MORPHOLOGY, INTERNAL STRUCTURE, AND ORIGIN OF GLAUCONITE PELLETS

Glauconite pellets exhibit considerable variety in morphology and internal structure. Recognized morphological types are: (1) ovoidal or spheroidal; (2) tabular or discoidal; (3) mammillated; (4) ellipsoidal; (5) vermicular; (6) composite; and (7) fossil casts, internal molds, or replacements. Types of internal structures include: (1) random microcrystalline, (2) oriented microcrystalline, (3) micaceous, (4) organic (?) replacements, (5) coatings on detrital grains, and (6) fibroradiated rims. These characteristics can be used to interpret the origin and/or subsequent history of pellet types. Suggested origins include: (1) chemical precipitation, (2) expansion and alteration of detrital mica, (3) alteration of fecal pellets, (4) alteration of clay fillings of fossil tests, (5) mechanical aggregation, and (6) chemical replacement. Not all glauconite pellets exhibit diagnostic characteristics with regard to their genesis. Original morphologies may be obscured by abrasion (reworking) prior to final burial. Internal structures may be changed by recrystallization or other diagenetic processes. It is concluded that glauconite pellets have multiple origins. They can form from several different parent materials and by several different processes. Frequently, however, characteristics which might reveal the original nature of the pellets have been lost during reworking and diagenesis. Inasmuch as glauconite occurrences differ in kind and variety of pellets, recognition of pellet types and their distribution is potentially useful for stratigraphic correlation or environmental determinations.     

New Discovery of Hipparion theobaldi Skull from the Late Miocene of Padhri, District Jhelum, Punjab, Pakistan and Associated Mammalian Fossil Assemblage

A fossil-bearing locality near Padhri village, Dhok Pathan, 55 km away from the tehsil Dina, Jhelum District, in the Potwar Plateau, Middle Siwaliks, Punjab, northern Pakistan, is significantly rich in mammalian fossils. This site has provided an abundant mammalian fossil fauna of Late Miocene age from the Dhok Pathan Formation (Fm.). The recovered material belongs to four families: Equidae (horses), Rhinocerotidae (rhinos), Bovidae (cows), and Suidae (pigs). We discovered a new skull of hipparionine Hipparion theobaldi from this locality along with 22 specimens from the associated assemblage of fossil mammals. The recovered material includes seven other species: the aceratheriine Chilotherium intermedium, boselaphines Tragoportax punjabicus, Selenoportax vexillarius, Pachyportax latidens, the antelope Gazella lydekkeri and suinine Propotamochoerus hysudricus. The specimens are isolated teeth, fragments of maxilla, mandibles and horn cores. The Dhok Pathan Fm. is generally composed of claystone, siltstone and sandstone beds and, based on the mammalian fauna, the Padhri fossil locality is dated as Late Miocene. Thi99s formation was deposited in a subtropical paleoenvironment and the predominance of fossil bovids indicates extremely moist conditions with small but frequent standing water bodies.     

华南早更新世巨猿动物群的ESR/U-系年代

华南的第四纪喀斯特洞穴堆积含有丰富的哺乳动物群化石,其中以步氏巨猿（Gigantopithecus blacki）为代表的巨猿动物群化石一直备受学术界关注。为建立巨猿动物群演化的绝对年代框架,本文采用牙化石ESR/U-系结合测年法测定重庆龙骨坡、广西田东吹风洞和么会洞以及广西崇左三合大洞动物群的地质年代。牙化石ESR/U-系结合测年法是将牙化石样品的ESR分析（古剂量和年剂量）与U-系分析（U-Th同位素）相结合用来模拟牙齿各个组织在地质时期的U-吸附过程,以计算牙组织中的U对古剂量的贡献,因此ESR/U-系年代比常规ESR年代更准确。本文测定了28个大型哺乳动物牙化石的ESR/U-系年代,结果表明龙骨坡动物群的地质年代为上新世晚期至早更新世早期,可限定为2.86~1.95Ma;吹风洞和么会洞动物群的地质年代在误差范围内一致,为1.97~1.38Ma;三合大洞动物群的地质年代为早更新世晚期至中更新世之初,约910~600ka。     

鄂西-三峡地区的古人类资源及相关研究进展

自20世纪50年代发现长阳人化石以来,迄今在鄂西-三峡地区已经发现了至少10处古人类化石地点,时代跨越了整个更新世时期,尤其以更新世中、晚期人类化石最为丰富。除人类化石外,在这一地区还发现了大量的古人类制作的石器、骨器、艺术品、装饰品等人类活动遗存,以及与古人类伴生的动物化石。近年的野外发掘及实验室研究证明鄂西-三峡地区更新世中期以来一直是古人类生存与繁衍昌盛的区域,该地区丰富的古人类资源对研究与中国古人类演化有关的一系列关键学术问题具有非常重要的价值。     

Dinosaur remains from the type Maastrichtian: an update

Isolated cranial and post-cranial remains of hadrosaurid dinosaurs have been collected from various outcrops in the type area of the Maastrichtian stage during the last few years. In the present contribution, dentary and maxillary teeth are recorded from the area for the first time. Post-cranial elements comprise a newly collected, fragmentary, large right metatarsal III and a broken ?right humerus, recently recognised in the collections of Teylers Museum (Haarlem). Unfortunately, none of these remains can be identified to species level. The available material suggests, however, that more than one taxon of non-lambeosaurine hadrosaurid and a possible euhadrosaurian are represented. Most of the new finds are stratigraphically well documented, which means that they may be linked to the recently published sequence-stratigraphic interpretation of the type Maastrichtian. Dinosaur remains recorded previously from the Maastrichtian type area are tabulated.

     

中国晚侏罗世多瘤齿兽类哺乳动物的发现及其意义

多瘤齿兽是一类已绝灭的哺乳动物,其以后部牙齿上有很多小瘤(小的隆起,或者小尖)来适于咀嚼植物为特征。总的来说,它们的门齿和臼齿与那些啮齿类相似,但在演化时间上多瘤齿兽比新生代的啮齿类早的多。多瘤齿兽是杂食者,或者说是成功开拓了其它脊椎动物无法开拓的植食生境的植食者(可以树叶、种子、蕨类、裸子植物,再加上蠕虫和昆虫为食)。由于它们多种食性和运动方式,多瘤齿兽成为中生代数量最多的哺乳动物,几乎占侏罗纪和白垩纪时期所有哺乳动物种类的一半。它们的支系是哺乳动物历史上生存时间最长的支系,出现于170 Ma前,大约绝灭于35 Ma。但是,因为多瘤齿兽具有很多独特的、高度特化的牙齿和头骨特征,古生物学家们长期困惑于它们的进化起源。最近,中国辽西发现了一件产自晚侏罗世髫髻山组的多瘤齿兽类哺乳动物。由于其牙齿上发育明显的纹饰,如很多小的脊、沟、凹槽等,新发现的哺乳动物被命名为皱纹齿兽(Rugosodon)。另一方面,由于与皱纹齿兽亲缘关系最近的哺乳动物产自西欧的侏罗纪地层,因此其种名被命名为欧亚皱纹齿兽(Rugosodon eurasiaticus)。新发现为晚侏罗世时期欧洲和亚洲的哺乳动物具有高度的相似性提供了最新的证据。皱纹齿兽是一种夜行的哺乳动物,生活于气候温和的湖滨,与长羽毛的恐龙近鸟龙、翼龙类达尔文翼龙、大量节肢动物、其它几种哺乳动物共同生活于一起。根据与现生哺乳动物的比较,并依据欧亚皱纹齿兽手部比例、末端指节的形态等,推论欧亚皱纹齿兽很可能是地栖哺乳动物,或者说地栖比攀爬的可能性更大。这一发现对于研究多瘤齿兽早期的演化、食性分异、运动适应起源等具有重要的科学意义。     

The generation at hot springs of sedimentary ore deposits, microbialites and life

Notwithstanding the current fashion which favours an epigenetic origin for what used to be termed SEDEX deposits, there are several lines of evidence to indicate that Phanerozoic base-metal orebodies of this type have at least some exhalative aspects. The fossil polychaete worms, which occur in Lower Carboniferous pyrite mounds at Tynagh and Silvermines in Ireland, have affinities to Paralvinella, an organism that lives attached to hydrothermal chimneys at the Juan de Fuca hot spring site in the Northeast Pacific. In addition, fossil tube worms, and their moulds, occur both in silica masses underlying the Carboniferous giant Red Dog sulphide orebody in Alaska and in Devonian barite and base-metal deposits in North America and in Russia, respectively. The development of sulphide and carbonate fossil microbialites over exhalative centres further supports generation of some mineral deposits on sea or lake floors. Carbonate microbialite mounds are also developing today over warm springs and seepages.The existence of an environment in which sulphide mineralisation developed at the sea floor has implications also in a different sphere. Life itself may have emerged in a similar milieu at 4.2 Ga from iron monosulphide bubbles. A primitive metabolism could have been driven by the high, long-lived and constant, redox potential of 300 mV made available across an iron monosulphide membrane which would have been spontaneously generated where sulphide-bearing, submarine, alkaline springs issued into the acidic, iron-bearing, Hadean ocean. The alkaline spring provided bisulphide to the iron-rich (carbonic) acid ocean for the precipitation of iron-monosulphide bubbles (probotryoids), as well as acetate (Shock, 1992) — the feeder to the biochemical Krebs cycle, driven in reverse by the high partial pressure of CO₂. In addition to its scientific significance, an understanding of these beginnings may well benefit research into many aspects of economic geology.Even more extreme redox contrasts are revealed by the presence of sedimentary jasper or iron formation in three of the major Carboniferous sulphide orebodies in Ireland. Pyritic sulphide microbialites also grew over some of the associated fossil hot-spring sites and may be recognised by their bacteriogenic δ³⁴S values (−20 to −40‰). Recognition of such fossil hot-spring sites could lead to further discoveries of SEDEX deposits.     

Differential diagenesis of strontium in archaeological human dental tissues

The investigation of prehistoric human migration from the measurement of Sr-isotope ratios within preserved tissue is critically dependent on the preservation of biogenic Sr. A number of recent studies have involved isotope ratio measurements on samples of archaeological tooth and bone, but doubt remains as to the extent of diagenesis in various skeletal tissues and the effectiveness of procedures designed to decontaminate them. The authors have compared Sr abundance and isotope ratios in enamel and dentine from archaeological teeth in order to assess the integrity of the biogenic Sr signal preserved within the respective tissues. It is concluded that enamel appears, in most cases, to be a reliable reservoir of biogenic Sr, but that dentine, and by implication bone, is not. The diagenesis of dentine is highly variable even between burials within a single site. For the majority of teeth, dentine diagenesis was not simply by addition of soil-derived Sr, but involved substantial, sometimes complete, turnover of the original biogenic material. It is suggested that, for most of the samples investigated, current decontamination techniques may not have been effective in isolating biogenic Sr from dentine. Similar considerations are likely to apply to archaeological and fossil bone, but the possibility arises to use dentine and enamel measurements to assess the effectiveness of decontamination procedures which may then be used for bone.     

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

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

Models of diffusion-limited uptake of trace elements in fossils and rates of fossilization

Many fossils are assumed to take up trace elements by a process of combined diffusion plus adsorption (DA), yet in principle composition profiles can be explained by several different diffusion-limited processes, including diffusion plus reaction or recrystallization (DR) and double-medium diffusion (DMD). The DA and DMD models are supported by REE and U composition profiles across fossil teeth, measured by laser-ablation ICP-MS, that show error-function - like diffusion profiles into enamel from the dentine-enamel interface and concentrations in the interior of enamel that are at original biogenic levels or higher. Published composition and age profiles in some Pleistocene bones may be better explained by a DR model. All three diffusion models imply linear behavior between age and distance squared, vastly simplifying U-series dating methods for Pleistocene fossils. Modeled uptake rates for fossil teeth yield a strict minimum bound on durations of about one decade to one century. The similarity of diffusion profiles in teeth, irrespective of depositional ages ranging from ∼30 ka to >30 Ma, implies that uptake occurred quickly, with a maximum duration of a few tens of kyr for typical fossil enamel; faster uptake is implied for typical fossil bone and dentine. Disparities in these uptake estimates compared to some archeological bone may reflect sampling and preservation bias for paleontological vs. archeological materials.     

Nd and Sr isotope compositions in modern and fossil bones - Proxies for vertebrate provenance and taphonomy

Rare earth elements (REE), while not essential for the physiologic functions of animals, are ingested and incorporated in ppb concentrations in bones and teeth. Nd isotope compositions of modern bones of animals from isotopically distinct habitats demonstrate that the ¹⁴³Nd/¹⁴⁴Nd of the apatite can be used as a fingerprint for bedrock geology or ambient water mass. This potentially allows the provenance and migration of extant vertebrates to be traced, similar to the use of Sr isotopes. Although REE may be enriched by up to 5 orders of magnitude during diagenesis and recrystallization of bone apatite, in vivo¹⁴³Nd/¹⁴⁴Nd may be preserved in the inner cortex of fossil bones or enamel. However, tracking the provenance of ancient or extinct vertebrates is possible only for well-preserved archeological and paleontological skeletal remains with in vivo-like Nd contents at the ppb-level. Intra-bone and -tooth REE analysis can be used to screen for appropriate areas. Large intra-bone Nd concentration gradients of 10¹-10³ are often measured. Nd concentrations in the inner bone cortex increase over timescales of millions of years, while bone rims may be enriched over millenial timescales. Nevertheless, ε_Nd values are often similar within one ε_Nd unit within a single bone. Larger intra-bone differences in specimens may either reflect a partial preservation of in vivo values or changing ε_Nd values of the diagenetic fluid during fossilization. However, most fossil specimens and the outer rims of bones will record taphonomic ¹⁴³Nd/¹⁴⁴Nd incorporated post mortem during diagenesis. Unlike REE patterns, ¹⁴³Nd/¹⁴⁴Nd are not biased by fractionation processes during REE-uptake into the apatite crystal lattice, hence the ε_Nd value is an important tracer for taphonomy and reworking. Bones and teeth from autochthonous fossil assemblages have small variations of ±1 ε_Nd unit only. In contrast, fossil bones and teeth from over 20 different marine and terrestrial fossil sites have a total range of ε_Nd values from -13.0 to 4.9 (n = 80), often matching the composition of the embedding sediment. This implies that the surrounding sediment is the source of Nd in the fossil bones and that the specimens of this study seem not to have been reworked. Differences in ε_Nd values between skeletal remains and embedding sediment may either indicate reworking of fossils and/or a REE-uptake from a diagenetic fluid with non-sediment derived ε_Nd values. The latter often applies to fossil shark teeth, which may preserve paleo-seawater values. Complementary to ε_Nd values, ⁸⁷Sr/⁸⁶Sr can help to further constrain the fossil provenance and reworking.     

Ediacaran ice-rafting and coeval asteroid impact,South Australia: insights into the terminal Proterozoic environment

Isolated quartzose pebbles, clusters of quartz granules, orthogonal aggregates of poorly sorted quartzose coarse sand, and ovoid pellets (≤2 mm long) of quartz silt occur in hemipelagic marine mudstone of the mid-Ediacaran Bunyeroo Formation exposed in the Adelaide Geosyncline (Adelaide Rift Complex), and ovoid pellets of quartz silt in cores of the correlative marine Dey Dey Mudstone from deep drillholes in the Officer Basin, South Australia. This detritus is interpreted respectively as dropstones, dumps, and frozen aggregates dispersed by sea ice possibly of seasonal origin, and till pellets transported by glacial ice. The ice-rafted material in the Bunyeroo Formation only has been found <10 m stratigraphically below and above a horizon of dacitic ejecta related to the 90 km diameter Acraman impact structure in the Mesoproterozoic Gawler Range Volcanics 300 km to the west. Furthermore, till pellets have been identified 4.4 to 68 m below distal Acraman ejecta in the Dey Dey Mudstone >500 km northwest of the impact site. The Acraman impact took place at a low paleolatitude (～12.5°) and would have adversely affected the global environment. The stratigraphic observations imply, however, that the impact occurred during, but did not trigger, a cold interval marked by sea ice and glacial ice, although the temporal relationship with Ediacaran glaciations elsewhere in Australia and on other continents is unclear. Release from the combined environmental stresses of a frigid, glacial climate near sea-level and a major impact in low latitudes may have been a factor influencing subsequent Ediacaran biotic evolution.     

陕西北部发现多个新近纪哺乳动物化石新地点及其意义

在陕北黄土高原下部的红土堆积中新发现29个新近纪哺乳动物化石地点,自北向南包括神木、榆阳、佳县、横山、子洲、志丹、安塞、甘泉等地,基本覆盖整个陕北黄土高原,填补了中新世时期中国哺乳动物地理格局中东西分界线附近的大片空白。动物组合以新近纪中国北方常见的三趾马动物群成员为主,包含有三趾马(Hipparion)、大唇犀(Chilotherium)、萨摩麟(Samotherium)、巨鬣狗(Dinocrocuta)、弓颌猪(Chleuastochoerus)、羚羊(Gazella)等,其组合特点类似于府谷老高川中部动物群。新发现的、多地点的化石材料进一步表明,在陕西北部晚中新世约6.7 Ma左右,森林-草原混合型三趾马动物群的分布可能相当广泛,而约7.8 Ma和约5.7 Ma两期的哺乳动物群的分布可能相对局限。

     

Identifying the accidental-natural mortality of leporids in the archaeological record: insights from a taphonomical analysis of a pitfall without evidence of human presence

Leporids (Lagomorpha, Mammalia), especially the mountain hare (Lepus timidus) and the European rabbit (Oryctolagus cuniculus), have been among the most abundant small game in western Europe since the Pleistocene. These animals are preferred prey for more than 40 predators, which increases the chances of finding their skeletal remains at archaeological or natural sites, and in particular karstic formations alternately occupied by Palaeolithic human societies and other predators. Moreover, specific eco-ethological characteristics for both species also offer the possibility to produce a substantial quantity of their bones accumulated by natural mortality without predation, making it more difficult to identify their origin in the fossil record. Despite this fact, the taphonomic signature of accidental-natural accumulations of leporids in karsts, such as pitfalls, has never been properly characterised. In order to address these issues, we carried out a detailed taphonomic study of leporid remains in a pitfall without any evidence of human activity, namely at Coulet des Roches (Monieux, Vaucluse, south-eastern France). At this site, leporids are the most abundant species throughout the Last Glacial Maximum sedimentary sequence. The bone accumulation was analysed in order to determine the most relevant criteria to identify a natural accumulation that results from the accidental fall of individuals in the pitfall. The relative proportions of each species are consistent with their current ethology, and their mortality profiles are compatible with the structure of a living natural population. The completeness rate of the different skeletal portions for both species is relatively high, bones are less fragmented and, unlike what might be expected, very few anatomical connections were preserved. The observed anatomical representation, breakage, and bone surface modification patterns are discussed and compared with available data concerning accumulations with predation. Taken together, the identified criteria contribute valuable help in the recognition of accidental mortality in the fossil record, as well as to evaluate the proportion of leporid bones accumulated naturally and those accumulated by predation, human or not, in a deposit.     

第四纪骨化石样品的多方法对比测年

本文报道作者用14C、铀系和ESR等多种测年技术对比测定第四纪骨化石样品年龄结果,对比分析骨化石中各含碳组分14C年龄的异同。在此基础上讨论诸测年方法的可靠性和测年精度,分析哪种含碳组分最能代表骨质样品的真实年龄。对晚于40 000aB.P.的骨质样品,作者倾向于样品中氨基酸的14C测年,而对更老的样品,铀系法应优先被选用。本文还对北京周口店山顶洞遗址骨化石样品中不同含碳组分的14C测年结果做了讨论。     

Extraction of Nd isotopes from bulk deep sea sediments for paleoceanographic studies on Cenozoic time scales

Nd isotopes preserved in fossil fish teeth and ferromanganese crusts have become a common tool for tracking variations in water mass composition and circulation through time. Studies of Nd isotopes extracted from Pleistocene to Holocene bulk sediments using hydroxylamine hydrochloride (HH) solution yield high resolution records of Nd isotopes that can be interpreted in terms of deep water circulation, but concerns about diagenesis and potential contamination of the seawater signal limit application of this technique to geologically young samples.In this study we demonstrate that Nd extracted from the > 63 μm, decarbonated fraction of older Ocean Drilling Program (ODP) sediments using a 0.02 M HH solution produces Nd isotopic ratios that are within error of values from cleaned fossil fish teeth collected from the same samples, indicating that the HH-extractions are robust recorders of deep sea Nd isotopes. This excellent correlation was achieved for 94 paired fish teeth and HH-extraction samples ranging in age from the Miocene to Cretaceous, distributed throughout the north, tropical and south Atlantic, and composed of a range of lithologies including carbonate-rich oozes/chalks and black shales. The strong Nd signal recovered from Cretaceous anoxic black shale sequences is unlikely to be associated with ferromanganese oxide coatings, but may be derived from abundant phosphatic fish teeth and debris or organic matter in these samples.In contrast to the deep water Nd isotopic signal, Sr isotopes from HH-extractions are often offset from seawater values, suggesting that evaluation of Sr isotopes is a conservative test for the integrity of Nd isotopes in the HH fraction. However, rare earth elements (REE) from the HH-extractions and fish teeth produce distinctive middle REE bulge patterns that may prove useful for evaluating whether the Nd isotopic signal represents uncontaminated seawater. Alternatively, a few paired HH-extraction and cleaned fish teeth samples from each site of interest can be used to verify the seawater composition of the HH-extractions. The similarity between isotopic values for the HH-extraction and fish teeth illustrates that the extensive cleaning protocol applied to fish teeth samples is not necessary in typical, carbonate-rich, deep sea sediments.     

广西柳州白莲洞遗址的铀系年龄

因涵盖新—旧石器过渡、出土人类化石及别具一格的石制品 ,广西柳州白莲洞遗址对古人类和石器文化的研究具有重要意义。新生碳酸盐岩铀系测年的结果表明 :该遗址新—旧石器间的过渡期不超过 3ka± ,短于基于钙板 1 4 C测年得出的 6 ka± ;西 6层钙板和石笋的 2 3 0 Th年龄为 16 0 ka± ,西 7层人牙化石的年代应大于此值 ;“白莲洞式”石片打制法呈清晰的演化脉络 ,时间跨度至少为 15 0 ka。邻近的柳江人地点和土博前洞铀系测年结果与本文一致。这些地点年代位置的大幅度前移 ,是我国晚更新世人类遗址已有年代框架被总体压缩的例证。具现代解剖特征的智人在中国出现的年代很可能比原认为的早得多     

四极杆电感耦合等离子体质谱仪测定动物牙化石中U和Th同位素

四极杆电感耦合等离子体质谱仪(Inductively Coupled Plasma-Quadrupole Mass Spectrometry,简称 ICP-QMS)可用于U和Th同位素分析。目前,ICP-QMS能实现精度大约为0.3 % (U)和1 % (Th)的测量分析,可提供误差在1 % ~10 % 的 230 Th/U年代数据。本文用ICP-QMS分析了采自意大利南都Loreto旧石器地点的4颗马牙化石样品,并对已发表的UTEVA树脂提纯U和Th的流程做了进一步改进,使其适用于动物牙化石样品。样品中的U和 Th含量的平均测量精度(2σ)分别为0.3 % 和0.6 %; 234 U/238 U和 230 Th/238 U活度比平均精度(2σ)分别为0.3 % 和0.8 % 。数据表明同一颗牙化石的不同组织的U含量可有数量级差别,同时它们的U-Th同位素活度比也可显著地离散( >2σ),从而导致不一致的 230 Th/U 年代结果。如今测定的各牙组织的U-Th同位素数据可用于模拟U的迁移历史; U-系分析与电子自旋共振测年技术相结合或可更好地估计样品的地质年代。     

The missing Myopus: plugging the gaps in Late Pleistocene small mammal identification in western Europe with geometric morphometrics

Lemmus and Myopus are two lemming species with distinct habitat requirements but which show very similar dental morphologies. They are thus extremely difficult to distinguish from one another in the fossil record on the basis of their dental remains, leading to poor understanding of the palaeobiogeographical evolution of Myopus as well as inaccurate palaeoenvrionmental reconstructions. Currently, the presence of Myopus in the fossil register from the Pleistocene is still debated and no firm occurrence of this lemming in western Europe has yet been confirmed for the Late Pleistocene. In this paper, we used geometric morphometrics on modern material to establish morphological differences between Lemmus and Myopus teeth (first lower and third upper molars). Morphological data were then used to build a robust linear discriminant model able to confidently classify isolated teeth of these two genera, and finally, linear discriminant models were used on fossil remains of Lemmus/Myopus from two Late Pleistocene archaeological/palaeontological sites (Grotte des Gorges and Gully Cave). This study demonstrates, for the first time, the presence of Myopus schisticolor in west European Late Pleistocene sites between the end of Marine Isotope Stage 3 and the beginning of the Holocene, during climatic events that favoured the development of taiga forest of birch and pine in these regions.     

Palaeoecology of a Late Weichselian vertebrate fauna from Nmre Lyngby, Denmark

Investigations at a Late Weichselian freshwater basin in northwestern Jutland, Denmark, yielded a fairly rich assemblage of vertebrate remains, mostly bones and teeth of small mammals. The remains are primarily allochthonous and the bones have been subjected to different taphonomic pathways and agents. AMS ¹⁴C-dates on terrestrial organic remains provided ages of Middle to Late Allerød time. Identifications revealed the first fossil record in Scandinavia of Rana arvalis, Sorex minutus, Ochotona cf. pusilla, Microtus gregalis, Microtus oeconomus , and Sicista cf. betulinu. Spermophilus cf. major and Desmana moschata , previously found only once and twice respectively, were retrieved, and Sorex araneus and Arvicola terrestris were recovered for the first time beyond the Atlantic chronozone. Ecologically, the Nørre Lyngby small mammal fauna can be characterized by its very high and almost equal proportions of boreal forest and steppe elements followed by a relatively high proportion of tundra elements. The fossil species share a modern area of sympatry north of the Caspian Sea from the river Volga in the west to the southern and western slopes of the Urals. If, however, the large Allerød mammals are added, the fauna is without modern analogues. The Nørre Lyngby fauna can be seen as a last expansion of the North European glacial fauna. Provided that an absolute chronology and a differentiated sea-level curve for the area can be established, the Nsrre Lyngby fauna could become important for studies in mammalian dispersal and migration rates.