Late Early Pliocene Research Articles

LATE MIOCENE–EARLY PLIOCENE EVOLUTION OF MEDITERRANEAN GOBIES AND THEIR ENVIRONMENTAL AND BIOGEOGRAPHIC SIGNIFICANCE

The Lago Mare phase at the end of the Messinian Salinity Crisis (MSC) in the Mediterranean has long been known for the Paratethyan affinities of its biota. The taxonomic level of these affinities and their origin, however, is subject to divergent interpretations. Here, we have studied otoliths of the Gobioidei from late Miocene and early Pliocene deposits from Italy and Greece and revised earlier studies including time-equivalent data from Romania and NW Turkey. Nowadays, gobies constitute the most speciose marine fish family in Europe and the most diverse endemic family in the Ponto-Caspian region. Furthermore, they are highly adapted to nearshore shallow marine, brackish, and freshwater environments, which makes them excellent candidates to explore short-term connections of waterways of different nature. The normal marine late Tortonian and pre-evaporitic Messinian deposits of the studied Italian and Greek locations contained a rich and diverse goby assamblage, but species with Paratethyan affinities were very rare and possibly originated from connections during the early Serravallian (late Badenian) and early Messinian (early Meotian). A rare fauna from a paralic environment from Cessaniti, Calabria, similar to the mangrove environments found in the present-day Guinea coastal area, revealed two species of the family Eleotridae and no gobies with Paratethyan affinities. Cessaniti provides a unique opportunity to recognize the presence of this type of environmental context with a unique gobioid assemblage in the Neogene of Europe. The shallow-water brackish-influenced sediments of Strada degli Archi just below the MSC show an increasing influence of Paratethyan gobiid taxa (Proterorhinus yigitbasi, Zosterisessor exsul n. sp.), which are not present in time-equivalent normal marine environments, but have also been identified in the Dacic Basin of Romania. Sediments of the stage 3 ot the MSC, especially those that accumulated during the Lago Mare event, were dominated by a diverse goby assemblage with Paratethyan affinities, while indigenous Mediterranean goby taxa disappeared probably because of the lack of suitable conditions for neritic demersal stenohaline fishes, except for the nektonic Aphia minuta. The sediments of the stage 3 of the MSC also included in one particular location and level the unusual Enigmacottus socialis n. gen., n. sp., a putative member of the family Psychrolutidae of uncertain origin, which constitutes about 70% of all otoliths obtained from that interval in Italy. Beginning with the Zanclean, the goby assemblage of the Mediterranean shows an almost exclusively Atlantic-Mediterranean composition. A total of 15 new species are described, 12 in the family Gobiidae, two of the Eleotridae, and one putative Psychrolutidae. The new taxa are: Eleotris omuamuaensis n. sp., Eleotris tyrrhenicus n. sp., Lesueurigobius stazzanensis n. sp., Gobius peloponnesus n. sp., Proterorhinus cretensis n. sp., Zosterisessor exsul n. sp., Benthophilus aprutinus n. sp., Benthophilus labronicus n. sp., Caspiosoma lini n. sp., Caspiosoma paulisulcata n. sp., Thorogobius petilus n. sp., Buenia pisiformis n. sp., Hesperichthys gironeae n. sp., Knipowitschia etrusca n. sp., and Enigmacottus socialis n. gen. et n. sp.

Baffin Bay late Neogene palynostratigraphy at Ocean Drilling Program Site 645

Analyses of marine and terrestrial palynomorphs of Ocean Drilling Program (ODP) Site 645 in Baffin Bay led us to define a new biostratigraphical scheme covering the late Miocene to Pleistocene based on dinocyst and acritarch assemblages. Four biozones were defined. The first one, from 438.6 m below sea floor (mbsf) to 388 mbsf, can be assigned a late Miocene to early Pliocene age (>4.5 Ma), based on the common occurrence of Cristadinium diminutivum and Selenopemphix brevispinosa. Biozone 2, spanning from an erosional unconformity to a recovery hiatus, is marked by the highest occurrences (HOs) of Veriplicidium franklinii and Cristadinium diminutivum, which suggest an early Pliocene age >3.6 Ma (∼4.5 to ∼3.6 Ma). Biozone 3, above the recovery hiatus and up to 220.94 mbsf, corresponds to a late Pliocene or early Pleistocene age based on occurrences of Bitectatodinium readwaldii, Cymatiosphaera? icenorum, and Lavradosphaera canalis. Finally, between 266.4 and 120.56 mbsf, Biozone 4, marked by the HO of Filisphaera filifera, Filisphaera microornata, and Habibacysta tectata, has an early Pleistocene age (>1.4 Ma). Our biostratigraphy implies that horizon b1 of the Baffin Bay seismic stratigraphy corresponds to the recovery hiatus at ODP Site 645, which suggests a very thick Pliocene sequence along the Baffin Island slope. Dinocyst assemblages and terrestrial palynomorphs in our records indicate that the late Miocene and (or) early Pliocene were characterized by relatively warm coastal surface waters and boreal forest or forested tundra vegetation over adjacent lands. In contrast, the early Pleistocene dinocyst assemblages above the recovery hiatus indicate cold surface waters, while pollen data suggest reduced vegetation cover on adjacent lands.

Diversification dynamics of freshwater bivalves (Unionidae: Parreysiinae: Coelaturini) indicate historic hydrographic connections throughout the East African Rift System

Invertebrates are exceptionally diverse, but many are in decline because of anthropogenic changes to their habitat. This situation is particularly problematic for taxa that are not well monitored or taxonomically poorly understood, because the lack of knowledge hampers conservation. Despite their important functional role in freshwater ecosystems, African bivalves of the family Unionidae remain poorly studied compared to their highly threatened relatives in Europe, the U.S.A. and Canada. To resolve relationships and to study diversification dynamics in space and time, we performed time-calibrated phylogenetic studies and biogeographical modeling on the unionids from the East African Rift System and surroundings, including representatives of all currently recognized Afrotropical genera except for Brazzaea (and Unio from southern Africa). Our analyses indicate that all sampled Afrotropical unionids belong to the tribe Coelaturini (subfamily Parreysiinae), as does the genus Moncetia from Lake Tanganyika, which is currently attributed to the family Iridinidae. Colonization of Africa from Eurasia by Parreysiinae occurred ~17 Ma ago, and the subsequent diversification of Coelaturini in Africa continued at a steady pace, although net diversification decreased over time as more niches and ecoregions became occupied. Clades in Coelaturini largely reflect drainage basins, with the oldest lineages and highest regional diversity occurring in Lake Tanganyika, followed by the Congo Basin watershed in general. The species assemblage of Lake Tanganyika reflects multiple independent events of colonization and intralacustrine diversification since the Late Miocene or Early Pliocene. The clades of other regions, including that containing the species from Lake Malawi, are comparatively young. Biogeographical analyses indicate that the colonization history was mainly driven by cladogenesis in sympatry, whereas few anagenetic events contributed to the modern distribution of Coelaturini. Ancestral range estimations demonstrate that Coelaturini originated in the Victoria and/or Tanganyika ecoregions, and that the Congo Basin played an essential role in the colonization of Africa by Coelaturini.

A catalogue of the vertebrate fossil record from the Guadix-Baza Basin (SE Spain)

In this paper, a catalogue of the vertebrate content of the Guadix-Baza Basin is presented. A total of 93 localities have been reviewed, providing more than 300 vertebrate species. These localities have been included in 11 biochronological units, ranging in age from the late Miocene (MN 13) to the Middle Pleistocene (MmQ 4), including also two MN 10 localities. The best-represented epoch in the Guadix-Baza Basin is the Pliocene (MN 14 to MN 16), with 41 sites. This is followed by the Early Pleistocene (MN17 and MmQ1 to MmQ3) with 30 sites. The vertebrate classes represented in the basin are Actinopterygii, Amphibia, Aves, Reptilia and Mammalia, this last one being the best represented. Among mammals, small mammals are in their turn the most abundant, particularly rodents. The families Muridae and Arvicolidae dominate the rodent assemblages, murids being the dominant family in the late Miocene and early Pliocene, and arvicolids the most abundant group in the late Pliocene and Pleistocene.

Amphibians and reptiles from the late Miocene and early Pliocene of the Ptolemais area (Western Macedonia, Greece)

We herein describe the amphibians and reptiles from the Ptolemais fossil assemblage, originating from 12 nearby localities in northwestern Greece, spanning from the late Miocene (MN 13) to the early Pliocene (MN 15). Amphibians are known exclusively of anurans, with the genera Latonia and Rana being identified, the latter constituting the oldest so far known record of that lineage in Greece. Turtles are represented by the testudinid cf. Testudo, whereas numerous other indeterminate testudinoids are known. Lizards include scincids, lacertids, and at least two anguids. Among them, the material referred to scincids and the anguid Anguis constitute one of only rather few such occurrences described in the fossil record of the Eastern Mediterranean. Snakes are represented by indeterminate “colubrines” and the genus Natrix. The different ages of the Ptolemais fossiliferous localities, along with their close geographic vicinity offer the opportunity to study potential survival/extinction patterns of its amphibians and reptiles across the Mio-Pliocene boundary, a time interval that has been crucial for European herpetofaunas.

Late Miocene and Early Pliocene coastal deposits from the Canary Islands: New records and paleoclimatic significance

The Canary Islands offer an outstanding context for paleoclimatic studies because their volcanic nature and the presence of datable lava flows, their antiquity, the existence of marine deposits and their location in the NE Atlantic. New records of Miocene and Pliocene coastal deposits are registered in the eastern Canary Islands, 100 km off the NW African coast.Late Miocene marine deposits are conglomerates and sandstones assigned to the Tortonian through a new 40Ar/39Ar age (9.60 ± 0.05 Ma) of an overlying lava flow at the Janubio site in Lanzarote Island. These deposits contain littoral-intertidal and intertropical genera of fossils, e.g. the gastropod Nerita and the coral Siderastrea, they are almost horizontal and were elevated up to 36 m in height by regional or local tectonics, yielding a relatively low rate of uplift of ~3.75 m/Ma.Furthermore, Early Pliocene coastal deposits studied, are mainly marine conglomerates and sandstones and derived aeolianites that are spread over the south of Lanzarote and the west of the Jandía peninsula of Fuerteventura Island. No associated lava flow permits their dating, but they contain marine fossils of littoral and intertropical genera, as the gastropods Nerita and Persististrombus and the coral Siderastrea. They are all inclined toward the coast in the form of a large layer elevated up to 70 m a.s.l., in a surrounding geological environment with gypsum and aeolianites that indicate a eustatic sea-level fall with a regressive effect in the area. These deposits, previously attributed to the Quaternary, are now assigned to the Zanclean because of its similarity in lithology, appearance and fossil content with deposits in western Fuerteventura and NE Gran Canaria.The nearby existence of paleosols with particular structures indicates the start of climatic seasonality in the region; and the only possible time interval in a global context (record of deep-sea oxygen isotopes and sea-level history) fits in the most notable Pliocene global climatic change (~4 Ma) that is registered in the Canary Islands by mean of these coastal and aeolian deposits.

Controls on the provenance of late Eocene to Quaternary Mozambique Channel shales (DSDP 25 Site 242)

Provenance determination of late Eocene to Quaternary sediments deposited at the DSDP 25 Site 242 may help to evaluate the mechanisms that have controlled the sediment deposition in the Mozambique Channel. To determine the provenance of the clay fraction, we measure major and trace element concentrations as well as strontium (87Sr/86Sr) and neodymium isotopic compositions (expressed as ƐNd(0)) of thirty-six sedimentary samples from DSDP 25 Site 242 on the eastern flank of the Davie Fracture Zone. Light Rare Earth Element (LREE) enrichment and Heavy REE (HREE) depletions against Post Archean Australian Shales (PAAS) associated with Ce anomalies higher than or equal to 0.90 for all the analyzed samples suggest very little influence of authigenic smectite incorporation. The absence of correlation of Al/Si and CIA with REE content, Eu/Eu*, Cr/Th, Th/Sc, and 87Sr/86Sr and ƐNd(0) suggests that chemical weathering has not modified these provenance proxies. Slight increase of Eu/Eu*, Cr/Th ratios, ƐNd(0) values associated with slight decrease in 87Sr/86Sr and Th/Sc ratios from the late Eocene to the Quaternary point to input of less differentiated and younger detritus to the DSDP 25 Site 242 with age. Based on variations in ƐNd(0) and Nd concentrations, we estimate an overall decrease of the Southeast African rivers (Congo/Zambezi) contribution from ~65.7% (Standard Deviation (S.D.) ~13.2) in the late Eocene to ~28.5% (S.D. ~10.0) in the early Pliocene. The causes for the low ƐNd(0) values and high Southeast African contribution between the late Eocene and the early Oligocene remain to be determined. It could record the onset of modern sedimentation in the Zambezi delta or the discharge of the Paleo Congo river in the Indian Ocean. The decrease of Zambezi contribution between the late Oligocene and early Pliocene is attributed to the cumulative effect of increasing tectonic activity of the Davie Fracture Zone and intensification of the Mozambique Current. The late Pliocene to Quaternary glacial-interglacial cycles promoted higher Zambezi contribution during glacial sea-level lowstands and in turn lower ƐNd(0) detrital values, whereas low Zambezi contributions are favored during interglacial highstand causing higher ƐNd(0) values. Hence, the modern dispersal pattern of fine-grained sediments within the Mozambique Channel is no younger than late Pliocene.

Geomorphological evolutionary history of the Melendiz River Valley, Cappadocia, Turkey

The Melendiz River is located at the east of Tuz Golu Fault Zone in western Cappadocia. In the central part of Melendiz River Valley, Ihlara Canyon attracts many tourists due to its landscape, cultural and archaeological values. The Melendiz Valley also encompasses geological and geomorphological features that exemplify the evolutionary history of western Cappadocia. In this study, the late Miocene–Quaternary geomorphological evolution of the Melendiz River Valley was investigated. The results indicate that a fluvial sedimentary sequence with ignimbrite intercalation was deposited during the late Miocene and early Pliocene. This was unconformably overlain by lacustrine limestone (Kisladag Formation) of Pliocene age. The Pliocene lake regressed westward because of the changes in the tectonic regime and geomorphological processes during the late Pliocene (~ 3 Ma ago) and the initial Melendiz River developed on the lake bottom. During the Quaternary the Melendiz River developed under the control of both the neotectonic regime and the climate. This development provoked a 160-m-deep incision into the Pliocene sediments and the early Pliocene–Miocene ignimbrites below, giving birth to the Ihlara Canyon. In the proper valley of the Melendiz River, six strath terraces and Holocene flood plain record the incision process.

Using Ostracode Amino Acid D/L Ratios and Microfossil Analysis to Correlate Alluvial Packages along the Lower Colorado River Corridor, with Insight into the Early Pliocene Integration of the Colorado River and the Gulf of California

The lower Colorado River corridor below Grand Canyon developed sometime between ∼5.3 Ma and ∼4.8 Ma, as evidenced by the first appearance of Colorado River-derived sediments of the Bouse Formation in basins along its modern course and the abrupt appearance of distinctive hematite-stained “C-suite” Colorado River sand grains near the base of the Wind Caves member of the Latrania Formation in the Salton Trough. The oldest recognized evidence for a through-flowing Colorado River is the ∼4.5 Ma to ∼3.5 Ma Bullhead Alluvium. Interest and debate focuses on whether a “pre-Bullhead” Colorado River might have first reached the Salton Trough at 5.3 Ma, prior to deposition of some of the Bouse Formation. Fine-grained but undated Colorado River sediments have been recognized on the Yuma Proving Grounds, Arizona, since the 1970s. These sediments have been correlated by some to the Bouse Formation, and thus, would pre-date the Bullhead Alluvium and might provide evidence for the existence of a “pre-Bullhead” Colorado River. In this study, I use the extent of amino acid racemization in ostracode valves and microfossil assemblages to test correlations between the fine-grained sediments on the Yuma Proving Grounds with other independently dated lower Colorado River corridor alluvial packages that were deposited at ∼5 Ma (Bouse Formation) and at ∼75 ka to ∼60 ka (Chemehuevi Formation). The results of this study confidently demonstrate that the fine-grained sediments on the Yuma Proving Grounds are not late Miocene or early Pliocene in age but instead are correlative with the late Pleistocene Chemehuevi Formation. Evidence for a “pre-Bullhead” Colorado River remains elusive.

Palaeovegetational evolution of the Çankırı-Çorum Basin during the Mio-Pliocene (Central Anatolia) based on the IPR analysis method

Reconstruction of past vegetation and climates in the Cankiri-Corum Basin, one of the largest basins of Central Anatolia, is important for understanding the regional palaeovegetation. In this study, the palaeovegetational and palaeoclimatic proxies of the basin within the late middle Miocene and early Pleistocene interval are presented using the Integrated Plant Record (IPR) vegetation analysis and the coexistence approach (CA). The IPR analysis allows the reconstruction of six types of zonal vegetation: broad-leaved deciduous forests (BLDF), mixed mesophytic forests (MMF), broad-leaved evergreen forests (BLEF), xeric open woodlands and xeric grasslands or steppes, all identified from the microfloras of Cankiri-Corum Basin. During the late middle Miocene, warm temperate and humid climatic conditions prevailed and the palaeovegetation in the Cankiri-Corum Basin was represented by BLEF and an ecotone between MMF and BLEF. The cooling from the late middle Miocene to early late Miocene had begun as well, as low precipitation periods in the climatic conditions during the same time interval were recorded in the basin. Presumably, the proportion of broad-leaved deciduous elements remained balanced because the palaeotopography did not change significantly during the late Miocene in the Cankiri-Corum Basin. The recorded cooling could be related to a global climatic change from the middle to late Miocene. During the Tortonian to Messinian transition, the palaeovegetation type was represented by BLDF and suggests a continuous cooling trend in the basin. The palaeovegetation types of the late late Miocene comprise MMF in the northern part of the Cankiri-Corum Basin and xeric grassland or steppe in the southern part of the basin. Warm and dry climatic conditions were recorded from the Tortonian to the Messinian; these warm conditions during the Messinian could be correlated to the Messinian salinity crisis. According to the IPR analysis results, the northern part of the Cankiri-Corum Basin palaeotopography seems to be higher in altitude than the southern part. Palaeovegetation types in the latest late Miocene and early Pliocene were characterised by MMF and an ecotone between BLDF and MMF in the northern part of the Cankiri-Corum Basin and open woodland vegetation in the southern part of the basin. The percentage of the broad-leaved deciduous component from the latest late Miocene and early Pliocene decreases in the Cankiri-Corum Basin, which could be related to beginning uplift starting changes in the palaeotopography. In the early Pliocene, this uplift was continued in the basin.

Studi Fasies Formasi Endapan Danau Untuk Menentukan Lingkungan Pengendapan Danau Limboto

The research area located in the lowland zone and the corrugated hilly zone which is dominated by sedimentary rocks. Therefore, this study aims to determine the geological features of the research area and the study of depositional environmental facies of the Lake Deposits Formation as an analysis of the depositional environment of Limboto Lake. The research method used is the surface geological mapping, measuring a section of stratigraphic and laboratory analysis. Field data consists of stratigraphical features of the research area. Laboratory analysis consists of petrography and stratigraphy-sedimentology analysis. It can be concluded facies and stratigraphy of research from older to youngest, consists of clastic limestones unit formed in Late Miocene-late Early Pliocene age, reef limestones formed in Late Miocene-early Late Pliocene age, sandstones unit formed in Late Pliocene-Pleistocene age, clay unit, and sandy clay unit are deposited in Holocene. Overall the study site consisted of marine, transitional and terrestrial deposition environment with Lake Deposits Formation facies is lake margin clastic deposits and meandering-stream environment deposits.

East African cichlid lineages (Teleostei: Cichlidae) might be older than their ancient host lakes: new divergence estimates for the east African cichlid radiation

BackgroundCichlids are a prime model system in evolutionary research and several of the most prominent examples of adaptive radiations are found in the East African Lakes Tanganyika, Malawi and Victoria, all part of the East African cichlid radiation (EAR). In the past, great effort has been invested in reconstructing the evolutionary and biogeographic history of cichlids (Teleostei: Cichlidae). In this study, we present new divergence age estimates for the major cichlid lineages with the main focus on the EAR based on a dataset encompassing representative taxa of almost all recognized cichlid tribes and ten mitochondrial protein genes. We have thoroughly re-evaluated both fossil and geological calibration points, and we included the recently described fossil †Tugenchromis pickfordi in the cichlid divergence age estimates.ResultsOur results estimate the origin of the EAR to Late Eocene/Early Oligocene (28.71 Ma; 95% HPD: 24.43–33.15 Ma). More importantly divergence ages of the most recent common ancestor (MRCA) of several Tanganyika cichlid tribes were estimated to be substantially older than the oldest estimated maximum age of the Lake Tanganyika: Trematocarini (16.13 Ma, 95% HPD: 11.89–20.46 Ma), Bathybatini (20.62 Ma, 95% HPD: 16.88–25.34 Ma), Lamprologini (15.27 Ma; 95% HPD: 12.23–18.49 Ma). The divergence age of the crown haplochromine H-lineage is estimated to 22.8 Ma (95% HPD: 14.40–26.32 Ma) and of the Lake Malawi radiation to 4.07 Ma (95% HDP: 2.93–5.26 Ma). In addition, we recovered a novel lineage within the Lamprologini tribe encompassing only Lamprologus of the lower and central Congo drainage with its divergence estimated to the Late Miocene or early Pliocene. Furthermore we recovered two novel mitochondrial haplotype lineages within the Haplochromini tribe: ‘Orthochromis’ indermauri and ‘Haplochormis’ vanheusdeni.ConclusionsDivergence time estimates of the MRCA of several Tanganyika cichlid tribes predate the age of the extant Lake Tanganyika basin, and hence are in line with the recently formulated “Melting-Pot Tanganyika” hypothesis. The radiation of the ‘Lower Congo Lamprologus clade’ might be linked with the Pliocene origin of the modern lower Congo rapids as has been shown for other Lower Congo cichlid assemblages. Finally, the age of origin of the Lake Malawi cichlid flock agrees well with the oldest age estimate for lacustrine conditions in Lake Malawi.

Geology of the Yeşilyuva and Kocabaş region and its geotectonic significance

Southwestern Turkey experienced a transition from crustal shortening to extension during Late Cenozoic, and evidence of this was recorded in different basin types in the east of Denizli region. The study area comprises a heterogeneous suite of Mesozoic to Recent igneous, metamorphic, and sedimentary rocks. Two main rock groups are distinguished in the area: the basement rocks of pre-Neogene age and the sedimentary cover of Neogene-Quaternary age. In the region, several Late Cenozoic structural basins are filled with terrestrial clastic and volcanic rocks. These basins are different in orientation, geometry, and nature of basin infills. In the studied area, the exposed basal units of the ophiolitic melange correspond to the Lycian Nappe complex. The first sedimentary cover unit, unconformably overlying the nappes, is represented by an E-W-trending basin that is filled with the Oligocene-Lower Miocene shallow marine-terrestrial deposits. The infill of the studied basin consists of the Caykavustu and the Akcay Formations which were deposited during the Late Oligocene and the Early Miocene, respectively. These basins developed as a piggy-back basin along the fault plane on the hanging wall blocks of normal faults. A graben basin (Yesilyuva-Kocabas) started to occur along with NE-SW-trending normal faults which were formed as a result of E-W extensional regime during the Late Miocene. The coarse clastics of the Kizilburun Formation of the Late Miocene age were deposited within an alluvial fan derived from the Elmadag Horst in the east of the basin. Whereas the coarse clastics of the Late Miocene basement were accumulated in front of the hanging fault blocks, the fine-grained clastics of the Saraykoy Formation overlie conformably the Kizilburun Formation. The sequence continues with the lacustrine limestones of the Aktepe Formation. Alkaline magmatics of Early-Late Pliocene cut all successions. E-W-trending fault systems formed with the N-S extensional regime affected the basin, and the recent E-W grabens (Curuksu and Acigol Graben) occurred during the Early Pliocene. The recent morphology of the studied area developed under the control of the Asagidagdere oblique fault zones which are located in the south of the Curuksu Graben.

Evolution of the Zonal Gradients Across the Equatorial Pacific During the Miocene–Pleistocene

Combining U k 0 37-and TEX 86-derived temperatures and oxygen isotopic values of mixed-layer and thermocline species from the IODP site U1338 (East Equatorial Pacific) and ODP Site 806 (West Equatorial Pacific) we assess the evolution of the zonal sea-surface temperature gradients and thermocline depth across the equatorial Pacific from the late Miocene through the Pleistocene. Data suggest a long-term shoaling of the thermocline along the equator throughout the Miocene-Pliocene that accelerated around 5.3 Ma. We identify a critical transition at about 3.8 Ma from a El-NinoNi˜Nino-like-dominated mean state during the late Miocene and early Pliocene to a La-Nina-like-dominated state during the late Pliocene-Pleistocene. This transition coincides with the restriction of the Indonesian seaway and the onset of ice growth in the northern hemisphere and in Antarctica that led to the long-term strengthening of the Walker circulation and affected low-latitude zonal gradient.

The Early Pliocene extinction of the mega-toothed shark Otodus megalodon: a view from the eastern North Pacific.

The extinct giant shark Otodus megalodon is the last member of the predatory megatoothed lineage and is reported from Neogene sediments from nearly all continents. The timing of the extinction of Otodus megalodon is thought to be Pliocene, although reports of Pleistocene teeth fuel speculation that Otodus megalodon may still be extant. The longevity of the Otodus lineage (Paleocene to Pliocene) and its conspicuous absence in the modern fauna begs the question: when and why did this giant shark become extinct? Addressing this question requires a densely sampled marine vertebrate fossil record in concert with a robust geochronologic framework. Many historically important basins with stacked Otodus-bearing Neogene marine vertebrate fossil assemblages lack well-sampled and well-dated lower and upper Pliocene strata (e.g., Atlantic Coastal Plain). The fossil record of California, USA, and Baja California, Mexico, provides such an ideal sequence of assemblages preserved within well-dated lithostratigraphic sequences. This study reviews all records of Otodus megalodon from post-Messinian marine strata from western North America and evaluates their reliability. All post-Zanclean Otodus megalodon occurrences from the eastern North Pacific exhibit clear evidence of reworking or lack reliable provenance; the youngest reliable records of Otodus megalodon are early Pliocene, suggesting an extinction at the early-late Pliocene boundary (∼3.6 Ma), corresponding with youngest occurrences of Otodus megalodon in Japan, the North Atlantic, and Mediterranean. This study also reevaluates a published dataset, thoroughly vetting each occurrence and justifying the geochronologic age of each, as well as excluding several dubious records. Reanalysis of the dataset using optimal linear estimation resulted in a median extinction date of 3.51 Ma, somewhat older than a previously proposed Pliocene-Pleistocene extinction date (2.6 Ma). Post-middle Miocene oceanographic changes and cooling sea surface temperature may have resulted in range fragmentation, while alongside competition with the newly evolved great white shark (Carcharodon carcharias) during the Pliocene may have led to the demise of the megatoothed shark. Alternatively, these findings may also suggest a globally asynchronous extinction of Otodus megalodon.

Reconstructing biogeographic temporal events in the evolution of the livebearer fish genus Jenynsia based on total evidence analysis (Cyprinodontiformes: Anablepidae)

The current distribution of the Neotropical ichthyofauna has been widely affected by the main geological events that occurred in South and Central America. However, robust biogeographic information is still scarce or absent for most fish families. The biogeographic relationships of the most diverse anablepid genus, Jenynsia, are herein analysed, using temporal and spatial approaches based on a total evidence dataset, including 167 morphological characters and seven nuclear genes, totalling 6075 bp. A time calibrated analysis recovered the origin of Jenynsia at the Miocene and the diversification of its two subgenera between the Late Miocene and Early Pliocene. This result combined with the analysis of reconstruction of ancestral states indicates that the ancestor of Jenynsia colonized the Paranean Sea, and the current distribution of the species of the genus is probably a result of geological events, including: (1) ancient connections between Iguaçu and upper Uruguay River basins; (2) sea level variation along the Pliocene in the South American Atlantic coast; and (3) the decrease of the Paranean Sea along the Pliocene and Pleistocene.

Diversification of shrub frogs (Rhacophoridae, Pseudophilautus) in Sri Lanka – Timing and geographic context

Pseudophilautus comprises an endemic diversification predominantly associated with the wet tropical regions of Sri Lanka that provides an opportunity to examine the effects of geography and historical climate change on diversification. Using a time-calibrated multi-gene phylogeny, we analyze the tempo of diversification in the context of past climate and geography to identify historical drivers of current patterns of diversity and distribution. Molecular dating suggests that the diversification was seeded by migration across a land-bridge connection from India during a period of climatic cooling and drying, the Oi-1 glacial maximum around the Eocene-Oligocene boundary. Lineage-through-time plots suggest a gradual and constant rate of diversification, beginning in the Oligocene and extending through the late Miocene and early Pliocene with a slight burst in the Pleistocene. There is no indication of an early-burst phase of diversification characteristic of many adaptive radiations, nor were there bursts of diversification associated with favorable climate shifts such as the intensification of monsoons. However, a late Miocene (8.8 MYA) back-migration to India occurred following the establishment of the monsoon. The back migration did not trigger a diversification in India similar to that manifest in Sri Lanka, likely due to occupation of available habitat, and consequent lack of ecological opportunity, by the earlier radiation of a sister lineage of frogs (Raorchestes) with similar ecology. Phylogenetic area reconstructions show a pattern of sister species distributed across adjacent mountain ranges or from different parts of large montane regions, highlighting the importance of isolation and allopatric speciation. Hence, local species communities are composed of species from disparate clades that, in most cases, have been assembled through migration rather than in situ speciation. Lowland lineages are derived from montane lineages. Thus, the hills of Sri Lanka acted as species pumps as well as refuges throughout the 31 million years of evolution, highlighting the importance of tropical montane regions for both the generation and maintenance of biodiversity.

Tologoi key section: A unique archive for pliocene-pleistocene paleoenvironment dynamics of Transbaikalia, Bikal rift zone

The multi-layered key section of Tologoi is situated on the Selenga River left bank, 15 km southwest of Ulan-Ude city (51º45′ N, 107º29’ E), in the Western Transbaikal region. It holds a long record of Quaternary sedimentation since early Late Pliocene through Holocene, with the only minor gap in the beginning of Early Pleistocene. Comprehensive studies have been carried out on the lithology, geochemistry, fauna succession and paleoenvironment reconstructions. This paper summarizes the data acquired on the geology and stratigraphy of the Tologoi section. The authors investigated the composition, structure and formation conditions of the section, as well as the intensity of weathering, rock geochemistry, grain size and biostratigraphy.

A late surviving Pliocene seal from high latitudes of the North Atlantic realm: the latest monachine seal on the southern margin of the North Sea.

BackgroundThe family of true seals, the Phocidae, is subdivided into two subfamilies: the southern Monachinae, and the northern Phocinae, following the subfamilies’ current distribution: extant Monachinae are largely restricted to the (sub-)Antarctic and the eastern Pacific, with historical distributions of the monk seals of the genus Monachus in the Caribbean, the Mediterranean and around Hawaii; and Phocinae to the northern temperate and Arctic zones. However, the fossil record shows that Monachinae were common in the North Atlantic realm during the late Miocene and early Pliocene. Until now, only one late Pliocene record is known from the Mediterranean, Pliophoca etrusca from Tuscany, Italy, but none from farther north in the North Atlantic.MethodsWe present the description of one partial phocid humerus collected in the early 20th century from the Antwerp area (Belgium), with an assessment of its stratigraphic origin using data from the literature.ResultsThe studied humerus was recovered during construction works at the former Lefèvre dock in the Antwerp harbour (currently part of the America dock). Combining the information associated to the specimen with data from the literature and from local boreholes, the upper Pliocene Lillo Formation is ascertained as the lithological unit from which the specimen originates. Morphologically, among other features the shape of the deltopectoral crest and the poor development of the supinator crest indicates a monachine attribution for this specimen. The development of the deltopectoral crest is closer to the condition in extant Monachinae than in extinct Monachinae.DiscussionThe presented specimen most likely represents a monachine seal and a literature study clearly shows that it came from the latest early to late Pliocene Lillo Formation. This would be the first known monachine specimen from the latest early to late Pliocene of the North Sea, and more broadly from the northern part of the North Atlantic realm. This humerus differs from the humerus of P. etrusca and suggests a higher diversity of Monachinae in the latest early to late Pliocene than previously assumed.

The evolution of the human foot.

There are 26 bones in each foot (52 in total), meaning that roughly a quarter of the human skeleton consists of foot bones. Yet, early hominin foot fossils are frustratingly rare, making it quite difficult to reconstruct the evolutionary history of the human foot. Despite the continued paucity of hominid or hominin foot fossils from the late Miocene and early Pliocene, the last decade has witnessed the discovery of an extraordinary number of early hominin foot bones, inviting a reassessment of how the human foot evolved, and providing fresh new evidence for locomotor diversity throughout hominin evolution. Here, we provide a review of our current understanding of the evolutionary history of the hominin foot.