Early Pleistocene Research Articles

Thermal stability of the electron spin resonance signal of modern continental barite

The electron spin resonance (ESR) method has been successfully applied to dating hydrothermal barite; however, there have been few studies of modern continental barite, such as that generated by fault movement or in sedimentary deposits. To better understand the geological processes involved in the formation of continental barite, its thermal characteristics and age firstly need to be defined. In this study, one fault barite sample and two sedimentary barite samples were obtained from continental sites in China for ESR signal thermal stability experiments. Microwave-power experiments indicate that 0.5 mW produces the maximum ESR signal intensity and the highest signal-to-noise ratio. Stepwise-heating results reveal that ESR signal intensities remain stable below 100 °C then show an increasing trend that peaks at ∼180 °C, following which they decrease rapidly between 180 and 320 °C and disappear at ∼380 °C. Isothermal heating results show that ESR signal intensities remain stable within a temperature range of 100–200 °C but show a decreasing trend for temperatures of 240–320 °C. These results indicate that the thermal decay of the ESR signal intensity for the three studied continental barites follows second-order decay kinetics. The thermal lifetimes calculated for the three samples are 6.3 × 108, 7.5 × 107, and 8.7 × 106 a, respectively. Thus, barite ESR dating can be used to date related geological events since early Pleistocene.

Conserved DNA sequence analysis reveals the phylogeography and evolutionary events of Akebia trifoliata in the region across the eastern edge of the Tibetan Plateau and subtropical China

BackgroundThe eastern edge of the Qinghai‒Tibet Plateau (QTP) and subtropical China have various regions where plant species originate and thrive, but these regions have been the focus of very few integrative studies. Here, we elucidated the phylogeographic structure of a continuous and widespread Akebia trifoliata population across these two regions.ResultsSixty-one populations consisting of 391 genotypes were examined to assess population diversity and structure via network distribution analysis, maximum likelihood phylogenetic tree reconstruction, divergence time estimation, demographic history inference, and ancestral area reconstruction of both conserved internal transcribed spacer (ITS) and chloroplast (rps16) DNA sequences. The results showed that the ITS region was more variable than the rps16 region and could be suitable for studying intraspecific phylogeography. The A. trifoliata population displayed high genetic diversity, genetic differentiation and obvious phylogeographical structure, possibly originating on the eastern QTP, expanding during the last glacial-interglacial cycle, diverging in the early Pleistocene and middle Pleistocene, and extensively migrating thereafter. The migration route from west to east along rivers could be largely responsible for the long-distance dispersal of this species, while three main refuges (Qinba Mountains, Nanling Mountains and Yunnan-Guizhou Plateau) with multiple ice shelters facilitated its wide distribution.ConclusionsOur results suggested that the from west to east long migration accompanying with the minor short reciprocal migration in the south-north direction, and the three main refuges (the Qinba Mountains, Nanling Mountains and Yunnan-Guizhou Plateau) contributed to the extant geographical distribution of A. trifoliata. In addition, this finding also strongly reduced the discrepancy between glacial contraction and postglacial expansion and the in situ survival hypothesis by simultaneously considering the existence of many similar climate-related ecological niches and migration influences.

Molecular phylogeny of the common wall lizard Podarcis muralis (Squamata: Lacertideae) in the southern Balkans

Abstract The lacertid wall lizards of the genus Podarcis (Wagler, 1830) originate from Western Europe and are divided into 24-25 species (Speybroeck et al., 2020). Despite the abundance of phylogenetic studies referring to the genus, the relationships among certain species, as well as the taxonomic status of some genealogical lineages, remain unclear due to great genetic diversity. The common wall lizard Podarcis muralis has a relatively wide distribution and despite the existence of various molecular studies focused on this species, its Greek populations had never been thoroughly sampled until now. To fill in this geographical gap, we sampled the species’ Greek distribution and constructed phylogenies that uncovered the presence of at least five monophyletic lineages that correspond to different geographic regions. Furthermore, species delimitation analyses assigned all lineages to a single species diversifying during the early Pleistocene (c. 1.93 mya). The strong association of the genetic lineages with specific geographical regions coupled with the Pleistocene diversification of the group imply the presence of multiple refugia within Greece and, by extension, the Balkan peninsula, supporting a refugia-within-refugia scenario. Finally, in an effort to clarify the position of these new samples within the larger phylogeny of P. muralis, a larger phylogeny was constructed which indicated that the Greek populations cluster with the central European, Italian and Turkish populations of the species.

Orbital- and millennial-scale Asian winter monsoon variability across the Pliocene–Pleistocene glacial intensification

Intensification of northern hemisphere glaciation (iNHG), ~2.7 million years ago (Ma), led to establishment of the Pleistocene to present-day bipolar icehouse state. Here we document evolution of orbital- and millennial-scale Asian winter monsoon (AWM) variability across the iNHG using a palaeomagnetically dated centennial-resolution grain size record between 3.6 and 1.9 Ma from a previously undescribed loess-palaeosol/red clay section on the central Chinese Loess Plateau. We find that the late Pliocene–early Pleistocene AWM was characterized by combined 41-kyr and ~100-kyr cycles, in response to ice volume and atmospheric CO2 forcing. Northern hemisphere ice sheet expansion, which was accompanied by an atmospheric CO2 concentration decline, substantially increased glacial AWM intensity and its orbitally oscillating amplitudes across the iNHG. Superposed on orbital variability, we find that millennial AWM intensity fluctuations persisted during both the warmer (higher-CO2) late Pliocene and colder (lower-CO2) early Pleistocene, in response to both external astronomical forcing and internal climate dynamics.

When the woolly rhinoceroses roamed East Asia: a review of isotopic paleoecology of the genus Coelodonta from the Tibetan Plateau to northern Eurasia

East Asia, being the evolutionary center of Coelodonta, offers a unique opportunity to explore the spatiotemporal paleoecologies of this genus. This study utilized bulk and serial stable carbon and oxygen isotope analyses on the Coelodonta nihowanensis and other ungulates from the Longdan fauna as well as two modern goats in the Linxia Basin, aiming to explore the paleoecology of C. nihowanensis at the periphery of the Tibetan Plateau during the Early Pleistocene. The isotopic results of these mammals indicated that C3 vegetation was possibly a major component of the local environment in the Linxia Basin, which was influenced by a seasonal summer monsoon. C. nihowanensis specimens in the Longdan fauna were possibly mixed feeders, as indicated by the wide distribution of their δ13C values and the intermediate δ18O values compared to other coexisting ungulates. Moreover, the comparison of the δ13C and δ18O values of similar taxa from the Linxia and Nihewan basins has revealed spatiotemporal differences in the paleoclimate and paleoenvironments of these two regions throughout the Early Pleistocene. This provides a holistic framework for understanding the paleoecology of the C. nihowanensis. The isotopic results of the C. nihowanensis in the Linxia and Nihewan basins suggested varied foraging ecologies across different sites and time spans during the Early Pleistocene. This underscores the adaptability of the C. nihowanensis to diverse environments from west to east in northern China. By scrutinizing the evolutionary ecological history of the woolly rhinoceroses from its ancestor, Coelodonta thibetana, to its final form, Coelodonta antiquitatis, this study sheds light on the ecological adaptation of this genus from the Pliocene to Late Pleistocene, spanning its migration from the Tibetan Plateau to northern Eurasia.

Three de novo assembled wild cacao genomes from the Upper Amazon

Theobroma cacao, the chocolate tree, is indigenous to the Amazon basin, the greatest biodiversity hotspot on earth. Recent advancement in plant genomics highlights the importance of de novo sequencing of multiple reference genomes to capture the genome diversity present in different cacao populations. In this study, three high-quality chromosome-level genomes of wild cacao were constructed, de novo assembled with HiFi long reads sequencing, and scaffolded using a reference-free strategy. These genomes represent the three most important genetic clusters of cacao trees from the Upper Amazon region. The three wild cacao genomes were compared with two reference genomes of domesticated cacao. The five cacao genetic clusters were inferred to have diverged in the early and middle Pleistocene period, approximately 1.83–0.69 million years ago. The results shown here serve as an example of understanding how the Amazonian biodiversity was developed. The three wild cacao genomes provide valuable resources for studying genetic diversity and advancing genetic improvement of this species.

Archaeological evidence of rodent consumption in North Africa: The Middle Stone Age of the rock shelter Ifri n'ammar in northeastern Morocco

This study presents undeniable evidence of anthropogenic exploitation of small mammals in Ifri n'Ammar rock shelter, located in the northeast of Morocco. Among the rodent species found at this site, Ctenodactylus gundi predominates in the assemblage of small mammals between approximately 130 ± 8 ka and 83 ± 6 ka. The taphonomic analysis of the fossil remains of this species, discovered alongside other components of the archaeological assemblage, clearly indicates that during the Middle Stone Age (MSA), humans consumed this species. Therefore, they are considered the main agents responsible for the accumulation of dental and postcranial remains of this species recorded in the shelter. Since the early Upper Pleistocene, bone elements bearing cut-marks and burn traces unequivocally attest to the consumption of this rodent by the hunter-gatherers at the Ifri n'Ammar rock shelter. Our findings regarding the exploitation of this species by humans in the northeastern region of Morocco are corroborated by ethnographic data, demonstrating that North African populations captured and consumed this large-sized rodent until the last century. The species Ctenodactylus gundi is known for its diurnal activity, gregarious and social habits, as well as its preference for rocky and arid environments.

Population Variation and Phylogeography of Cherry Blossom (Prunus conradinae) in China.

Prunus conradinae (subgenus Cerasus, Rosaceae) is a significant germplasm resource of wild cherry blossom in China. To ensure the comprehensiveness of this study, we used a large sample size (12 populations comprising 244 individuals) which involved the fresh leaves of P. conradinae in Eastern, Central, and Southwestern China. We combined morphological and molecular evidence (three chloroplast DNA (cpDNA) sequences and one nuclear DNA (nr DNA) sequence) to examine the population of P. conradinae variation and differentiation. Our results revealed that Central, East, and Southwest China are important regions for the conservation of P. conradinae to ensure adequate germplasm resources in the future. We also found support for a new variant, P. conradinae var. rubrum. We observed high genetic diversity within P. conradinae (haplotype diversity [Hd] = 0.830; ribotype diversity [Rd] = 0.798), with novel genetic variation and a distinct genealogical structure among populations. There was genetic variation among populations and phylogeographic structure among populations and three geographical groups (Central, East, and Southwest China). The genetic differentiation coefficient was the lowest in the Southwest region and the gene exchange was obvious, while the differentiation was obvious in Central China. In the three geographic groups, we identified two distinct lineages: an East China lineage (Central China and East China) and a Southwest China lineage ((Central China and Southwest China) and East China). These two lineages originated approximately 4.38 million years ago (Mya) in the early Pliocene due to geographic isolation. P. conradinae expanded from Central China to East China at 3.32 Mya (95% HPD: 1.12-5.17 Mya) in the Pliocene. The population of P. conradinae spread from East China to Southwest China, and the differentiation time was 2.17 Mya (95% (HPD: 0.47-4.54 Mya), suggesting that the population of P. conradinae differentiated first in Central and East China. The population of P. conradinae experienced differentiation from Central China to Southwest China around 1.10 Mya (95% HPD: 0.11-2.85 Mya) during the early Pleistocene of the Quaternary period. The southeastern region of East China, near Mount Wuyi, likely serves as a refuge for P. conradinae. This study establishes a theoretical foundation for the classification, identification, conservation, and exploitation of germplasm resources of P. conradinae.

Phylogenomics of Tetraopes longhorn beetles unravels their evolutionary history and biogeographic origins

Tetraopes longhorn beetles are known for their resistance to milkweed plant toxins and their coevolutionary dynamics with milkweed plants (Asclepias). This association is considered a textbook example of coevolution, in which each species of Tetraopes is specialized to feed on one or a few species of Asclepias. A major challenge to investigating coevolutionary hypotheses and conducting molecular ecology studies lies in the limited understanding of the evolutionary history and biogeographical patterns of Tetraopes. By integrating genomic, morphological, paleontological, and geographical data, we present a robust phylogeny of Tetraopes and their relatives, using three inference methods with varying subsets of data, encompassing 2–12 thousand UCE loci. We elucidate the diversification patterns of Tetraopes species across major biogeographical regions and their colonization of the American continent. Our findings suggest that the genus originated in Central America approximately 21 million years ago during the Miocene and diversified from the Mid-Miocene to the Pleistocene. These events coincided with intense geological activity in Central America. Additionally, independent colonization events in North America occurred from the Late Miocene to the early Pleistocene, potentially contributing to the early diversification of the group. Our data suggest that a common ancestor of Tetraopini migrated into North America, likely facilitated by North Atlantic land bridges, while closely related tribes diverged in Asia and Europe during the Paleocene. Establishing a robust and densely sampled phylogeny of Tetraopes beetles provides a foundation for investigating micro- and macroevolutionary phenomena, including clinal variation, coevolution, and detoxification mechanisms in this ecologically important group.

Greening a lost world: Paleoartistic investigations of the early Pleistocene vegetation landscape in the first Europeans' homeland

The scarcity of pictorial reconstructions focusing on Quaternary flora and vegetation prompts a reevaluation of traditional zoocentrism in future paleoartistic research. Here we present paleoartistic renderings depicting vegetation landscapes around the Orce Archaeological Zone (OAZ), encompassing sites dating from 1.6 to 1.2 million years ago during the Early Pleistocene of the Guadix-Baza Basin in southern Spain. Four pieces are based on fossil pollen data from Venta Micena 1 (VM1), Barranco León (BL), and Fuente Nueva 3 (FN3). The artwork considers altitudinal belt distribution, taxonomic and structural diversity, extinct taxa in the Iberian Peninsula post-Early Pleistocene, and those previously extinct at higher latitudes in Europe. This essay visually represents the coexistence of mesophytic, thermophytic, and xerophytic plant communities within a glacial refugium of woody species. Lastly, employing a non-conventional iconographic approach, we portray a female Homo individual in the forest refugium to draw up on possible adaptive traits of these early Europeans.

A Poorly Known Catfish Clade in an Endangered Neotropical Biodiversity Hotspot: Relationships and Distribution Patterns of the Cambeva variegata Group (Siluriformes: Trichomycteridae)

The Cambeva variegata group (CVG) is endemic to a region situated in the intersection of two endangered biodiversity hotspots, Cerrado and Atlantic Forest, and drained by two important South American river basins, the upper Rio Paraná and upper Rio São Francisco basins. Presently, CVG comprises two nominal species, besides some still undescribed. We first performed a molecular phylogenetic analysis (total of 3368 bp) for five species of the CVG and 30 outgroups, which supported the monophyly of the CVG and its inclusion in Cambeva. Most morphological character states distinguishing the CVG from congeners are also present in Scleronema, possibly consisting of plesiomorphic features. We also performed the first time-calibrated phylogeny of the group, which supported possible relationships between present geographical distribution patterns and palaeogeographical events. The estimated time of origin of CVG in the Middle Miocene is nearly contemporaneous to a past hydrographical configuration when part of the upper Rio Paraná basin was connected to the Rio São Francisco basin. The first CVG lineage split occurring in the Miocene end corresponds to a major break in that palaeo basin. Species diversification between the Pliocene and early Pleistocene is compatible with final drainage rearrangement. This study highlights the urgent need for more detailed studies on the diversity and phylogenetic relationships of still poorly known organisms in this highly diverse and threatened region.

Osteology of Crocodylus palaeindicus from the late Miocene–Pleistocene of South Asia and the phylogenetic relationships of crocodyloids

Fossil crocodylian remains have been documented from India and other parts of South Asia since the mid-nineteenth century, but specimens attributed to several extinct and extant species of Crocodylus have largely been neglected in modern taxonomic treatments. Here, we present a detailed anatomical description of the extinct species Crocodylus palaeindicus, which we restrict to the late Miocene to early middle Pleistocene of India. Using an autapomorphy-based approach to species-level identification, we regard Crocodylus sivalensis as a junior synonym of C. palaeindicus and provide taxonomic re-identifications of all specimens previously referred to these two species. We present a new diagnosis for C. palaeindicus that facilitates its distinction from the extant mugger crocodile, C. palustris, which does not unequivocally appear in the fossil record prior to the Pleistocene. The lack of clear spatiotemporal overlap, coupled with the otherwise lengthy ghost lineage implied by their sister-taxon relationship in our phylogenetic analyses, provides tentative support that the extant species either is the descendant of C. palaeindicus or originated via budding cladogenesis. An expanded phylogenetic analysis recovers the late Miocene African C. checchiai and Pliocene South American C. falconensis as species within the Neotropical Crocodylus clade, supporting an African origin for this radiation. We also recover Kinyang, from the early–middle Miocene of Kenya, as a crocodyline, rather than an osteolaemine as originally described, and it is potentially the stratigraphically earliest known member of the Crocodylus lineage. Other notable results from our phylogenetic analyses suggest that crocodyloids might not have been present in North America prior to the late Neogene arrival of Crocodylus, with Albertosuchus knudsenii, Prodiplocynodon langi and ‘Crocodylus’ affinis all recovered outside of Crocodyloidea. Furthermore, we demonstrate that an alligatoroid placement for the recently erected latest Cretaceous–Palaeogene East Asian clade Orientalosuchina is highly labile, with relationships at the ‘base’ of Crocodylia unstable.

Laser ablation MC-ICPMS U-Th and U-Th-Pb dating of Quaternary zircons from Jeju Island, Korea

BackgroundLaser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) emerged in the mid-1980s and rapidly became a crucial dating tool. The advent of femtosecond LA systems has substantially reduced volatility-dependent mass fractionation. This study showcases U-Th and U-Th-Pb dating results of Quaternary zircons collected from Jeju Island, Korea, utilizing an advanced femtosecond laser-connected multi-collector (MC)-ICPMS.FindingsZircon grains from trachyte samples near the Baeknokdam lake (JJ616-1), Yeongsil (JJ08-1), Chunwangsa (JJ09-1), and Oraidong (JJ09-3) provided weighted mean 238U-230Th ages of 28.7 ± 1.6 ka (n = 56/64, MSWD = 3.8), 81.8 ± 10.9 ka (n = 11/12, MSWD = 1.6), 92.6 ± 4.6 ka (n = 49/51, MSWD = 2.2), and 117.6 ± 8.2 ka (n = 48/50, MSWD = 3.2), respectively. The age determination for JJ08-1 zircon aligned well with the recommended value (82 ± 6 ka). Zircons from Sanbangsan (JJ615-1) and Wonmansa (JJ08-2) trachytes yielded common Pb and radioactive disequilibrium-corrected weighted mean 238U-206Pb ages of 785 ± 5 ka (n = 27/28, MSWD = 0.90) and 743 ± 8 ka (n = 28/30, MSWD = 0.79), respectively. The weighted mean 238U-206Pb ages of Penglai and 61.308 reference zircons were determined to be 4226 ± 21 ka (n = 22/25, MSWD = 3.8) and 2488 ± 20 ka (n = 19/20, MSWD = 1.8), respectively. These ages are concordant with the recommended values.ConclusionsOur data provides additional evidence of trachyte magmatism occurring in Jeju Island during the transitional period between the Early and Middle Pleistocene and the Late Pleistocene. The zircon samples analyzed in this study could serve as reference age data for Quaternary geochronology research.

Vegetation response to climate changes in the eastern Arctic during the Middle Gelasian age of the Early Pleistocene

Palynological analysis of sediments from El'gygytgyn Lake document vegetation changes in the Eastern Arctic from early marine isotope stage (MIS) 74 to late MIS 80 (c.2.1–1.9 MA) and close the last remaining gap in the El'gygytgyn pollen record. Cooler climates were characterized by a mix of Larix forest-tundra, shrub Betula tundra, and herb-dominated communities. During interglaciations, Larix forests with tree Betula and Alnus, and perhaps with a minor component of Picea and tree Pinus, characterized areas that today are tundra. These forests included a rich shrub understory of Betula, Duschekia, Salix, and Pinus pumila. Although MIS 77 has been considered a “super” interglaciation, the data do not indicate that this stage was exceptionally warm. Interstadial conditions are denoted by pollen assemblages that indicate the regional vegetation was dominated by Larix forest -tundra and an absence of Pinus pumila. The palynological results from this Early Pleistocene interval demonstrate the need to: 1) modify the El'gygytgyn age model; 2) reevaluate the relationship of sediment facies to climate change; and 3) reconsider the occurrence and/or definition of “super” interglaciations.

Sedimentological evolution of the Quibas site: High-resolution glacial/interglacial dynamics in a terrestrial pre-Jaramillo to post-Jaramillo sequence from southern Iberian Peninsula

The sedimentary infill of the Quibas karstic site (Early Pleistocene, southern Spain) represents the only continuous succession with remains of continental vertebrates in Europe from pre-Jaramillo to post-Jaramillo age. The Quibas site, with a significant paleontological record, is dated between 1.1 and 0.9 Ma and offers a unique opportunity to carry out a paleoclimatic reconstruction of the time period immediately after the arrival of the first humans to western Europe. For this reason, defining the dominant sedimentary processes in the different stratigraphic units and the associated paleoenvironment is essential. The Quibas site is made up of two karstic features with two stratigraphic sequences: Quibas-Cueva, containing six lithostratigraphic units, and Quibas-Sima, which contains seven lithostratigraphic units. The detailed description and analyses of the stratigraphic sections have allowed the characterization of various autochthonous and allochthonous facies of cave deposits. Paleoclimatic proxies, inferred from sedimentological analyses, reveal a record of several alternating humid and arid phases resulting from the Early Pleistocene glacial-interglacial cycles, allowing correlation to the marine oxygen isotope record. The lowermost units (pre-Jaramillo) were deposited during a long-lasting interglacial, correlated to MIS 33–31. It was followed by an increase in aridity in the intermediate units of Quibas-Sima and uppermost unit of Quibas-Cueva (Jaramillo), revealing the beginning of a glacial period at the start of the Jaramillo subchron (1 Ma), which can be correlated to MIS 30. The upper Jaramillo and post-Jaramillo units suggest these were deposited in alternating periods of aridity and humid conditions, although less humid than the pre-Jaramillo period, probably representing the MIS 29 interglacial, the MIS 28 glacial and the MIS 27 interglacial.

Characteristics and Geological Conditions of Coastal Zone Quaternary Sediment Formations in The Binh -Tri -Thien Area under The Context of Global Sea Level Change

Quaternary sediments in the Binh Tri Thien coastal zone are diverse in both material composition and development history. From land to sea, there are 4 structural regions: i) marginal plain region; ii) Coastal lagoon region; iii) Coastal sand dunes region; and iv) Monocline coastal subsidence region. In the vertical direction, all four regions have five sedimentary cycles as follows: a) Early Pleistocene (Q11); b) Early middle Pleistocene (Q12a); c) Late middle Pleistocene (Q12b); d) Early late Pleistocene (Q13a); e) Late late Pleistocene (Q13b-Q2). Four structural zones are characterized by different lithofacies complexes: 1) In the lowstand systems tract (LST) at the beginning of each cycle in all 4 structural zones, the SmaLST facies complex is present; 2) In the transgressive systems tract (TST), there are the following lithofacies complexes: a) region I: MsbTST; b) region II: MlgTST; c) region III: SmTST; d) region IV: Msam,mTST; 3) In the highstand systems tract (HST) there are the following facies complexes: a) Region I: (MsabHST); b) Region II: MslgHST; c) Region III: SmvHST; d) Region IV: SmmHST. The difference in sedimentary facies in the transgressive and highstand systems tract depends on the differentiation of four geological structure regions.

Hominin population bottleneck coincided with migration from Africa during the Early Pleistocene ice age transition

Two recently published analyses make cases for severe bottlenecking of human populations occurring in the late Early Pleistocene, one case at about 0.9 Mya based on a genomic analysis of modern human populations and the low number of hominin sites of this age in Africa and the other at about 1.1 Mya based on an age inventory of sites of hominin presence in Eurasia. Both models point to climate change as the bottleneck trigger, albeit manifested at very different times, and have implications for human migrations as a mechanism to elude extinction at bottlenecking. Here, we assess the climatic and chronologic components of these models and suggest that the several hundred-thousand-year difference is largely an artifact of biases in the chronostratigraphic record of Eurasian hominin sites. We suggest that the best available data are consistent with the Galerian hypothesis expanded from Europe to Eurasia as a major migration pulse of fauna including hominins in the late Early Pleistocene as a consequence of the opening of land routes from Africa facilitated by a large sea level drop associated with the first major ice age of the Pleistocene and concurrent with widespread aridity across Africa that occurred during marine isotope stage 22 at ~0.9 Mya. This timing agrees with the independently dated bottleneck from genomic analysis of modern human populations and allows speculations about the relative roles of climate forcing on the survival of hominins.

Dental shape evolution of the giant panda (Ailuropoda, Ursidae) during the Quaternary

ABSTRACT The giant panda is well known to have unique dentition, adapted to bamboo exclusive diet. The teeth are used to cut and grind the bamboo. However, it is unclear how these teeth evolved through geographical time. Here, we present the first geometric morphometric analysis of all cheek teeth of the giant panda, based on the large fossil collection of the giant panda teeth found from the Pleistocene deposits of southern China. Our analyses reveal the substantial intraspecific variation of the giant panda teeth, but no significant interspecific differences in Ailuropoda, supporting the basic function of the giant panda teeth has already formed since the Early Pleistocene. Among the cheek teeth, the premolars show the highest interspecific variation, suggesting a continuous increase in the feeding efficiency of the bamboo diet, which may facilitate the giant panda to grow a larger body size from Early Pleistocene species to A. melanoleuca. The Late Pleistocene A. m. baconi and two modern two subspecies show largely overlapped morphospace for all teeth, and the variation ranges are also similar, suggesting a fully established feeding apparatus and implying a similar diet. Our analyses provide new information on the giant panda evolution and adaptation.

Re-investigation of fossil Lemmini specimens from the early and Middle Pleistocene of Western and Central Europe: Evolutionary and paleoenvironmental implications

The current study focuses on the emblematic Myopus/Lemmus species complex (tribe Lemmini) in the European Pleistocene fossil record. The members of the two genera occupy distinct ecological niches and have different external appearances, but they are remarkably similar in their dental morphology, so that they were commonly thought of as undistinguishable in the fossil record. Thus, more or less all European Lemmini fossils have been assigned to the genus Lemmus. In the Early Pleistocene site of Schernfeld (Germany), the species Lemmus kowalskii had been described. It was thought by some authors that all Lemmini from Early to late Middle Pleistocene belong to this species.In the current study, we investigated Lemmini molar morphology from Western and Central European sites including Schernfeld (Early Pleistocene), Sackdillinger Höhle (Sackdilling Cave), and Koněprusy C718 (both early Middle Pleistocene), as well as other fossil localities with fewer specimens, formerly assigned to Lemmus kowalskii. Using an extensive modern referential material of Lemmus and Myopus, this study proposes to re-evaluate taxonomic status of the Middle and Early Pleistocene Lemmini. This modern referential also allows a better understanding of the morphology of Lemmus kowalskii specimens and its variability.Our results highlight the very high variation within fossil populations, as well as significant statistical differences between populations of the Early and Middle Pleistocene localities. A large part of these fossil specimens is firmly identified as Myopus sp., including the L. kowalskii holotype. Our identifications demonstrate that in most Early and Middle Pleistocene sites considered in this study, both genera (Lemmus and Myopus) are present. Possible interpretations and consequences for current view of lemming history are discussed, as well as some of the paleoecological and paleoenvironmental implications.

Otoliths of the Gobiidae from the Neogene of tropical America

Otoliths are common and diverse in the Neogene of tropical America. Following previous studies of Neogene tropical American otoliths of the lanternfishes (Myctophidae), marine catfishes (Ariidae), croakers (Sciaenidae), and cusk-eels (Ophidiiformes), we describe here the otoliths of the gobies (Gobiidae). The Gobiidae represent the richest marine fish family, with more than 2000 species worldwide and about 250 in America. In the fossil record too they are the species richest family in the Neogene of tropical America. We have investigated otoliths sampled from Ecuador, Pacific and Atlantic Panama, Atlantic Costa Rica, Dominican Republic, Venezuela, and Trinidad, ranging in age from late Early Miocene (late Burdigalian) to late Early Pleistocene (Calabrian). Most of the studied material originates from the collection expeditions of the Panama Paleontology Project (PPP). Our study represents the first comprehensive record of fossil gobies from America, and we recognize 107 species, of which 51 are new to science, 35 are in open nomenclature, and 19 represent species that also live in the region today. Previously, only two fossil otolith-based goby species have been described from the Neogene of tropical America. The dominant gobies in the fossil record of the region are from the Gobiosomatini, particularly of genera living over soft bottoms or in deeper water such as Bollmannia, Microgobius, Antilligobius, and Palatogobius. Another purpose of our study is to provide a first comprehensive account of otoliths of the extant Gobiidae of America, which we consider necessary for an adequate identification and interpretation of the Neogene otoliths. We studied otoliths of 130 extant American gobiid species and figured 106 of them for comparison. We also present a morphological analysis and characterization of the extant otoliths as a basis for the identification of fossil otoliths. Problems that commonly arise with the identification of fossil otoliths and specifically of fossil goby otoliths are addressed and discussed. A comparison of the history of the Gobiidae in tropical America reveals a high percentage of shared species between the Pacific and the Atlantic basins during the Late Miocene (Tortonian and Messinian) from at least 11 to 6 Ma. A recording gap on the Pacific side across the Pliocene allows a comparison again only in the late Early Pleistocene (Calabrian, 1.8 to 0.78 Ma), which shows a complete lack of shared species. These observations support the effective closure of the former Central American Seaway and emersion of the Isthmus of Panama in the intervening time. Groups that today only exist in the East Pacific were also identified in the Miocene and Pliocene of the West Atlantic, and there is also at least one instance of a genus now restricted to the West Atlantic having occurred in the East Pacific as late as the Pleistocene. The evolution of gobies in tropical America and the implications thereof are extensively discussed. Furthermore, observations of fossil gobies in the region are discussed in respect to paleoenvironmental indications and paleobiogeographic aspects.