scholarly journals New wombats from Riversleigh, northwestern Queensland, include pouch young

2018 ◽  
Author(s):  
Philippa Brewer
Keyword(s):  
Middle Miocene ◽  
Middle Eocene ◽  
Large Degree ◽  
Species Level ◽  
Late Oligocene ◽  
Additional Species ◽  
Variable Species ◽  
Degree Of Confidence ◽  
Qualitative Characters ◽  
Insight Into

Despite an estimated molecular divergence date of 40 million years (middle Eocene) between wombats and their closest living relative, the koala, the fossil record of wombats is poor. The two oldest described wombats, Nimbavombatus boodjamullensis and Rhizophascolonus crowcrofti, are both early Miocene in age. The former is known from maxillae, upper cheek teeth and isolated lower molars from Riversleigh in northwestern Queensland. The latter is known only from the isolated teeth from central Australia. Here we describe additional specimens of Rhizophascolonus from Riversleigh that are late Oligocene to middle Miocene in age as well as at least one additional species. Excitingly, the new specimens show an ontogenetic range from pouch young with occlusal cusp details intact to fully adult specimens with heavily worn teeth. The unworn teeth from Riversleigh are compared with those pouch young from two extant wombat taxa and the extant koala. In addition, comparisons of quantitative and qualitative characters of all known Rhizophascolonus specimens with other koala and wombat taxa reveal a large degree of variation in the sample of Rhizophascolonus teeth from Riversleigh. However, the number of species of Rhizophascolonus present is difficult to ascertain and it is not inconceivable that there is only one or two highly variable species present. Despite uncertainty at the species level, these new specimens provide an unprecedented insight into this enigmatic group, and we can now start to reconstruct intrafamilial relationships with a greater degree of confidence. Furthermore, occlusal morphology can now be used to help clarify interfamilial relationships in the suborder Vombatiformes, which in addition to wombats and koalas, includes five additional extinct families.

scholarly journals New wombats from Riversleigh, northwestern Queensland, include pouch young

2018 ◽  
Author(s):  
Philippa Brewer
Keyword(s):  
Middle Miocene ◽  
Middle Eocene ◽  
Large Degree ◽  
Species Level ◽  
Late Oligocene ◽  
Additional Species ◽  
Variable Species ◽  
Degree Of Confidence ◽  
Qualitative Characters ◽  
Insight Into

Despite an estimated molecular divergence date of 40 million years (middle Eocene) between wombats and their closest living relative, the koala, the fossil record of wombats is poor. The two oldest described wombats, Nimbavombatus boodjamullensis and Rhizophascolonus crowcrofti, are both early Miocene in age. The former is known from maxillae, upper cheek teeth and isolated lower molars from Riversleigh in northwestern Queensland. The latter is known only from the isolated teeth from central Australia. Here we describe additional specimens of Rhizophascolonus from Riversleigh that are late Oligocene to middle Miocene in age as well as at least one additional species. Excitingly, the new specimens show an ontogenetic range from pouch young with occlusal cusp details intact to fully adult specimens with heavily worn teeth. The unworn teeth from Riversleigh are compared with those pouch young from two extant wombat taxa and the extant koala. In addition, comparisons of quantitative and qualitative characters of all known Rhizophascolonus specimens with other koala and wombat taxa reveal a large degree of variation in the sample of Rhizophascolonus teeth from Riversleigh. However, the number of species of Rhizophascolonus present is difficult to ascertain and it is not inconceivable that there is only one or two highly variable species present. Despite uncertainty at the species level, these new specimens provide an unprecedented insight into this enigmatic group, and we can now start to reconstruct intrafamilial relationships with a greater degree of confidence. Furthermore, occlusal morphology can now be used to help clarify interfamilial relationships in the suborder Vombatiformes, which in addition to wombats and koalas, includes five additional extinct families.

scholarly journals Revision of fossil Bibionidae (Insecta: Diptera) from French Oligocene deposits

Zootaxa ◽  
2017 ◽  
Vol 4225 (1) ◽  
pp. 1 ◽  
Author(s):  
JOHN SKARTVEIT ◽  
ANDRÉ NEL
Keyword(s):  
New Species ◽  
Single Species ◽  
Large Degree ◽  
Species Level ◽  
New Combinations ◽  
Late Oligocene ◽  
Early Oligocene ◽  
Taxonomical Level ◽  
Three New Species ◽  
Eleven Species

All available material of fossil Bibionidae from French Oligocene localities, including the German locality of Kleinkembs right next to the border with France, is revised, and the species redescribed. Several publications (notably Heer 1856, Oustalet 1870 and Théobald 1937) have dealt with this material but there is a large degree of duplication leading to numerous synonyms. In addition, many of the named species have been assigned to the wrong genus. We have found seven species of Penthetria, eleven species of Plecia, seven species of Bibio and a single species of Dilophus in the material of previously named species. Three new species, Penthetria luberonica sp. n., Bibio aquaesextiae sp. n. and Bibiodes provincialis sp. n. are described from French Oligocene localities. The following new combinations are proposed: Penthetria claripennis (Théobald, 1937), Penthetria gigantea (Théobald, 1937), Penthetria graciliventris (Théobald, 1937), Penthetria longiventris (Théobald, 1937), Penthetria nervisinuata (Théobald, 1937), Penthetria subterranea (Théobald, 1937), Plecia morio (Heer, 1849), Bibio major (Oustalet, 1870), Dilophus luteipennis (Théobald, 1937). Many of the species occur from several outcrops, and distinctive faunas can be recognized from Early Oligocene (e.g., Célas and Monteils), Middle Oligocene (e.g., Céreste and Bois d’Asson) and Late Oligocene (e.g. Aix-en-Provence and the German outcrop of Rott). The late Oligocene localities also share some species with the Early Miocene locality of Radoboj, Croatia, but none with the younger locality of Öhningen, Southern Germany. For a number of named species, the type material is poorly preserved and cannot be recognized at the species level, these are commented on and assigned to the lowest taxonomical level to which they can be identified with certainty. The type materials of a number of species appear to be lost; these are placed to genera to the extent that this is possible from the original descriptions and illustrations. Bibio nigripennis Théobald, 1937, nec Brunetti, 1913 is a primary junior homonym and the name must be replaced. The species is moved to the genus Plecia and renamed Plecia theobaldi nom.n. 

The Evolutionary History and Diversity of Australian Mammals

1999 ◽  
Vol 21 (1) ◽  
pp. 1
Author(s):  
M. Archer ◽  
R. Arena ◽  
M. Bassarova ◽  
K. Black ◽  
J. Brammall ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Late Triassic ◽  
Early Eocene ◽  
Late Oligocene ◽  
Mammal Evolution ◽  
Initial Description ◽  
Fossil Records ◽  
First Time

Palaeodiversity and relationships of all groups of Australian mammals are reviewed. The fossil record spanning this time is of variable quality. 'Dark Ages' about which nothing is known in terms of Australian mammal evolution include the late Triassic to late Jurassic, late Cretaceous to late Paleocene and middle Eocene to middle Oligocene. Very little is known about the early Cretaceous and late Miocene. The late Oligocene to middle Miocene record documents the highest levels of biodiversity known for the continent, comparable to that which characterises the lowland rainforests of Borneo and Brazil. Order Monotremata spans at least the last 110 million years and includes four families. The enigmatic Ausktribosphenos from 115 million-year-old sediments in Victoria may represent an archaic monotreme, specialised peramurid or previously undocumented order of mammals but is unlikely to represent a placental as suggested in the initial description. Order Microbiotheria is represented in the early Eocene (~55 mya) by two genera similar in morphology to early Eocene taxa from Argentina. Order Peramelemorphia spans the early Eocene to Holocene and includes at least five families. Order Dasyuromorphia spans at least the late Oligocene to Holocene and includes at least three families. Other dasyuromorphian-like marsupials are indeterminate in terms of family-level affinities. Order Notoryctemorphia spans the early Miocene to Holocene with one family. Order Yalkaparidontia spans the late Oligocene to middle Miocene with one genus. Order Diprotodontia spans the late Oligocene to Holocene, represented throughout by three major groups: Phalangerida (eight families), Vombatomorphia (seven families) and Macropodoidea (at least three families). A possible placental condylarth (Tingamarra) has been recorded from the early Eocene. An archaeonycteridid bat (Australonycteris) is known from the early Eocene. Among bats, the late Oligocene to middle Miocene is dominated by rhinolophoids, many of which have European, Asian and African affinities. Mystacinids, megadermatids, hipposiderids and molossids are well-represented in the Oligocene to Miocene deposits. Vespertilionids are uncommon in the Oligocene to Miocene but become more diverse in the Pliocene to Holocene. Emballonurids and rhinolophids appear for the first time in the Plio-Pleistocene. Pteropodids are unknown prior to the Holocene. Murids span the early Pliocene to Holocene. In the oldest assemblage at Riversleigh, one undescribed lineage resembles archaic forms otherwise only known from the fossil records of Africa and Eurasia.

Metamorphic constraints on the thermal evolution of the central Himalayan Orogen

1988 ◽  
Vol 326 (1589) ◽  
pp. 257-280 ◽  
Keyword(s):  
Middle Miocene ◽  
Thermal Evolution ◽  
Middle Eocene ◽  
Structural Evolution ◽  
Late Oligocene ◽  
Main Central Thrust ◽  
Early Stages ◽  
Early Oligocene ◽  
Mineral Assemblages ◽  
Early Late

Recent studies that integrate conventional thermobarometry of pelitic mineral assemblages with thermodynamic modeling of garnet zoning reveal complex Tertiary P -T paths for the Greater Himalayan metamorphic sequence in the central Himalaya. Viewed in light of our current understanding of the structural evolution of the Himalaya, these data provide insights into the relations between tectonic and thermal processes during orogenesis. In this paper, we present an interpretive model for tectonothermal evolution of the Greater Himalaya in the central part of the range. This model involves: (1) middle Eocene—early Oligocene burial to depths of more than 30 km during the early stages of collision between India and Asia; (2) early—late Oligocene uplift and cooling; (3) late Oligocene heating and renewed burial synchronous with the early stages of anatectic melting and leucogranite plutonism; (4) latest Oligocene-middle Miocene rapid uplift and continued leucogranite production associated with ramping on the structurally lower Main Central Thrust and tectonic denudation on structurally higher low-angle detachment systems; and (5) middle Miocene—Recent rapid cooling during the final stages of uplift to the surface.

scholarly journals The Cenozoic Malaguide Basin from Sierra Espuña (Murcia, S Spain): An Example of Geological Heritage

Geosciences ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Santiago Moliner-Aznar ◽  
Manuel Martín-Martín ◽  
Tomás Rodríguez-Estrella ◽  
Gregorio Romero-Sánchez
Keyword(s):  
Middle Eocene ◽  
Geological Heritage ◽  
Passive Margin ◽  
Early Miocene ◽  
Late Oligocene ◽  
Deep Basin ◽  
Sedimentary Evolution ◽  
Early Oligocene ◽  
Upper Oligocene ◽  
Very High

The Cenozoic Malaguide Basin from Sierra Espuña (Internal Betic Zone, S Spain) due to the quality of outcropping, areal representation, and continuity in the sedimentation can be considered a key-basin. In the last 30 years, a large number of studies with very different methodological approaches have been done in the area. Models indicate an evolution from passive margin to wedge-top basin from Late Cretaceous to Early Miocene. Sedimentation changes from limestone platforms with scarce terrigenous inputs, during the Paleocene to Early Oligocene, to the deep basin with huge supplies of turbidite sandstones and conglomerates during the Late Oligocene to Early Miocene. The area now appears structured as an antiformal stack with evidence of synsedimentary tectonics. The Cenozoic tectono-sedimentary basin evolution is related to three phases: (1) flexural tectonics during most of the Paleogene times to create the basin; (2) fault and fold compartmentation of the basin with the creation of structural highs and subsiding areas related to blind-fault-propagation folds, deforming the basin from south to north during Late Oligocene to Early Aquitanian times; (3) thin-skin thrusting tectonics when the basin began to be eroded during the Late Aquitanian-Burdigalian. In recent times some works on the geological heritage of the area have been performed trying to diffuse different geological aspects of the sector to the general public. A review of the studies performed and the revisiting of the area allow proposing different key-outcrops to follow the tectono-sedimentary evolution of the Cenozoic basin from this area. Eight sites of geological interest have been selected (Cretaceous-Cenozoic boundary, Paleocene Mula Fm, Lower Eocene Espuña-Valdelaparra Fms, Middle Eocene Malvariche-Cánovas Fms, Lowermost Oligocene As Fm, Upper Oligocene-Lower Aquitanian Bosque Fm, Upper Oligocene-Aquitanian Río Pliego Fm, Burdigalian El Niño Fm) and an evaluation has been performed to obtain four parameters: the scientific value, the educational and touristic potential, and the degradation risk. The firsts three parameters obtained values above 50 being considered of “high” or “very high” interest (“very high” in most of the cases). The last parameter shows always values below 50 indicating a “moderate” or “low” risk of degradation. The obtained values allow us considering the tectono-sedimentary evolution of this basin worthy of being proposed as a geological heritage.

scholarly journals Late oligocene–early miocene shortening in the Thrace Basin, northern Aegean

2021 ◽  
Author(s):  
Ümitcan Erbil ◽  
Aral I. Okay ◽  
Aynur Hakyemez
Keyword(s):  
Large Scale ◽  
Middle Eocene ◽  
Early Miocene ◽  
Fold Axis ◽  
Late Oligocene ◽  
The Balkans ◽  
Sedimentary Sequences ◽  
The North ◽  
Early Oligocene ◽  
Thrace Basin

AbstractLate Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.

Late Paleogene paleotopographic evolution of the northern Cordilleran orogenic front: Implications for demise of the orogen

2021 ◽  
Author(s):  
Majie Fan ◽  
Kurt N. Constenius ◽  
Rachel F. Phillips ◽  
David L. Dettman
Keyword(s):  
Initial Phase ◽  
Middle Eocene ◽  
High Elevation ◽  
Late Eocene ◽  
Crustal Extension ◽  
Late Oligocene ◽  
Slab Rollback ◽  
Basin Floor ◽  
Climate Cooling ◽  
High Range

The paleotopographic history of the North American Cordilleran orogen holds the key to understanding mechanisms of orogenesis and subsequent orogenic collapse. It has been suggested that the orogenic front in western Montana (USA) and Alberta (Canada) was more than 4 km high during Late Cretaceous−early Eocene contractional deformation and during the initial phase of extension in the middle Eocene; however, the late Eocene−Oligocene topographic evolution during continued extensional collapse remains poorly constrained. Here we extend the paleotopographic record in the Kishenehn Basin in northwestern Montana and southeastern British Columbia (Canada) to the late Oligocene by studying δ18O values of fossil mollusks and cement and paleosol carbonates. The molluscan taxa changed from three sympatric groups with preferred habitats ranging from tropical wet, semi-arid subtropical, and temperate during the middle and late Eocene, to mainly a single group associated with temperate environment during the Oligocene, reflecting a decline in molluscan biodiversity induced by climate cooling across the Eocene−Oligocene transition. Reconstructed δ18O values of alpine snowmelt and basinal precipitation decreased by 1.4‰ and 3.8‰, respectively, from the middle to late Eocene, reflecting climate cooling and ∼1 km surface uplift of the basin floor. The reconstructed alpine snowmelt δ18O values then increased by 2.9‰ in the Oligocene suggesting a ∼0.5 km drop in elevation of the orogenic front. Collectively, the results of our new and previously published δ18O data chronicle the paleotopographic response to the change from flat-slab subduction to slab rollback over a 45 m.y. period. These data suggest that the orogenic front was characterized by high elevation (>4 km) in the ancestral Lewis-Clark-Livingston ranges during latest Cretaceous−early Eocene (ca. 75−52 Ma) contraction. The initial phase of extension related to the Kishenehn Basin created a lowland basin with a surface elevation of only ∼1.5 km during the early middle Eocene (ca. 46−44 Ma) whereas the ranges remained >4 km high. The high range elevations were sustained for at least 12 m.y. in the middle to late Eocene concurrent with extension, while the basin floor elevation was uplifted to ∼2.5 km by the latest Eocene (ca. 36−34 Ma). Basin aggradation can explain at most half of the 1 km basin floor uplift. The remaining amount (at least 0.5 km) and sustained high range elevation suggest that range denudation and crustal extension was compensated by the isostatic and thermal effects of slab rollback and/or passage of a slab window and infusion of hot asthenosphere beneath the continent. The range elevation in the orogenic front decreased ∼0.5 km by the late Oligocene (ca. 28 Ma), associated with a decrease in rock uplift rate associated with extension. A post-Oligocene elevation drop of ∼1 km resulted in both the ranges and basin floor reaching modern topography in the Kishenehn Basin drainage, likely due to the regional effect of Neogene Basin and Range extension. This study, along with the previous investigation of the Kishenehn Basin by Fan et al. (2017), are the first studies that systematically investigate paleorelief of the orogenic belt by reconstructing paleoelevations of the mountains and the basin at the same time. The results highlight that the Cordilleran orogenic front of northern Montana and southern British Columbia sustained its high elevation edifice for at least 12 m.y. after the start of extension. We suggest that initial crustal extension did not result in orogenic demise because of concurrent thermal and isostatic uplift.

scholarly journals Structural setting and tectonic evolution of the Bahariya Depression, Western Desert, Egypt

GeoArabia ◽  
2003 ◽  
Vol 8 (1) ◽  
pp. 91-124 ◽  
Author(s):  
Adel R Moustafa ◽  
Ati Saoudi ◽  
Alaa Moubasher ◽  
Ibrahim M Ibrahim ◽  
Hesham Molokhia ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Tectonic Evolution ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Western Desert ◽  
Normal Faults ◽  
Surface Mapping ◽  
Early Mesozoic ◽  
Hydrocarbon Fields ◽  
Stable Area

ABSTRACT An integrated surface mapping and subsurface study of the Bahariya Depression aided the regional subsurface interpretation. It indicated that four major ENE-oriented structural belts overlie deep-seated faults in this part of the ‘tectonically stable’ area of Egypt. The rocks of the Bahariya area were deformed in the Late Cretaceous, post-Middle Eocene, and Middle Miocene-and subsurface data indicated an early Mesozoic phase of normal faulting. The Late Cretaceous and post-Middle Eocene deformations reactivated the early normal faults by oblique slip and formed a large swell in the Bahariya region. The crest was continuously eroded whereas its peripheries were onlapped by Maastrichtian and Tertiary sediments. The tectonic evolution of the Bahariya region shows great similarity to the deformation of the ‘tectonically unstable’ area of the northern Western Desert where several hydrocarbon fields have been discovered. This similarity may indicate that the same phases of deformation could extend to other basins lying in the ‘tectonically stable’ area, such as the Asyut, Dakhla, Nuqura, and El Misaha basins.

scholarly journals Additional records and stratigraphic distribution of the middle Eocene carettochelyid turtle Anosteira pulchra from the Uinta Formation of Utah, North America

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9775
Author(s):  
Brent Adrian ◽  
Patricia A. Holroyd ◽  
J. Howard Hutchison ◽  
KE Beth Townsend
Keyword(s):  
North America ◽  
New Records ◽  
Middle Eocene ◽  
Single Species ◽  
Uinta Basin ◽  
Stratigraphic Framework ◽  
Multiple Levels ◽  
Land Mammal ◽  
Anatomical Information ◽  
Insight Into

Background Anosteira pulchra is one of two species of the obligately-aquatic freshwater clade Carettochelyidae (pig-nosed turtles) from the Eocene of North America. Anosteira pulchra is typically rare in collections, and their distribution is poorly documented. The Uinta Formation [Fm.] contains a diverse assemblage of turtles from the Uintan North American Land Mammal Age. Whereas turtles are abundantly preserved in the Uinta Fm., A. pulchra has been reported only from a few specimens in the Uinta C Member. Methods We describe new records of Anosteira pulchra from the Uinta Basin and analyze the distribution of 95 specimens from multiple repositories in the previously published stratigraphic framework of the middle and upper Uinta Fm. Results Here we report the first records of the species from the Uinta B interval, document it from multiple levels within the stratigraphic section and examine its uncommon appearance in only approximately 5% of localities where turtles have been systematically collected. This study details and extends the range of A. pulchra in the Uinta Fm. and demonstrates the presence of the taxon in significantly lower stratigraphic layers. These newly described fossils include previously unknown elements and associated trace fossils, with new anatomical information presented. This study provides insight into the taxonomy of Anosteira spp. in the middle Eocene, and suggests the presence of a single species, though no synonymy is defined here due to limits in Bridger material.

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