The Miocene mammal record of the Vallès-Penedès Basin (Catalonia)

The land mammal record of the Vallès-Penedès Basin (Catalonia, NE Spain) ranges from the early Miocene (Ramblian) to the late Miocene (Turolian), that is from about 20 to 7 Ma. Here we present an updated review of the mammal succession focusing on biochronology as well as on environmental and faunal changes. Based on faunal similarities with central Europe, we interpret this basin as a transitional zone between the forested environments of northern regions and the more arid landscapes of the inner Iberian Peninsula. The quality of the Vallès-Penedès record and its chronostratigraphic control is clearly better for the late Aragonian and the Vallesian (between 12.6–9.0 Ma), especially for small mammals. Therefore, we analyze small mammal diversity dynamics during this interval. Contrary to previous analyses, which found an abrupt extinction event coinciding with the early/late Vallesian boundary (the Vallesian Crisis), our results show that this pattern is due to uneven sampling. Instead, taxonomic richness slowly decreased since the late Vallesian as a result of a series of extinctions that mostly affected forest-dwelling taxa.     

Siwalik synopsis: A long stratigraphic sequence for the Later Cenozoic of South Asia

The Tertiary sediments of northern Pakistan are an exceptional record of terrestrial sedimentation and represent most of Neogene time. Foremost is the Siwalik Group of the Potwar Plateau, for which multiple, superposed fossil levels span ∼18–6 Ma. Well-developed magnetostratigraphic control provides secure dating so that Siwalik fossil horizons may be interpolated into a time scale with resolution to 100,000 years. We describe the geographic setting of the Potwar, give an overview of the temporal distribution of faunas, and discuss changes in paleohabitat and paleoecology with coinciding faunal change, as seen from the Siwalik viewpoint. The long Siwalik biostratigraphy of many successive assemblages with its resolved time scale may be compared directly with other well-dated sequences. Immigrant arrival and timing of faunal change may be traced. The basins of the Iberian Peninsula show somewhat different timing of introduction of hipparionine horses, and faunal turnover in the Siwaliks clearly precedes the Vallesian crisis in Spain. In contrast to the increasingly seasonal precipitation of the late Miocene Potwar, the paleohabitat of coeval North China appears to have been moist and equable, with high diversity faunas. Continued development and comparison of resolved Neogene records allow increasing resolution of the patterns of faunal change on regional to global levels.     

Explaining the end of the hominoid experiment in Europe

The Vallesian Crisis involved the extinction of most of the hominoids that settled successfully in Europe during the middle and early Late Miocene, including Dryopithecus, Ankarapithecus and Graecopithecus. This event has been dated at 9.6 Ma, predating by more than one million years the spread of the C4 grasses and the retreat of forests over large parts of the globe at 7-8 Ma. The finding of macrofloral remains in the Terrassa section (Vallès-Penedès Basin) sheds new light on the nature of vegetational change associated with the hominoid extinction. This section presents an abundant late Vallesian vertebrate fauna and has been accurately dated at 9.2 - 9 Ma by paleomagnetism. Therefore, it provides the best indication of the kind of vegetation that occupied the area after the Vallesian Crisis. It is suggested that the extinction of the late Miocene Western European hominoids was not related to the spread of grasses, but to a significant increase of a floral association dominated by deciduous trees.     

Impact of the Middle Miocene climate transition on elongate,cylindrical foraminifera in the subtropical Pacific

Fifty-eight species of elongate, cylindrical benthic foraminifera (here referred to as the Extinction Group) belonging to genera that became extinct during the mid-Pleistocene Climate Transition (MPT), were documented (~ 50 kyr resolution) through the early middle Miocene (15–13 Ma) in two sites on opposite sides of the subtropical Pacific Ocean (ODP Sites 1146, South China Sea; ODP Site 1237, southeast Pacific). The study was undertaken to investigate the response of the Extinction Group (Ext. Gp) to the major cooling during the middle Miocene Climate Transition (MCT) to look for clues that might explain the causes of the extinction during the glacials of the mid-Pleistocene Climate Transition. Ext. Gp faunal differences between the two sites (attributed to regional and bathymetric differences in food supply to the seafloor) are greater than those that occurred through the 2 myr time span at either site. The middle Miocene Climate Transition was not an interval of enhanced species turnover or a decline in Ext. Gp abundance, in contrast to the major extinctions that occurred during the mid-Pleistocene Climate Transition. Distinct changes in the composition of the Ext. Gp faunas did occur through this time (more pronounced in Site 1237). At both sites the pre-middle Miocene Climate Transition faunas were transformed into their post-middle Miocene Climate Transition composition during the period of major cooling (14.0–13.7 Ma). During this transition interval the faunal composition swung back and forth between the two end member faunas. These faunal changes are attributed to changes in productivity (decrease in South China Sea, increase in southeast Pacific), brought about by major changes in global climate and continental aridity.     

Biogeographic relationships of African carnivoran faunas, 7–1.2 Ma

This study analyses the carnivore component of African fossil faunas from three time slices: 7–5 Ma, 4–3 Ma, and 2.5–1.2 Ma, using cluster analysis and principal coordinate analysis (PCO) of presence/absence data on genera. The faunas mostly cluster by time slice, with the exception of Laetoli (Tanzania) and Ahl al Oughlam (Morocco), which differ from all other faunas. The separation during the Late Miocene of a Chado–Libyan bioprovince from the remainder of Africa is supported. No such distinctions are present in the other time slices. Taxonomic distance is not generally correlated with geographic distance, though if Langebaanweg is removed from the 7–5 Ma time slice, the correlation at that time is significant. Comparison of these paleontological results with phylogeographic studies of modern species leads to some general comments on the analytic power of the fossil record with regard to interregional migrations.     

Geopalaeontological setting,chronology and palaeoenvironmental evolution of the Baccinello-Cinigiano Basin continental successions (Late Miocene,Italy)

The Latest Miocene succession of the Baccinello-Cinigiano Basin in southern Tuscany (Italy) recorded a faunal turnover documenting the extinction of an older, insular, endemic faunal complex characterised by the extinct ape Oreopithecus bambolii and the setting of a new, continental, European faunal complex including the colobine monkey Mesopithecus. A similar turnover pattern (Late Miocene ape/Latest Miocene Cercopithecidae) is generally observed in Late Miocene continental successions of Eurasia, from Spain to central Europe, Southwest Europe, the near East, and Southwest Asia. Abundant literature reports that the Late Miocene Eurasian hominoid primate distribution closely tracks the climatic/environmental changes occurring during the 12–9 Ma interval, until their extinction in western Europe. In the primate record, the dispersion of Cercopithecidae and the contraction of hominids is interpreted as an event depicting a pattern of “continentalisation” in the Old World. The sedimentary succession of the Baccinello-Cinigiano basin, one of the longest continuous vertebrate-bearing continental successions in the Neogene Italian record, contributes to the debate on this hypothesis. This paper provides an overview of the main characteristics of the sedimentary succession, the chronological constraints (biochronology, radiometric datings, magnetostratigraphy), and the palaeoenvironmental evolution as derived from palaeobiological approaches and from the study of stable carbon and oxygen isotope contents along the entire sedimentary succession. The 2 myr geological history of the Baccinello Cinigiano Basin, which documents the evolutionary history of Oreopithecus and associated faunas, does not have a direct relation with the event of the Messinian Salinity Crisis. The evolutionary history of Baccinello-Cinigiano Basin and its palaeontological record have been mainly driven by the regional tectonism and palaeogeographic changes that affected the northern Tyrrhenian regions in Late Miocene (Latest Tortonian–Messinian) times.     

Miocene pollen record of KC-1 core in the Qaidam Basin,NE Tibetan Plateau and implications for evolution of the East Asian monsoon

Thick Cenozoic deposits in the Qaidam Basin provide great potential for understanding the tectonic history, paleoclimatic changes, and evolution of the East Asian Monsoon. This study examines the pollen record from the KC-1 core for the interval covering the later Early to Late Miocene (18–5 Ma). Thermophilic taxa percentages are high between 18 and 14 Ma and decrease after this time, a pattern which fits well with the Middle Miocene Climatic Optimum (MMCO) between 18 and 14 Ma and global climatic cooling after 14 Ma. During the same period, xerophytic taxa percentages gradually increase and those of the conifers gradually decrease, suggesting an aridification process in the Qaidam region driven by the gradual strengthening of the East Asian winter monsoon (EAWM) and weakening of the East Asian summer monsoon (EASM). The global climate cooling process appears to have driven the climatic development of the Qaidam Basin region throughout the Miocene, but the uplift of the Tibetan Plateau also contributed.     

The age of immigration of the vertebrate faunas found at Gargano (Apulia,Italy) and Scontrone (l’Aquila,Italy)

Recently a discussion is taking place about the Scontrone (l’Aquila) and Gargano (Apulia, Italy) mammal faunas and the age of their immigration. Mazza and Rustioni (2008) dated the Scontrone mammal fossils as Tortonian on the basis of their position in the Lithothamnium Limestone and came to the conclusion that some elements of the Scontrone and Gargano faunas must have colonised the area in Oligocene or Early Miocene times. Van den Hoek Ostende et al. (2009) disagreed with this interpretation and suggested a Late Miocene (10 Ma) age for the time of immigration. We think the arguments to place Scontrone in the Tortonian are not convincing. An analysis of the potential ancestors of each of the Gargano faunal components shows that a Messinian age for the immigration is fully compatible with the distribution of these ancestors in the European Miocene.     

Cenozoic long-term terrestrial climatic evolution in Germany tracked by δ18O of rodent tooth phosphate

Even though the Cenozoic has been recognized as a period of important climate change, long-term climatic changes that took place in the continental domain are still questioned. For an area, southern Germany, for which other long-term palaeoclimatic records exist, analysis of oxygen isotope composition of small mammal teeth has been carried out for localities ranging in age from the late Eocene (c.36 Ma) to the middle Miocene (c.10 Ma). Comparison of this long-term continental δ¹⁸O record with the marine record reveals comparable trends. The major Cenozoic climatic events are thus recognized in the continental oxygen isotope record.Through comparison with other quantitative palaeoclimatic reconstructions available for the studied area, temperatures in southern Germany are broadly estimated to have fluctuated between 12 °C and 25 °C from late Eocene to early late Miocene. According to the different available chronological frameworks, either a ～ 2 °C (considering the classical biostratigraphy) or a ～ 6 °C (considering a revised biostratigraphy) decrease in mean air temperature is estimated for the Eocene/Oligocene boundary.     

陕西府谷晚中新世蓝牛化石(英文)

尽管中国发现的中新羚(偶蹄目,牛科,蓝牛族)化石较少,但由于其重要的生物年代学意义而备受重视,被作为与欧洲Vallesian期动物群对比的重要分子。描述了新近在陕西府谷喇嘛沟发现的头骨标本。依据下颌骨形态与牙齿特征,将其归入Miotragocerus gregarius (Schlosser,1903)。新发现的材料完善了该种的鉴定特征:中等大小的蓝牛类;角心强烈后倾, 中等分散度,具前后两条棱,横断面呈椭圆形;雄性个体角心前的额骨部分强烈隆升,雌性个体则无明显隆起;脑颅部分成梯形,其最大宽度在角心后,最小宽度在枕骨位置上;基枕骨前后突之间没有沟槽发育;P2与P3具发育且后置的次尖;p4下后尖前后向扩展。对比研究表明,该种较Miotragocerus spectabilis原始,而后者为中国发现的蓝牛类的最后代表且于中新世末期绝灭。对比巴基斯坦以及欧洲的蓝牛,认为中国的Miotragocerus可能与欧洲的种类关系较为密切,而不同于巴基斯坦的Tragoportax。最新的研究资料表明,Miotragocerus在中国主要发现于晚中新世中晚期(Turolian期),可能在8Ma之前从欧洲迁移至东亚,由于剧烈的气候及生态环境的改变于晚中新世末期与Urmiatheriinae等大型牛科化石一起绝灭。     

Creodonts and carnivores from the Middle Miocene Muruyur Formation at Kipsaraman and Cheparawa,Baringo District,Kenya

The Middle Miocene Muruyur Formation (ca 14.5 Ma), Tugen Hills, Kenya, has yielded a huge creodont and a variety of carnivores ranging in size from mongoose-sized viverrids and herpestids to lion-sized amphicyonids. The fauna partly fills what used to be a major gap in our knowledge of Neogene African carnivores, spanning the period between the better known Early Miocene assemblages of western Kenya and eastern Uganda, and the Late Miocene and Plio–Pleistocene faunas of East Africa. Present in the deposits are Megistotherium, two species of Hecubides, one species of Agnotherium, Herpestes, Vishnuictis, and one or two undetermined felids.     

Neogene–Quaternary Mammalian Paleobiogeography of the Indian Subcontinent: An appraisal

A biostratigraphic evaluation of the Indian subcontinent Neogene–Quaternary mammal genera at 1 Ma intervals reveals a strong correlation between faunal turnovers (first and last appearances and immigrations), diversity and major tectonic and climate-induced sea level and vegetation changes at 23–22, 20–18, 17–16, 15–14, 11–10, 9–8, 3–2 and 1–0 Ma. The Early Miocene collision of Afro-Arabian and Eurasian Plates, followed by the Middle Miocene Climate Optima and the presence of evergreen rainforests, most likely facilitated the dispersals into and out of the subcontinent from the west along the coast and included African proboscideans, primates, creodonts, thryonomyid rodents and Asian chalicotheres, rhinos, suids, anthracotheres, carnivores and muroid rodents. The Late Miocene and Early Pleistocene cooler and drier conditions, the spread of grasslands and sea level drops may have influenced the exchange of African monkeys, Eurasian carnivores, bovids, equids, camelid, and South Asian suids, leporids and murids. Immigrations from the east (East and SE Asia) occurred mostly during the Miocene and involved primarily small mammals.     

Late Miocene paleoenvironmental changes in North Africa and the Mediterranean recorded by geochemical proxies (Monte Gibliscemi section,Sicily)

The astronomically tuned marls of the Monte Gibliscemi section, Sicily, constitute an archive to trace the late Miocene palaeoenvironmental conditions (~ 9.7–7.0 Ma) in North Africa. Here we have utilised carbonate content and Al-normalised geochemical proxies to trace changes in terrigenous source area and bottom-water ventilation. The terrigenous input into the section is dominated by North African river systems draining into the Eastern Mediterranean. The proxy parameters indicate that the palaeoenvironmental conditions in North Africa were humid from 9.5 Ma onward with high fluvial input to the Mediterranean. Increases in the Si/Al and Mg/Al ratios occurred from 8.4 to 8.2 Ma and from 8.05 to 7.75 Ma, with maximum values similar to those of Messinian diatomites. These peaks indicate conditions of enhanced biosiliceous productivity and the presence of authigenic clay formation. Sluggish water circulation in the Mediterranean during those times is inferred from the Mn/Al and V/Al behaviour. Late Miocene changes of the Betic (southern Spain) and Rifian (Morocco) Mediterranean–Atlantic gateways are interpreted as the driving force for the changes in water circulation and the transgression associated with the opening of the Rifian corridor is interpreted to occur at 7.8 Ma.     

Diversification and extinction patterns among Neogene perimediterranean mammals

The best mammalian fossil record during the Neogene of Western Europe is that of the rodents, the most successful and diversified mammal order. The study of origination and extinction during the Neogene (24-3 Ma BP) in one of the best-documented areas, Spain and southern France, gives an insight into the dynamics of these communities and indicates the possible nature of the driving forces. Three main periods of time show a high rate of origination: the late Burdigalian (17.5 Ma BP), the early Vallesian (11.5-11 Ma BP) and the early Pliocene (4.2-3.8 Ma BP). Two of these high origination-rate periods are immediately followed by important extinction events during which all cohorts are deeply affected (11.5-11 Ma BP and 4.2-3.8 Ma BP). The most important extinction event seems to occur during the early Vallesian (11.5-11 Ma BP), which probably includes the middle/late Miocene boundary. At the Miocene/Pliocene boundary, and during the early Pliocene, the faunal turnover seems to become faster, inducing a strong decrease of the mean species duration. Whereas the main immigration event, which occurs at 17.5 Ma BP, can be related to other faunal migrations in terms of the closure of the Tethys, as it occurs also in eastern Africa and in southwest Asia, the middle/late Miocene boundary event may have been related to a period of ice growth in the Southern Hemisphere. The extinction event that affects the planktonic foraminifera at 12 Ma BP cannot be chronologically correlated to this southwestern European land-mammal extinction event, because the calibration of the marine fossil record during that time-span has to be precise. Some limited terrestrial faunal exchanges that occur during the Messinian between southwestern Europe and northwestern Africa do not deeply affect the general faunal dynamics. Both allochthonous cohorts of immigrants become rapidly extinct. Several endemic rodent faunas, indicating insular conditions, have been reported from the southern edge of the western European continent from the middle Miocene up to the Pliocene. All show low taxonomic diversity, strong endemism and short survival. Some of them, like those of the Gargano Islands during the late Miocene, underwent peculiar morphological changes and also speciation. The large number of rodent genera coevolving in the Gargano Islands is indicative of the large surface areas of these islands. The general geographic pattern of southwestern Europe during the Neogene may therefore correspond to a large continental province including Spain and southern France with some kind of fast-modifying archipelago on its southern rim.     

The scimitar-toothed cat Machairodus aphanistus (Carnivora: Felidae) in the Vallès-Penedès Basin (NE Iberian Peninsula)

Here, we revise all the published and unpublished scimitar-toothed cat remains from the Vallès-Penedès Basin (NE Iberian Peninsula), in order to confirm their taxonomic attribution to Machairodus aphanistus as well as to provide more precise information about its chronological distribution in this basin. The studied material (including dentognathic as well as postcranial remains) comes from the following localities: Can Mata indeterminate (late MN7+8 or MN9), Creu Conill 22 (MN9), Can Poncic 1 (MN9), Can Llobateres 1 (MN9), Santiga (MN9), La Tarumba 1 (MN10), Viladecavalls (MN10), Ronda Oest Sabadell ROS-D3 (MN10), and Torrent de Febulines (MN10). Most of the studied material fits well with the morphologic and metrical features characteristic of the Vallesian species M. aphanistus, with the exception of the remains from Creu Conill 22 (an undescribed partial P4 formerly attributed to this taxon), which belongs in fact to a medium-sized hyaenid. From a biostratigraphic viewpoint, the removal of the Creu Conill material from the hypodigm of M. aphanistus has important implications, because this locality (11.1 Ma) was considered to record the first appearance datum of this taxon in the Vallès-Penedès Basin. However, the report of a previously unpublished talus from Can Mata (late MN7+8 or MN9) indicates that this taxon was present in this basin at least by the earliest Vallesian. Therefore, our results indicate that the first appearance datum of Machairodus in the Vallès-Penedès Basin might be somewhat younger than previously assumed, although dating uncertainties for the Can Mata remains preclude a more precise assessment. In contrast, the new mandibular remains from ROS-D3 (MN10) are likely coeval with those from La Tarumba 1, with the last appearance datum of M. aphanistus in the Vallès-Penedès Basin corresponding to Torrent de Febulines (ca. 9.1 Ma). The postcranial material described from various Vallès-Penedès localities further indicates that M. aphanistus displayed less cursorial adaptations than its purported descendant Homotherium.     

Step-wise change of Asian interior climate preceding the Eocene–Oligocene Transition (EOT)

Understanding the global climate change from greenhouse to icehouse conditions at the Eocene–Oligocene Transition (EOT) 34 million years ago requires climatic records from oceanic as well as continental realms of the key Late Eocene “doubthouse” period preceding this switch. Here, we report integrated stratigraphic results from well-dated Late Eocene continental mudflat to saline lake paleoenvironments of the Xining Basin (northeastern Tibetan Plateau, western China) recording regional and global change. Cyclostratigraphic analysis strongly suggests continuous dominance of the 41-kyr obliquity cycle in the whole late Eocene interval down to the base of polarity chron C18n.2n at 39 Ma with additional input of the ~ 100-kyr eccentricity cycle up to the base of chron C13r at ~ 34.7 Ma. This might imply that high-latitude climates dominated the area long before the EOT, probably related to incipient ice-volume fluctuations. Furthermore, our results reveal two paleoenvironmental deterioration steps preceding the Eocene–Oligocene Transition. The first step occurs in the top of chron C17n.1n at ~ 36.6 Ma. This age closely corresponds to (1) the high-altitude pollen appearance in chron C16.2r at ~ 36.4 Ma in the same section, (2) the recently dated final retreat of the Tarim Sea in western China, and (3) a shift from precession to obliquity dominance in the Atlantic Ocean. This near co-occurrence suggests global change at this time. We hypothesize this change is related to an increase in incipient ice sheet volume leading to passing threshold conditions for the high-altitude pollen appearance and Tarim Sea retreat, finally leading to decreased moisture availability in the Xining Basin. At the second step, in the base of chron C13r at ~ 34.7 Ma, a substantial increase in clastic sedimentation rates is observed. This might relate to increased climate variability preceding the greenhouse to icehouse transition at the EOT that prevented landscapes to attain equilibrium configurations.     

Late Miocene hominoid from Niger

African Late Miocene hominoids are rare, having been reported from six localities in Kenya, Ethiopia and Chad ranging in age from 10.5 to 5.5 Ma. We here report the occurrence of a hominoid in Niger associated with a vertebrate fauna which indicates an age of between 11–5 Ma. The Niger fossil locality is 940 km north of the nearest known extant hominoids, 1000 km west of the nearest recorded fossil hominoid from Chad.     

Stratigraphic distribution of the radiolarian Spongodiscus biconcavus Haeckel at IODP Site U1340 in the Bering Sea and its paleoceanographic significance

The temporal and spatial distributions of the radiolarian species Spongodiscus biconcavus Haeckel are investigated to understand the paleoceanographic evolution of the Bering Sea region during the last 4.3 Myr based on extensive study of samples collected at Site U1340 during the IODP Expedition 323. The biostratigraphic resolution for the region is also improved by multidisciplinary studies of radiolarians, diatoms, dinoflagellates, ebridians, and silicoflagellates. The results demonstrate that the abundance variation of S. biconcavus during the last 4.3 Myr is closely related to global climate changes, and the species can be used as a warm water and climate proxy in the Bering Sea. Based on the downhole profiles of S. biconcavus and other parameters, we conclude that the southern Bering Sea was associated with a warm water mass prior to 3.147 Ma but it gradually cooled thereafter. From 2.793 Ma to 0.889 Ma, a cold water mass and sea-ice predominated in the Bering Sea, in response to the early Northern Hemisphere glaciation (NHG). Furthermore, the climate suddenly became much cooler post 0.889 Ma. Nevertheless, a reversal of this cooling trend occurred after the Mid-Pleistocene Climatic Transition (∼1.2 Ma), marked by reoccurrence of warm water and reduced sea-ice in the Bering Sea until the final retreat of warm water mass from the Bering Sea after 0.239 Ma. These processes are correlated with biogeographic expansion and retreat of warm water planktonic species.