliocene (5.3-2.6 Ma) of Tibet witnessed the drying of the northern Tibetan Plateau and the approach to the Pleistocene Ice Age within the background of intensifying Indian and East Asian monsoons. Yet little is known about Pliocene mammals living on the high Tibetan Plateau despite the fact that fossil mammals elsewhere consti- tute an important knowledge base for terrestrial environments. The late Miocene to Pleistocene Zanda Basin at the northern foothills of the Himalayas affords a welcome opportunity to evaluate the biological response to environ- mental change at high elevations. Abundant, well-preserved fossil mammals and fish from an 800-m continuous section of fine- to coarse-grained sediments thus open a rare window into a past biological world. For example, the discovery of an ancestral wooly rhino from Zanda Basin that was the precursor of its late Pleistocene megafaunal descendants leads to our "out-of Tibet" hypothesis, suggesting that the high Tibetan Plateau was a Pliocene cradle for Ice Age cold adaptations. In this paper, we document in detail the mammalian biostratigraphy, chronology, and paleozoogeography based on Zanda Basin fossil mammals. Our high-resolution biostratigraphy and biochronology offer for the first time independent constraints that both support and modify recent magnetostratigraphic correlations. Using charac- teristic Pliocene and Pleistocene mammals, particularly the small mammal assemblages in the lower part of the section and monodactylid Equus from the upper section, we propose a correlation to C1n to C3An.1r, with an age range of ~400 Ka to 6.4 Ma. Within the 800-m Zanda section, the lower 0-150 m is of latest Miocene age, spanning 6.4-5.3 Ma. Sparsely fos- siliferous, the lower section has produced five taxa so far: Ochotona, Panthera, Qurliqnoria, Palaeotragus ,a nd Hipparion—all are consistent with a late Miocene age. The middle 150-620 m section spans the entire Pliocene. This section is by far the most fossiliferous, including such typical Pliocene small mammals as Prosiphneus, Mimomys, Apodemus ,a ndTrischizolagus, as well as large mammals such as Coelodonta thibetana, Hipparion zandaense, Chasmaporthetes, Nyctereutes, Meles, Antilospira, and others. In the upper 620-800 m section the fos- sils are rare, but do include characteristic Pleistocene taxa such as Equus. Zoogeographically Zanda Basin mammals are a mixture from two major sources. Taxa such as Mimomys, Prosiphneus, Trischizolagus, Chasmaporthetes, Nyctereutes, Meles ,a ndXenocyon are commonly found in north China or east Asia. In contrast, several forms, such as unique species of pikas (Ochotona), squirrels (Aepyosciurus), and ancestral Tibetan antelope (Qurliqnoria), seem to belong to an indigenous Tibetan fauna evolved within the plateau. A lack of shared taxa with the Oriental Realm suggests a formidable barrierby the Himalayas despite a short distance (~100 km) between Zanda Basin and the Indian subcontinent.

The timing history and driving mechanisms of C4 expansion and Tibetan uplift are hotly debated issues. Paleoenvironmental evidence from within the Tibetan Plateau is essential to help resolve these issues. Here we report results of stable C and O isotope analyses of tooth enamel samples from a variety of late Cenozoic mammals, including deer, giraffe, horse, rhino, and elephant, from the Qaidam Basin in the northeastern Tibetan Plateau. The enamel-delta C-13 values are < -89 parts per thousand for modern samples and

All previous records of the lamniform shark, Archaeolamna kopingensis, are based on isolated teeth. Here we describe a partial skeleton from the Sharon Springs Formation of the Pierre Shale Group of western Kansas, U.S.A. The specimen includes portions of the upper and lower jaws with articulated teeth. The dentition consists of two files of upper and lower anterior teeth that, together with a single file of intrabullar intermediate teeth, are housed in a dental bulla, as well as multiple files of lateral teeth, along with at least two files of lower symphysial teeth and a single file of upper symphysial teeth. The intrabullar intermediate tooth is slightly shorter than the other anterior teeth and has a median cusp with distinctive distal curvature. The dental sequence of A. kopingensis is unique among both extinct and extant lamniforms. Associated with the jaws are fragments of the neurocranium and multiple vertebral centra. A sagittal section through a centrum shows that this shark deposited 1...

Fossil ceratioid anglerfishes are described from the Upper Miocene (upper Mohnian) deposits of the Puente Formation, Los Angeles Basin, California. The specimens were collected from the laminated turbiditic deposits of the Yorba Member in the eastern sector of the Los Angeles Basin during the construction of a new metro rail line. Five taxa (Borophrynecf.apogon; Chaenophryneaff.melanorhabdus; Leptacanthichthyscf.gracilispinis; Linophrynecf.indica; Oneirodessp.) belonging to two families, Linophrynidae and Oneirodidae, are described based on nine metamorphosed females. A detailed osteological analysis of the fossils has revealed that they can be tentatively assigned to extant species, suggesting that little or no relevant morphological change has characterized these taxa at least since the Late Miocene. Biogeographic considerations suggest that the Late Miocene ceratioid assemblages of the Los Angeles Basin are strikingly similar to those that currently inhabit the tropical and subtropical eastern Pacific region. From a paleoenvironmental point of view, the excellent preservation of the specimens suggests a reduced turbulence and velocity of the turbidity fluxes. Finally, the comparative study of the bathymetric ranges of the ceratioid taxa recognized in the fossil assemblage described in this paper suggests that the minimum depth of the depositional environment might be estimated at approximately 1,000 m.

A new species of early Miocene croaker of the genus Pogonias (Perciformes: Sciaenidae) from the marine upper Olcese Sand, southeastern San Joaquin Valley, Kern County, California is described based on saccular ( = sagittae) otoliths. This is the first fossil record of the genus Pogonias from the eastern Pacific Rim. It is hypothesized that this new species of Pogonias or its ancestor emigrated from the Gulf Stream of the western Atlantic into the eastern Pacific via the Panama seaway during or prior to the late early Miocene.

Qaidam Basin is the largest terrestrial basin of the Tibetan Plateau and has the most continuous sedimentary record in the Cenozoic. Although constituting the first known fossil vertebrates of the Tibetan Plateau and discovered in early scientific expeditions in the 1930s, mammalian fossils from Qaidam Basin have not played a significant role in studying the basin stratigraphy. Our explorations in the Qaidam Basin during the past 8 years have resulted in the first well documented collection of fossil vertebrates from there. In addition to being the best organisms for terrestrial biostratigraphy in the Cenozoic, the new fossil vertebrates offer a unique window into the ancient biotas that chronicle the late Cenozoic uplift of the plateau and associated environmental changes. Here we establish for the first time a faunal sequence of early Oligocene to early Pliocene age. Four mammalian faunas are recognized: Olongbuluk Mammal Fauna (middle Miocene), Tuosu Mammal Fauna (early late Miocene), Shengou Mammal Fauna (early late Miocene), and Huaitoutala Mammal Fauna (early Pliocene). All four mammal faunas can be directly or indirectly tied to a paleomagnetic section in the Olongbuluk–Huaitoutala area, permitting robust calibration of the chronology of these faunas. At least four fish faunas are also found: Lulehe Fish Fauna (late early to early late Oligocene), Shengou Fish Fauna (early late Miocene), Eboliang Fish Fauna (late late Miocene to early Pliocene), and Yahu Fish Fauna (early Pliocene). The fish faunas represent the only records of their respective times in the Tibetan Plateau and thus by themselves cannot be used for age determination. However, these fish faunas are either integrated into paleomagnetic sections or directly tied to mammal faunas of known ages, permitting independent assessment of their chronology. Zoogeographically, Qaidam mammal faunas show increasing endemism through time, presumably related to topographic barriers formed by the growth and uplift of the Tibetan Plateau and to climatic changes triggered by the same tectonic process. Fishes that were trapped in internally drained basins developed pachyostotic morphologies caused by hypersaline environments, which are associated with the increasing aridity of the Tibetan Plateau since early Pliocene.

A new species of the genus Totoaba (family Sciaenidae) based upon otoliths from the late early Miocene marine upper Olcese Sand, Kern County, southern San Joaquin Valley, California is described. This is the first fossil occurrence for the genus, and it is hypothesized that Totoaba evolved entirely in the eastern Pacific realm. Within the upper Olcese Sand, this species represents but one component of a complex sciaenid fauna, which could provide insight into the evolution and distribution of the family Sciaenidae. An ontogenetic series of this species is defined, and ontogenetic changes in its otoliths are discussed.

A new species of sciaenid, Seriphus lavenbergi sp. nov., is described from the late Miocene Yorba Member of the Puente Formation, southern California. The holotype is represented by an incomplete disarticulated skull with the right saccular (= sagitta) otolith in situ, an extremely rare occurrence. This is the earliest known geological occurrence of Seriphus and represents a second species within the genus. It is hypothesized that the ancestor of Seriphus emigrated from the Gulf Stream of the Atlantic into the Pacific via the Panama Seaway and the genus evolved entirely in the eastern Pacific.

We describe an associated skull and lower jaws of a new species of primitive skunk, Martinogale (subfamily Mephitinae), from the late Miocene Dove Spring Formation (late Clarendonian), Kern County, California. It is also the first occurrence of this genus in the Tertiary of the West Coast of North America. The new species is among the best-preserved primitive fossil skunks and represents one of the earliest members of the New World mephitines. As the smallest skunk so far known, the new Martinogale features some of the most primitive cranial and dental morphologies in mephitines. The new information permits a phylogenetic analysis of basal taxa from North America, which suggests a New World clade for all known fossil and living taxa from North and South America. We place this New World clade in a tribe (Mephitini) of its own. New World mephitines share the following derived characters: presence of a P4 parastyle, m1 hypoconid dominant in talonid, and presence of a lingual cingulum on lower canines. We further postulate that New World skunks are the result of a single immigration event, and the new California skunk is close to the origin of the New World skunks.

International audience; The Kunlun Pass Basin, at the foothill of Yuzhu Mountain (6224 m asl and the highest peak of the Kunlun Range), records Plio-Pleistocene fine-grained sediments sandwiched between glacial moraines. We document a new vertebrate fossil assemblage, the Yuzhu Fauna, with 16 mammal and 2 fish species that provide insights into basin chronology as well as the paleoenvironment adjacent to alpine glaciations in the Pliocene, in which the mammals and fishes lived. The Yuzhu Fauna consists of the following eight small mammals: Petenyia sp., Aepyosciurus sp., Nannocricetus mongolicus, cf. Orientalomys sinensis, Mimomys n. sp., Prosiphneus cf. P. eriksoni, Ochotona minor, Ochotona cf. O. lagreli, and eight large mammals: Rhinocerotidae indet., Hipparion (Proboscidipparion) pater, Qurliqnoria sp., Bovidae indet., cf. Panthera blytheae, Hyaeninae indet., Vulpes qiuzhudingi, and aff. Arctomeles sp. Two cyprinid fishes are also included: Gymnocypris sp. and Triplophysa sp. The Yuzhu Fauna has a distinctly early–middle Pliocene appearance, substantially earlier than previous age estimates, sharing broad similarities with vertebrate fossil assemblages from North China in general and the Zanda Fauna in southern Tibet in particular, including three carnivorans (Vulpes qiuzhudingi, cf. Panthera blytheae, and aff. Arctomeles sp.), one artiodactyl (Qurliqnoria), and at least two rodents (Aepyosciurus and Prosiphneus) and a lagomorph (Ochotona). We re-interpret published magnetostratigraphy to arrive at a correlation of the Yuzhu Fauna to the lower part of Chron 2Ar (Gilbert Chron 4.2–3.6 Ma), and the entire basin sequence spanning part of chrons 1n through 3n.3n, i.e., ~ 4.9–0.5 Ma. Our revised magnetic age for the Kunlun Pass Basin strata implies a slip rate of 7.2–6.1 mm/year along this part of the Kunlun Pass strike-slip fault system, much slower than its modern rate of off set.

The ‘third pole’ of the world is a fitting metaphor for the Himalayan–Tibetan Plateau, in allusion to its vast frozen terrain, rivalling the Arctic and Antarctic, at high altitude but low latitude. Living Tibetan and arctic mammals share adaptations to freezing temperatures such as long and thick winter fur in arctic muskox and Tibetan yak, and for carnivorans, a more predatory niche. Here, we report, to our knowledge, the first evolutionary link between an Early Pliocene (3.60–5.08 Myr ago) fox, Vulpes qiuzhudingi new species, from the Himalaya (Zanda Basin) and Kunlun Mountain (Kunlun Pass Basin) and the modern arctic fox Vulpes lagopus in the polar region. A highly hypercarnivorous dentition of the new fox bears a striking resemblance to that of V. lagopus and substantially predates the previous oldest records of the arctic fox by 3–4 Myr. The low latitude, high-altitude Tibetan Plateau is separated from the nearest modern arctic fox geographical range by at least 2000 km. The apparent connection between an ancestral high-elevation species and its modern polar descendant is consistent with our ‘Out-of-Tibet’ hypothesis postulating that high-altitude Tibet was a training ground for cold-environment adaptations well before the start of the Ice Age.

Pantherine felids (‘big cats’) include the largest living cats, apex predators in their respective ecosystems. They are also the earliest diverging living cat lineage, and thus are important for understanding the evolution of all subsequent felid groups. Although the oldest pantherine fossils occur in Africa, molecular phylogenies point to Asia as their region of origin. This paradox cannot be reconciled using current knowledge, mainly because early big cat fossils are exceedingly rare and fragmentary. Here, we report the discovery of a fossil pantherine from the Tibetan Himalaya, with an age of Late Miocene–Early Pliocene, replacing African records as the oldest pantherine. A ‘total evidence’ phylogenetic analysis of pantherines indicates that the new cat is closely related to the snow leopard and exhibits intermediate characteristics on the evolutionary line to the largest cats. Historical biogeographic models provide robust support for the Asian origin of pantherines. The combined analyses indicate that 75% of the divergence events in the pantherine lineage extended back to the Miocene, up to 7 Myr earlier than previously estimated. The deeper evolutionary origin of big cats revealed by the new fossils and analyses indicate a close association between Tibetan Plateau uplift and diversification of the earliest living cats.

The Tibetan Plateau is the youngest and highest plateau on Earth, and its elevation reaches one-third of the height of the troposphere, with profound dynamic and thermal effects on atmospheric circulation and climate. The uplift of the Tibetan Plateau was an important factor of global climate change during the late Cenozoic and strongly influenced the development of the Asian monsoon system. However, there have been heated debates about the history and process of Tibetan Plateau uplift, especially the paleo-altimetry in different geological ages. Here we report a well-preserved skeleton of a 4.6 million-y-old three-toed horse ( Hipparion zandaense ) from the Zanda Basin, southwestern Tibet. Morphological features indicate that H. zandaense was a cursorial horse that lived in alpine steppe habitats. Because this open landscape would be situated above the timberline on the steep southern margin of the Tibetan Plateau, the elevation of the Zanda Basin at 4.6 Ma was estimated to be ∼4,000 m above sea level using an adjustment to the paleo-temperature in the middle Pliocene, as well as comparison with modern vegetation vertical zones. Thus, we conclude that the southwestern Tibetan Plateau achieved the present-day elevation in the mid-Pliocene.

Ice Age megafauna have long been known to be associated with global cooling during the Pleistocene, and their adaptations to cold environments, such as large body size, long hair, and snow-sweeping structures, are best exemplified by the woolly mammoths and woolly rhinos. These traits were assumed to have evolved as a response to the ice sheet expansion. We report a new Pliocene mammal assemblage from a high-altitude basin in the western Himalayas, including a primitive woolly rhino. These new Tibetan fossils suggest that some megaherbivores first evolved in Tibet before the beginning of the Ice Age. The cold winters in high Tibet served as a habituation ground for the megaherbivores, which became preadapted for the Ice Age, successfully expanding to the Eurasian mammoth steppe.

A mid-Pliocene fauna (4.2–3.1 Ma) was recently uncovered in the Zanda (Zhada) Basin in the southwestern Himalaya, at an elevation of about 4200 m above sea level. These fossil materials provide a unique window for examining the linkage among tectonic, climatic and biotic changes. Here we report the results from isotopic analyses of this fauna and of modern herbivores and waters as well as paleo-temperature estimates from the Zanda Basin. The δ13C values of enamel samples from modern wild Tibetan asses, and domesticated horses, cows and goats in the area are −9.4±1.8‰, which indicate a diet comprising predominantly of C3 plants and are consistent with the current dominance of C3 vegetation in the region. The enamel-δ13C values of the fossil horses, rhinos, deer, and bovids are −9.6±0.8‰, indicating that these ancient mammals, like modern herbivores in the area, also fed primarily on C3 vegetation and lived in an environment dominated by C3 plants. The lack of significant C4 plants in the basin suggests that the area had reached high elevations (>2.5 km) by at least the mid-Pliocene. Taking into account the changes in the δ13C of atmospheric CO2 in the past, the enamel-δ13C values suggest that the average modern-equivalent δ13C value of C3 vegetation in the Zanda Basin in the mid-Pliocene was ∼1–2‰ lower than that of the C3 biomass in the basin today. This would imply a reduction in annual precipitation by about 200–400 mm in the area since then (assuming that the modern C3δ13C–precipitation relationship applied to the past). Consistent with this inference from the δ13C data, the enamel-δ18O data show a significant shift to higher values after the mid-Pliocene, which also suggests a shift in climate to much drier conditions after ∼4–3 Ma.Paleo-temperature estimates derived from a fossil bone-based oxygen isotope temperature proxy as well as the carbonate clumped isotope thermometer for the mid-Pliocene Zanda Basin are higher than the present-day mean annual temperature in the area. After accounting for late Cenozoic global cooling, these paleo-temperature estimates suggest that the paleo-elevation of the Zanda Basin in the mid-Pliocene was similar to or slightly (less than ∼1 km) lower than its present-day elevation, which is consistent with the inference from the δ13C data.