Do Ecosystems Ever Converge? Evidence From Faunal Size Distributions Of Late Miocene North American Mammals

2005 ◽  
Author(s):  
W. David Lambert
Keyword(s):  
Late Miocene ◽  
North American ◽  
Size Distributions

scholarly journals Late Miocene to Pliocene Tsunami Deposits in Tegal Buleud, South Sukabumi, West Java, Indonesia

2019 ◽  
Vol 13 (12) ◽  
pp. 80
Author(s):  
Yan Rizal ◽  
Aswan Aswan ◽  
Jahdi Zaim ◽  
Mika R. Puspaningrum ◽  
Wahyu D. Santoso ◽  
...  
Keyword(s):  
Late Miocene ◽  
Flame Structure ◽  
Tectonic Activity ◽  
Tsunami Deposit ◽  
Size Distributions ◽  
Volcanic Island ◽  
Tsunami Deposits ◽  
West Java ◽  
Foraminiferal Assemblage ◽  
Grain Size Distributions

Java is a volcanic island arc formed by the northwards subduction of the Eurasian and Australian Plates. Due to this active subduction, Java has been frequently shocked by earthquakes, which might induce tsunami events. However, there are hardly any ancient geological records of tsunami events in the area. This study aims to determine the presence and to identify sedimentary characters of tsunami deposit in Tegal Buleud, South Sukabumi, West Java. In the study area, there were 4 tsunami layers which were found as thin intercalation within the claystone layer of the Bentang Formation. Those paleotsunami deposits characterized by the occurrence of irregular/disturbed structure such as siltstone rip up, clay clasts, and flame structure occur in normal graded bedding sandstone layer. The grain-size distributions show bimodal and multimodal patterns, with mixing of marine microfossils from inner and middle neritic. The planktonic foraminiferal assemblage indicates that the age of the sediment comparable to N19 (equivalent to Late Miocene - Early Pliocene, at about 5.33 – 3.6 Ma), suggested that these paleotsunami layers were deposited due to the Mio-Pliocene tectonic activity. All the paleotsunami deposits found in Study area are the first and oldest tsunami deposit recorded in Java even in Indonesia. With the discovery of the previously unexplored Late Miocene to Pliocene tsunami deposits found in the study area, the result of this study can be used as a reference for the identification of the Tertiary tsunami deposits present in other parts of Indonesia.

Spatiotemporal palaeodiversity patterns of modern crocodiles (Crocodyliformes: Eusuchia)

2019 ◽  
Vol 189 (2) ◽  
pp. 635-656 ◽  
Author(s):  
Ane De Celis ◽  
Iván Narváez ◽  
Francisco Ortega
Keyword(s):  
South America ◽  
Least Squares ◽  
Late Miocene ◽  
North American ◽  
Fossil Record ◽  
Generalized Least Squares ◽  
Global Scale ◽  
Biotic Factors ◽  
Species Dynamics ◽  
Over Time

Abstract Eusuchia is a crocodyliform clade with a rich and diverse fossil record dating back to the Mesozoic. There are several recent studies that analyse crocodyliform palaeodiversity over time, but none of them focuses exclusively on eusuchians. Thus, we estimated subsampled eusuchian palaeodiversity species dynamics over time not only at a global scale, but also by continents and main crocodylian lineages (Alligatoroidea, Crocodyloidea and Gavialoidea). These estimates reveal complex spatiotemporal palaeodiversity patterns, in which two maxima can be detected: the first during the Palaeocene and the second, which is also the biggest, in the middle-late Miocene. The Palaeocene shift is related to a North American alligatoroid diversification, whereas the middle–late Miocene maximum is related to a diversification of the three main Crocodylia lineages in Gondwanan land masses, but especially in South America. Additionally, a model-based study using generalized least squares was carried out to analyse the relationships between different abiotic and sampling proxies and eusuchian palaeodiversity. The results show that palaeotemperature is the most important factor amongst the analysed proxies, in accordance with previous studies. However, the results suggest that, along with palaeotemperature, other abiotic and/or biotic factors might also be driving eusuchian palaeodiversity dynamics.

scholarly journals Physical and chemical properties of pollution aerosol particles transported from North America to Greenland as measured during the POLARCAT summer campaign

2011 ◽  
Vol 11 (4) ◽  
pp. 11771-11808 ◽  
Author(s):  
B. Quennehen ◽  
A. Schwarzenboeck ◽  
J. Schmale ◽  
J. Schneider ◽  
H. Sodemann ◽  
...  
Keyword(s):  
Black Carbon ◽  
North American ◽  
The Arctic ◽  
Size Distributions ◽  
American Continent ◽  
Air Masses ◽  
Accumulation Mode ◽  
North American Continent ◽  
The North ◽  
Aitken Mode

Abstract. Within the framework of the POLARCAT-France campaign, aerosol physical, chemical and optical properties over Greenland were measured onboard the French ATR-42 research aircraft. The Lagrangian particle dispersion model FLEXPART was used to determine air mass origins. The study focuses particularly on the characterization of air masses transported from the North American continent. Air masses that picked up emissions from Canadian and Alaskan boreal forest fires as well as from the cities on the American east coast were identified and selected for a detailed study. Measurements of CO concentrations, aerosol chemical composition, aerosol size distributions, aerosol volatile fractions and aerosol light absorption (mainly from black carbon) are used in order to study the relationship between CO enhancement, ageing of the air masses, aerosol particle concentrations and size distributions. Aerosol size distributions are in good agreement with previous studies, even though, wet scavenging potentially occurred along the pathway between the emission sources and Greenland leading to lower concentrations in the aerosol accumulation mode. The measured aerosol size distributions show a significant enhancement of Aitken mode particles. It is demonstrated that the Aitken mode is largely composed of black carbon, while the accumulation mode is more dominated by organics, as deduced from aerosol mass spectrometric AMS and aerosol volatility measurements. Overall, during the campaign rather small amounts of black carbon from the North American continent were transported towards Greenland. An important finding given the potential climate impacts of black carbon in the Arctic.

scholarly journals Patterns of evolution in North American Neogene mammals

1992 ◽  
Vol 6 ◽  
pp. 146-146
Author(s):  
Louis Jacobs ◽  
Christine Janis
Keyword(s):  
Late Miocene ◽  
North American ◽  
Morphological Changes ◽  
Ground Squirrels ◽  
Deer Mice ◽  
Leg Length ◽  
Vegetational Change ◽  
Late Neogene ◽  
Tree Squirrels

The Neogene of North American represents a time of climatic change from an initially warm, non-arid climate to one with the development of increasing aridity, with warming temperatures through the early part and fluctuating (but basically cooler) temperatures through the later part. This reflects the classic story of a vegetational change from woodland to savanna and eventually to prairie. Note that the transition to true savanna in the Late Miocene was considerably earlier than the first savannas in the Pliocene of the Old World. The evolutionary trends in mammals reflect these climactic and vegetational changes.Some general broad trends are as follows: the replacement of terrestrial and subfossorial moles and geomyid rodents with more specialized fossorial ones; a decrease in the diversity of brachydont rodents and an increase in the diversity of hypsodont ones (including saltatorial forms), and a late Neogene diversification of microtines and deer mice; a decline in the diversity of tree squirrels and terrestrial beavers, and an increase in diversity of ground squirrels and aquatic beavers; the replacement of carnivores belong to more archaic families by more modern types; taxa and an increase in body size, leg length, and hypsodonty in most ungulate taxa, including oreodonts, protoceratids, camelids, antilocaprids, rhinos and equine horses although a couple of taxa show an apparent reversal of these trends: dromomerycids (cervoids) and some anchitherine horses show other morphological changes that suggest progressively more woodland-adapted (rather than savanna-adapted) forms. Tapirs and (to a lesser extent) peccaries seem little affected by the Neogene changes, and persist until the Recent.The Neogene was also punctuated by immigration events (primarily from Asia) and extinctions. The start of the Neogene shows surprisingly little change, with many Paleogene “holdovers”: some new forms appear as either the result of evolution in situ (e.g. equine horses and osteoborine dogs) or as immigrants (e.g. chalicotheres and hemicyonine “dog bears”). The initial major immigrations are during the late Early Miocene, marked by the Asian appearances of true felids (replacing the “false saber-tooths” or nimravids), pecoran ruminants (replacing the hypertragulids), more derived rhinos (replacing the diceratherine rhinos), neomustelids and procyonids. Archaic suoids such as anthracotheres and entelodonts become extinct at this time, and only the more derived ticholeptine oreodonts survive this period. The start of the Middle Miocene is notable for the appearance of proboscideans and deer mice. The Late Miocene sees the decline and eventual disappearance of hedgehogs, archaic carnivores (hemicyonine bears and amphicyonids), most browsing ungulates (oreodonts, protoceratids, many camelids, anchitherine horses, dromomerycids, merycodontine antilocaprids, hornless ruminants, chalicotheres, bunodont gomphotheres), and rhinos. New taxa appearing including ursine bears (immigrants), oversized camels and more derived gomphotheres (in situ evolution). The Pliocene marks a new wave of immigration: microtines, hyenas, true saber-tooths, and cervids come in from Asia; ground sloths (two families appearing in the Late Miocene), glyptodonts, armadillos and capybaras come in from South America. Most mammals that survived the end Miocene extinctions persist, but for many of them (such as horses, camels and antilocaprids) the generic diversity is greatly reduced.

scholarly journals New insights on the Early Pleistocene equids from Roca-Neyra (France, central Europe): implications for the Hipparion LAD and the Equus FAD in Europe

2020 ◽  
pp. 1-20
Author(s):  
Omar Cirilli ◽  
Raymond L. Bernor ◽  
Lorenzo Rook
Keyword(s):  
Central Europe ◽  
Late Miocene ◽  
North American ◽  
Statistical Analyses ◽  
Early Pleistocene ◽  
Morphological Description ◽  
The North ◽  
Azov Sea

Abstract We undertake a redescription of the equid sample from the Early Pleistocene of Roca-Neyra, France. This locality has been recently calibrated at the Pliocene/Pleistocene boundary (2.6 ± 0.2 Ma) and therefore it is of interest for the first appearance of the genus Equus and last appearance of hipparionine horses. The Roca-Neyra equid sample, re-analyzed herein using morphological, morphometrical, and statistical analyses, has revealed the co-occurrence of Plesiohipparion cf. ?P. rocinantis and Equus cf. E. livenzovensis. The analysis undertaken on several European, African, and Asian “Hipparion” sensu lato species from late Miocene to Early Pleistocene has revealed different remnant Hipparion lineages in the Plio-Pleistocene of Europe: Plesiohipparion, Proboscidippaion, and likely Cremohipparion. The discovery of the first European monodactyl horse, Equus cf. E. livenzovensis correlates Roca-Neyra with other 2.6 Ma European localities in Italy, Spain, and in the Khapry area (Azov Sea region). The morphological description of the Equus cf. E. livenzovensis lower cheek teeth has highlighted intermediate features between the North American Pliocene species Equus simplicidens and Early Pleistocene European Equus stenonis. Our study supports the hypothesis that E. livenzovensis is a plausible evolutionary predecessor for the Equus stenonis group. These observations underscore the importance of Roca-Neyra as an important locality for the last European hipparions and the first Equus in the Early Pleistocene of Europe.

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