我国部分地区E1^3—E2^1孢粉属种演变的古气候意义

通过对我国部分地区古新世晚期一始新世早期孢粉植物群演化发展规律的分析研究,结合国内外地层学研究的新进展,提出我国古新世晚期气候以暖湿为特征,且暖期的结束与始新世/古新世界限相吻合或接近,因此可以本次暖期的结束作为古新世的顶界。     

Palaeoskapha sichuanensis gen. et sp. nov. (Menispermaceae) from the Eocene Relu Formation in western Sichuan, West China

Palaeoskapha sichuanensis gen. et sp. nov. of Menispermaceae is described here for the first time based on a well preserved fossil fruit. The specimen was found in the Relu Formation of western Sichuan, West China. The specimen, straight, boat-shaped endocarp with large ventral condyle, clearly belongs to the tribe Tinosporeae. The wide aperture of the double condyle, combined with a whole shape not deeply invaginated, indicates a genus different from what was already known to science for this tribe. This fossil widens the distribution of the tribe during Eocene from North America and Europe to Asia, where it was formerly unknown.     

Correlation between the Paleocene/Eocene boundary and the Ilerdian at Campo, Spain

The Ilerdian is a well-established Tethyan marine stage, which corresponds to an important phase in the evolution of larger foraminifera not represented in the type-area of the classical Northwest-European stages. This biostratigraphic restudy of its parastratotype in the Campo Section (northeastern Spain) based on planktic foraminifera, calcareous nannofossils, dinoflagellate cysts and the distribution of the stable isotopes ∂¹³C and ∂¹⁸O is an attempt to correlate the Paleocene/Eocene boundary based on a characteristic carbon isotope excursion (CIE) marking the onset of the Initial Eocene Thermal Maximum (IETM) and the Ilerdian stage. The base of this ∂¹³C excursion has been chosen as the criterion for the recent proposal of the Global Stratotype Section and Point (GSSP) of the base of the Eocene (= base of the Ypresian) in the Dababiya Section (Egypt) to which an age of 54.9 Ma has been attributed. This level is also characterized by a marked extinction among the deep-water benthic foraminifera (Benthic Foraminifera Extinction Event, BFEE), a flood of representatives of the planktic foraminiferal genus Acarinina and the acme of dinoflagellate cysts of the genus Apectodinium. In the Campo Section, detailed biozonations (planktic foraminifera, calcareous nannofossils, dinoflagellate cysts) are recognized in the Lower and Middle Ilerdian. The correlation with the Ypresian stratotype is based on dinoflagellate cysts and calcareous nannofossils. The base of the Ilerdian is poor in planktic microfossils and its precise correlation with the redefined Paleocene/Eocene boundary remains uncertain.     

The first species of Hapalodectes (Mesonychia,Mammalia) from the middle Paleocene of China (Qianshan Basin,Anhui Province) sheds light on the initial radiation of hapalodectids

A lower jaw of the mesonychian Hapalodectes is reported from Nongshanian sediments (Upper Doumu Formation; middle Paleocene) of the Qianshan Basin (Anhui Province, China). The fragmentary mandible is only the third specimen of Hapalodectidae discovered in Paleocene deposits, and the first in south east China; it is moreover the oldest, the two other specimens having been found in Gashatan (late Paleocene) localities. The premolars and molars of the new fossil are morphologically similar to Hapalodectes dux (late Paleocene of Mongolia), which has been considered to be the most primitive hapalodectid, but their relative proportions recall H. paleocenus and the Eocene Hapalodectes species. As a result, the fossil described herein appears to be different from the other previously described species of Hapalodectes in being morphologically intermediate between H. dux and the other Hapalodectes species, notably the Bumbanian Hapalodectes hetangensis and H. huanghaiensis from China; it is thus identified as a new species, Hapalodectes lopatini (possibly a male individual). Its discovery is important because it sheds light on the initial radiation of hapalodectids. The presence of one primitive hapalodectid in Mongolia previously suggested the Mongolian Plateau as the centre of origination of this carnivorous family, but the discovery of H. lopatini in older sediments from south‐east China challenges this hypothesis. In the earliest Eocene, Hapalodectes dispersed from Asia to North America; this event being part of the ‘East of Eden’ dispersals. This event resulted in the geographical separation of two distinct Hapalodectes groups, in North America and south‐eastern China respectively.     

Fossil moonseeds from the Paleogene of West Gondwana (Patagonia,Argentina)

Premise of the Study

The fossil record is critical for testing biogeographic hypotheses. Menispermaceae (moonseeds) are a widespread family with a rich fossil record and alternative hypotheses related to their origin and diversification. The family is well‐represented in Cenozoic deposits of the northern hemisphere, but the record in the southern hemisphere is sparse. Filling in the southern record of moonseeds will improve our ability to evaluate alternative biogeographic hypotheses.

Methods

Fossils were collected from the Salamanca (early Paleocene, Danian) and the Huitrera (early Eocene, Ypresian) formations in Chubut Province, Argentina. We photographed them using light microscopy, epifluorescence, and scanning electron microscopy and compared the fossils with similar extant and fossil Menispermaceae using herbarium specimens and published literature.

Key Results

We describe fossil leaves and endocarps attributed to Menispermaceae from Argentinean Patagonia. The leaves are identified to the family, and the endocarps are further identified to the tribe Cissampelideae. The Salamancan endocarp is assigned to the extant genus Stephania. These fossils significantly expand the known range of Menispermaceae in South America, and they include the oldest (ca. 64 Ma) unequivocal evidence of the family worldwide.

Conclusions

Our findings highlight the importance of West Gondwana in the evolution of Menispermaceae during the Paleogene. Currently, the fossil record does not discern between a Laurasian or Gondwanan origin; however, it does demonstrate that Menispermaceae grew well outside the tropics by the early Paleocene. The endocarps’ affinity with Cissampelideae suggests that diversification of the family was well underway by the earliest Paleocene.     

New Eocene fossil fruits and leaves of Menispermaceae from the central Tibetan Plateau and their biogeographic implications

Menispermaceae are a pantropical and temperate family with an extensive fossil record during the Paleogene period, especially in North America and Europe, but with much less evidence from Asia. The latest fossil evidence indicates a succession of tropical to subtropical flora on the central Tibetan Plateau during the Paleogene. However, the biogeographic histories of these floras are still unresolved. Here, we report on endocarps and leaves of Menispermaceae from the Middle Eocene of Jianglang village, Bangor County, central Tibetan Plateau. The endocarps belong to two genera: Stephania, which is characterized by a horseshoe-shaped endocarp and with one lateral crest ornamented by spiny to rectangular ribs, and a condyle area; and Cissampelos (s.l.), which has two characteristic lateral ridges and a conspicuous external condyle. Associated leaves belong to the genus Menispermites, and are characterized by actinodromous primary venation, brochidodromous secondary veins, entire margins, and the presence of marginal secondary veins. The biogeographic history of Menispermaceae is complex, but evidence from these new fossils indicates an early diversification of the group in Asia, probably in response to the warming climate during the Eocene. The Jianglang flora appears to be part of a boreotropical flora, connecting Asia with North American and European floras during the Middle Eocene. The modern distribution of menispermaceous taxa found in Jianglang, as well as other families represented in the Jianglang flora, show that a tropical to subtropical climate occurred during the Eocene in central Tibet.     

Sinopaninae and Arfianinae (Hyaenodontida,Mammalia) from the Early Eocene of Europe and Asia; evidence for dispersal in Laurasia around the Paleocene/Eocene boundary and for an unnoticed faunal turnover in Europe

Hyaenodontida are represented in Europe by three subfamilies: Proviverrinae, Arfianinae and Sinopaninae. Here, we review all the specimens of Arfianinae and Sinopaninae known to date in Europe and Asia. A new Galecyon species is erected: Galecyon gallus nov. sp. We discuss the taxonomic position of the two Asian hyaenodontidans Anthracoxyaena palustris and Arfia langebadreae; the genus Anthracoxyaena is synonymized with Arfia. The analysis of the European and Asian arfianines and sinopanines provides new data concerning the dispersals and faunal events that occurred during the Early Eocene in Laurasia. The Arfianinae and Sinopaninae appeared in Europe around the Paleocene/Eocene boundary (reference-level MP7). The sinopanines are widespread in Europe; they are known in Dormaal (Belgium, reference-locality of the level MP7), Rians, Soissons, Pourcy, Try, Le Quesnoy (France), and Abbey Wood (England). The analysis of the paleogeographic distribution of all Oxyaenodonta and Hyaenodontida at and after the MP7 supports the existence of two European provinces: the North Province and Mesogean Province. We show that the Arfianinae and Sinopaninae rapidly disappeared from Europe; they are unknown in Avenay (reference-locality of the level MP8+9) and younger localities. Their disappearance from Europe is synchronous with that of the Oxyaenodonta. These observations support the existence of a faunal turnover, which occurred between the reference-levels MP7 (Dormaal) and MP8+9 (Avenay). The hypothesis of a dispersal from Europe to North America during the Paleocene-Eocene transition for the Arfianinae and Sinopaninae is supported. Moreover, the study of Arfianinae supports a dispersal from Europe to Asia around the P/E boundary, followed by a short period of endemic evolution. However, our study does not support a close relationship between Arfia and the “Arfia-like South Asian Proviverrinae” (Kyawdawia, Indohyaenodon, Paratritemnodon and Yarshea).     

Paleocene and Eocene floras of Russia and adjacent regions: Climatic conditions of their development

Climatic changes in the western and central regions of Russian Eurasia in the Paleocene and in the first half of the Eocene were caused by the dynamics and rearrangement of the systems of marine seaways: the longitudinal one, which connected the Arctic Basin with marginal seas of the Northern Peri-Tethys, and the latitudinal one, which connected the latter seas with the Atlantic. As these systems were progressively reduced, the climate in the middle latitudes changed from paratropical to a subtropical monsoon climate with a moist summer, and later to a climate with a moist winter, and, in the Late Eocene, to a humid climate without any marked seasonal variation in precipitation. The type of flora changed in agreement with these changes. In the Paleogene, cold currents constantly influenced the climate of the Northwestern Pacific rim and facilitated the development of a warm-temperate mesophilic flora.     

Fertile Woodwardia from the middle Eocene of South China and its implications for palaeogeography and palaeoclimate

The genus Woodwardia, which together with the genera Anchistea and Lorinseria comprise the subfamily Woodwardioideae of Blechnaceae, has a disjunct distribution across Central and North America, Europe and the temperate to tropical areas of Asia. Fossil records of Woodwardia occur throughout the Paleogene and Neogene of North America, Europe and Asia. However, well-preserved fertile pinna fossils of this genus have not yet been reported in South China. In this paper, a new species, W. changchangensis Naugolnykh et Song, sp. nov. is described from the middle Eocene of the Changchang Basin, Hainan Island, South China. Macromorphological and micromorphological features of the fertile pinna show a straight pinna rachis, alternate, subtriangular pinnules, acute pinnule apices, almost entire or slightly undulate pinnule margins, long-ovoid sori, stalked sporangia and spores with wing-like folds on the surface, which are characterised in detail. Overall, the present fossil is most similar to the extant species Woodwardia japonica, which mostly grows in warm and moist environments. The discovery of this new species from the Changchang Basin of Hainan Island indicates that this genus has been distributed in the low-latitude tropical regions of South China from as early as the middle Eocene. Based on this find, and previous studies of other ferns from the same site, we infer that the climate of the Palaeo-Hainan landscape during deposition of the Changchang Formation was warm and humid, similar to conditions prevailing today across this region.     

A new species of Lygodium (Schizaeaceae) from the Buxin Formation (middle Paleocene), Sanshui Basin,South China

The morphology, epidermal features and details of the conducting tissues are described for Lygodium sterile pinnules from the oil-bearing middle Paleocene strata of the Sanshui Basin, Guangdong Province, South China. A new species, Lygodium sanshuiense n. sp., is erected on the basis of being petiolulate, with palmately-lobed sterile pinnules that are often strongly dissected and have acute to acuminate apices. Lygodium is typically associated with mesic floras and its presence in the Buxin palaeoflora suggests the overall regional palaeoclimate was subtropical and humid during the middle Paleocene.     

New specimens of the mesonychid Dissacus praenuntius from the early Eocene of Wyoming and evaluation of body size through the PETM in North America

The Mesonychia is a group of archaic carnivorous mammals of uncertain phylogenetic affinities with a Holarctic distribution during the Paleogene. Intensive fossil collecting efforts in the Bighorn Basin, Wyoming, have resulted in recovery of the largest sample and most complete specimens yet known of the mesonychid Dissacus praenuntius from the second biozone of the Wasatchian North American Land Mammal Age (Wa-0). The Wa-0 biozone corresponds to the body of the Paleocene-Eocene Thermal Maximum (PETM), a brief but intense global warming event that occurred ~56 myr ago that significantly impacted terrestrial mammal faunas, including dwarfing in many mammal lineages. To evaluate the potential response of this lineage to climate change, we compared the PETM sample of D. praenuntius with those recovered from just before the PETM in the last biozone of the Clarkforkian North American Land Mammal Age (Cf-3) and just after the PETM in the Wa-1 biozone. While the sample size is still too small to say with certainty, tooth size (as a proxy for body weight) of D. praenuntius appears to be smaller during the late PETM than during either the pre-PETM Cf-3, or post-PETM Wa-1 biozones, suggesting the possibility of a muted dwarfing response to the PETM. However, the pattern observed for D. praenuntius differs from that of many other PETM mammals, as the shift to smaller body size is less pronounced and may have only occurred in late Wa-0.     

Biogeography of Eocene bryozoans from the St Vincent Basin, South Australia

The first extensive and stratigraphically detailed taxonomic study of the Middle to Late Eocene Bryozoa of the St Vincent Basin has identified more than 200 species of Cheilostomata and 50 species of Cyclostomata. There are three biogeographic groups: basin endemic, Australian and global. Two-thirds (116) of the cheilostome species and seven genera are currently considered endemic to this basin. Most species are endemic to Australia and similar to those found in the Oligo-Miocene of Victoria. The Cellariidae are a common component of most Australian Cainozoic deposits, but the species are highly dissimilar, with 13 of the 17 species here being new. The global component indicates that biogeographic links with regions outside Australia still existed in the Eocene. The cyclostome genus Reticrescis is only known from the Australian and Antarctic Eocene. Ten genera have their first occurrence in the Eocene St Vincent Basin. The Phidoloporidae and Smittinidae represent the most diverse and ubiquitous groups at a geological time close to their time of origination. Contemporaneous sediments in Antarctica, eastern Europe and North America also have a diverse fauna of this family, pointing to a strong Tethyan link. Rhamphosmittina lateralis (MacGillivray) is still extant in New Zealand, having an exceptionally long time range of 40 million years. Overall, the fauna has a distinct Late Cretaceous character. A new genus of Onychocellidae appears similar to genera that were common in Cretaceous Tethyan faunas but rare during the Cainozoic. This similarity ends in the Oligocene, after which the Australian bryozoan became endemic     

Stability and change in Tethyan planktic foraminifera across the Paleocene–Eocene transition

Examination of planktic foraminifera in the Tethys basin during the Paleocene–Eocene transition reveals two stasis intervals that are separated by a major saltation event coincident with the P–E short-term perturbation in global climate and oceanography. Changes occurred at many spatial and temporal scales as well as many taxonomic and ecologic hierarchical levels, though with various rates and magnitudes. The stasis intervals are marked by slow changes at the species level and account for 50% of the observed first and last appearances during a 2.5 Myr interval. The saltation event is marked by rapid changes at the species and morpho-guild levels and accounts for the remaining 50% of first and last appearances during an interval of about 100–200 kyr. Despite these changes, many taxonomic and ecologic units, such as the depth assemblages and genera, and faunal parameters, such as species richness and turnover rates, are stable with respect to the P–E perturbation. This coexistence of change and stability marks the crisis of Tethyan planktic foraminifera across the P–E transition and reveals the possible dynamics of ecological evolution.     

Paleogene fossil fruits of Stephania (Menispermaceae) from North America and East Asia

Stephania Loureiro is a large genus within Menispermaceae, with approximately 60 extant species naturally distributed in tropical to subtropical areas in Asia and Africa, and a few in Oceania. This genus possesses highly characteristic endocarps that facilitate identification of extant and fossil specimens. Here, we report some well-preserved fossil fruits of Stephania from North America and East Asia. The specimens indicate the endocarps were bony or woody with an obovate to obovate-rotund outline and a horseshoe-shaped locule. The endocarp length varies from 4.7 to 8.3 mm, and width from 3.7 to 7.0 mm. The endocarp has a clear foramen in the central area and is surrounded by a keel with ribs running along the dorsal surface. Only one lateral crest develops on each side of the endocarp. Two new species are recognized: Stephania wilfii Han & Manchester sp. nov. from the Paleocene to Eocene of Wyoming (USA), and Stephania jacquesii Han & Manchester sp. nov. disjunct between the late Eocene of Oregon (USA) and the late Oligocene of Guangxi Province (China). In addition, on the basis of more detailed morphological comparative analyses, we transfer the fossils formerly treated as Diploclisia auriformis (Hollick) Manchester from the early Eocene of London Clay, and the middle Eocene of Alaska and Oregon to Stephania auriformis (Hollick) Han & Manchester comb. nov. These fossil materials indicate a broader biogeographic distribution for the ancestors of extant Stephania lineages. This finding enhances our knowledge of the taxonomic and morphological diversity of Stephania and provides new evidence concerning its phytogeographic history.     

Surface-water chemistry and fertility variations in the tropical Atlantic across the Paleocene/Eocene Thermal Maximum as evidenced by calcareous nannoplankton from ODP Leg 207, Hole 1259B

Calcareous nannoplankton assemblages at Ocean Drilling Program (ODP) Site 1259 on Demerara Rise (western equatorial Atlantic) underwent an abrupt and fundamental turnover across the Paleocene/Eocene Thermal Maximum (PETM) ~55.5 m.y. ago. The PETM is marked by a dissolution interval barren or nearly-barren of nannofossils due to the rapid acidification of the world oceans. Toweius, Fasciculithus, and Chiasmolithus sharply decrease at the onset, whereas Chiasmolithus, Markalius cf. M. apertus, and Neochiasmolithus thrive immediately after the event, which also signals the successive first appearances of Discoaster araneus, Rhomboaster, and Tribrachiatus. The environmental indications of these changes were further investigated by correspondence analysis on quantitative nannofossil counts. The PETM event has been attributed to CO₂-forced greenhouse effects. At Site 1259, the elevated pCO₂ and subsequent lowered surface-water pH values at the onset of the PETM caused intensive carbonate dissolution, producing the nannofossil-barren interval. The chemically stressed habitats may well have also induced the evolution of ephemeral nannofossil “excursion taxa”, such as Rhomboaster and malformed discoasters (D. araneus and Discoaster anartios). Based on its sudden increase, Markalius cf. M. apertus is considered to have been a local opportunistic species that took advantage of the surface-water changes. At the same time, a presumably higher runoff from continental areas fertilized the western equatorial Atlantic as indicated by an increase in the abundance of r-mode specialists preferring high-nutrient conditions, such as Chiasmolithus, Coccolithus pelagicus, and Hornibrookina arca. Contrasts between the results of this study and previous work at ODP Site 690 in the Southern Ocean, the New Jersey continental margin, and the central paleoequatorial Pacific further demonstrate that the response to the PETM can be influenced by local differences in geologic setting and oceanographic conditions.     

中国东北古新世乌云植物群:榆科叉脉榆

根据叶结构特征,将黑龙江省古新世乌云植物群中的榆科叶化石确定为叉脉榆(Ulmus furcinervis (Borsuk) Ablaev),叶化石二级脉达缘且在叶缘区分叉、三级脉及顶、叶缘锯齿两侧边凸出.重新研究了前人鉴定为小叶普拉榆(Planera cf. microphylla auct. non Newberry)和乌云珍珠梅(Sorbaria wuyungensis Tao et Xiong)的叶化石并将其归入叉脉榆.     

Fossil history of the Menispermaceae (Ranunculales)

The Menispermaceae family (Ranunculales) includes more than 500 extant species. Climbers represent the majority of this family, and these plants are now distributed in all of the tropical and subtropical regions of Americas, Asia and Africa. Their endocarps show a characteristic shape that is easily identified in the fossil floras. Numerous fossil leaves are also mentioned in the literature, but the methods for identifying these fossils are often outdated and need revision. Four tribes of Menispermaceae are present in the fossil record, including Fibraureae, Menispermeae, Pachygoneae and Tinosporeae. Only the Anomospermeae are potentially lacking. The Menispermaceae appear in the Palaeocene, and are common in the Eocene, of Europe and in North America as represented by endocarps and locule-casts. The species of this age show morphological diversification, corresponding with the current familial diversity. A few specimens from the Cretaceous period could be part of this Angiosperm family. Fossils after the Eocene are scarcer, despite several relatively rich outcrops. The maximal expansion of the Menispermaceae during the Palaeocene/Eocene limit correlates with the thermal optimum of the early Tertiary and also parallels the maximal expansion of tropical and subtropical floras. The relative richness of the Eocene era in Menispermaceae could be a consequence of more intense sampling in some regions. The bias in tribe representation can be explained by evolution, ecology or taphonomic hypotheses.     

中国东北古新世乌云植物群：榆科叉脉榆

根据叶结构特征。将黑龙江省古新世乌云植物群中的榆科叶化石确定为叉脉榆（Umus furcinervis(Borsuk)Ablaev)。叶化石二级脉达缘且在叶缘区分叉,三级脉及顶,叶缘锯齿两侧边凸出。重新研究了前人鉴定为小叶普拉榆（Planera cf.microphylla auct.non Newberry)和乌云珍珠梅（Sorbaria wuyungensis Tao et Xiong)的叶化石并将其归入叉脉榆。     

中国东北古新世植物群：广义山茱萸科美中果和白令叶

描述并厘定了黑龙江省嘉荫县古新世乌云植物群中的广义山茱萸科绝灭类型镘形美中果 (Amersiniaobtrul lataManchester,CraneetGolovneva)和假古老白令叶 (Beringiaphyllumpseudoantiquum (Golovneva)Manchester,CraneetGolovneva)。将前人鉴定为昆栏树属 (未定种 ) (Trochodendronsp .)的果序化石归入镘形美中果 ;将前人确定为鲜艳杨 (Populuscarneosa)、假原始叶南蛇藤 (Celastrophyllumsubprotophyllum)、古老荚 (Viburnumantiquum)、粗糙荚 (V .asperum)、疏齿荚叶 (Viburniphyllumfinale)、乌云原始叶 (Potophyllumwuyunense)、海丹原始叶 (近似种 ) (P .cf.hay denii)、卵圆原始叶 (P .ovatifolium)和不规则克里木 (Credneriainordinata)等归入假古老白令叶     

中国东北古新世植物群:广义山茱萸科美中果和白令叶

描述并厘定了黑龙江省嘉荫县古新世乌云植物群中的广义山茱萸科绝灭类型镘形美中果(Amersinia obtrullata Manchester, Crane et Golovneva)和假古老白令叶(Beringiaphyllum pseudoantiquum (Golovneva) Manchester, Crane et Golovneva).将前人鉴定为昆栏树属(未定种)(Trochodendron sp.)的果序化石归入镘形美中果;将前人确定为鲜艳杨(Populus carneosa)、假原始叶南蛇藤(Celastrophyllum subprotophyllum)、古老荚(Viburnum antiquum)、粗糙荚(V. asperum)、疏齿荚叶(Viburniphyllum finale)、乌云原始叶(Potophyllum wuyunense)、海丹原始叶(近似种)(P. cf. haydenii)、卵圆原始叶(P. ovatifolium)和不规则克里木(Credneria inordinata)等归入假古老白令叶.