Large Mammal Fossils Research Articles

Mammalian faunal change of the Miocene Dove Spring Formation, Mojave region, southern California, USA, in relation to tectonic history

Tectonic processes drive the evolution of basins through local and regional changes in topographic relief, which have long-term effects on mammalian richness and distribution. Mammals respond to the resulting changes in landscape and climate through evolution, shifts in geographic range, and by altering their community composition. Here, we evaluate the relationship between tectonic episodes and the diversification history of fossil mammals in the Miocene Dove Spring Formation (12.5−8.5 Ma) of southern California, USA. This formation contains a rich fossil record of mammals and other vertebrates as well as structural and sedimentological evidence for tectonic episodes of basin extension, rotation, and translation. We used several methods to compare the fossil record to the tectonic history of the Dove Spring Formation. We updated the formation’s geochronology to incorporate current radiometric dating standards and measured additional stratigraphic sections to refine the temporal resolution of large mammal (>1 kg) fossil localities to 200-kyr (or shorter) intervals. Observed species richness over time follows the same trend as the number of localities and specimens, suggesting that richness reflects sampling intensity. Estimates of stratigraphic ranges with 80% confidence intervals were used to conduct per capita diversification analysis and a likelihood approach to changes in faunal composition from one time interval to the next. While edge effects influence time bins at the beginning and end of the study interval, we found changes in diversification rates and faunal composition that are not solely linked to preservation. Several rare species appear at 10.5 Ma and persist through the top of the formation despite variable preservation rates. Changes in faunal composition at 12.1 Ma and 10.5 Ma are not associated with elevated preservation rates, which indicates that some faunal changes are not primarily driven by sampling effort. The lower portion of the formation is characterized by high origination rates and long residence times. The upper portion has high per capita extinction rates that increased in magnitude as basin rotation and translation progressed from 10.5 Ma. The greatest change in faunal composition coincided with basin rotation and translation that interrupted a long-running extensional period. Tectonics played key roles in the diversity of mammals by determining fossil productivity and shaping the landscapes that they inhabited.

Rhinocerotoid fossils of the Linxia Basin in northwestern China as late Cenozoic biostratigraphic markers

This study reports on rhinocerotoid fossils from the Oligocene-Pleistocene strata of the Linxia Basin of Gansu Province, northwestern China. Rhinoceroses have been important components of mammalian faunas of these beds, and include the Late Oligocene giant rhinos (paraceratheres) and the Late Miocene hornless rhinos (aceratheres). As a result of their high diversity, wide geographical distribution and rapid evolution, rhinoceroses are good markers for stratigraphic division and may be used for intercontinental correlations. The Late Oligocene fauna of the Linxia Basin occurs in the lower part of the Jiaozigou Formation. Among 12 species of large mammal fossils, nine are of the superfamily Rhinocerotoidea, and giant rhinos are dominant. Rhinoceroses of the Middle Miocene fauna reflect a forest environment. Comparison with contemporaneous European rhinoceroses suggests a dispersal route for populations along the north side of the Tibetan Plateau. Rhinoceroses were most abundant in the Linxia Basin in the Late Miocene times. The most primitive species of the genus Chilotherium and the huge elasmotheres are key indicators for the base of the Upper Miocene (Tortonian). From the Late Miocene to Early Pliocene, the assemblages of the three-toed horse Hipparion comprise five horizons, each of which has different rhinocerotid fossils as markers of division and correlation. Because of the strong competition by ruminants, rhinoceroses declined greatly in the Early Pleistocene fauna. At that time, only a species of the woolly rhino persisted, but as an intermediate form, Coelodonta nihowanensis of the Linxia Basin can still connect the Pliocene Zanda Basin of the Tibetan Plateau and the Early Pleistocene Nihewan Basin of the North China Plain.

Using historical research to constrain the provenance and age of the first recorded collection of extinct Pleistocene large mammal fossils from the Naracoorte Caves, South Australia

ABSTRACT Fossil collections housed in museums are a rich source of data for palaeontologists; however, some early collections lack detailed contextual information. The Naracoorte Caves in South Australia contain World Heritage listed Quaternary vertebrate fossil accumulations, particularly those of large, extinct mammals. The first recorded collection of extinct Pleistocene large mammal fossils from Naracoorte was from Specimen Cave in 1908. Unfortunately, these fossils were collected without stratigraphic and contextual information and so lack the detail required to relate them and their provenance to new excavations in the cave. As a result, the scientific value of this fossil collection is greatly reduced. Here we report on our research into the history of fossil collecting in Specimen Cave and recover information on the stratigraphic provenance and age of the 1908 fossil collection. We analysed newspaper articles, reports, written correspondence and cave inscriptions. Our research confirmed that the 1908 collection originated from the same area as the modern excavation and revealed a history of exploration and excavation work within the cave. Our research also led to the discovery of a cave inscription that contains the name of William Reddan, an important historical figure of the Naracoorte Caves and the first person to report the Specimen Cave fossil material. These findings place the 1908 fossil collection within the current geochronological context for the site and greatly increase the scientific value of this important material.

Mud redeposition during river incision as a factor affecting authigenic 10Be/9Be dating: Early Pleistocene large mammal fossil‐bearing site Nová Vieska, eastern Danube Basin

ABSTRACTThis study examines the suitability of the authigenic 10Be/9Be dating method to the dating of the deposits of an incising river, taking as an example the Nová Vieska river terrace, which accumulated during the neotectonic inversion of the Danube Basin (western Slovakia). The succession was formed by a wandering river with minor preservation of proximal floodplain muds. The frequent occurrence of mud intraclasts reflects significant input of eroded material from underlying, older successions. The ages of 13 authigenic 10Be/9Be dating samples formed three groups: (1) samples from below the base of the river terrace yielded dates of ~4.13–3.70 Ma (including uncertainties); (2) muddy intraclasts from the river terrace gave an age range of ~2.79–1.96 Ma; and (3) in situ muddy layers had ages in the range of ~1.91–1.39 Ma. The large mammal fossil assemblage from channel thalweg deposits yielded a biostratigraphic age of ~3.6–2.2 Ma, matching the age of intraclasts, and thus emphasising the redeposited origin of those fossils. The relatively wide range of authigenic 10Be/9Be dating ages is interpreted as a result of the redeposition of mud from older strata on three scales: decimetre‐scale intraclasts, millimetre‐scale rip‐up clasts mixed into the newly formed beds, and formation of two authigenic rims with different age and 10Be/9Be records around individual particles. Considering these observations, an age range of in situ layers of ~1.91–1.39 Ma is proposed as the depositional age of the river terrace, with the most probable age falling within the most recent part of this interval. The effect of redeposition is thus shown to be potentially limiting to the application of authigenic 10Be/9Be dating to incising rivers, and stands in marked contrast to aggrading river settings, where redeposition of older sediments is limited and the degree of 10Be/9Be variability is low.

Extended-range luminescence chronologies for the Middle Pleistocene units at the Sima del Elefante archaeological site (Sierra de Atapuerca, Burgos, Spain)

The Sima del Elefante site is located within the Sierra de Atapuerca karst system (Burgos, northern Spain), and forms part of a series of important Early, Middle and Late Pleistocene archaeological complexes that have been dated previously with luminescence techniques (Gran Dolina, Galería Complex, Sima de los Huesos, Galería de las Estatuas). This study focuses on the upper Middle Pleistocene units (TE18 and TE19) at Sima del Elefante, which contain Acheulean and transitional lithic assemblages (Mode 2/3), as well as large and small mammal fossils. Importantly, these uppermost units are associated with a sediment plug located in the cave's interior at Galería Baja, which marks the closure of a significant palaeoentrance to the Atapuerca karst system. Establishing the accumulation history of these related deposits is important for understanding both Lower Palaeolithic technological dynamics via comparisons with similar levels at other Atapuerca sites (i.e., Gran Dolina and Galería Complex), as well as past human occupation patterns and carnivore use of (and accessibility to) the caves. We present single-grain TT-OSL and multi-grain pIR-IR chronologies for the Sima del Elefante upper sequence and the Galería Baja sediment cone, as well as U-series dating results for a stalagmitic crust capping the combined clastic infill sequence. The paired luminescence ages for the upper occupation levels are in agreement with each other and reveal that the host deposits accumulated 576–481 ka for the TE18 stratified scree layers, 266–237 ka for TE19 and 206–250 ka for the Galería Baja upper cone section (weighted mean 2σ age ranges). A concordant U-series age of 202 ± 65 ka is obtained for the overlying stalagmitic crust at Galería Baja. The Sima del Elefante ages are consistent with those previously obtained using U-series and biochronology, confirming that there is an erosional unconformity and complex carbonate deposition phase associated with the upper layers of unit TE18 and that the original cave entrance likely closed by ∼200 ka. Chronological correlation with other Atapuerca sites reveals potential equivalence between TE18 and unit TD8 (at Gran Dolina), and between TE19 and units GIIb–GIIIb (at Galería Complex) and, possibly, TD10.1 and TD10.2 (at Gran Dolina), though more refined dating is required to confirm the latter.

Geology and Quaternary environments of the Tategahana Paleolithic site in Nojiri-ko (Lake Nojiri), Nagano, central Japan

Excavation of the Tategahana Paleolithic site at Nojiri-ko (Lake Nojiri), central Japan, began in 1962, and the 21st excavation was performed in 2014. The Upper Pleistocene to Holocene fluvio-lacustrin Nojiri-ko Formation is distributed in and around Nojiri-ko. Fossils such as those of Naumann's elephant (Palaeoloxodon naumanni) and Yabe's giant deer (Sinomegaceros yabei), representing the ice age in Japan, have been excavated there in large quantities; at least 46 Naumann's elephants have been found. The fossils have been excavated in strata dating to 37.9–60.4 ka, comparable to MIS 3. Analysis of fossil pollen assemblages indicates that the vegetation at the time was a mixture of coniferous and broad-leaved trees. Bone instruments and spiral flakes made from elephant and deer bones, and stone tools created from stone, not found in the peripheral region, have been excavated from the Nojiri-ko Formation, and concentrated clusters of different types of fossilized elephant bones have been found.The top horizon containing elephant remains is 37.9 ka old, and thus older than MIS 2 (the Last Glacial Maximum), making it unlikely that Naumann's elephant disappeared from Nojiri-ko only because of climatic cooling. Findings strongly suggest that the occurrence of these large mammal fossils is the result of human activity. The Tategahana Paleolithic site provides important insights into the transitional phase from Asian Paleanthropine to Homo sapiens in Japan.

The palaeoenvironment of the middle Miocene pliopithecid locality in Damiao, Inner Mongolia, China

Damiao, Inner Mongolia, has three main fossil horizons representing the early, middle, and late Miocene. The middle Miocene locality DM01 is the only primate locality from the region and also represents the latest occurrence of pliopithecoids in northern China. The presence of pliopithecoid primates in central Asia after the middle Miocene climatic optimum seems to contradict the general trend of strengthening climatic zonality and increasing aridity. To investigate this enigma, we employ faunal similarity, ecometrics, and stable isotope analysis. Our results support previous inferences concerning the presence of locally humid environments within the increasingly arid surroundings that characterized central Asia. Hypsodonty, estimated mean annual precipitation (MAP), local sedimentology, and large mammal fossils suggest more humid and possibly more forested and wooded environments for the DM01 locality. We compared our results with the adjacent fossil-rich middle Miocene Tunggur localities. However, the small mammal fauna and isotope data are consistent with a mosaic of forest and grassland environment for all Damiao localities. Based on our results, Tunggur may have been too seasonal or not sufficiently humid for pliopithecids. This is supported by the higher mean hypsodonty and lower estimated MAP estimates, as well as slightly higher δ13C values. We suggest that DM01, the driest known Asian pliopithecid locality, may have been a more humid refugium within a generally drier regional context.

Gavkosh – a new locality yielding large mammal fossils in the Bakhtiari Formation in Lorestan Province, Iran

Gavkosh – a new locality yielding large mammal fossils in the Bakhtiari Formation in Lorestan Province, Iran

Comparing the large mammal fossil record and the archaeological record during the mid to late Quaternary in southern Africa

Dwarf antelope species were commonly united in the tribe “Neotragini” (Bovidae, Mammalia) due to their general morphological appearance. However, phylogenetic analyses have shown that not all dwarf antelopes are closely related, so it was suggested to restrict the name Neotragini to the type genus Neotragus. In our study we use mitochondrial cytochrome b sequences and linear skull measurements to further investigate the similarity of all three Neotragus species. Our analyses support the close relationship of N. moschatus and N. batesi. However, N. pygmaeus – the type species, which was never before included in phylogenetic analyses – is not closely related. It might share a most recent common ancestor with another “dwarf antelope”, the Klipspringer Oreotragus oreotragus, and the duikers in the taxon Cephalophini. Hence, we suggest resurrecting the genus Nesotragus von Dueben, 1846 for Nesotragus moschatus and N. batesi.

Bois-de-Riquet (Lézignan-la-Cèbe, Hérault): A late Early Pleistocene archeological occurrence in southern France

The Bois-de-Riquet archeological site (Lézignan-la-Cèbe, Hérault, France) provides significant paleontological and archeological data about the first occupations of Western Europe. Although only partially excavated, the site has already yielded an exceptionally rich paleontological assemblage as well as some stone artefacts. The archeostratigraphical unit “US2” is encased within a basalt flowstone radiometrically dated to 1.57 Ma. The sedimentary infill has preserved large and small mammal fossils, as well as coprolites. Biochronological interpretations suggest an age of around 1.3–1.1 Ma for the accumulation. A few basalt artefacts were exhumed alongside the fossil bones. Interpretation of the lithics has required the elaboration of a strict selection protocol based upon extensive knapping experiments with local basalt. This paper presents results from the interdisciplinary study of the Bois-de-Riquet site in the aim of contextualizing these discoveries. The microstratigraphical analysis of the deposits is presented with recent geological interpretations in order to contribute a better understanding of the main features of this assemblage, and its remarkable preservation within the thermal and textural boundary between a basalt flowstone's base and its entablature.

A Pleistocene Rhinocerotid (Mammalia, Perissodactyla) from Yage, Shizuoka Prefecture, central Japan

A fossil rhinocerotid tooth from the Yage Formation (Middle to Late Pleistocene), Yage in Shizuoka Prefecture, is described. The present specimen shows the following characteristics of the second lower incisor: tusk-like shape, enamel on the labial side, a teardrop-shaped cross section of the tooth crown, and an oval cross section of the root. The specimen is similar to the genus Rhinoceros in having a large and robust shape. However, owing to a lack of other elements, generic and specific identification are not possible. Previously, several large mammal fossils had been reported from the Yage area, but there were no rhinocerotids among them. Thus, this report is the first record of a rhinocerotid from the area. The Yage specimen suggests rhinocerotids were widely distributed during the Pleistocene of Far East Asia.

Middle to Late Pleistocene ice extents, tephrochronology and paleoenvironments of the White River area, southwest Yukon

Sedimentary deposits from two Middle to Late Pleistocene glaciations and intervening non-glacial intervals exposed along the White River in southwest Yukon, Canada, provide a record of environmental change for much of the past 200 000 years. The study sites are beyond the Marine Isotope stage (MIS) 2 glacial limit, near the maximum regional extent of Pleistocene glaciation. Non-glacial deposits include up to 25 m of loess, peat and gravel with paleosols, pollen, plant and insect macrofossils, large mammal fossils and tephra beds. Finite and non-finite radiocarbon dates, and twelve different tephra beds constrain the chronology of these deposits. Tills correlated to MIS 4 and 6 represent the penultimate and maximum Pleistocene glacial limits, respectively. The proximity of these glacial limits to each other, compared to limits in central Yukon, suggests precipitation conditions were more consistent in southwest Yukon than in central Yukon during the Pleistocene. Conditions in MIS 5e and 5a are recorded by two boreal forest beds, separated by a shrub birch tundra, that indicate environments as warm or warmer than present. A dry, treeless steppe-tundra, dominated by Artemisia frigida, upland grasses and forbs existed during the transition from late MIS 3 to early MIS 2. These glacial and non-glacial deposits constrain the glacial limits and paleoenvironments during the Middle to Late Pleistocene in southwest Yukon.

The Janda cavity at Fruška Gora, the first cave assemblage from the southeast Pannonian lowland (Vojvodina, Serbia)

The recently discovered Janda cavity yielded the first large mammal fossil assemblage of the Late Pleistocene age in the southeast Pannonian lowland (Vojvodina), outside the karst region of Serbia. The cavity is formed in the Badenian reef limestone on the northern hillside of the Fruška Gora mountain. The paper provides a paleontological description and taphonomic data on mammal remains collected from the loose sediments or scree. Herbivores are represented by Bison priscus (Bojanus, 1827), which is the most abundant species, followed by Megaloceros giganteus (Blumenbach, 1803) and Equus germanicus Nehring, 1884, with several remains of Mammuthus sp. and Coelodonta antiquitatis (Blumenbach, 1799). Carnivores are represented by Ursus spelaeus ingressus (Rabeder et al., 2004), Crocuta crocuta spelaea (Goldfuss, 1823), Panthera leo spelaea (Goldfuss, 1810), as well as Canis lupus Linnaeus, 1758. Wolf remains are characterized by their large size, almost reaching the size of hyenas, which is in contrast with the finds of rather small Pleistocene wolves from the caves in the mountainous part of Serbia. The faunal composition and the presence of mostly grazing forms among the herbivores indicate glacial conditions and an open landscape in the surroundings of the site during the formation of the Janda cavity infill. Taphonomic observations indicate the cave hyena as a dominant bone accumulating agent. In contrast to other cave hyena sites in Serbia, where mostly small and medium sized prey remains were accumulated, prey preference for large and extra large mammals is noted. It is supposed that this is the consequence of the differences between mountainous and lowland landscapes and environments, climatic conditions, different composition of animal and plant associations, and also in different modes of competitions between predators.

New data on the age of neopleistocene sediments in the Tunka rift valley (Southwestern Baikal Region) derived from 14C dating of large mammal fossils

New data on the age of neopleistocene sediments in the Tunka rift valley (Southwestern Baikal Region) derived from 14C dating of large mammal fossils

Was FLK North levels 1–2 a classic “living floor” of Oldowan hominins or a taphonomically complex palimpsest dominated by large carnivore feeding behavior?

From excavation at FLK North levels 1–2 in 1960–1962, Mary Leakey reported approximately 1200 Oldowan artifacts and 3300 large mammal fossils as a hominin “living floor”. Preliminary taphonomic analysis by Bunn seemed supportive, based on the presence of some cut-marked bones, the concentration of several dozen bovid individuals, and the relative abundance of limbs and mandibles over other axial elements. Recent taphonomic analysis of Leakey's entire fossil assemblage by Domínguez-Rodrigo and Barba, however, documents a minor hominin role at the site, contrasted to the dominant role of carnivores. Felids brought prey animals; hyenas scavenged from abandoned felid meals. At different times, hominins butchered several bovids and discarded artifacts at this dynamic location. Since 2006, renewed excavations at FLK North and other sites by the Olduvai Paleoanthropology and Paleoecology Project (TOPPP) have expanded artifact and fossil samples and implemented new analytical approaches to clarify taphonomic histories of the Olduvai paleolandscape. At FLK North, > 1000 new large mammal fossils from levels 1 to 2 show minimal butchery evidence amid abundant evidence of carnivore gnawing/fracture, rodent gnawing, and sediment abrasion. To help guide future excavation and analyses, we have developed several alternative working hypotheses of site formation.

Large mammal fossil occurrences and associated archaeological evidence in Pleistocene contexts of peninsular India and Sri Lanka

The Indian subcontinent represents a rich source of diverse paleoanthropological data in the form of pollen assemblages, various isotopic records, vertebrate and invertebrate fossil assemblages, and prehistoric stone tools in a range of palaeoecological contexts. Most of the Quaternary fossil evidence, including hominin specimens, comes from the fluvial sediments of the Narmada and other similar rivers. Although abundant and well-preserved vertebrate fossil assemblages are known from the Siwalik Hills and Karewa deposits in the north, similar evidence is less well-known from peninsular India and Sri Lanka to the south. With the exception of two occurrences in Gujarat and Bihar, there is an almost complete absence of Neogene fossil evidence older than the Middle Pleistocene in peninsular India and late Middle Pleistocene in Sri Lanka. The richest non-fluvial sources of vertebrate fossils are represented by the Kurnool cave-complex in southern India and numerous cave and open-air deposits in Sri Lanka, the majority of which are Upper Pleistocene age. This unique faunal record of peninsular India and Sri Lanka probably played a critical role in influencing the dispersal, settlement, and subsistence behaviors of Pleistocene hominins. This paper summarizes the known Pleistocene megafauna fossil occurrences from peninsular India and Sri Lanka and includes key lithic associations with these assemblages.

What is the boundary for the quaternary period and Pleistocene epoch? The contribution of turnover patterns in large mammalian complexes from North-Western mediterranean to the debate

Assuming that the Quaternary has to be recognized as a formal chronostratigraphic/geochronological unit (having a Sub-Erathem/Sub-Era rank, as recommended by the International Commission on Stratigraphy (ICS), or better a System/ Period rank, as suggested by several scientists), what boundary should be chosen? Should the lower boundary of the Quaternary coincide with the base of the Gelasian Stage (2.6 Ma) as proposed by the ICS? If so, should the Quaternary and Pleistocene lower boundaries be the same or should be different? To contribute to the debate, the Villafranchian large mammal fossil record from the North-Western Mediterranean region have been revised in order to correlate the diversity and structural dynamics of reconstructed faunal complexes with the changes in environmental conditions occurring from the Middle Pliocene to the Early Pleistocene.According to the results obtained, two major faunal renewals are detectable at the transition from the early to middle Villafranchian [~2.7-2.5 Ma, about at the time of the transition from the Middle (Zanclean Stage) to the Late Pliocene (Gelasian Stage)], and from the middle to late Villafranchian (~2.0-~1.9 Ma, shortly before the official Plio-Pleistocene boundary). The faunal renewal from the early (V1) to the middle (V2) Villafranchian faunal complexes (that means from the MN16a “zone”/Triversa FU to MN16b “zone”/Montopoli FU) is linked to the Middle Pliocene climate worsening, in turn related to the onset of bipolar glaciations followed by glacial-interglacial cycles of moderate amplitude (orbital periodicity of 41 ka). The resulting increase in aridity and more intense seasonality caused the disappearance of several forest-dwelling taxa, especially small carnivores and arboreal-scansorial taxa, whereas new large grazers, mixed feeders or even browsers appeared. This renewal (already called the “Equus-elephant event”) can be regarded as a true turnover phase, due to the high percentage of last and new appearances, and to the important ecological structural changes in faunal complexes, involving mainly the herbivore guild. These faunal changes indicate that forests or woodlands gradually gave way to more open environments (including Artemisia steppe) alternating with warm-temperate deciduous forests. Moreover, this event can be considered as the starting point for a dispersal phase leading to a progressive standing richness increase during the following Pliocene (middle Villafranchian, V3). Around 2.0-1.8 Ma (late Villafranchian, V4), despite the extinction of some small browsing and grazing ­ruminants, diversity notably increased due to the progressive appearance of a number of carnivores. Indeed, the so-called “wolf-event” involved several large and small Carnivora, such as the powerful scavenger Pachycrocuta brevirostris, the jaguar-like Panthera gombazsoegensis, and coo­perative foraging canids. On the other hand, minor phyletic adjustments and some new appearances (especially grazers) affected herbivore guild. This relatively long dispersal phase, and correlated moderate turnover pulses, seems to be less important than the early/middle Villafranchian ­renewal phase, especially as far as France and the Italian peninsula are concerned. As a result, taking into account the importance of faunal renewal at the Middle to Late Pliocene transition, it seems more reasonable to extend the base of the Pleistocene downwards from 1.81 Ma (official Plio/Pleistocene boundary) to 2.6 Ma (base of Pliocene Gelasian Stage). Accordingly, the base of the Gelasian seems to be the most appropriate lower boundary for both the Quaternary Period and Pleistocene Epoch.

New carbon dates link climatic change with human colonization and Pleistocene extinctions

Drastic ecological restructuring, species redistribution and extinctions mark the Pleistocene-Holocene transition, but an insufficiency of numbers of well-dated large mammal fossils from this transition have impeded progress in understanding the various causative links. Here I add many new radiocarbon dates to those already published on late Pleistocene fossils from Alaska and the Yukon Territory (AK-YT) and show previously unrecognized patterns. Species that survived the Pleistocene, for example, bison (Bison priscus, which evolved into Bison bison), wapiti (Cervus canadensis) and, to a smaller degree, moose (Alces alces), began to increase in numbers and continued to do so before and during human colonization and before the regional extinction of horse (Equus ferus) and mammoth (Mammuthus primigenius). These patterns allow us to reject, at least in AK-YT, some hypotheses of late Pleistocene extinction: 'Blitzkrieg' version of simultaneous human overkill, 'keystone' removal, and 'palaeo-disease'. Hypotheses of a subtler human impact and/or ecological replacement or displacement are more consistent with the data. The new patterns of dates indicate a radical ecological sorting during a uniquely forage-rich transitional period, affecting all large mammals, including humans.

Late Pliocene to late Pleistocene environments preserved at the Palisades Site, central Yukon River, Alaska

The Palisades Site is an extensive silt-loam bluff complex on the central Yukon River preserving a nearly continuous record of the last 2 myr. Volcanic ash deposits present include the Old Crow (OCt; 140,000 yr), Sheep Creek (SCt; 190,000 yr), PA (2.02 myr), EC (ca. 2 myr), and Mining Camp (ca. 2 myr) tephras. Two new tephras, PAL and PAU, are geochemically similar to the PA and EC tephras and appear to be comagmatic. The PA tephra occurs in ice-wedge casts and solifluction deposits, marking the oldest occurrence of permafrost in central Alaska. Three buried forest horizons are present in association with dated tephras. The uppermost forest bed occurs immediately above the OCt; the middle forest horizon occurs below the SCt. The lowest forest bed occurs between the EC and the PA tephras, and correlates with the Dawson Cut Forest Bed. Plant taxa in all three peats are common elements of moist taiga forest found in lowlands of central Alaska today. Large mammal fossils are all from common late Pleistocene taxa. Those recovered in situ came from a single horizon radiocarbon dated to ca. 27,000 14C yr B.P. The incongruous small mammal assemblage in that horizon reflects a diverse landscape with both wet and mesic environments.

Biogeography and migration routes of large mammal faunas in South–East Asia during the Late Middle Pleistocene: focus on the fossil and extant faunas from Thailand

Thailand has long held a key position in South–East Asia because of its location at the boundary of the Indochinese and Sundaic provinces, the major biogeographical regions of South–East Asia. These provinces are distinct climatically, floristically and faunistically. The present-day limit between them is located at the Kra Isthmus, in peninsular Thailand. Previous studies of the Javanese large mammal fossil faunas and the recent study of fossil large mammal faunas from Thailand strengthen the hypothesis of a “continental” migration route (in contrast with the “insular” hypothesis via Taiwan and the Philippines) during the Late Middle/Late Pleistocene period. Thailand was even part of this migration route. During the glacial periods, the faunal exchanges were favored by the emersion of a huge continental shelf called Sundaland (South–East Asian continental area connected to Borneo and Indonesia islands by land bridges), when the sea level was low. No geological, biogeographical or paleobiogeographical evidence supports the hypothesis of a migration route via Taiwan and the Philippines. Analysis of the extant and Late Middle Pleistocene large mammal faunas (Carnivora, Primates, Proboscidea and Ungulata) points out the antiquity of the Indochinese and Sundaic provinces. This idea is also supported by the fact that mainland faunas already displayed modern character, whereas the Javanese faunas were mainly composed of endemic forms. However, the occurrence of the extinct species, Elephas namadicus found in a Malaysian site (Tambun) indicates that the limit between the two provinces, if not close to the present place, was located more southward than today, possibly in peninsular Malaysia. It is also confirmed by the presence of northern species, such as Ailuropoda melanoleuca baconi and Crocuta crocuta ultima, in Late Middle Pleistocene sites of Thailand. In fact, because of climatic cooling that occurred in the northern hemisphere during the Pleistocene, the northern faunas had to move southward. To our knowledge, the hypothesis of the antiquity of the South–East Asian provinces with a boundary south of the present-day one is mentioned here for the first time. Previous biogeographical studies were based mainly on insular data from the Philippine Archipelago (geological and mainly present-day zoogeographical data) but also from Indonesia and Borneo (paleontological data). However, the recent discovery of Thai large mammal faunas from Late Middle Pleistocene allows to bridge the gap in the fossil record between the northern faunas of South–East Asia and the southern ones. These Thai faunas are characterized mainly by extant forms but some are today absent from the Thai territory ( Ailuropoda melanoleuca, Crocuta crocuta, Pongo pygmaeus, Sus cf. barbatus, Rhinoceros cf. unicornis, Cervus eldii).