Paleocene-Eocene Boundary Research Articles

A revised Paleocene (Teurian) dinoflagellate cyst zonation from eastern New Zealand

Organic-walled dinoflagellate cyst (dinocyst) assemblages are documented from Paleocene (New Zealand Teurian Stage) sediments in five sections from eastern New Zealand: Tawanui, Angora Road and Toi Flat-1 core in the East Coast Basin, mid-Waipara River in the Canterbury Basin, and ODP Site 1121 on the eastern margin of Campbell Plateau. Based on dinocyst results from these sections, along with published earliest Paleocene records from the East Coast, Canterbury and Great South Basins, a revised Paleocene (Teurian) dinocyst zonation is proposed. The zones are labelled as NZDP — New Zealand Dinocyst Paleocene — and are all interval zones. The eight zones, NZDP1 to NZDP8, encompass the entire Paleocene, from the Cretaceous–Paleogene boundary at 66.04Ma to the Paleocene–Eocene boundary at 55.96Ma. Correlation of the NZDP zones with the International and New Zealand Time Scales is provided, and is primarily based on correlation with calcareous nannofossil biostratigraphy. Three new dinocyst species are described: Leptodinium? pustulatum sp. nov., Cerodinium angulatum sp. nov., and Vozzhennikovia tawanuiensis sp. nov.

A Study on Temperature Changes in Paleocene-Eocene Boundary based on Planktonic Foraminifera in Binak 4 Subsurface Section in Bushehr Province, Southwest of Iran

This study seeks to investigate and identify Paleocene-Eocene boundary in Binak 4 subsurface section in Bushehr province and the effect of temperature changes on the behaviour of planktonic foraminifera. In order to do so, 13 genera and 46 species from Planktonic foraminifera were identified, and two assemblages comprising warm water foraminiferal assemblage and cool water foraminiferal assemblage were segregated. The study of biological events on foraminifera under investigation utilizing universal biozonation led to 5 biozone and 5 subzone segregates. According to the known fossil assemblages and the defined biozones, age in this study was considered late Paleocene (late Selandian) to latest early Eocene (Ypresian). Biostratigraphic evidences (episodic extinction in cool water foraminiferal assemblages and diversity in warm water foraminiferal assemblages) at depths of 8750-8760 (ft.) are indicative of temperature changes and introducer of a global event termed ‘Paleocene-Eocene Thermal Maximum’ (PETM) at this depth. Moreover, In view of the extinction of late Paleocene index species at depths of 8760-8770 (ft. ) and the emergence of early Eocene index species at depths of 8640-8650 (ft.), Paleocene-Eocene boundary is located at depths of 8750-8760 (ft..) in P5 biozone or P5-E1 biozone.

Enhanced terrestrial input supporting the Glomospira acme across the Paleocene-Eocene boundary in Southern Spain

Following the deep-sea benthic foraminiferal extinction event (BEE) across the Paleocene Eocene Thermal Maximum (PETM), certain groups of agglutinated benthic foraminifera bloomed and dominated the foraminiferal assemblage. In particular, the widespread proliferation of Glomospira, Glomospirella and Repmanina species, known as the “Glomospira acme”, has been recorded in bathyal to abyssal depths of the eastern North Atlantic and Tethys oceans. The Glomospira acme has been traditionally linked to the widespread rise in the calcite compensation depth (CCD) during the PETM, although recent studies suggest that calcite dissolution was not the only factor responsible for the acme. In order to investigate alternative paleoenvironmental causes that may have contributed to the Glomospira acme, we studied the Glomospira spp. abundances, their variations in test sizes, and the provenance of organic matter sources as indicated by lipid biomarkers in the Alamedilla section (southern Spain). Test size analysis for the acme interval reveals a reduction in test size characteristic of rapid population growth and reproduction due to the lack of interspecific competition after the BEE. Biomarkers for terrestrial sources suggest an increased influx of refractory organic matter to the seafloor across the PETM, and particularly during the Glomospira acme. We hypothesize that this influx may have favored the proliferation of detritivorous taxa such as Glomospira spp., which may have fed on refractory organic detritus that was not easily digested by other calcareous or agglutinated species. In summary, we suggest that an increased input of refractory organic matter across the PETM must have exacerbated the environmental stress caused by calcite dissolution and global warming leading to the Glomospira acme.

Dental and tarsal anatomy of ‘Miacis’ latouri and a phylogenetic analysis of the earliest carnivoraforms (Mammalia, Carnivoramorpha)

ABSTRACT One of the earliest basal carnivoraforms, Miacis latouri, previously known by only two teeth from the earliest Eocene of Dormaal, Belgium, is here described based on about 280 new specimens from Dormaal, allowing illustration of almost the entire deciduous and permanent dentition and thus giving information on the dentition of an early basal carnivoraform species and its variability. Based on the dental features, we refer the species to a new genus, Dormaalocyon. We identify possible sexual dimorphism in D. latouri that is less pronounced than in Uintacyon rudis. We also describe for the first time the tarsal bones (calcaneum and astragalus) of D. latouri; these indicate arboreal capabilities for this species. In order to ascertain the position of Dormaalocyon among basal carnivoraforms, we performed a phylogenetic analysis of the carnivoramorphans. Among basal carnivoraforms, three groups are recovered: the Uintacyon group, Oodectes group, and the Vulpavus group. Dormalocyon is one of the most primitive carnivoraforms and is closely related to North American Vulpavus and Miacis species. We propose that the two latter genera are North American with an ancestry that involves the European Dormaalocyon; this implies a dispersal of carnivoraforms from Europe to North America near the Paleocene-Eocene boundary. Finally, the topology of the phylogenetic tree supports a Paleocene radiation of the carnivoraforms, which is presently unknown.

Shifts in diversification rates and clade ages explain species richness in higher‐level sedge taxa (Cyperaceae)

Understanding heterogeneity in species richness across the tree of life is a challenge in evolutionary biology. The sedge family, Cyperaceae, is classified into tribes that exhibit a roughly 200-fold range in species richness. The Cyperaceae present an excellent case study in the determinants of species richness within higher-level taxa. We used secondary calibration based on prior studies and fossils from a rush (Juncaceae) and five sedges to calibrate two previously published Cyperaceae phylogenies, then compared our results to previous molecular clock analyses. We used an information-theoretic approach to identify shifts in lineage diversification rates and phylogenetic generalized least squares to fit alternative models of clade species richness. Our results suggest a late Cretaceous origin for Cyperaceae (76-89 mya). The inferred 0.06 speciation events Ma(-1) is comparable to overall diversification rates in the order Poales but faster than angiosperm background rates. A threefold increase in diversification rate at the base of the species-rich SDC+FAEC clade is correlated with climatic changes during the Paleocene-Eocene boundary (ca. 55 mya). The greater driver of among-clade variance in species richness, however, is clade age (simple R(2) = 0.334, P = 0.0006). Although shifts in diversification rates play a role in the generation of heterogeneous patterns of species richness, our study demonstrates that variance in clade age alone explains ca. 33% of among-clade variation in species diversity, which stands in contrast to the general pattern for angiosperms.

Biostratigraphic Study of the Paleocene–Eocene Boundary in Northern Tunisia, North Africa

AbstractA new section at Jebel Gorraa, in northern Tunisia, contains the Paleocene–Eocene transition interval. Sample analysis of the section delivers abundant and diverse microfauna of planktonic and benthic foraminifera. Biostratigraphically, the Acarinina sibaiyaensis index‐species is identified for the first time in this region, which allows us to specify the location of the Paleocene–Eocene boundary as well as the first E1 biozone of the lower Eocene. Samples from this biozone contain calcitic tests poorly preserved with an enrichment of iron oxide signifying a period of upheaval in local marine environments linked to the global warming of the Paleocene–Eocene Thermal Maximum (PETM), the marker for the P/E boundary.

Do the large carbon isotopic excursions in terrestrial organic matter across Paleocene–Eocene boundary in India indicate intensification of tropical precipitation?

Five distinct transient warming (hyperthermal) events (Paleocene–Eocene Thermal Maximum [PETM], H1/ETM2/ELMO, H2, I1, and I2), marked by negative carbon isotope excursions (CIEs) occurred between Late Paleocene and Early Eocene (~56 to 52Ma) interval. However, not many records of either the PETM or definitive Early Eocene Hyperthermals (EEHs) are yet available from terrestrial realm in the tropics except two neo-tropical sections of Colombia and Venezuela (Jaramillo et al., 2010). Therefore, response of the tropical biosphere to these warming events is not very well known. Here we report high resolution carbon isotope (δ13C) chemostratigraphy, biomarker, calcareous nannofossils, and pollen data from the Cambay shale Formation of Western India (paleolatitude~5°S), which show complete preservation of all the above CIE events including the PETM, hitherto unknown from tropical terrestrial record. Comparatively larger magnitudes of CIEs for all the hyperthermal events (the PETM and EEHs) point towards a possible intensification of precipitation during the PETM and all the early Eocene hyperthermal/CIE events. This inference is supported by data of lignin phenols and presence of tropical rain forest elements spanning the entire time period ~56–52Ma and suggest that higher organic burial and soil erosion favored deposition of thick lignitic seams as a consequence of high tropical precipitation.

Paleoecology of archaeocete whales throughout the Eocene: Dietary adaptations revealed by microwear analysis

Archaeocete whales originated from within terrestrial artiodactyls around the Paleocene–Eocene boundary and gave rise to modern toothed whales (Odontoceti) and baleen whales (Mysticeti) at the end of the Eocene. The cetacean transition from life on land to life in water is documented by archaeocete fossils reflecting stages of increasing aquatic adaptation throughout the Eocene. During this time, feeding and diet in cetaceans supposedly changed from herbivory or omnivory to piscivory and carnivory. It is still not fully understood whether an early dietary shift was the reason for cetaceans to abandon land, or whether aquatic feeding evolved later, at a semiaquatic stage. To assess archaeocete diet and its evolution through time, we analyzed dental enamel microwear of an early Eocene pakicetid, middle Eocene protocetids, and middle-to-late Eocene basilosaurids. We quantified wear features on shearing facets of upper and lower cheek teeth using low-magnification stereoscopic microwear analysis. Results were compared with the microwear of extant fully-aquatic odontocetes, semiaquatic pinnipeds, and terrestrial carnivores. The microwear of archaeocetes strongly resembles that of modern pinnipeds and, to a lesser extent, odontocetes that include cephalopods, crustaceans, bivalves and gastropods, as well as marine birds and mammals besides fish in their diet. The degree of aquatic adaptation in archaeocetes seems to be reflected in their diet. Aquatic feeding is already indicated for the late early Eocene terrestrial Pakicetus inachus since its microwear already resembles that of the middle Eocene semiaquatic protocetids. Middle-to-late Eocene fully-aquatic basilosaurids turn out to be separated from the protocetids and P. inachus in all parts of the study and apparently ingested more or larger hard items. We conclude that cetaceans were not primarily piscivorous, and that piscivory and carnivory, where present in modern cetaceans, evolved from a very diverse diet in Eocene archaeocetes that included various kinds of invertebrates and vertebrates. Inclusion of mammals in the cetacean diet is not a recent dietary specialization but might be as old as the middle Eocene, implied by a microwear signal in Qaisracetus arifi similar to those of the modern hyena and the killer whale. Consumption of mammal meat was very likely well-established in middle-to-late Eocene forms (heavy gouging and extremely destructive macroscopic wear in Basilosaurus isis).

Climate‐driven generation of a fluvial sheet sand body at the Paleocene–Eocene boundary in north‐west Wyoming (USA)

AbstractAn unusually thick and laterally persistent fluvial sand body crops out at the Paleocene–Eocene boundary within the northern part of the Bighorn Basin in northwest Wyoming, USA. The generation of this ‘Boundary Sandstone’ was previously ascribed to a period of reduced subsidence; however, a new carbon isotope record presented herein shows it to be intimately correlated to the Paleocene–Eocene Thermal Maximum (PETM), an extreme global warming event ca. 56 Ma. This study evaluates the impacts of the PETM on fluvial deposition in the basin by integrating sedimentological data with geochemical, palaeoichnological, and palaeobotanical proxy records. Compared to pre‐ and post‐PETM fluvial sand bodies, the Boundary Sandstone is more highly amalgamated, both vertically and laterally, but shows no changes in lithofacies associations, palaeodispersal directions, palaeoflow depths, or palaeochannel widths. At its thickest, the Boundary Sandstone resides entirely within the main body of the PETM, an ca. 113 kyr time interval when global pCO2 levels and temperatures were at their highest, and local mean annual rainfall low, floodplains well drained and vegetation comparatively sparse. The totality of data sets imply that the Boundary Sandstone is related to the preferential removal of fine‐grained floodplain deposits by either: (i) rapid readjustments in river gradients related to documented short‐term precipitation oscillations or (ii) reductions in the cohesiveness of overbank sediments related to decreased rooting density and water table fluctuations. Hence, short‐term climate perturbations may manifest within large‐scale depositional patterns in ways ostensibly like tectonics.

Scolecophidia (Serpentes) of the Late Oligocene and Early Miocene, North America, and a fossil history overview

An abundant fossil record of the snake clade Scolecophidia exists in Europe; however, the minute snake is noticeably absent in reports about the North American Paleogene and Neogene. Presented here are four localities from Florida, USA, that contain scolecophidian remains older than the Pleistocene: Thomas Farm (late Early Miocene, Hemingfordian Land Mammal Age, LMA), Live Oak (Oligocene-Miocene transition, latest Arikareean LMA), White Springs 3B (late Arikareean LMA), and Brooksville 2 (Late Oligocene, middle Arikareean LMA). These remains extend their known existence by about 26m.y. and are now the oldest reported scolecophidian remains in North America. Molecular evidence on extant scolecophidians concludes that these tiny snakes have a Gondwanan origin. Interestingly, the oldest record of a scolecophidian is from Europe (Belgium) and dates back to the middle Paleocene (MP 1–5). The earliest African record of the snake clade comes from the Paleocene-Eocene boundary in Morocco. The clade is apparently absent from Europe and Middle East deposits dating from the latest Eocene through to the latest Oligocene (MP 19–30) and to the Early Miocene (MN 4). A portion of this time is known as the booid ‘Dark Period’ which represents an apparent response to global aridization and cooling. Scolecophidians appear to re-emerge into the southern Eurasian record in the Early Miocene (MN 4) and become widely dispersed throughout Europe and Middle East. The fossil record of these minute snakes is largely absent in southern Asia and South America. It is possible that the current lack of a decent fossil scolecophidian record outside of Europe and Middle East is due mainly to a bias in the methodology to recover fossils; wet sieving sediments through<1.0mm mesh is needed to recover the minuscule vertebrae.

Unraveling the Paleocene-Eocene thermal maximum in shallow marine Tethyan environments: the Tunisian stratigraphic record

Despite the increasing understanding of the Paleocene-Eocene thermal maximum (PETM) in open marine environments, shallow marine settings remain relatively unexplored. We investigated an upper Paleocene to lower Eocene shallow-water sequence near Kalaat Senan in Tunisia (Sidi Nasseur and Wadi Mezaz sections) in order to generate a stratigraphic framework of the PETM in a shallow marine fine-grained siliciclastic setting of the Southern Tethys. These sections expose the top part of the El Haria Formation (Fm.), the Chouabine Fm. and the lower part of the limestone bearing El Garia Fm., covering the upper Paleocene- lower Eocene (NP9a to NP11). The PETM interval is situated near the top of the El Haria Fm. and the re- gional stratigraphy is compared to the well-known Egyptian setting. The isotope record of total organic car- bon (δ 13 Corg) reveals the characteristic negative carbon isotope excursion (CIE), comparable to the δ 13 Corg record of the Global Boundary Stratotype Section and Point of the Eocene at Dababiya (Egypt). Although the Tunisian PETM interval is quite expanded, no anomalous beds are observed and only the CIE core is part- ly represented as the top part of the PETM is truncated. In addition to a well-expressed CIE, the position of the Paleocene-Eocene boundary is supported by the appearance of nannoplankton (Discoaster araneus) and foraminiferal (e. g. Acarinina multicamerata) marker taxa. Furthermore, ostracode and benthic foraminifer- al turnovers coincide with the onset of the PETM and are characterized by the disappearance of many com- mon Paleocene taxa (e. g. Frondicularia aff. phosphatica) in this area. The lowest occurrences of Alo- copocythere attitogonensis and Buntonia? tunisiensis (ostracodes), Reophax sp. 1 (benthic foraminifera) and Fasciculithus tonii (calcareous nannoplankton) may be applicable for regional correlation. These results in- dicate that characteristic PETM taxa evolved and/or dispersed immediately after the main δ 13 Corg shift.

Paleohydrological and paleoenvironmental changes recorded in terrestrial sediments of the Paleocene–Eocene boundary (Normandy, France)

The Paleocene–Eocene boundary (55.8Ma) is associated with the Paleocene–Eocene Thermal Maximum (PETM), which is characterized by a negative Carbon Isotope Excursion (CIE), reflecting a major perturbation of the carbon cycle, and by an extreme and rapid global warming. The Cap d'Ailly area (Upper Normandy, France), in which previous studies have revealed the Paleocene–Eocene transition, is a reference locality for organic-rich terrestrial and lagoonal deposits of the “Sparnacian” stage, widespread in Northwestern Europe. In this study, we focus on the organic matter content of the Vasterival section. Organic data (Rock-Eval, palynofacies, biomarker analyses and compound specific isotope analyses) were acquired in order to constrain the paleoenvironmental and paleohydrological changes that occurred at the Paleocene–Eocene boundary. Stable carbon isotope compositions of higher plant leaf wax n-alkanes reveal a CIE of −4.5‰, extending throughout the second half of the studied section. Palynofacies observations reveal: (i) an abrupt shift from a closed, quiescent marsh pond to an open eutrophic swamp subjected to algal blooms, concomitant with the onset of the CIE; and (ii) the evolution from a swamp to a tidal flat due to the marine transgression that occurred during the PETM. Higher plant biomarkers and their hydrogen isotopic composition compared to nitrogen analyses suggest: (i) dry episodes just before the PETM that may help to understand the triggering of this hyperthermal event; and (ii) a moister climate associated with a stronger seasonality during the early PETM.

Climatic and diagenetic signals in the stable isotope geochemistry of dolomitic paleosols spanning the Paleocene–Eocene boundary

The precipitation of primary dolomite in soil is rare and controversial, and its occurrence indicates highly unusual geochemical and climatic conditions. We utilize isotopic and petrographic techniques, including clumped isotope thermometry, to evaluate diagenetic alteration and preservation of primary climatic signal in dolomitic paleosol nodules from a section spanning the Paleocene–Eocene boundary in central Utah. Isotopic measurements differentiate samples into groups that may be interpreted in terms of alteration; however moderate burial depths and extreme warmth during the interval of soil formation make it difficult to reach definitive conclusions from isotope values alone. With the addition of petrographic analysis, including cathodoluminescence and scanning electron microscopy, we are able to identify textural differences between samples suggesting differing amounts of recrystallization. We conclude that while some nodules have experienced significant diagenetic alteration the original nodule mineralogy is dolomite, and the majority of sampled nodules retain a primary paleoclimate signal. Early Paleogene temperatures recorded at this site are considerably warmer than those suggested for the continental interior from alternate proxies, a result that may be partially the result of the clumped isotope temperatures recording warm season soil temperatures, rather than mean annual air temperature. Soil water isotopic composition is suggestive of heightened aridity, particularly through the Paleocene–Eocene Thermal Maximum (PETM).

Evolution of the Paleocene-Early Eocene larger benthic foraminifera in the Tethyan Himalaya of Tibet, China

The Paleocene-Early Eocene larger benthic foraminifera (LBF) in the far eastern Neo-Tethyan Ocean of Tibet still remain poorly known. Here, we present a novel, high-resolution larger foraminiferal biozonation from the shallow-water limestones in Tibet, which will improve our current understanding of the larger foraminiferal evolution in the eastern Neo-Tethyan Ocean. Based on one continuous section at Tingri and three separate sections at Gamba, ten Shallow Benthic Zones (SBZ 1–10) have been designated in Tibet by following the principle of Oppel Zone. In contrast to those in Europe, the Paleocene LBFs in Tibet are characterized by high diversification of Lockhartia, Kathina, Daviesina, Miscellanea, Ranikothalia, and Operculina and show progressively increasing diversity of genera and species during SBZ 2–5. Adult dimorphism and large shell size of some LBFs as well as differentiation of the diversity between genera and species initiated as early as SBZ 3. It suggests that the occurrence of the Larger Foraminifera Turnover (LFT) was probably not synchronous in the entire Neo-Tethyan Ocean, because in Europe, the LFT was generally thought to occur at the beginning of SBZ 5. During the Early Eocene, the LBFs in Tibet decreased markedly on the generic level and increased on the species level, and some new genera (Alveolina, Orbitolites, Nummulites, Assilina, Discocyclina) have gained predominance in Tibet. It is nearly identical to the evolution of the LBFs in Europe and indicates a high-degree homogenization of the LBFs in the entire Neo-Tethyan Ocean. Furthermore, the Paleocene-Eocene (P-E) boundary in shallow-water environments has been clearly identified by us, and it is situated in the upper part of SBZ 5 and associated with no evident biotic turnover of shallow benthic foraminiferal communities. The possible diachroneity of the LFT in the Neo-Tethyan Ocean and the evident lagging of the Paleocene-Eocene Thermal Maximum (PETM) behind the LFT imply that the LFT could only be the result of a natural evolutionary process and has no linkage with the PETM. Notably, a transient but distinct larger foraminiferal extinction and origination (LFEO) event has been found in Tibet, which is characterized by a sudden disappearance of all Paleocene lamellar-perforate LBFs, such as Lockhartia, Kathina, Daviesina, Miscellanea, Ranikothalia, and Operculina, and the initial dominance of the Early Eocene porcellaneous-walled Alveolina. The LFEO marks the boundary between SBZ 5 and 6, and might only occur in the low-latitude areas of the Neo-Tethyan Ocean. Surprisingly, the LFEO coincides with the initial recovery of the Carbon Isotope Excursion (CIE), and their synchronicity implies that some possible mechanisms causing the rapid recovery of the CIE probably had also led to the LFEO in the shallow-water environments.

Evidence for abundant isolated magnetic nanoparticles at the Paleocene–Eocene boundary

New rock magnetic results (thermal fluctuation tomography, high-resolution first-order reversal curves and low temperature measurements) for samples from the Paleocene-Eocene thermal maximum and carbon isotope excursion in cored sections at Ancora and Wilson Lake on the Atlantic Coastal Plain of New Jersey indicate the presence of predominantly isolated, near-equidimensional single-domain magnetic particles rather than the chain patterns observed in a cultured magnetotactic bacteria sample or magnetofossils in extracts. The various published results can be reconciled with the recognition that chain magnetosomes tend to be preferentially extracted in the magnetic separation process but, as we show, may represent only a small fraction of the overall magnetic assemblage that accounts for the greatly enhanced magnetization of the carbon isotope excursion sediment but whose origin is thus unclear.

Northward range extension of a diminutive-sized mammal (Ectocion parvus) and the implication of body size change during the Paleocene–Eocene Thermal Maximum

An abrupt global warming event marks the Paleocene–Eocene boundary, known as the Paleocene–Eocene Thermal Maximum (PETM). The event is distinguished in the strata globally by a significant negative excursion of δ13C ratio values. The response of the terrestrial biota to the abrupt climatic change has been well studied in northern Wyoming in the Bighorn Basin, where it has been observed that the mammalian fauna during the global warming event is represented by smaller, but morphologically similar species to those found later in the Eocene. Various hypotheses have been proposed to explain the observation smaller body sizes during the global warming event. In this article, evidence is presented to support the hypothesis that the observed body size decrease during the PETM was influenced by the appearance of smaller southern species who extended their geographic range northward during the abnormal global warming event. Using disperse organic carbon isotopic ratios of bulk sediment, the negative excursion of δ13C was located in the Piceance Creek Basin of western Colorado, 400km to the south of the Bighorn Basin. Below the stratigraphic level marking the negative carbon excursion in the Piceance Creek Basin are five specimens of the phenacodontid mammal (Ectocion parvus), a diminutive species of the genus Ectocion restricted to the basal Eocene (Wa-0 Biozone) in northern Wyoming. The five specimens of E. parvus are associated with a late Paleocene (Clarkforkian) mammalian fauna in Colorado, implying that the diminutive species extended its geographic range northward during the global warming event. This evidence supports biogeographic models that assume poleward biogeographic shifts during global warming events, and will have modern day implications for the conservation of species as global temperatures rise in the near future.

Earliest record ofPlatychoerops(Primates, Plesiadapidae), a new species from Mouras Quarry, Mont de Berru, France

Plesiadapids are extinct relatives of extant euarchontans (primates, dermopterans, and scandentians), which lived in North America and Europe during the Paleocene and Early Eocene. The only genus of plesiadapid whose species are absent from Paleocene strata is Platychoerops. Further, Platychoerops is the only group found in sediments post-dating the Paleocene-Eocene boundary (PEB) by a substantial period of time based on large samples. It is also substantially different from other plesiadapids in dental features thought to reflect ecology. Its evolution has been linked to the rapid global climate change and faunal turnover marking the PEB. Platychoerops and Plesiadapis tricuspidens have been reconstructed as members of a single lineage by some authors. We describe a specimen (right p3-m3) that we attribute to a new species, Platychoeropsantiquus, from the unequivocally Paleocene (MP6) Mouras Quarry of Mont de Berru, France. It has strong morphological affinities to Platychoerops daubrei yet co-occurs with many specimens of Plesiadapis tricuspidens, as well as the plesiadapid Chiromyoides campanicus. The existence of a species of Platychoerops prior to the PEB decouples the evolution of Platychoerops from the climate change and faunal turnover event associated with the PEB. Furthermore, the co-occurrence of Platychoerops with P. tricuspidens refutes the idea of a single lineage for these taxa. Instead, Platychoerops may be more closely related to North American Plesiadapis cookei (a previous alternate hypothesis). We suggest character displacement in a Paleocene immigrant population of P. cookei resulting from competition with sympatric P. tricuspidens, as a likely scenario for the evolution of Platychoerops.

Contrasting biogeographic and diversification patterns in two Mediterranean-type ecosystems.

The five Mediterranean regions of the world comprise almost 50,000 plant species (ca 20% of the known vascular plants) despite accounting for less than 5% of the world’s land surface. The ecology and evolutionary history of two of these regions, the Cape Floristic Region and the Mediterranean Basin, have been extensively investigated, but there have been few studies aimed at understanding the historical relationships between them. Here, we examine the biogeographic and diversification processes that shaped the evolution of plant diversity in the Cape and the Mediterranean Basin using a large plastid data set for the geophyte family Hyacinthaceae (comprising ca. 25% of the total diversity of the group), a group found mainly throughout Africa and Eurasia. Hyacinthaceae is a predominant group in the Cape and the Mediterranean Basin both in terms of number of species and their morphological and ecological variability. Using state-of-the-art methods in biogeography and diversification, we found that the Old World members of the family originated in sub-Saharan Africa at the Paleocene–Eocene boundary and that the two Mediterranean regions both have high diversification rates, but contrasting biogeographic histories. While the Cape diversity has been greatly influenced by its relationship with sub-Saharan Africa throughout the history of the family, the Mediterranean Basin had no connection with the latter after the onset of the Mediterranean climate in the region and the aridification of the Sahara. The Mediterranean Basin subsequently contributed significantly to the diversity of neighbouring areas, especially Northern Europe and the Middle East, whereas the Cape can be seen as a biogeographical cul-de-sac, with only a few dispersals toward sub-Saharan Africa. The understanding of the evolutionary history of these two important repositories of biodiversity would benefit from the application of the framework developed here to other groups of plants present in the two regions.

Paleocene magneto-biostratigraphy and climate-controlled rock magnetism from the Belluno Basin, Tethys Ocean, Italy

The Paleocene South Ardo section consists of ~113m of red to gray marls and calcareous marls continuously exposed along the South Ardo riverbed in the Venetian Southern Alps of Northern Italy. Magneto-biostratigraphic data imply that the section extends from magnetic polarity Chron C29r across the Cretaceous-Paleogene boundary to Chron C24r across the Paleocene–Eocene boundary, and from calcareous nannofossil Micula murus Zone in the Maastrichtian to Zone NP10 in the Ypresian. The average sediment accumulation rate, calculated by means of magnetic-polarity correlation with published Paleocene time scales, was found to vary from ~1.2 to 23m/Myr throughout the section, and was used to calibrate the age of key calcareous nannofossil biohorizons, thus augmenting the resolution of existing time scales, as well as to migrate to the time domain the observed vertical variations of rock-magnetic properties. Our analyses allow to extend back into the Paleocene the temporal correlation between rock-magnetic properties and Earth's long-term climate previously observed in the neighboring late Paleocene–early Eocene Cicogna section. In detail, the composite South Ardo–Cicogna rock-magnetic dataset, which extends from ~65Ma to 52.5Ma, reveals that the warmer and more humid the climate, the higher the detrital hematite content of the sediments relative to maghemite/magnetite. We infer that our climate-controlled rock-magnetic curve reflects the efficiency of the silicate weathering mechanism to buffer pCO2 long-term variations, and thus Earth's climate, during the Paleocene–Eocene.

An outline of the Geology of New Caledonia; from Permian–Mesozoic Southeast Gondwanaland active margin to Cenozoic obduction and supergene evolution

The geological evolution of New Caledonia may be divided into three phases. The Gondwanan phase (Permian-Early Cretaceous), is marked by subduction along the SE Gondwaland margin. At that time, proto-New Caledonia was located in a fore-arc region in which volcanic-arc detritus accumulated; whilst accretion and subduction of oceanic and terrigenous material formed an accretionary complex metamorphosed into the blueschist facies. During the Late Cretaceous-Eocene, marginal rifting isolated New Caledonia, and after a short period of shallow water terrigenous sedimentation associated with minor volcanic activity, only pelagic sediments accumulated. A new NE-dipping subduction appeared to the E of New Caledonia at the Paleocene-Eocene boundary, it generated the eclogite-blueschist complex of northern New Caledonia, consumed the eastern Australian Plate, and eventually ended with Late Eocene obduction when the Norfolk Ridge blocked the subduction zone. Finally, during the post-Eocene phase, New Caledonia definitively emerged; this episode mainly corresponds to prominent regolith development and minor tectonic events that lead to the present morphology and to the development of supergene nickel ores.