Página 1 dos resultados de 1643 itens digitais encontrados em 0.005 segundos

Sediment deformation in Miocene and post-Miocene strata, Northeastern Brazil: Evidence for paleoseismicity in a passive margin

ROSSETTI, Dilce F.; BEZERRA, F. H. R.; GOES, Ana M.; Brito Neves, Benjamim Bley de
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.15%
Stratigraphic intervals characterized by varied and complex styles of soft-sediment deformation structures are well preserved in Miocene and Late Pleistocene to Holocene deposits of a sedimentary basin located in Northeastern Brazil. The Miocene strata, represented by the Barreiras Formation, record only brittle structures, including numerous faults and fractures with straight and high angle-dipping planes that are often filled with sands derived from overlying beds. Folds consisting of broad anticlines and synclines are also present in this unit. The late Pleistocene to Holocene deposits, named Post-Barreiras Sediments, contain an indurated sandy package with a large variety of ductile and brittle deformation structures (i.e., massive sandstones with isolated sand fragments and breccias, undulatory strata, sand dykes and diapirs, sinks and bowls, pebbly pockets, plunged sediment mixtures, fitted sand masses, cone-shaped cracks, fault grading and sedimentary enclaves). These features, confined to sharp-based stratigraphic horizons that progressively grade downward into undisturbed deposits, are related to seismic shocks of high surface-wave magnitude (i.e., Ms>5 or 6). Amalgamated seismites suggest that previously formed seismites were affected by subsequent seismic-wave propagation. Seismic waves caused by activity along one...

Early Miocene bivalves from the Cape Melville Formation, King George Island, West Antarctica

Anelli, L. E.; Rocha-Campos, A. C.; Dos Santos, P. R.; Perinotto, José Alexandre de Jesus; Quaglio, F.
Fonte: Geological Society Australia Inc Publicador: Geological Society Australia Inc
Tipo: Artigo de Revista Científica Formato: 111-132
ENG
Relevância na Pesquisa
37.15%
Seven species of marine bivalves, including six new taxa, are described from the Cape early Miocene Melville Formation which crops out on the Melville Peninsula, King George Island, West Antarctica. The bivalve assemblage includes representatives of the families Nuculidae, Ennucula frigida sp. nov., E. musculosa sp. nov.; Malletidae, Neilo (Neilo) rongelii sp. nov.; Sareptidae, Yoldia peninsularis sp. nov.; Limopsidae, Limopsis psimolis sp. nov.; Hiatellidae, Panopea (Panopea) sp. cf. P. regularis; and Pholadomyoida (Periploma acuta sp. nov.). Species studied come from four sedimentary sections measured in the upper part of the unit. Detailed morphologic features of nuculoid and areoid species are exceptionally well preserved and allow for the first time reconstruction of muscle insertions as well as dentition patterns of Cenozoic taxa. Known geological distribution of the species is in agreement with the early Miocene age assigned to the Cape Melville Formation. The bivalve fauna from Cape Melville Formation is the best known from Antarctic Miocene rocks, a time of complex geologic, paleogeographic and paleoclimatic changes in the continent. The new fauna introduces new taxonomic and palaeogeographic data that bear oil the question of opening of sea gateways and distribution of Cenozoic biota around Antarctica.

Évolution de la végétation et du climat pendant le miocène au Portugal

Pais, João
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Artigo de Revista Científica
Publicado em 25/03/2010 FRA
Relevância na Pesquisa
37.05%
These work presents the quantitative and qualitative inventory and the stratigraphic distribution of fossil plants (spores, pollens, sterns, leaves and seeds) recognized the Miocene of the portuguese part of Tagus basin. For each lithostratigraphic unit, associations with ecological (paleoclimatic) meaning are defined. It was also possible to follow the evolution of the vegetation and the climate during the considered cronostratigraphic interval which includes most of the Miocene (Aquitanian to lower-middle Tortonian).

Miocene lithological, foraminiferal and palynological data from the Belverde borehole (Portugal)

Legoinha, P.; Sousa, Lígia; Pais, João; Ferreira, João; Amado, Ana Rita; Ribeiro, Isabel
Fonte: Universidad de Salamanca Publicador: Universidad de Salamanca
Tipo: Artigo de Revista Científica
Publicado em //2002 ENG
Relevância na Pesquisa
37.15%
XVIII Jornadas de Paleontología, 2002; Preliminary data on litho stratigraphy and biostratigraphy of the Belverde borehole (http://www. dct.Jct.unl.pt/ SondagemISondagem/colunalindex_col.html) is presented. The borehole attained 619,77 m of depth, crossing 130 m of Plio-Pleistocene and 460 m of Miocene dep osits. Main lithologies are fine sands , marl s and biocalcarenites. A coral reef was recognized in the lower part of the borehole (530-585 m). Gamma ray, neutrons and sonic diagraphies were obtained. Eight 87Sr/86Sr isotopic ages (H. Elderfield, Cambridge University)and the presence of some of the main planktonic foraminifera markers were used to establish the chronostratigraphic framework. Plankt onic spikes are related to the major transgression s of the Lower Tagus Basin (LTB): M. Burdigalian (sample Belv 459 ; 446 m), L. Serravallian (Belv 76; 244 m) and L. Tortonian (Belv 51, 202 m). Benthi c assemblages are dominated by Ammonia, Elphidium and Nonion. Spores suggest a mild and humid climate during the uppermost Burdigalian to the Tortonian. Pollen is scarce. Thirty dinoflagellates taxa (26 Gonyaulacoids and 4 Peridinioids) have been identi fied, indicating coastal to shallow marine environments. In the uppermost Burdigalian to the Tortonian the presence of peridinioids and scarce acritarchs suggest influence of inshore to brackish environments. Several 87Sr /86Sr ages obtained by H. Elderfield (Cambridge University) fit well with the biostratigraphy for the Lower an Middle Miocene...

Miocene mammal reveals a Mesozoic ghost lineage on insular New Zealand, southwest Pacific

Worthy, Trevor Henry; Tennyson, Alan J. D.; Archer, Michael; Musser, Anne M.; Hand, Suzanne J.; Jones, Craig; Douglas, Barry J.; McNamara, James A.; Beck, Robin M. D.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
37.22%
New Zealand (NZ) has long been upheld as the archetypical example of a land where the biota evolved without nonvolant terrestrial mammals. Their absence before human arrival is mysterious, because NZ was still attached to East Antarctica in the Early Cretaceous when a variety of terrestrial mammals occupied the adjacent Australian portion of Gondwana. Here we report discovery of a nonvolant mammal from Miocene (19-16 Ma) sediments of the Manuherikia Group near St Bathans (SB) in Central Otago, South Island, NZ. A partial relatively plesiomorphic femur and two autapomorphically specialized partial mandibles represent at least one mouse-sized mammal of unknown relationships. The material implies the existence of one or more ghost lineages, at least one of which (based on the relatively plesiomorphic partial femur) spanned the Middle Miocene to at least the Early Cretaceous, probably before the time of divergence of marsupials and placentals >125 Ma. Its presence in NZ in the Middle Miocene and apparent absence from Australia and other adjacent landmasses at this time appear to reflect a Gondwanan vicariant event and imply persistence of emergent land during the Oligocene marine transgression of NZ. Nonvolant terrestrial mammals disappeared from NZ some time since the Middle Miocene...

Miocene waterfowl and other birds from central Otago, New Zealand

Worthy, Trevor Henry; Tennyson, Alan J. D.; Jones, C.; McNamara, James A.; Douglas, Barry J.
Fonte: Taylor and Francis Publicador: Taylor and Francis
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
37.22%
Abundant fossil bird bones from the lower Bannockburn Formation, Manuherikia Group, an Early-Middle Miocene lacustrine deposit, 16–19 Ma, from Otago in New Zealand, reveal the “St Bathans Fauna” (new name), a first Tertiary avifauna of land and freshwater birds from New Zealand. At least 23 species of birds are represented by bones, and probable moa, Aves: Dinornithiformes, by eggshell. Anatids dominate the fauna with four genera and five species described as new: a sixth and largest anatid species is represented by just one bone. This is the most diverse Early-Middle Miocene duck fauna known worldwide. Among ducks, two species of dendrochenines are most numerous in the fauna, but a tadornine is common as well. A diving petrel (Pelecanoididae: Pelecanoides) is described, so extending the geological range of this genus worldwide from the Pliocene to the Middle Miocene, at least. The remaining 16 taxa are left undescribed but include: a large species of gull (Laridae); two small waders (Charadriiformes, genus indet.), the size of Charadrius bicinctus and Calidris ruficollis, respectively; a gruiform represented by one specimen similar to Aptornis; abundant rail (Rallidae) bones, including a common flightless rail and a rarer slightly larger taxon...

A sphenodontine (Rhynchocephalia) from the Miocene of New Zealand and palaeobiogeography of the tuatara (Sphenodon)

Jones, M.; Tennyson, A.; Worthy, J.; Evans, S.; Worthy, T.
Fonte: Royal Soc London Publicador: Royal Soc London
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
37.28%
Jaws and dentition closely resembling those of the extant tuatara (Sphenodon) are described from the Manuherikia Group (Early Miocene; 19–16 million years ago, Mya) of Central Otago, New Zealand. This material is significant in bridging a gap of nearly 70 million years in the rhynchocephalian fossil record between the Late Pleistocene of New Zealand and the Late Cretaceous of Argentina. It provides the first pre-Pleistocene record of Rhynchocephalia in New Zealand, a finding consistent with the view that the ancestors of Sphenodon have been on the landmass since it separated from the rest of Gondwana 82–60 Mya. However, if New Zealand was completely submerged near the Oligo-Miocene boundary (25–22 Mya), as recently suggested, an ancestral sphenodontine would need to have colonized there-emergent landmass via ocean rafting from a currently unrecorded and now extinct Miocene population. Although an Early Miocene record does not preclude that possibility, it substantially reduces the temporal window of opportunity. Irrespective of pre-Miocene biogeographic history, this material also provides the first direct evidence that the ancestors of the tuatara, an animal often perceived as unsophisticated, survived in New Zealand despite substantial local climatic and environmental changes.; Marc E.H Jones...

A new species of the diving duck Manuherikia and evidence for geese (Aves : Anatidae : Anserinae) in the St Bathans Fauna (Early Miocene), New Zealand

Worthy, Trevor Henry; Tennyson, Alan J. D.; Hand, Suzanne J.; Scofield, Richard Paul
Fonte: SIR Publishing Publicador: SIR Publishing
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
37.15%
A new species of the diving duck Manuherikia, larger than its two congeners, is described based on a humerus and several referred ulnae from the St Bathans Fauna, lower Bannockburn Formation, Manuherikia Group, of Early Miocene (19–16 Ma) age, in New Zealand. Evidence for anserines in the St Bathans Fauna is evaluated. Two coracoid fragments, a scapula and a proximal radius reveal a goose most similar to Cereopsis and Cnemiornis, so indicating the presence of the Cnemiornis lineage in New Zealand in the Early Miocene. Two more coracoids are provisionally interpreted as a small unusual anserine perhaps close to Cereopsis. These records extend the diversity of waterfowl described from the St Bathans Fauna to six named species in four genera, plus an additional two unnamed anserines, globally the richest Miocene waterfowl fauna known.; Trevor H. Worthy, Alan J. D. Tennyson, Suzanne J. Hand & R. Paul Scofield

Isotope geology and Miocene magmatic evolution along the northern border of the Menderes Massif (NW Anatolia, Turkey); Isotopengeologie und die Miozäne magmatische Entwicklung entlang des Nordrandes des Menderes-Massivs (NW Anatolien, Türkei)

Hasözbek, Altug
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
37.32%
In the Aegean region, complex geodynamic processes including subduction, continent-continent collision, and back-arc extension occurred from the Eocene to the present time. In NW Anatolia (Turkey), the products of these events are widely exposed. Especially, Miocene granites along the northern border of the Menderes Massif demonstrate prominent geologic features associated with these complex geodynamic events. In order to determine the magmatic evolution of the northern boundary of the Menderes Massif and to understand its tectono-magmatic position in the Aegean region, during and after the collision of the Anatolide-Tauride platform with the Sakarya Continent, two regions in NW Anatolia (Simav and Alaçam regions) were examined by detailed mapping, geochemical, isotopic and geochronological studies. After the closure of the Neo-Tethys and the collision of the Menderes Platform with the Sakarya Continent during the Cretaceous, a nappe package consisting of four main tectonic zones was formed in NW Anatolia. These are: (1) Menderes metamorphics, (2) Meta-ophiolithic nappe complex, (3) Afyon Zone, and (4) Bornova Flysch Zone. This nappe package, stacked together by the collision, was intruded and stitched by Early Miocene granitic plutons that constitute a NE-SW trending magmatic belt that evolved in a thick continental crust. In the Simav region...

Eocene-Miocene carbon-isotope and floral record from brown coal seams in the Gippsland Basin of southeast Australia

Holdgate, G.; McGowran, B.; Fromhold, T.; Wagstaff, B.; Gallagher, S.; Wallace, M.; Sluiter, I.; Whitelaw, M.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
37.35%
The carbon-isotope and palynological record through 580 m thick almost continuous brown coal in southeast Australia's Gippsland Basin is a relatively comprehensive southern hemisphere Middle Eocene to Middle Miocene record for terrestrial change. The carbon isotope δ¹³Ccoal values of these coals range from − 27.7‰ to − 23.2. This isotopic variability follows gymnosperm/angiosperm fluctuations, where higher ratios coincide with heavier δ¹³C values. There is also long-term variability in carbon isotopes through time. From the Eocene greenhouse world of high gymnosperm-heavier δ¹³Ccoal values, there is a progressive shift to lighter δ¹³Ccoal values that follows the earliest (Oi1?) glacial events around 33 Ma (Early Oligocene). The overlying Oligocene–Early Miocene brown coals have lower gymnosperm abundance, associated with increased %Nothofagus (angiosperm), and lightening of isotopes during Oligocene cooler conditions. The Miocene palynological and carbon-isotope record supports a continuation to the Oligocene trends until around the late Early Miocene (circa 19 Ma) when a warming commenced, followed by an even stronger isotope shift around 16 Ma that peaked in the Middle Miocene when higher gymnosperm abundance and heavier isotopes prevailed. The cycle between the two major warm peaks of Middle Eocene and Middle Miocene was circa 30 Ma long. This change corresponds to a fall in inferred pCO₂ levels for the same period. The Gippsland data suggest a link between gymnosperm abundance...

METALLOGENETIC CONTROLS ON MIOCENE HIGH-SULPHIDATION EPITHERMAL GOLD MINERALIZATION, ALTO CHICAMA DISTRICT, LA LIBERTAD, NORTHERN PERÚ

Montgomery, Allan Trevor
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
37.22%
The Alto Chicama district, Central Andean Cordillera Occidental, La Libertad, northern Perú, hosts the 14 M oz, Miocene Lagunas Norte high-sulphidation epithermal Au-(Ag) deposit (Latitude 7° 56ʹ30ʺ S; Longitude 78°14ʹ50ʺ W), in addition to several important, epithermal and mesothermal precious ± base-metal vein systems and porphyry Cu-Au-(Mo) deposits and prospects. The district is underlain by lower Oligocene-to-Middle Miocene, subaerial, Calipuy Supergroup volcanic rocks, unconformably overlying Upper Jurassic – Lower Cretaceous marine sedimentary strata affected by late Eocene-early Oligocene thin-skinned fold and thrust deformation. Mineralization at Lagunas Norte is largely hosted by intensely-folded Valanginian Chimú Formation quartz arenite, but extends into overlying, weakly-deformed, Lower Miocene dacitic volcaniclastic deposits. Fold- and thrust-related deformation at the deposit, and subsequent magmatic and hydrothermal activity, were localized along a long-lived, crustal-scale cross-strike discontinuity. Hydrothermal activity at Lagunas Norte was associated with local extension within an overall regional compressive regime. Ore formation occurred during the terminal stages of andesitic-to-dacitic magmatism in the deposit area...

Sedimentology of the Miocene Nullarbor Limestone; Southern Australia

GILLESPIE, LAURA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
37.28%
The Miocene Nullarbor Limestone is the most recent formation in the Cenozoic Eucla Group and was deposited in the Eucla Basin, southern Australia, at ~38°S paleolatitude during the early to middle Miocene. The rocks form the modern surface of the vast, karsted Nullarbor Plain. Older Eucla Group marine carbonates (Eocene-earliest Miocene) are cool-water in nature and dominated by bryozoans and echinoderms. The Nullarbor Limestone is subtropical in composition and rich in coralline algae (rhodoliths and articulated types), large and small benthic foraminifera and molluscs. Diverse zooxanthellate corals are also present but not numerous. Deposition is interpreted to have taken place in three main paleoenvironments: rhodolith gravels, seagrass banks, and open seafloors. The Southern Ocean extended inboard ~450 km from the shelf edge during Nullarbor Limestone deposition. Interpreted paleodepths ranged from the top to the base of the photic zone, implying a small slope over a wide shelf. The Miocene Eucla platform is therefore interpreted to have been epeiric in nature. Paleoenvironment distribution is explained using epeiric platform sedimentation patterns and comparisons with modern environments. Open seafloor environments...

Sélaciens du Miocène terminal du bassin d'Alvalade (Portugal). Essai de synthèse

Antunes, M. T.; Balbino, A. C.; Cappetta, H.
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Artigo de Revista Científica
Publicado em 28/12/2010 FRA
Relevância na Pesquisa
37.15%
A rich uppermost Miocene selachian fauna from the Alvalade Basin (represented by more than 10.000 teeth) is accounted for. It is the most modern miocene fauna of neritic habit under warm-temperate to subtropical conditions, known in the european Miocene.

Description de restes squelettiques de Latidae: Lates (?) sp. (Poissons téléostéens, Percoidei) du Miocène inférieur et moyen du bassin du Bas Tage (environs de Lisbonne, Portugal)

Antunes, M. T.; Caudant, J.
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Artigo de Revista Científica
Publicado em 30/12/2010 FRA
Relevância na Pesquisa
37.22%
Several Lower and Middle Miocene localities in the Lower Tagus basin near Lisbon yielded Latidae fragmentary remnants. No really decisive character has been recognized that would allow us to state these remnants could surely be ascribed to the genus Lates Cuv. & Val., although we regard this as nearly certain. There are some differences between the Miocene latidae under study and the type species Lates niloticus L. this suggests us to report the concerned remnants to a Lates (?) sp. that could belong to a new, hitherto undescribed species. The occurrence of Lates in fluviatile or lagoonal beds in the Lower Tagus basin Miocene series is not at all surprising under a paleoeciological view point. Even less if account is taken of the presence in the same levels of Siluriforms remnants belonging to Bagridae and Ariidae, two families that are well represented in Africa. Bagrid spines have been found at Quinta das Pedreiras in association with Lates (?) sp. remnants. The Lates (?) sp. discovery in the Lower and Middle Miocene from the Lower Tagus basin results in extending to the West this genus' biogeographic distribution. It is indeed the first discovery of this genus on Europe's Atlantic coasts. No matter which was the geographic origin of these fishes...

Miocene marine-continental correlations in the Lisbon area and some discussion related to personnal experience

Antunes, M. T.
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Artigo de Revista Científica
Publicado em 30/12/2010 ENG
Relevância na Pesquisa
37.22%
Sandpit exploitation near Lisbon allowed collecting of many Miocene, non marine fossils. These sands are part of the mostly marine Miocene series in the Lower Tagus basin. The particularly favourable situation led several researchers to deal with marine-continental correlations. Difficulties often concern methodologic aspects. Some poorly based interpretations exerced a lasting influence. A critical approach is presented. Analysis requires data. Methods based upon models often lead to the temptation of fitting data in order to confirm a priori conclusions, or of mixing up data as if of equal statistic value while they have not at all the same weight. Erroneous interpretations' uncritical repetition for many years "upgraded" them into absolute truth. Another point is endemism vs. europeism. Miocene mammals from Lisbon compared well with corresponding French, contemporaneous taxa, while this was apparently not true for Spanish ones. Too much accent had been put on the endemic character of Spanish, or even regional, mammalian faunas. Nationalist bias and sensationalism also weigh, albeit negatively. Meanwhile nearly all the more evident examples as the rhinoceros Hispanotherium are discredited as Iberian endemisms. Taxa may appear as endemic just because they have not yet been found elsewhere. At least for the medium to large-sized mammals...

Etude de populations de Glycymeris (Bivalvia, Glycymerididae) du Miocène d'Aquitaine, Sud-Ouest de la France Studyof Glycymeris (Bivalvia, G1ycymerididae) populations from the Aquitaine Miocene, SW France

Cahuzac, B.; Cluzaud, A.; Lesport, J. F.; Ringeade, M.
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Artigo de Revista Científica
Publicado em //1992 ENG
Relevância na Pesquisa
37.15%
Abundant crops of Glycymeris have been made in the neritic bioclastic deposits of the Aquitaine Basin. After an outline about the Chattian taxa, the 5 Lower Miocene lineages are presented; G. cor is plainly predominant. Then, the Middle Miocene faunas are also detaiIed, G. inflatus and G. bimaculatus being the most frequent taxa. A test of biometrical analysis about the G. cor species is presented.

Multiproxy reconstruction of the palaeoclimate and palaeoenvironment of the Middle Miocene Somosaguas site (Madrid, Spain) using herbivore dental enamel

Domingo, Laura; Cuevas-González, Jaime; Grimes, Stephen T.; Hernández Fernández, M.; Lopez-Martinez, N.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 918459 bytes; application/pdf
ENG
Relevância na Pesquisa
37.15%
16 pages, 11 figures, 3 tables.-- Available online Nov 17, 2008.-- This work is a contribution from the research groups UCM-CAM 910161 on Geologic Record of Critical Periods: Palaeoclimatic and Palaeonvironmental Factors, and UCM-CAM 910607 on Evolution of Cenozoic Mammals and Continental Palaeoenvironments.; Profound palaeoclimatic changes took place during the Middle Miocene. The Miocene Climatic Optimum (~ 20 to 14–13.5 Ma) was followed by a sudden (~ 200 ka) decrease in temperature and an increase in aridity around the world as a consequence of the reestablishment of the ice cap in Antarctica. Somosaguas palaeontological site (Madrid Basin, Spain) has provided a rich record of mammal remains coincident with this global event (Middle Miocene Biozone E, 14.1–13.8 Ma). It contains four fossiliferous levels (T1, T3-1, T3-2 and T3-3, with T1 being the oldest) that span an estimated time of ~105–125 ka. Scanning Electron Microscope (SEM) and Rare Earth Element (REE) analyses performed on herbivore tooth enamel (Gomphotherium angustidens, Anchitherium cf. A. cursor, Conohyus simorrensis, Prosantorhinus douvillei and ruminants) indicate that diagenetic processes have not been intense enough as to obscure the original geochemical signal. Stable isotope (δ18OCO3...

Paleosols and paleoenvironments of the middle Miocene, Maboko Formation, Kenya

Retallack, Gregory; Wynn, Jonathan; Benefit, Brenda; McCrossin, Monte
Fonte: Academic Press Publicador: Academic Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.22%
The middle Miocene (15 Ma) Maboko Formation of Maboko Island and Majiwa Bluffs, southwestern Kenya, has yielded abundant fossils of the earliest known cercopithecoid monkey (Victoriapithecus macinnesi), and of a kenyapithecine hominoid (Kenyapithecus africanus), as well as rare proconsuline (Simiolus leakeyorum, cf. Limnopithecus evansi) and oreopithecine apes (Mabokopithecus clarki, M. pickfordi), and galagids (Komba winamensis). Specific habitat preferences can be interpreted from large collections of primate fossils in different kinds of paleosols (pedotypes). Fossiliferous drab-colored paleosols with iron-manganese nodules (Yom pedotype) are like modern soils of seasonally waterlogged depressions (dambo). Their crumb structure and abundant fine root-traces, as well as scattered large calcareous rhizoconcretions indicate former vegetation of seasonally wet, wooded grassland. Other fossiliferous paleosols are evidence of nyika bushland (Ratong), and early-successional riparian woodland (Dhero). No fossils were found in Mogo paleosols interpreted as saline scrub soils. Very shallow calcic horizons (in Yom, Ratong, and Mogo paleosols) and Na-montmorillonite (in Mogo) are evidence of dry paleoclimate (300-500 mm MAP=mean annual precipitation). This is the driest paleoclimate and most open vegetation yet inferred as a habitat for any Kenyan Miocene apes or monkeys. Victoriapithecus was abundant in dambo wooded grassland (Yom) and riparian woodland (Dhero)...

Tooth Root Size, Chewing Muscle Leverage, and the Biology of Homunculus patagonicus (Primates) from the late early Miocene of Patagonia

Perry,Jonathan M. G.; Kay,Richard F.; Vizcaíno,Sergio F.; Bargo,M. Susana
Fonte: Ameghiniana Publicador: Ameghiniana
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 EN
Relevância na Pesquisa
37.15%
Inferences about the diet of Miocene platyrrhine monkeys have relied upon the morphology of the molar teeth, specifically the crests on the molars. Using a library of Micro-CT images of a broad comparative sample of living platyrrhines (callitrichines, cebines, pitheciids and atelids), late early Miocene Homunculus, and the early Miocene Tremacebus and Dolichocebus, we extend these inferences by examining the surface areas of the tooth roots, anchor points for the periodontal ligaments. From muscle scars on the skull, we estimate the mechanical leverage of the chewing muscles at bite points from the canine to the last molar. Extant platyrrhines that gouge bark to obtain exudates do not have especially large canine roots or anterior premolar roots compared with their less specialized close relatives. Extant platyrrhines that have more folivorous diets have much larger molar roots than do similar-sized more frugivorous species. Homunculus patagonicus has large postcanine roots relative to body size and poor masticatory leverage compared to the extant platyrrhines in our sample. The large postcanine roots, heavy tooth wear, and moderately-long shearing crests suggests a diet of abrasive, resistant foods. However, relatively poor jaw adductor leverage would have put the masticatory apparatus of Homunculus at a mechanical disadvantage for producing high bite forces compared to the condition in extant platyrrhines. Tremacebus and Dolichocebus...

Dietary evaluation of a hipparionin horse population from the middle Miocene of Oaxaca, southeastern Mexico

Bravo-Cuevas,Victor M.; Priego-Vargas,Jaime
Fonte: Instituto de Geología, UNAM Publicador: Instituto de Geología, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2009 EN
Relevância na Pesquisa
37.15%
The first paleodietary interpretation of a hipparionin horse population from the middle Miocene El Camarón Formation (late early Barstovian, K-Ar dated 15.0 ± 0.8 to 16.7 ± 0.71 Ma) of Oaxaca, southeastern Mexico is presented. The species is formally referred to Cormohipparion aff. C. quinni and its dietary behavior were evaluated by the extended mesowear analysis method. A cluster analysis compared the Oaxacan species with 23 selected extant species and fossil hipparionins from the Neogene of North America, Europe, and Africa. The mesowear pattern of the Oaxacan hipparionin is comparable to that of the mixed feeder Cormohipparion quinni from the late Barstovian of northern Great Plains. These species display a combination of high relief and round cusps characteristic of a relatively high-abrasion diet. This suggests that the population of C. aff. C. quinni was a mixed feeder that incorporated abrasive food items into the diet (grass and/or extrinsic grit). The results provide evidence for the existence of local grazing habitats in southern tropical North America during the early middle Miocene (ca. 15 Ma), and give additional support that savanna-like habitats were present in high and low latitudes of North America during the mid Miocene (~18-12 Ma).