Oligocene Research Papers - Academia.edu (original) (raw)

The African palm fossil record is limited but the data provide an outline of palm evolution from the Late Cretaceous through the Neogene. Pollen attributed to palms is reported from the Aptian (125–112 Mya), but the earliest unequivocal record in Africa is Campanian (83.5–70.6 Mya). Palms diversified 83.5–65.5 Mya and became widespread, although most records are from the west and north African coasts. Many taxa were shared between Africa and northern South America at that time, but a few were pantropical. Extirpations occurred throughout the Palaeogene, including a notable species turnover and decline at the Eocene–Oligocene boundary (33.9 Mya), a change that resulted in the elimination of nypoid palms from Africa. The Neogene plant macrofossil record is better sampled than the Palaeogene, although few palms are documented. Thus, the low diversity of African palms today is more likely the result of Palaeogene, rather than Neogene extinctions. Newly discovered palm fossils of leaves, petioles and flowers from the Late Oligocene (27–28 Mya) of north-western Ethiopia document the abundance and dominance of palms in some communities at that time. The fossils represent the earliest records of the extant genera Hyphaene (Coryphoideae) and Eremospatha (Calamoideae). © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 151, 69–81.

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- Paleobotany, Arecaceae, Palms, Eocene-Oligocene transition

Život v zanikajícím oceánu Thetys Xiphactinus žil v období křídy před více než 80 miliony lety, tedy v době, kdy pevninu ovládali dinosauři. Tento až šest metrů dlouhý a tunu vážící predátor byl králem podvodního světa, přestože oceán obývaly i větší obludy. Příkladem může být osmimetrový žralok Cretoxyrhina. Xiphactinus však disponoval bojovým arsenálem v podobě zubů ostrých jak meče, jejichž čepele byly i 30 centimetrů dlouhé. Největší známá ryba, která žila na naší planetě, dostala, jméno Leedsichthys a žila v období jury. Zkameněliny tohoto neuvěřitelného tvora, který se živil převážně planktonem, byly poprvé objeveny u britského Peterborough v roce 1886. Obří prehistorická ryba mohla vážit až 45 tun a měřila okolo třiceti metrů na délku. V období třetihor, a to v oligocénu, bylo na území dnešní Moravy moře. V sedimentech z tohoto období-v tzv. menilitovém souvrství, lze nalézt řadu fosilních pozůstatků rybovitých obratlovců, a to jak žraloků (Selachii). Jenže pro ty byste museli s prutem až kamsi k Brnu.

- by Lukáš Hanzl
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- Paleontology, Miocene, Oligocene, Thetis

The Silver Cliff Volcanic Center (20-35MA) of Custer County, Colorado is located in the Wet Mountain Valley, and is east of the Sangre de Cristo Mountains and west of the Wet Mountains and the Rosita Hills volcanic area. Previous studies... more

- by Jessica C Kinninger and +1
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- Obsidian, Caldera Volcanoes, Rio Grande Rift, Silicic Volcanism

This contribution, the third part of a monographic series, deals with the biogeography of the Tethys and Paratethys sea basins in the Late Oligocène and Early Miocene and includes reviews of the stratigraphy and paleogeography of the Paratethys, descriptions of the biogeographic distribution of planktonic foraminifers, nanno-and organic-walled phytoplankton, benthos (benthic foraminifers, ostracodes, and mollusks), and the ich-thyofauna, and provides biogeographic zonation based on these groups. The final section deals with the evolution of the main biochores in the western Eurasian basins during the second half of the Paleogene and Miocene.

- by Sergey Popov
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- Miocene, Oligocene, Palaeogeography of Eastern Paratethys
- by CLUZAUD Alain
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- Systematics, Miocene, Oligocene
- by Oleg Amitrov
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- Systematics (Taxonomy), Ukraine, Eocene, Kazakhstan

Mesozoic and Cenozoic strata of the San Jacinto Fold Belt (Colombian Caribbean) provide insights about sedimentary environments and paleogeo-graphic evolution in the transition between the northern Andes and the South Caribbean deformed belt. We report new provenance (conventional sandstone petrography, heavy mineral analysis, and detrital zircon U-Pb geochronology and typology) and micropaleontologic data (palynology, calcareous nannofossils, and foraminifera) in samples collected from the lower Eocene (San Cayetano Formation) and upper Eocene-Oligocene (Toluviejo and Ciénaga de Oro Formations) rocks in boreholes drilled by the Colombian Agencia Nacional de Hidrocarburos as well as from recently exposed Oligocene outcrops from the Ciénaga de Oro Formation. Sandstone petrography shows modal variations, with high feldspar content in the lower Eocene rocks and high quartz content in the Oligocene deposits. This shift in compositional maturity may be due to climatic variations, tectonic activity, and/or changes in source areas. Heavy mineral analyses indicate variations that suggest sources primarily related to felsic igneous and/or low-grade metamorphic and mafic and ultramafic rocks. Zircon U-Pb geochronology displays age populations mainly in the Late Cretaceous, Late Jurassic, Permian-Triassic, and Precambrian (ca. 900-1500 Ma). In addition, zircon typology analyses indicate that the igneous zircons came primarily from monzogranites and granodiorites. Finally, the micro-paleontologic and sedimentary data sets indicate that the sediments were deposited in tropical coastal and shallow marine environments. The sediments were transported by short rivers from the crystalline mas-sifs of the Lower Magdalena Valley and the northern Central Cordillera basements, while distal transport of sediments may have occurred along longer rivers, which brought sediments from southern regions located between the Central and Western Cordilleras.

- by Edward Osorio-Granada and +2
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- Sedimentary provenance, Eocene, Paleogeography, Oligocene

Fossil leaf compressions from the Late Oligocene (27.23 Ma) Guang River flora of northwestern Ethiopia include a new record of Vepris and the earliest record of Clausena and the subfamily Aurantioideae. These fossils, along with most other African rutaceous fossils, are associated with a tropical moist forest community. The large number of Rutaceae taxa in eastern Africa during the Late Oligocene and Early Miocene is likely due to a radiation within Africa or dispersal to Africa associated with the continental expansion of moist tropical forest during this time interval.

- by Aaron D Pan
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- Paleobotany, Tropical forest, Citrus, Oligocene

Abstract: A moderately diverse larger foraminiferal fauna from the north-east Italian ‘Arenarie e calcari di S. Urbano’ formation with important stratigraphic, palaeoecological and palaeobiogeographical implications is described with respect to its position in the Western Tethys area. The fauna is dominated by hyaline perforated and porcellaneous forms including Amphistegina, Archaias, Austrotrillina, Miogypsinoides, Neoplanorbulinella, Neorotalia, Nummulites, Operculina and Spiroclypeus. The presence of Miogypsinoides complanatus allows the age of the formation to be determined as late Chattian (Shallow Benthic Zone SBZ 23). The palaeoenvironmental setting is interpreted as a shallow ramp environment ranging from (1) well lit, highly translucent, shallowest part of the photic zone characterized by Archaias and Austrotrillina, the deeper part of the inner ramp with Nummulites, to (2) the shallow part of the middle ramp with Spiroclypeus and miogypsinids and Operculina, to (3) a deeper middle-ramp setting dominated by coralline rhodoliths along with lepidocylinids. The presence of Archaias hensoni Smout and Eames shows that members of much more diverse Middle Eastern associations of shallow-water larger porcellaneous foraminifera are also present in the north-western parts of the Western Tethys, and reveals a corresponding diversity gradient among larger foraminiferal faunas in the Western Tethys, which is related to a decrease in temperature.

- by James Nebelsick
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- Paleontology, Microfacies, Oligocene, Larger Bentich Foraminifera

Oligocene carbonate ramps and platforms are widespread and though they are important carbonate reservoirs, detailed studies on the facies organization, platform type and internal architecture are scarce. Within this context, the Chattian carbonate units cropping out in Salento (southern Italy) allow detailed study of the distribution of skeletal components and facies architecture. The lower Chattian Castro Limestone, previously considered as a fringing reef, is reinterpreted as a distally steepened ramp with a distal talus induced by a paleo-escarpment in the substrate. Epiphytic biota and sediment dweller organisms thriving in seagrass meadows dominated production in the shallow-water euphotic zone. Seawards, large rotalid foraminifers dominated a detritic mesophotic zone. Near the edge of the escarpment, also in the mesophotic zone, luxurious growth of corals built discrete mounds with no evidences of wave-resistant growth fabrics. Basinward, 25°to 30°dipping clinobeds abut against the escarpment where coral rudstone/floatstone textures resulted from downfall of corals and sediments. The upper Chattian Porto Badisco Calcarenite represents a homoclinal ramp dominated by packstone textures. In the euphotic inner ramp, autochthonous biota suggests the occurrence of extensive seagrass meadows. Basinward, large rotalid packstone and small coral mounds developed in mesophotic conditions, and rhodolithic floatstone to rudstone and large lepidocyclinid packstone characterize the sediments of the deeper oligophotic zone. Comminuted skeletal debris, depleted of light-dependent organisms, typifies deposition in the dysphotic/aphotic zone. In both examples, the middle ramp (meso-oligophotic zones) was the most prolific in terms of carbonate production, whereas shallow-water seagrass-related production (euphotic) was much less important. Corals built mounds, also in the mesophotic zone but never reached sea level. Hydrodynamic conditions in the meso-oligophotic zone are better explained by breaking of internal waves, and their induced up-and down-slope currents, instead of the surface storm waves.

- by Michele Morsilli and +1
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- Evolutionary Biology, Geology, Sedimentology, Ecology

The extensive outpouring of the Oligocene Trap basalts over eastern Africa and western Arabia was interrupted by a period of quiescence marked by the deposition of terrestrial sediments. These so-called intertrappean beds are often lignitiferous and yield recurrent floras and faunas, sometimes represented by endemic mammals. We intended to highlight the peculiar features of these sedimentary intercalations using a large-scale approach including eastern Africa and the western Arabian peninsula. Starting from a new mapping in the Eritrean highland, the intertrappean beds resulted a continuous level that was a few tens of meters thick and traceable for some tens of kilometers. They consist of fluvial red, green and gray mudstones and siltstones with subordinate channelized pebbly sandstones, and lignite seams. Two new 40Ar–39Ar datings constraint the age of the intertrappean beds between 29.0 Ma and 23.6 Ma. The outcrops near Mendefera have yielded the remains of two proboscidean families, the Deinotheriidae and the Gomphoteriidae. The morphological grade of the two Mendefera proboscideans would suggest a more derived stage than that of representatives of the same families from other Oligocene African sites (e.g., Chilga, Ethiopia). An Oligocene age could be inferred for them. The occurrence of the genus Prodeinotherium at Mai Gobro possibly represents the first occurrence of this taxon, while the Gomphotheirum sp. might represent the oldest occurrence of this taxon in Africa before its dispersal towards Asia and Europe. Proboscideans have also been found in the lowland intertrappean beds of Dogali near Massawa. These sediments were contiguous with the Eritrean highland intertrappean beds during the Oligocene, but are now tectonically displaced from them by two thousand meters of vertical topographical distance. Dogali is also known for the occurrence of possible Deinotheriidae remains and the primitive elephantoid Eritreum. Entering the Ethiopian highland, an inspection of the Agere Selam (Mekele) intertrappean beds revealed the occurrence of lacustrine limestones and diatomites, which were contrastingly quite subordinate with respect to the fine clastic sediments found in the nearby Amba Alaji area. Further south, the intertrappean section in the Jema valley (100 km north of Addis Ababa and close to the Blue Nile gorge) is 120 m thick with predominant clastic sediments and a few diatomite's at the top. Literature information from 35 additional sites, including northern Kenya, Yemen, Sudan and Saudi Arabia sections, confirms the fluvial and lacustrine depositional environment of the intertrappean beds, underlines the interest in their mammal fauna (Chilga, Losodok), and reports exploitable coal seams for some of them. As for the vegetal landscape in which the intertrappean beds were deposited, pollen and plant analysis results indicative of a tropical wet forest, similar to that of present-day western Africa. Another common feature of the intertrappean beds is their relatively limited thickness, averaging a few tens of meters, but reaching a few hundred meters in graben-related basins, such as Delbi Moye in southern Ethiopia. In most cases only thin, lens-shaped successions were deposited above the hummocky topography of their volcanic substratum, commonly unaffected by significant faulting. An average duration of the intertrappean beds is from one to three million years. This time interval is commonly matched by a few tens (or more rarely, hundreds) of meters of sediments left over after erosive episodes or depositional starvation. As to the lateral continuity of the intertrappean beds, the present-day outcrops show large differences: from some tens of kilometers in the Mendefera area, to a few tens of kilometres in the Jema valley, and to a few hundreds meters in the Agere Selam (Mekele) area. Even if it is difficult to quantify the original size of the sedimentation areas, it nevertheless proves that the intertrappean basins exceed thousands of square kilometers in only a single case (Mendefera), but were quite restricted in most cases. Their most likely endorheic and local character, together with a regional ill-defined fluvial network, was the effect of a water-course rerouting caused by the progressive rising of the eastern African and Arabian plateaux. Chronological constraints for the intertrappean beds can be inferred from the age of the hosting Trap succession and by the stratigraphical position that they occupy. Intervolcanic sedimentary episodes are typically found in the basaltic and subordinately rhyolitic successions that followed the 31–29 Ma old basaltic widespread paroxysm. With due caveats deriving from the discontinuous availability of datings specifically dedicated to this issue, we regard the age of the intertrappean beds as mostly encompassed in the interval from 29 to 27 Ma at the transition between the Early and Late Oligocene in the Ethiopia/Yemen Trap core. In marginal areas, such as SW Arabia, Eritrea and Kenya, the volcanic activity above the intertrappean beds resumed later, and its quiescence allowed a more prolonged period of sedimentation. The intertrappean beds fall in the second cooling event of the Oligocene climatic deterioration. During the contemporaneous apparent drop in the global sea-level and closure of the Tethyan Ocean between Arabia and southwestern Asia, connections were established between the African and the Eurasian continents. At that time, southwestern Asia was experiencing severe aridity with faunal exchanges toward the luxuriously vegetated eastern Africa.

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

- by Christophe Lécuyer
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- Evolutionary Biology, Geology, Climate Change, Stable Isotope Geochemistry

2013.15 These maps (rectilinear projection) are from the PALEOMAP PaleoAtlas for ArcGIS (Scotese, 2013a-f). This is a digital atlas of plate tectonic, paleogeographic, and paleoclimatic reconstructions designed for use with the GIS software, ArcMap (ESRI). Table 1 lists the various types of maps that comprise the PALEOMAP PaleoAtlas. The maps included in this folio are highlighted in bold text (Table 1).
The last map in each folio is a rectilinear graticule that can be overlain on the maps to provide a geographic reference frame. A rectilinear projection was used because it can be easily georeferenced in ArcMap and transformed into a variety of other map projections. The rectilinear, or plate caree map projection can also be directly “wrapped” onto a spherical projection, like the oneused by Google Earth. A set of Google Earth paleoglobes has made from the maps in this folio. These Google Earth paleoglobes can be downloaded at: www.globalgeology.com.
If the map you need is missing, or if there doesn’t seem to be a map folio for the exact time interval of interest, please contact me (cscotese@gmail.com). Table 2 lists all the time intervals that comprise the PALEOMAP PaleoAtlas for ArcGIS. The PaleoAtlas contains one map for every stage in the Phanerozoic, as well as 6 maps for the late Precambrian. Eventually, Map Folios, like this one, will be published for every time interval in the PALEOMAP PaleoAtlas. The following section is a brief description of the maps that makeup the Map Folio.

- by Christopher Scotese
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- Geology, Paleoclimatology, Paleoceanography, Tectonics

Three new vertebrate localities are reported from within the Bloom Basin of the North Unit of Badlands National Park, Interior, South Dakota. These sites were discovered during paleontological surveys and monitoring of the park's boundary fence construction activities. This report focuses on a new fauna recovered from one of these localities (BADL-LOC-0293) that is designated the Bloom Basin local fauna. This locality is situated approximately three meters below the Bloom Basin limestone bed, a geographically restricted stratigraphic unit only present within the Bloom Basin. Previous researchers have placed the Bloom Basin limestone bed at the contact between the Chadron and Brule formations. Given the unconformity known to occur between these formations in South Dakota, the recovery of a Chadronian (Late Eocene) fauna was expected from this locality. However, detailed collection and examination of fossils from BADL-LOC-0293 reveals an abundance of specimens referable to the characteristic Orellan taxa Hypertragulus calcaratus and Leptomeryx evansi. This fauna also includes new records for the taxa Adjidaumo lophatus and Brachygaulus, a biostratigraphic verification for the biochronologically ambiguous taxon Megaleptictis, and the possible presence of new leporid and hypertragulid taxa. The Bloom Basin local fauna represents the earliest Orellan local fauna described from the Big Badlands of South Dakota and provides crucial insights into the age and stratigraphic position of the Bloom Basin limestone bed. The results of this study emphasize the vital importance of paleontological monitoring of high impact activities as a tool for discovering significant new localities and faunas and protecting crucial natural resources.

- by Ed Welsh
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- Badlands, Eocene-Oligocene transition, White River Group, Mammalian Biostratigraphy

Korth, William W., Robert J. Emry, Clint A. Boyd, and Jeff J. Person. Rodents (Mammalia) from Fitterer Ranch, Brule Formation (Oligocene), North Dakota. Smithsonian Contributions to Paleobiology, number 103, vi + 45 pages, 17 figures, 15 tables, 1 appendix, 2019.—Eighteen rodent species are recognized from the Fitterer Ranch fauna of North Dakota on the basis of more than a thousand collected specimens. Of the species recognized, four are new: the prosciurine aplodontiids Prosciurus hogansoni and Altasciurus leonardi, the heliscomyid Heliscomys borealis, and the cricetid Eumys lammersi. A previously described castorid from this fauna, Oligotheriomys primus Korth, 1998, is considered a synonym of “Eutypomys” magnus Wood, 1937, on the basis of the recovery of lower dentitions but is retained in the genus Oligotheriomys. A single specimen is questionably referred to Microparamys, a genus elsewhere limited to the Eocene (Clarkforkian-Chadronian land mammal ages). The rodent fauna appear...

- by Robert Emry
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- Biostratigraphy, Vertebrate Paleontology, Rodentia, Oligocene

The extant megamouth shark, Megachasma pelagios (Lamniformes: Megachasmidae), is a large filter-feeding fish. We here describe a new species of Megachasma, M. applegatei, sp. nov., a putative sister species of the extant M. pelagios, based on isolated teeth from late Oligocene-early Miocene (late Chattian-Aquitanian) marine deposits in California and Oregon, U.S.A. Although showing a megachasmid tooth design, teeth of M. applegatei, sp. nov., exhibit a wide morphological range and are reminiscent to those of odontaspidid sharks with strong heterodonty. Megachasma applegatei, sp. nov., could have commonly measured approximately 6 m in total length and likely had a wide range of diet, possibly including small fishes and planktonic invertebrates. The fossil record indicates that either M. applegatei, sp. nov., was broadly adapted to a wide bathymetric tolerance or was a nektopelagic feeder over both deep and shallow water habitats.

- by Douglas J Long and +1
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- Evolutionary Biology, Marine Biology, Systematics (Taxonomy), Ichthyology

Lower Oligocene, shallow-water carbonates of the Calcareniti di Castelgomberto formation (Monti Berici, Italy, Southern Alps) are studied in detail with respect to fabric and component distributions in order to trace paleoecological changes along a monotonous sedimentary stacking pattern. The carbonates are dominated by coralline algal rudstones with a packstone to wackestone matrix. Non-geniculate coralline algae include six genera: Lithoporella melobesioides, Mesophyllum, Neogoniolithon, Spongites, Sporolithon, and Subterraniphyllum. The algae are found in the form of encrusting thalli, rhodoliths, and coralline debris. Non-algal components include larger, small benthic, and planktonic foraminifera associated with bryozoans, zooxanthellate corals, and echinoderms. Four carbonate facies are distinguished: (1) coralline algal facies, (2) coralline algal-coral facies, (3) coralline algallarger foraminiferal facies, and (4) coralline algal debris facies. Marly horizons also occur in the section. The facies and coralline algal content are interpreted with respect to light intensity, hydrodynamic energy, biotic interactions, and substrate stability. Facies development along the studied section shows systematic variations, suggesting asymmetric sea-level changes with rapid regressions and gradual transgressions.

- by James Nebelsick
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- Paleoecology, Taphonomy, Palaeoecology, Carbonate Sedimentology

This paper describes five species of dicotyledonous fossil wood from the lower Oligocene Tsuyazaki Formation in Tsuyazaki, Fukuoka Pre fecture, northern Kyushu: Rhus palaeojavan;ca (Anacardiaceae), Alnus scalarifonne (Betu]aceae), Hamamelis prejaponica (Hamamelidaceae), Magnoliaceoxylol1 palaeogenica (Magnoliaceae) and Sonl1eratia kyu shuensis (Sonneratiaceae). This brings the number of species described from the Tsuyazaki locality to 19. Among these 19 species modern equi· valents of all species. except for Sonneralia, occur in temperate to sub tropical forests. SOl1neraria is found today in mangrove vegetation of tropical to subtropical regions. The presence of Sonneralia may sug gest a warmer climate in Kyushu during the early Oligocene.

- by Rashmi Srivastava
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- Japan, Biodiversity, Fossil Wood, Alnus

We have compiled 20,000 km of digital seismic data and several wells over a region of approximately 700,000 km 2 to better improve the correlation of the Mexican sector of the Gulf of Mexico (MGOM) with the better studied and more explored U.S. sector. This grid of regional 2D lines -collected by the University of Texas in the 1970s along with published seismic transects collected by Pemex -includes seismic lines we have digitized using SEG-Y converter software and incorporated into the SEG-Y database. Using this combined digital database, we interpreted 20 surfaces ranging in age from Late Jurassic to Recent. Seismic and well data from the eastern and southeastern shelf of Mexico published from Pemex allow for improved correlation of shelfal units with shelf and deep basinal units of the MGOM now deformed by the Mexican Ridges passive-margin foldbelt. Data from the eastern margin of Mexico shows that listric normal growth faults terminate downslope on toe thrusts and folds of the deepwater Mexican Ridges. Ages of units show that the Mexican Ridges initiated in post-Middle Miocene time and therefore postdate the Paleogene Laramide deformational phase that affected Mexico. Seismic facies of Late Eocene and Oligocene units show a sequence of clastic materials linked to an earlier uplift and erosional event in central Mexico. We have incorporated a dense seismic grid around the Chicxulub crater on the Yucatan platform area and correlated these units that may include possible KT ejecta reservoir facies within the deepwater sequences in the adjacent MGOM.

- by Anthony Rodriguez
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- Geology, Regional Studies, Pleistocene, Mexico

Until recently, few well-described rodent faunae from the Whitneyan North American Land Mammal Age [NALMA] were known, hindering studies of rodent diversity, biogeography, and evolutionary patterns during the Oligocene. This study describes a new Whitneyan rodent assemblage from the Obritsch Ranch paleontological locality in the Little Badlands region of North Dakota. Specimens were collected from three stratigraphi-cally restricted sampling intervals within the middle to upper Brule Formation, resulting in the recognition of fourteen rodent species, five of which are elsewhere known to first appear in Whitneyan faunae. Described is one new species, the eomyid Paradjidaumo obritschorum, and the first cranial material of the heteromyid rodent Proharrymys Korth and Branciforte, 2007. The rodent fauna from the upper two sampling intervals at Obritsch Ranch and the uppermost fauna recently described from the nearby Fitterer Ranch paleontological locality share four taxa in common with the late Whitneyan Blue Ash local fauna from southwestern South Dakota, indicating these two North Dakota rodent faunae are also from the late Whitneyan. Increasing knowledge of Whitneyan rodent faunae in North America reveals unusually high survivorship of rodent species from the older Orellan NALMA into the Whitneyan NALMA and much geographic variation in the diversity, distribution, and relative abundance of different rodent families between individual Whitneyan rodent faunae. Those factors help explain prior difficulties in differentiating Orellan and Whitneyan rodent faunae and in identifying biostratigraphically useful rodent taxa for the Whitneyan. Overall, Whitneyan rodent faunae from North America display an increase in the diversity of aplodontiids, cricetids, and sciurids and a decrease in eomyid and ischyromyid diversity relative to the Orellan.

- by Clint A Boyd
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- Fossil Mammals, Rodents, Oligocene

Described are remains of Paleogene bivalves from localities at Poljšica near Podnart, Slovenia. Determined were 40 distinct bivalve forms that prove the Early Oligocene age of fossiliferous biocalcirudites. The beds contain numerous... more

- by Aleš Šoster
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- Bivalves, Fossils, Slovenia, Paleogene

Samples collected from the Oligocene Vima Formation in the Transylvanian Basin revealed abundant and diverse foraminifera assemblages. Among benthics, 139 taxa belonging to 76 genera, 43 families, 26 superfamilies, 11 suborders and 8 orders were identified. A large number of agglutinated and calcareous benthic foraminifera species are reported and illustrated for the first time from the Oligocene of the Transylvanian Basin.

The description of new material and the reassessment of specimens previously assigned to Gelocus quercyi lead us to
propose a new genus for this species, Mosaicomeryx gen. nov. Moreover, the description of a juvenile skull and other
specimens of Prodremotherium elongatum, and comparison with Dremotherium, provide evidence that these two genera
are not closely related as previously thought. A phylogenetic analysis based on 40 dental, cranial and postcranial features
highlights the misidentification of Gelocus quercyi and suggests that Mosaicomeryx gen. nov. is closely related to
Prodremotherium elongatum. Mosaicomeryx quercyi and Prodremotherium elongatum form a monophyletic group of stem
Pecora that first appeared in Western Europe by the late Early Oligocene (MP2526), and Prodremotherium elongatum
persisted up to MP28; following this time both taxa appear to be replaced by Dremotherium and Amphitragulus. This time
interval covers two major Oligocene faunal and climate changes: Extinction 1 (MP24), associated with regression of the
inner European sea, and Extinction 3/Migrations 3 (MP28), associated with Late Oligocene Warming.

- by Bastien Mennecart
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- Systematics (Taxonomy), European Studies, Phylogeny, Ruminantia

Biostratigraphic analysis of the Eocene-Oligocene transition (E-O) at the Menzel Bou Zelfa and Jhaff composite section in the Cap Bon Peninsula (North East Tunisia) allowed us to recognize a continuous planktic foraminiferal biozonation: E14 Globigerinatheka semiinvoluta Zone, E15 Globigerinatheka index Zone, E16 Hantkenina alabamensis Zone and O1 Pseudohastigerina naguewichiensis Zone. A quantitative study of benthic and planktic foraminifera assemblages was carried out and the richness and diversity of foraminifera allowed us to reconstruct the paleoenvironmental evolution from marine to terrestrial environments. From the Eocene E14 Zone, the foraminiferal association characterizes a relatively warm climate with considerable oxygen content and a dominance of keeled and spinose planktic foraminifera, which became extinct at the E/O boundary, possibly due to cooling of the planktic environment. Nevertheless, the small benthic foraminifera do not show an extinction event at the Eocen...

- by chaima grira
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- Geology, Geophysics, Paleoclimatology, Paleoceanography
- by Eustoquio Molina
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- Planktonic Foraminifera, Benthic foraminifera, Miocene, Chronostratigraphy

Oligocene carbonate ramps and platforms are widespread and though they are important carbonate reservoirs, detailed studies on the facies organization, platform type and internal architecture are scarce. Within this context, the Chattian carbonate units cropping out in Salento (southern Italy) allow detailed study of the distribution of skeletal components and facies architecture. The lower Chattian Castro Limestone, previously considered as a fringing reef, is reinterpreted as a distally steepened ramp with a distal talus induced by a paleo-escarpment in the substrate. Epiphytic biota and sediment dweller organisms thriving in seagrass meadows dominated production in the shallow-water euphotic zone. Seawards, large rotalid foraminifers dominated a detritic mesophotic zone. Near the edge of the escarpment, also in the mesophotic zone, luxurious growth of corals built discrete mounds with no evidences of wave-resistant growth fabrics. Basinward, 25° to 30° dipping clinobeds abut against the escarpment where coral rudstone/floatstone textures resulted from downfall of corals and sediments. The upper Chattian Porto Badisco Calcarenite represents a homoclinal ramp dominated by packstone textures. In the euphotic inner ramp, autochthonous biota suggests the occurrence of extensive seagrass meadows. Basinward, large rotalid packstone and small coral mounds developed in mesophotic conditions, and rhodolithic floatstone to rudstone and large lepidocyclinid packstone characterize the sediments of the deeper oligophotic zone. Comminuted skeletal debris, depleted of light-dependent organisms, typifies deposition in the dysphotic/aphotic zone. In both examples, the middle ramp (meso-oligophotic zones) was the most prolific in terms of carbonate production, whereas shallow-water seagrass-related production (euphotic) was much less important. Corals built mounds, also in the mesophotic zone but never reached sea level. Hydrodynamic conditions in the meso-oligophotic zone are better explained by breaking of internal waves, and their induced up- and down-slope currents, instead of the surface storm waves.

- by Michele Morsilli and +1
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- Sedimentology, Carbonate Sedimentology, Sedimentary geology and stratigraphy, Carbonate Platform
- by Aaron D Pan and +1
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- Paleobotany, Plant Biology, Arecaceae, Palms

The ichnological study of fluvial fan and lacustrine Oligocene deposits in the NE Ebro Basin has allowed the recognition of three ichnoassemblages having a strong correlation with depositional facies associations. Lacustrine deposits lack bioturbation due to the hydrologically closed character of the lake that caused hypersalinity and made it inhospitable for benthic life. Terminal lobe deposits of the fluvial fan, which were sedimented in low wetland areas around the lake, bear a moderately diverse ichnoassemblage dominated by horizontal Taenidium barretti, Cochlichnus anguineus and bird footprints (Gruipeda isp.). This assemblage can be assigned to the 'shorebird ichnofacies', a subset of the Scoyenia ichnofacies that characterizes the subaerial part of low-energy shore areas. Crevasse splay deposits in medial fluvial fan areas present a different assemblage also belonging to the Scoyenia ichnofacies. It includes most of the trace fossils found in the terminal lobes, except for the bird tracks, plus very abundant vertical burrows (Taenidium barretti and unnamed ornamented burrows). The presence of deep-tier traces of terrestrial invertebrates is consistent with the more proximal fan setting, having greater relief and consequently a lower mean groundwater position than lowland areas. Fluvial channels only bear irregularly clustered tunnel structures of unknown affinity formed after abandonment of the channel. Thus, trace fossil assemblages are mostly controlled by the position and fluctuations of water tables, which are the cause for their composite nature.

- by Alberto Saez
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- Evolutionary Biology, Geology, Sedimentology, Ichnology
- by Eustoquio Molina
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- Taxonomy, Planktonic Foraminifera, Betic Cordillera, Miocene
- by Oleg Amitrov
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- Stratigraphy, Kazakhstan, Gastropods, Paleogene
- by David Arpad
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- Archaeology, Ichnology, Paleoecology, Taphonomy
- by Esperanza Cerdeño and +1
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- Mendoza, Oligocene, Notohippidae
- by Anthony Rodriguez
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- Geology, Structural Geology, Salt Tectonics, Regional Studies

Small perch-like fishes from the Oligocene of the Paratethys have been traditionally assigned to Serranus budensis (Heckel, 1856). A morphological revision of the holotype and specimens previously assigned to S. budensis from the Outer Carpathians, Poland, is provided herein. They are re-assigned to the species Oligoserranoides budensis (Heckel, 1856) — Percoidei incertae sedis. New specimens assigned to Ol. budensis from the Outer Carpathians, Poland, are introduced. Our results reveal that Ol. budensis is very similar to the species Caucasoserranoides morozkiensis, Carpathoserranoides brnoensis, Carpathoserranoides polonicus and Oligoserranoides comparabilis, and further studies are necessary to revise the validity of those species. Ol. budensis shares many characters with genera Lutjanus and Ocyurus of the superfamily Lutjanoidea. Ol. budensis differs from Lutjanoidea in having a toothless palatine. The palaeobiogeography of Oligocene small perch-like fishes in the Paratethys is presented and discussed.

- by Geologica Acta and +2
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- Systematics (Taxonomy), Paleontology, Poland, Palaeography

The biostratigraphic analysis of the Eocene-Oligocene transition of the Menzel Bou Zelfa and Jhaff sections in northeastern Tunisia (Cap Bon peninsula) allows us to identify a continuous planktic forami-niferal biozonation. The following biozones were recognized: Globigerinatheka semiinvoluta Zone (E14), Globigerinatheka index Zone (E15), (Hantkenina alabamensis Zone (E16) of the upper Eocene and Pseu-dohastigerina naguewichiensis Zone (O1) of the lower Oligocene. A rapid mass extinction event in planktic foraminifera occurred at the Eocene-Oligocene transition, including the extinction of the turborotalids (Turborotalia cerroazulensis, Turborotalia cocoaensis and Turborotalia cunialensis) followed by a significant size reduction of the genus Pseudohastigerina and the extinction of the hantkeninids (Hantkenina ala-bamensis, Hantkenina brevispina, Hantkenina nanggulanensis and Cribrohantkenina lazzarii), which mark the Eocene/Oligocene boundary. These species were tropical and subtropical surface and intermediate dwellers, with distinctive morphologies (carinate turborotalids and spinose hantkeninids), which were well adapted species of k-strategy. The surviving planktic foraminifera species were quite similar in morphology with globular chambers (globigerinids) and small planispiral (pseudohastigerinids), which were opportunistic species of r-strategy. The recognition of a 4 m thick interval, between the extinction of turborotalids and hantkeninids, indicates that the section is continuous and one of the most expanded throughout the Eocene-Oligocene transition. This section could serve as an auxiliary section (hypo-stratotype) for the complete definition of the Global Stratotype Section and Point for the Eocene/ Oligocene boundary, which mark the base of the Rupelian Stage.

- by Eustoquio Molina and +1
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- Geology, Paleoecology, Biostratigraphy, Micropaleontology
- by Eustoquio Molina and +1
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- Biostratigraphy, Micropaleontology, Planktonic Foraminifera, Benthic foraminifera

Oligocene and Miocene fossil decapods from Puerto Rico and Cuba have been poorly known; new collections from these regions as well as from the Dominican Republic have now yielded several new reports. One new genus, Psygmophthalmus, and several new species (Neocallichirus aetodes, Neocallichirus? quisquellanus, Calappa pavimenta, Necronectes collinsi, Portunus yaucoensis, and Psygmophthalmus lares) are named herein. New combinations include Euphylax domingensis (Rathbun 1919), Megokkos feldmanni (Nyborg et al. 2003), and Neocallichirus vaughni (Rathbun 1918). Specimens of a callianassoid and brachyuran indeterminate at the family, genus, and species level are also described and illustrated, and emended descriptions are provided for Euphylax domingensis and Megokkos feldmanni. Scylla costata Rathbun, 1919, and three indeterminate species of Portunus are also reported. Ceronnectes De Angeli and Beschin, 1998, is a member of the Cancridae, not the Portunidae as originally reported. Most of the Caribbean taxa reported herein belong to tropical or subtropical extant genera that inhabit both carbonate and siliciclastic, soft, shallow marine substrates, supported by the occurrence of most of the fossils in clastic units. The Cenozoic genera reported herein exhibited either a Tethyan or North Pacific distribution, typical of Eocene and Oligocene decapods of the region. The open Caribbean Seaway facilitated dispersal of fauna throughout the region between the Atlantic and Pacific oceans.

- by Jorge Velez-Juarbe
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- Paleontology, Paleobiogeography, Decapoda, Paleogeography
- by Karen Black
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- Biostratigraphy, Vertebrate Palaeontology, Marsupials, Biocorrelation
- by Friðgeir Grímsson and +1
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- Biogeography, Fossil, Oligocene, Fagaceae

The Australian pre-Pleistocene fossil record of Accipitridae (eagles, hawks, old-world vultures) comprises one latest Oligocene or early Miocene and one middle Miocene species, each represented by partial bones. Globally, most fossil accipitrids are based on single bones. The recent discovery of an older and considerably more complete accipitrid from late Oligocene sediments in Australia is therefore significant. It is derived from the Pinpa Local Fauna from the Namba Formation at Lake Pinpa, South Australia (~26-24 Ma). The fossil, described as Archaehierax sylvestris gen. et sp. nov., represents a raptor that was larger than the blackbreasted buzzard Hamirostra melanosternon but smaller and more gracile than the wedge-tailed eagle Aquila audax. Comprehensive morphological and molecular phylogenetic analyses resolved Archaehierax as a basal accipitrid, not closely related to any living subfamily and perhaps the sister taxon to all other accipitrids exclusive of elanines. Relatively short wings similar to species of Spizaetus and Spilornis suggest it was adapted for flight within enclosed forests. Additional accipitrid fossils from the Namba Formation, a distal femur and a distal humerus, are incomparable with the holotype of A. sylvestris; they may represent distinct species or smaller individuals of the new taxon. lsid:zoobank.org:pub:6A25C569-3E9F-43B8-AAF8-F36CE405C06E ARTICLE HISTORY

- by Michael Lee
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- Paleontology, Ornithology, Phylogenetics, Osteology
- by David R Greenwood
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- Paleobotany, Australia, Eocene, Miocene