Late Eocene and early Oligocene teleost and associated ichthyofauna of the Jebel Qatrani Formation, Fayum, Egypt

Fishes from the late Eocene and Oligocene Jebel Qatrani Formation of the Fayum, Egypt, have been collected for many years, but have not been extensively studied. Collections from various sites in the formation, predominantly representing riverine and shallow lake deposits, include remains of several fishes not known previously. The teleost fishes from these collections [representing Characiformes, Siluriformes, Cichlidae, Latidae (= Centropomidae), and Channidae] include species that are similar to those found in the older, underlying, Qasr el Sagha Formation (catfishes), as well as species of fishes previously unrecorded from the Fayum (cichlids and latids), or even from the Tertiary of Africa (channids). It has been suggested that the Jebel Qatrani Formation represents an area of swampy rivers with overgrown banks and floating vegetation and at least one small lake. The fish remains support this reconstruction of the palaeoenvironment, and further indicate that open riverine habitat was also probably available.     

Facies dynamics in Eocene to Oligocene circumalpine carbonates

A new concept, termed ‘Facies Dynamics’ (defined as changes of specific carbonate facies types in time and space, which are controlled by phylogenetic, ecological and geological parameters), is introduced. This concept aims to define and interpret spatial and temporal changes of carbonate facies patterns. It is based on Middle Eocene to Early Oligocene shallow-water carbonate facies types from the circumalpine area (north-eastern Italy, northern Slovenia, Austria and southern Bavaria), which are compared with respect to dominating biogenic components and their distributions along a shelf gradient. This comparison has lead to the distinction and definition of 14 Major Facies Types (MFTs), which are dominated by coralline algae, larger and smaller foraminifera, corals and bryozoans. The presence and distribution of these MFTs from three different time slices (Middle Eocene, Late Eocene and Early Oligocene) is compared. Nine aspects of facies dynamics are distinguished: origination, extinction, immigration, emigration, expansion, reduction, stasis, shift, and replacement of MFTs. These changes are controlled by regional changes in ecological parameters, but also by global events, especially extinction patterns at the Middle/Late Eocene boundary and at the Eocene/Oligocene boundary.     

Discussions on the Palaeogeography and Palaeoclimatology of the Late Eocene Epoch and Oligocene Epoch North Jiangsu

In the present paper, using the spore-pollen analysis, we try to explain the general law of the evolution of the palaeogeography and palaeoclimatology of the fifth member of Funing group in the late Eocene Epoch, and of Dainan formation and Sanduo formation in the Oligocene Epoch, in the region of North Jiangsu. In the period of Funing group No. 5 member, this region was occupied with shallow lakes and mountains and of Central North-Subtropical climate. At then time, the topography of Dainan group was characterized by the richness of rivers, lakes, low mountains and hills. The climate of Dainan formation may be classified into the Northern North-Subtropical climate. The topography Sanduo formation was ranged from low mountain and hills to plains, and its climate was belonged to the Northern North-Subtropical climate. Two plates and two figures are presented in the paper.     

A new basilosaurid (Cetacea, Pelagiceti) from the Late Eocene to Early Oligocene Otuma Formation of Peru

Cynthiacetus peruvianus nov. sp. is a new basilosaurid species, from Late Eocene to Early Oligocene Otuma Formation of Peru. It is the first described archaeocete in South-America and is represented by a sub-complete skeleton. C. peruvianus differs from C. maxwelli (middle to Late Eocene of Egypt and United States) principally in having one cuspid less on both mesial and distal sides of p3 and p4. Cynthiacetus is among the largest basilosaurids. Its more characteristic features are located on its postcranial skeleton: large vertebrarterial foramina on cervical vertebrae and absence of ventral expansion of the transverse process on C3-C5. Besides, C. peruvianus presents the greatest number of thoracic vertebrae (20) and ribs observed in Cetacea and the first thoracics have an almost vertical neural spine. A preliminary parsimony analysis establishes the monophyly of the Basilosauridae on the basis of three unambiguous cranial synapomorphies. However, within the Basilosauridae, the most diagnostic characters are observed on the postcranial skeleton.     

Biochronology and paleoclimatic implications of Middle Eocene to Oligocene planktic foraminiferal faunas

Planktic foraminiferal assemblages have been analyzed quantitatively in six DSDP sites in the Atlantic (Site 363), Pacific (Sites 292, 77B, 277), and Indian Ocean (Sites 219, 253) in order to determine the nature of the faunal turnover during Middle Eocene to Oligocene time. Biostratigraphic ranges of taxa and abundance distributions of dominant species are presented and illustrate striking similarities in faunal assemblages of low latitude regions in the Atlantic, Pacific and Indian oceans. A high resolution biochronology, based on dominant faunal characteristics and 55 datum events, permits correlation between all three oceans with a high degree of precision. Population studies provide a view of the global impact of the paleoclimatic and paleoceanographic changes occurring during Middle Eocene to Oligocene time.Planktic foraminiferal assemblage changes indicate a general cooling trend between Middle Eocene to Oligocene time, consistent with previously published oxygen isotope data. Major faunal changes, indicating cooling episodes, occur, however, at discrete intervals: in the Middle Eocene 44-43 Ma (P13), the Middle/Late Eocene boundary 41-40 Ma ( ), the Late Eocene 39-38 Ma ( ), the Eocene/Oligocene boundary 37-36 Ma (P18), and the Late Oligocene 31-29 Ma ( ). With the exception of the boundary, faunal changes occur abruptly during short stratigraphic intervals, and are characterized by major species extinctions and first appearances. The Eocene/Oligocene boundary cooling is marked primarily by increasing abundances of cool water species. This suggests that the boundary cooling, which marks a major event in the oxygen isotope record affected planktic faunas less than during other cooling episodes. Planktic foraminiferal faunas indicate that the boundary event is part of a continued cooling trend which began during the Middle Eocene.Two hiatus intervals are recognized in low and high latitude sections at the Middle/Late Eocene boundary and in the Late Eocene ( ). These hiatuses suggest that vigorous bottom water circulation began developing in the Middle Eocene, consistent with the onset of the faunal cooling trend, and well before the development of the psychrosphere at the boundary.     

Differential effects of temperature change and human impact on European Late Quaternary mammalian extinctions

Species that inhabited Europe during the Late Quaternary were impacted by temperature changes and early humans, resulting in the disappearance of half of the European large mammals. However, quantifying the relative importance that each factor had in the extinction risk of species has been challenging, mostly due to the spatio‐temporal biases of fossil records, which complicate the calibration of realistic and accurate ecological niche modeling. Here, we overcome this problem by using ecotypes, and not real species, to run our models. We created 40 ecotypes with different temperature requirements (mean temperature from ?20 °C to 25 °C and temperature range from 10 °C to 40 °C) and used them to quantify the effect of climate change and human impact. Our results show that cold‐adapted ecotypes would have been highly affected by past temperature changes in Europe, whereas temperate and warm‐adapted ecotypes would have been positively affected by temperature change. Human impact affected all ecotypes negatively, and temperate ecotypes suffered the greatest impacts. Based on these results, the extinction of cold‐adapted species like Mammuthus primigenius may be related to temperature change, while the extinction of temperate species, like Crocuta crocuta, may be related to human impact. Our results suggest that temperature change and human impact affected different ecotypes in distinct ways, and that the interaction of both impacts may have shaped species extinctions in Europe.     

Oxygen isotope ranking of late Eocene and Oligocene planktonic foraminifers: Implications for Oligocene sea-surface temperatures and global ice-volume

Oxygen isotope analyses of late Eocene and Oligocene planktonic foraminifers from low and middle latitude sites in the Atlantic Basin show that different species from the same samples can yield significantly different isotopic values. The range of isotopic values observed between species is greatest at low-latitudes and declines poleward. Many planktonic foraminifers exhibit a systematic isotopic ranking with respect to each other and can therefore be grouped on the basis of their isotopic ranking. The isotopic ranking of some taxa, however, appears to vary geographically and/or through time.Isotopic and paleontologic data from DSDP Site 522 indicate that commonly used isotopic temperature scales underestimate Oligocene sea surface temperatures. We suggest these temperature scales require revision to reflect the presence of Oligocene glaciation. Comparison of isotopic and paleontologic data from Sites 522, 511 and 277 suggests cold, low-salinity surface waters were present in high southern latitudes during the early Oligocene. Lowsalinity, high latitude surface waters could be caused by Eocene/Oligocene paleogeography or by the production of warm saline bottom water.     

Evolutionary patterns from mass originations and mass extinctions

The Fossil Record 2 database gives a stratigraphic range of most known animal and plant families. We have used it to plot the number of families extant through time and argue for an exponential fit, rather than a logistic one, on the basis of power spectra of the residuals from the exponential. The times of origins and extinctions, when plotted for all families of marine and terrestrial organisms over the last 600 Myr, reveal different origination and extinction peaks. This suggests that patterns of biological evolution are driven by its own internal dynamics as well as responding to upsets from external causes. Spectral analysis shows that the residuals from the exponential model of the marine system are more consistent with 1/f noise suggesting that self-organized criticality phenomena may be involved.     

Palaeontological data and identifying mass extinctions

It is often assumed that mass extinctions may be read directly from the fossil record. However, recent work on the Cretaceous-Tertiary (K-T) boundary has shown the difficulty of doing this. For example, it is hard to tell whether the stratigraphic ranges of taxa are complete or not, and what the shape of an extinction really is. Range completeness may be assessed by (1) a statistical approach to the relative completeness of ranges of taxa, and (2) tests based on collecting effort near the ends of ranges. Tests carried out recently suggest that the record is good in parts and getting better. Hence, palaeontologists ought to be able to document the nature of extinction events ever more precisely.     

The end and the beginning: recoveries from mass extinctions

The evolutionary consequences of mass extinctions depend as much on the processes of survival and recovery following these biotic crises as on the patterns of extinction themselves. Paleontologists are currently documenting biotic recoveries from six major mass extinctions and several smaller biotic crises. Although the immediate responses are remarkably similar after each event, with low-diversity assemblages dominated by widespread, eurytopic species, the recovery response in the long-term is more varied. Lineages that survive the extinction can lack the resilience for recovery, whereas others vanish from the fossil record seemingly to return from the dead after several million years.     

Late Quaternary reptile extinctions: size matters,insularity dominates

Aim A major Late Quaternary vertebrate extinction event affected mostly large‐bodied ‘megafauna’. This is well documented in both mammals and birds, but evidence of a similar trend in reptiles is scant. We assess the relationship between body size and Late Quaternary extinction in reptiles at the global level. Location Global. Methods We compile a body size database for all 82 reptile species that are known to have gone extinct during the last 50,000 years and compare them with the sizes of 10,090 extant reptile species (97% of known extant diversity). We assess the body size distributions in the major reptile groups: crocodiles, lizards, snakes and turtles, while testing and correcting for a size bias in the fossil record. We examine geographical biases in extinction by contrasting mainland and insular reptile assemblages, and testing for biases within regions and then globally by using geographically weighted models. Results Extinct reptiles were larger than extant ones, but there was considerable variation in extinction size biases among groups. Extinct lizards and turtles were large, extinct crocodiles were small and there was no trend in snakes. Lizard lineages vary in the way their extinction is related to size. Extinctions were particularly prevalent on islands, with 73 of the 82 extinct species being island endemics. Four others occurred in Australia. The fossil record is biased towards large‐bodied reptiles, but extinct lizards were larger than extant ones even after we account for this. Main conclusions Body size played a complex role in the extinction of Late Quaternary reptiles. Larger lizard and turtle species were clearly more affected by extinction mechanisms such as over exploitation and invasive species, resulting in a prevalence of large‐bodied species among extinct taxa. Insularity was by far the strongest correlate of recent reptile extinctions, suggesting that size‐biased extinction mechanisms are amplified in insular environments.     

Eocene and Oligocene chitons (Polyplacophora) from the Paris and Hampshire Basins

Eocene and Oligocene chitons (Polyplacophora) from the Paris Basin of N France are described along with comparative material from the Hampshire Basin of the UK. The assemblages include eight species, five of which are new: Ischnochiton fehsei sp. nov., Stenoplax monila sp. nov., Chaetopleura gaasi sp. nov., C. abbessi sp. nov. and Tonicella lira sp. nov. Other taxa in the assemblages are Leptochiton cf. algesirensis, I. vectensis and S. anglica.     

The explosive diversification of the diatom genus Chaetoceros across the Eocene/Oligocene and Oligocene/Miocene boundaries in the Norwegian Sea

Eocene to middle Miocene stratigraphic changes in species richness, abundance and valve size of Chaetoceros resting spores in the Norwegian Sea (DSDP Site 338) were investigated in order to understand past productivity and paleoenvironmental changes in upwelling regions. As a result, drastic resting spore events were recognized in a 6 myr interval across the Eocene/Oligocene boundary (EO Event), the Oligocene/Miocene boundary (OM Event) and in the early middle Miocene (emM Event). The EO Event was characterized by explosive diversification at both the morpho-generic and specific levels, an increase in abundance, and a decrease in valve size from the upper Eocene through the lowest Oligocene. The OM Event was defined by a two-fold increase in species richness. During the emM Event spore abundance decreased rapidly, and species richness and valve size decreased gradually. These changes may indicate changes in the nutrient supply, especially in upwelling regions. The increased species richness suggests a change from a stable water column with a constant nutrient supply in the Eocene to an unstable one with a sporadic nutrient supply by increased vertical mixing in the Oligocene, based on evaluation of the ecologic differences between dinoflagellate cysts and Chaetoceros resting spores. The role of main primary producer might have switched from dinoflagellates and/or nannoplankton in the Eocene to diatoms, especially Chaetoceros, in the Oligocene in the Norwegian Sea. Increased resting spore species richness during the OM Event may show that environmental changes such as global cooling and nutrient mixing led to a diversification of the spore producing genus Chaetoceros. The emM Event might have been affected by changes in paleoceanographic conditions, perhaps a decrease in nutrient supply. This study presents the first paleoceanographic analysis using not only the total resting spore abundance but also the abundances of individual species, and establishes the value of spore taxonomy and diatom analysis including spores.     

Immunocompromised host: from the early events until the impact of acquired immunodeficiency syndrome

The concept that microorganisms can modulate the host resistance was historically reviewed in the present article. The importance of African trypanosomiasis in the development of the research on immunosuppression as well as the impact of human immunodeficiency virus infection are discussed. Each day new opportunistic organisms establish a constant challenge for the correct diagnosis of concomitant infections in acquired immunodeficiency syndrome. The importance of parasite infection in the balance of host resistance in the third world was emphasized. Finally, some aspects of Leishmania as opportunistic organisms were presented.     

Microbes and mass extinctions: paleoenvironmental distribution of microbialites during times of biotic crisis

Widespread development of microbialites characterizes the substrate and ecological response during the aftermath of two of the 'big five' mass extinctions of the Phanerozoic. This study reviews the microbial response recorded by macroscopic microbial structures to these events to examine how extinction mechanism may be linked to the style of microbialite development. Two main styles of response are recognized: (i) the expansion of microbialites into environments not previously occupied during the pre-extinction interval and (ii) increases in microbialite abundance and attainment of ecological dominance within environments occupied prior to the extinction. The Late Devonian biotic crisis contributed toward the decimation of platform margin reef taxa and was followed by increases in microbialite abundance in Famennian and earliest Carboniferous platform interior, margin, and slope settings. The end-Permian event records the suppression of infaunal activity and an elimination of metazoan-dominated reefs. The aftermath of this mass extinction is characterized by the expansion of microbialites into new environments including offshore and nearshore ramp, platform interior, and slope settings. The mass extinctions at the end of the Triassic and Cretaceous have not yet been associated with a macroscopic microbial response, although one has been suggested for the end-Ordovician event. The case for microbialites behaving as 'disaster forms' in the aftermath of mass extinctions accurately describes the response following the Late Devonian and end-Permian events, and this may be because each is marked by the reduction of reef communities in addition to a suppression of bioturbation related to the development of shallow-water anoxia.     

Signatures of random and selective mass extinctions in phylogenetic tree balance

Current models of diversification with evolving speciation rates have trouble mimicking the extreme imbalance seen in estimated phylogenies. However, these models have not incorporated extinction. Here, we report on a simple simulation model that includes heritable and evolving speciation rates coupled with mass extinctions, Random (but not selective) mass extinctions, coupled with evolving among-lineage variation in speciation rates, increase imbalance of postrecovery clades. Thus, random mass extinctions are plausible contributors to the imbalance of modern clades. Paleontological evidence suggests that mass extinctions are often random with respect to ecological and morphological traits, consistent with our simulations. In contrast, evidence that the current anthropogenic mass extinction is phylogenetically selective suggests that the current extinction episode may be qualitatively different from past ones in the way it reshapes future biotas.     

TNF signaling: early events and phosphorylation

Tumor necrosis factor-alpha (TNF) is a major mediator of apoptosis as well as immunity and inflammation. Inappropriate production of TNF or sustained activation of TNF signaling has been implicated in the pathogenesis of a wide spectrum of human diseases, including cancer, osteoporosis, sepsis, diabetes, and autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, and inflammatory bowel disease. TNF binds to two specific receptors, TNF-receptor type I (TNF-R1, CD120a, p55/60) and TNF-receptor type II (TNF-R2, CD120b, p75/80). Signaling through TNF-R1 is extremely complex, leading to both cell death and survival signals. Many findings suggest an important role of phosphorylation of the TNF-R1 by number of protein kinases. Role of TNF-R2 phosphorylation on its signaling properties is understood less than TNF-R1. Other cellular substrates as TRADD adaptor protein, TRAF protein family and RIP kinases are reviewed in relation to TNF receptor-mediated apoptosis or survival pathways and regulation of their actions by phosphorylation.