The Vallesian Mammal Turnover: A Late Miocene record of decoupled land-ocean evolution

In Western Europe, the change from the Middle Miocene forest-adapted mammalian faunas to the more open woodland faunas of the later Neogene, took place through an abrupt critical period known as the Vallesian Crisis. The Vallesian Crisis involved the disappearance of most of the forest-adapted elements characterizing the middle Miocene, such as tapirs, rhinoceroses, wet-adapted artiodactyls, hominoids, rodents, and the large carnivores of the families Nimravidae and Amphicyonidae. Detailed analysis in the well-calibrated and mostly complete sequence of the type area of the Vallesian Mammal stage, the Vallès-Penedès Basin (NE Spain), reveals that entries were always above the level of exits during the early Vallesian, reaching a diversity maximum at the end of this time. At 9.75 Ma, the Vallesian Crisis involved a sudden decrease of diversity, caused by high extinction levels, well above the number of entries. This event can be correlated with Mi7, a minor isotopic shift at about 9.6 Ma. The correlation of the Vallesian Crisis with such a minor isotopic shift is in contrast with previous, more significant isotopic shifts which had little ecological effects on the terrestrial ecosystems. This inconsistency between the global climate change inferred from the oceanic record and its effect on the structure of the late Miocene terrestrial ecosystems calls for some caution when inferring direct, linear relationships between climate change and mammalian turnover. In contrast with the Plio-Pleistocene glacial-interglacial dynamics, the effects of this climate forcing seem to have been more complex during Miocene times. An alternative pattern of change can be envisaged by proposing a “House of Cards” effect for the Vallesian Crisis. Increasing diversity levels after a prolonged period of stability enhanced terrestrial ecosystems to evolve into a self-organized critical state, which suddenly dropped after a critical threshold was surpassed. In contrast to other critical periods, the final decline of the Vallesian chronofauna was more dependent on the critical state of the system than on the magnitude of the agent which induced the crisis.     

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.     

The oldest Eurasian hominoid.

Engelswies is an early Miocene vertebrate locality in southern Germany with a rich assemblage of terrestrial mammals, invertebrates and fossil plants. It is dated to 16.5-17.0 Ma based on magnetostratigraphy, biostratigraphy and lithostratigraphy, and includes among the faunal remains a hominoid upper molar fragment, the oldest hominoid so far identified from Europe. The evidence from Engelswies suggests that hominoids arrived in Eurasia about 17 Ma, roughly contemporaneously with pliopithecoids and Deinotherium, and before the last marine transgression to isolate Eurasia from Africa. Thick enamel and low dentine penetrance may have been key adaptations that contributed to the success of hominoids of dentally modern aspect in western Eurasia and ultimately to their ability to spread to eastern Eurasia and Africa in the middle and late Miocene.     

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.     

First hominoid from the Late Miocene of the Irrawaddy Formation (Myanmar)

For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l.) associated mammal fauna from Irrawaddy Formation deposits dated between 10.4 and 8.8 Ma by biochronology and magnetostratigraphy. This hominoid documents a new species of Khoratpithecus, increasing thereby the Miocene diversity of southern Asian hominoids. The composition of the associated fauna as well as stable isotope data on Hipparion (s.l.) indicate that it inhabited an evergreen forest in a C3-plant environment. Our results enlighten that late Miocene hominoids were more regionally diversified than other large mammals, pointing towards regionally-bounded evolution of the representatives of this group in Southeast Asia. The Irrawaddy Formation, with its extensive outcrops and long temporal range, has a great potential for improving our knowledge of hominoid evolution in Asia.     

Intraspecific variation and evolutionary trends of Alicornops simorrense (Rhinocerotidae) in Spain

The Spanish material of Alicornops simorrense constitutes the best representation of the species in Western Europe. It provides interesting data on the metrical and morphological intraspecific variation of A. simorrense and its evolutionary trends from late Middle Miocene to the early Late Miocene. From late Aragonian to early Vallesian, a slight increase in size is observed, but without clear limits among series. During the late Vallesian, A. simorrense evolved in central Spanish basins into a second species, A. alfambrense, greater in size and with more robust proportions. In the Vallés-Penedés basin, A. simorrense shows a noticeable increase in size, while maintaining its proportions, during the Vallesian. A. simorrense was a very abundant species, an open woodland dweller, with gregarious behaviour, whose extinction was probably linked to the climatic change that took place at the end of the Vallesian and the beginning of the Turolian.     

The Leporid Datum: a late Miocene biotic marker

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On the systematic status of the late Neogene hominoids from Yunnan Province,China

Late Miocene and Pliocene hominoids from Yunnan Province in southern China have been recovered from four sites or site complexes: Xiaolongtan, Yangyi, Shihuiba and Yuanmou. Of these, Shihuiba and Yuanmou are among the most prolific fossil hominoid sites in Eurasia, and they have yielded important evidence that is critical for documenting the evolutionary history, biogeography and paleobiology of later Neogene hominids. The aim of this paper is to clarify their taxonomy and nomenclature, and to present a preliminary synthesis of their phylogenetic relationships and biogeography. The morphological pattern and degree of variation observed in the fossil samples is consistent with there being a single, sexually dimorphic species represented at each site. Provisionally, we consider the Shihuiba, Xiaolongtan and Yuanmou samples to belong to two separate species within a single genus. The valid names for these species are Lufengpithecus lufengensis (from Shihuiba) and L. keiyuanensis (from Xiaolongtan and Yuanmou). From a phylogenetic perspective, the currently available evidence suggests that Lufengpithecus is either a primitive hominid that represents the sister taxon of the Ponginae+Homininae or a primitive sister taxon to the Ponginae. We tend to favor the second alternative, but acknowledge that a more comprehensive comparative analysis is needed to substantiate the phylogenetic and taxonomic affinities of Lufengpithecus. Importantly, the Yunnan fossil apes provide a unique temporal perspective on the evolutionary history of hominoids. Their continued occurrence during the late Miocene and Pliocene (approximately 8-2Ma), when hominoids became extinct throughout the rest of Eurasia, suggests that southern China (and presumably southeast Asia in general) was an important refugium for hominoids, including the ancestors of the orang-utans and gibbons. The uplift of the Tibetan plateau and its impact on regional climatic conditions may have been an important contributing factor in isolating the hominoids geographically and ecologically. We speculate that changed climatic condition in the mid-Pliocene, and possibly the arrival of Homo soon after, may have precipitated the regional extinction of large hominoids in southern China and in mainland southeast Asia.     

Mandible of Ouranopithecus macedoniensis (Hominidae,primates) from a new late Miocene locality of Macedonia (Greece)

In 1990, a new late Miocene locality named “Nikiti 1” or NKT, was discovered near the village of Nikiti (Chalkidiki, Macedonia, Greece) about 100 km east of Thessaloniki City. The locality is situated in the Nikiti Formation, which consists of yellowish sands, gravels and pebbles and has been dated to late Vallesian–early Turolian. Among the initially collected fossils there is a mandible of a hominoid primate, which is described, compared, and attributed to Ouranopithecus macedoniensis. A short review of the species in Macedonia and its phylogenetic relationships are also given. © 1993 Wiley-Liss, Inc.     

Fossil apes from the vallès‐penedès basin

Currently restricted to Southeast Asia and Africa, extant hominoids are the remnants of a group that was much more diverse during the Miocene. Apes initially diversified in Africa during the early Miocene, but by the middle Miocene they extended their geographical range into Eurasia, where they experienced an impressive evolutionary radiation. Understanding the role of Eurasian hominoids in the origin and evolution of the great‐ape‐and‐human clade (Hominidae) is partly hampered by phylogenetic uncertainties, the scarcity and incompleteness of fossil remains, the current restricted diversity of the group, and pervasive homoplasy. Nevertheless, scientific knowledge of the Eurasian hominoid radiation has significantly improved during the last decade. In the case of Western Europe, this has been due to the discovery of new remains from the Vallès‐Penedès Basin (Catalonia, Spain). Here, I review the fossil record of Vallès‐Penedès apes and consider its implications. Although significant disagreements persist among scholars, some important lessons can be learned regarding the evolutionary history of the closest living relatives of humans. © 2012 Wiley Periodicals, Inc.     

Biochronological, taphonomical, and paleoenvironmental background of the fossil great ape Pierolapithecus catalaunicus (Primates, Hominidae)

The Late Aragonian (late middle Miocene) stratigraphic sequence of Abocador de Can Mata (ACM) from Els Hostalets de Pierola (Vallès-Penedès Basin, Catalonia, Spain), rich in fossil vertebrate localities, provides a unique opportunity to study the evolution of western Eurasian hominoids. Among these sites, Barranc de Can Vila 1 (BCV1) recently delivered a well-preserved hominoid partial skeleton of a new genus and species, Pierolapithecus catalaunicus. On the basis of the small-mammal fauna recovered at BCV1, we infer an early MN 7+8 age, between 12.5 and 12Ma, for this site. The spatial distribution of macromammal fossils, the relative abundances of skeletal elements, and their state of preservation suggest that different agents were involved in the accumulation of the P. catalaunicus individual and the remaining taxa. Carnivore marks occur on some bones of the P. catalunicus skeleton, documenting the action of predators and/or scavengers in this case. In contrast, carnivore marks are extremely rare on other macromammal remains, which seem to be derived from adjacent alluvial-fan plain areas. The small-mammal fauna from BCV1 and the large-mammal fauna from the ACM series, indicate the presence of considerably humid and warm forest environments. The compositions of the small-mammal fauna from BCV1 and from other Late Aragonian sites from the Vallès-Penedès area are similar to those from France and central Europe. The former are clearly distinct from those of Iberian inner basins, where the environment appears to have been drier, thus precluding the dispersal of hominoids into that area.     

Fossil record and dynamics of Late Miocene small mammal faunas of the Vienna Basin and adjacent basins,Austria

The Late Miocene small mammal assemblages of the hinterland of Lake Pannon in Austrian Basins are represented by 99 species-level taxa and 30,400 specimens. The fossil-bearing localities can be grouped into eight intervals spanning about three million years from the Early Vallesian to the Middle Turolian. Each time slice is characterised by the occurrence and/or dominance of certain species. The retreat of Lake Pannon is reflected by a distinct diversification. This pattern may be a regional signal due to increasing habitat availability but may also be taphonomically biased due to a rather poor Earliest Vallesian record. Nevertheless, the overall community structure is quite stable throughout the Vallesian and no indication of a Vallesian Crisis can be detected. Instead, a moderate turnover occurs with the onset of the Turolian, reflected by the increasing abundance of xerophilic taxa.     

Dental remains of Equatorius africanus from Kipsaramon, Tugen Hills, Baringo District, Kenya.

Forty-one isolated large hominoid teeth, as well as most of the mandibular and three maxillary teeth associated with a partial skeleton, were recovered from middle Miocene Muruyur sediments near Kipsaramon in the Tugen Hills, Baringo District, Kenya. The isolated teeth were collected as surface finds and the skeleton was excavated in situ at locality BPRP#122 dated between 15.58 Ma and 15.36 Ma. The majority of the teeth recovered at BPRP#122 are referable to a minimum of five individuals of the hominoid Equatorius africanus. Three of the teeth, however, are provisionally assigned to Nyanzapithecus sp. The new hominoids from Kipsaramon add to an increasing inventory of specimens that suggest greater large hominoid taxonomic diversity from the middle Miocene of Kenya than was previously recognized. It is suggested that there are two large-bodied hominoid species present at Mabako, only one of which is assignable to Equatorius.     

Le gisement de Freiria de Rio Maior,Portugal, et sa faune de Mammiferes; Nouvelle espece de Rotundomys,consequences stratigraphiques

A new locality, close to Freiria de Rio Maior, provided a mammalian fauna associated with Charophytes, secds,Ostracods, Gastropods and Urodels. The most abundant remains correspond to a new species: Rotundomys freiriensis. This fauna has been dated as the Upper Vallesian base (MN 10), corresponding to the most recent level with small mammals found in the portuguese Miocene. Thus, the Freiria limestone succession is correlated to Cartaxo, Almoster, etc., limestones which are so developed in the Ribatejo area.     

Regional impacts of global climate change: a local humid phase in central Iberia in a late Miocene drying world

The end of the Miocene was an eventful period of changes in climate and geography, and a restructuring of terrestrial plant and mammals. The tendency towards global aridification has attracted much recent interest, making the late Miocene a striking case‐study for testing current and near‐future scenarios involving global warming. Little is known about the consequences of global changes in temperature and precipitation at regional or local scales. Given its geographical position and extraordinary fossil record, the Iberian Peninsula offers many insights into short‐ and long‐term shifts in climate, and the local response. Here, we explore the diet and ecology of large‐mammals through tooth‐wear patterns, and examine changes in local climate and habitat conditions in central Spain in a period (9.1–6.3 Ma) for which there exists a dearth of palaeoenvironmental information. Relatively dry climates and open‐woodland landscapes evolved locally during the late Vallesian and early Turolian (9.0–7.7 Ma). Unexpectedly, we detect a period of high precipitation and a peak of humidity at the end of the Turolian (7.0 Ma) that prompted the development of wetter, more forested habitats, suggesting that the traditional view of the late Miocene as a steppe landscape is a misconception. We also find a period of relatively drier and warmer conditions from the early Ventian onwards. Overall, our finding that a local episode of increased humidity in central Spain was synchronous with a global warming trend in Europe provides evidence that the greatest climatic changes may have an opposite impact at regional and local scales.     

Bio-magnetostratigraphy and environment of the oldest Eurasian hominoid from the Early Miocene of Engelswies (Germany)

The paleobiogeography of hominoids exhibits a puzzling pattern of migrations between and within Africa and Eurasia. A precise dating of hominoid-bearing localities is therefore essential to reveal the timing, direction and possible causes of dispersals. Here, we present a bio-magnetostratigraphic analysis of the section of Engelswies (Southern Germany, Upper Freshwater Molasse, North Alpine Foreland Basin) where the oldest Eurasian hominoid was found. Our paleomagnetic results reveal a very short normal and a reverse magnetic polarity for the entire section. The polarity record is correlated to the Astronomical Tuned Neogene Time Scale using an integrated stratigraphic approach. This approach follows the chronostratigraphic framework for the Upper Freshwater Molasse, which combines magnetostratigraphy with biostratigraphic, lithostratigraphic and ⁴⁰Ar/³⁹Ar dating results. According to this outcome, the reverse polarity of the Engelswies section most likely correlates to magnetochron C5Cr. The origin of the short normal polarity remains enigmatic. The magnetostratigraphic calibration and the evolutionary level of the Engelswies small mammal fauna suggest an age of 17.1-17.0 Ma (Early Karpatian, Early Miocene) for the oldest Eurasian hominoid, and roughly confirm the estimates of Heizmann and Begun (2001). The estimated age suggests that the first hominoids in Eurasia are contemporaneous with Afro-Arabian afropithecins, and dispersal may have been facilitated by intra-Burdigalian (∼18-17 Ma) sea-level low stands and the beginning of the Miocene Climate Optimum. The paleoclimatic and environmental reconstruction of the Engelswies locality indicates a lakeshore environment near dense subtropical rain forest vegetation, where paratropical temperatures (mean annual temperature around 20 °C) and humid conditions (mean annual precipitation > 1.100 mm) prevailed.     

Orbital forcing and the spread of C4 grasses in the late Neogene: stable isotope evidence from South African speleothems

Reconstructing Plio-Pleistocene African paleoenvironments is important for models of early hominin evolution, but is often hampered by low-resolution or discontinuous climatic data. Here, we present high-resolution stable oxygen and carbon isotope time series data from two flowstones (secondary cave deposits) from the South African hominin-bearing Makapansgat Valley. The age of the older of the two flowstones (Collapsed Cone) is constrained by magnetostratigraphy to approximately 4-5 Ma; the younger flowstone (Buffalo Cave) grew between 2.0-1.5 Ma, as determined by magnetostratigraphy and orbital tuning of the isotopic data. The carbon isotope data is used as a proxy for the proportion of C(4) grasses in the local environment and the oxygen isotope data reflects monsoon rainfall intensity. The carbon isotope evidence indicates that in the late Miocene/early Pliocene, the local environment was dominated by C(3) vegetation, whereas, in the Plio-Pleistocene, it was composed of a mixture of C(3) and C(4) vegetation. This suggests that C(4) grasses became a significant part of the Makapansgat Valley ecosystem at approximately 4-5 Ma, towards the end of the late Neogene global expansion of C(4) grasses. After this initial expansion, South Africa experienced further fluctuations in the proportion of C(3) and C(4) vegetation during the Plio-Pleistocene, in response to regional and global climatic changes. Most notably, the Buffalo Cave flowstone provides evidence for C(4) grass expansion at ca. 1.7 Ma that we suggest was a response to African aridity caused by the onset of the Walker Circulation in the Pacific Ocean at this time.     

Molecular evidence for the age, origin, and evolutionary history of the American desert plant genus Tiquilia (Boraginaceae)

Although the deserts of North America are of very recent origin, their characteristic arid-adapted endemic plant lineages have been suggested to be much older. Earlier researchers have hypothesized that the ancestors of many of these modern desert lineages first adapted to aridity in highly localized arid or semi-arid sites as early as the late Cretaceous or early Tertiary, and that these lineages subsequently spread and diversified as global climate became increasingly arid during the Cenozoic. No study has explicitly examined these hypotheses for any North American arid-adapted plant group. The current paper tests these hypotheses using the genus Tiquilia (Boraginaceae), a diverse North American desert plant group. A strongly supported phylogeny of the genus is estimated using combined sequence data from three chloroplast markers (matK, ndhF, and rps16) and two nuclear markers (ITS and waxy). Ages of divergence events within the genus are estimated using penalized likelihood and a molecular clock approach on the ndhF tree for Tiquilia and representative outgroups, including most of the major lineages of Boraginales. The dating analysis suggests that the stem lineage of Tiquilia split from its nearest extant relative in the Paleocene or Eocene ( approximately 59-48 Ma). This was followed by a relatively long period before the first divergence in the crown group near the Eocene/Oligocene boundary ( approximately 33-29 Ma), shortly after the greatest Cenozoic episode of rapid aridification. Divergence of seven major lineages of Tiquilia is dated to the early-to-mid Miocene ( approximately 23-13 Ma). Several major lineages show a marked increase in diversification concomitant with the onset of more widespread semi-arid and then arid conditions beginning in the late Miocene ( approximately 7 Ma). This sequence of divergence events in Tiquilia agrees well with earlier researchers' ideas concerning North American desert flora assembly.     

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。