Discovery of the Silurian global events

Silurian faunal turnovers and extinctions have been known for a long time and the period yield a well documented record of bioevents (Jeppsson 1990 Barnes et al. 1995 Gradstein et al. 2004 Fig. 3). These events have historically been referred to by different names, depending on the group of taxa at hand, and this has from time to time led to some confusion. Along with improved biostratigraphy and stable isotope stratigraphy, however, it is now clear that the various published names sometimes...

Causes of the TJB extinctions

The end-Triassic drop in diversity was selective but notable for the rapid loss of specific marine taxa, such as ammonoids, conodonts, radiolarians and infaunal bivalves, suggesting physical processes that strongly affected ocean bioproductivity (Tanner et al. 2004). Moreover, the temporary loss of scleractinian corals and almost all calcareous nannoplankton has suggested to some a calcification crisis coincident with the above losses (Hautmann 2004 Schootbrugge et al. 2007). These biotic...

Conodonts

The Conodonta (a phylum or subphylum) is usually identified as one of the most significant groups to have suffered complete extinction at the end of the Triassic. This is misleading. Detailed reviews of conodont extinctions emphasize that conodonts suffered high rates of extinction and low rates of origination throughout the Triassic (e.g. Clark 1983, 1986, 1991 Sweet 1988 Kozur and Mock 1991 Aldridge and Smith 1993 De Renzi et al. 1996). During the Triassic, conodont diversity was highest...

Mass Extinction a general view

Geology Department, Faculty of Science, Minia University, Minia 61519, Egypt, aelewa link.net Mass extinction is considered as the most subject matter in paleontology that received several debated input. When looking to the past, we find five major mass extinctions, I believe, in the fossil record (e.g. Late Ordovician, Late Devonian, Late Permian, Late Triassic and Late Cretaceous). Some authors believe in six mass extinctions by adding Cambrian to the previous five events, some others speak...

The Raup extinction model and the kill curve

Raup (1991, 1996) suggested an extinction model that overcomes the problems of the Darwin-Lyell, namely the passive replacement of faunas after extinctions and the different times required for a taxon to disappear from the geological layers. Passive replacement is used in the sense that the replacing fauna took advantage of the lack of the replaced one and did not compete directly with it. A direct competition would mean an active replacement. The formulation of the extinction model involved...

References

Abdel-Gawad GI, El Sheikh HA, Abdelhamid MA, EL Beshtawy MK, Abed M, F rsich FT (2004) Stratigraphic studies on some upper Cretaceous succession in Sinai, Egypt. Egypt. J Paleont 263-303 Abdelhamid MA, El Qot GM (2001) Upper Cretaceous Echinoid from Gabel El Hamra and Gabel El Minsherah, North Sinai, Egypt. MERC Ain Shams University, Earth Science 15, 1-20 Abdelhamid MA, Azab MM (2003) Aptian Cenomanian echinoids From Egypt. Review Pleobiologie, Geneve 22 (2) 851-876 Abdelhady AA (in Press)...

Land plants

An extensive literature documents the lack of a major extinction turnover of the terrestrial macroflora and microflora at the TJB (e.g. Orbell 1973 Schuurman 1979 Pedersen and Lund 1980 Fisher and Dunay 1981 Brugman 1983 Niklas et al. 1983 Knoll 1984 Ash 1986 Traverse 1988 Edwards 1993 Cleal 1993a, b Kelber 1998 Hallam 2002 Tanner et al. 2004 Lucas and Tanner 2004, 2007b Galli et al. 2005 Ruckwied et al. 2006 Kuerschner et al. 2007). Thus, for example, Ash (1986) reviewed the global record of...

Climate change and megafauna

Climate change, and associated fluctuations in sea levels, has dramatically altered the region's vegetation, as discussed above. In particular, the existence of a savannah corridor running through the middle of Sundaland, a concept which seems foreign when we think of Southeast Asia, appears to have been the norm during the Pleistocene. Like other continents, Southeast Asia hosts a number of disharmonious assemblages, and the presence of this corridor provides a ready explanation for these...

Discussion and conclusions

The macrofaunal categories employed to infer paleoenvironmental conditions. Collectively the methods of establishment of the optimum conditions for the paleoecology are more precisely approached by analyzed the association grouply. We employ several lines of evidence from invertebrate fossils to propose a paleoenvironmental interpretation. The disappearance of many species and the general depletion of oyster diversity in late Cenomanian deposits are induced by the coeval sea-level rise and...

Tetrapods

The idea of a substantial nonmarine tetrapod (amphibian and reptile) extinction at the TJB began with Colbert (1949, 1958), and has been more recently advocated by Olsen et al. (1987, 1990, 2002a, b), largely based on the tetrapod fossil record of the Newark Supergroup (eastern North America). Weems (1992), Benton (1994), Lucas (1994), Tanner et al. (2004) and Lucas and Tanner (2004, 2007b) rejected this conclusion, arguing against building a case for extinction on the very incomplete...

Habitat fragmentation destruction modification

In addition to the previous example, the work of Greuter (1972, 1979, 1995)-a systematic botanist-on island taxa indicated that island taxa, and insects predominate in these assemblages, exhibit some particularities. First, the earlier the habitation of the island by humans, as it happens in the Aegean and the Mediterranean in general, the lower the extinction rates unlike the islands in the Pacific where the human occupation varies inversely with extinction rates (Pimm et al. 1995). The first...

Hawashiya Formation

Hawashiya Formation is characterized by a decrease in faunal diversity and high reflux of course clastics, which indicate nearshore environment of high energy agitated conditions. Appearance of gypsiferous lamina indicates lagonal environment and arid conditions. Appearance of oyster bivalve again suggested stability in environment and homogeneous oxygenation percentage. They nevertheless could be met in the early circalittoral. Their accumulation seems rather localized in the early...

Sea level changes

Changes in sea level have had such an unparalleled influence on Southeast Asia's geography and biota that a detailed treatment of these changes was necessary. Sea level changes occur due to the movement of huge volumes of water from oceans to ice sheets, and back again (Lambeck et al. 2002). These movements are a result of oscillations between glacial and interglacial climatic conditions, and have seen sea levels fall as low as 140 m below present (Lambeck et al. 2002). Regional changes in sea...

Lessons from island ecology

Perhaps the first attempt to explain the extinctions of species from islands was done by Ricklefs and Cox (1972 1978) who investigated the extinction of some bird species from the Lesser Antilles archipelago. The explanation involved the principle of 'taxon cycle', a term which parallels the life of a taxon with the life of an individual. The term was coined by Wilson (1961 see also Ricklefs and Birmingham 2002 for a more recent account of the concept) and it roughly describes the initial...

Southeast Asias megafauna

Unlike North America and Australia, many species of megafauna can still be found living in Southeast Asia. These include such charismatic species as the giant panda (Ailuropoda melanoleuca), the orangutan (Pongo pygmaeus), the Javan and Sumatran rhinoceroses (Rhinoceros sondaicus and Dicerorhinus sumatraensis), the Asian elephant (Elephas maximus) and the tiger (Panthera tigris). Southeast Asia's extinct megafauna is less well known to general audiences, but include several species of...

Early Silurian Ireviken Event

The Silurian global paleogeography was dominated by the vast Gondwanan continent, which covered much of the southern circumpolar areas. Laurentia, Baltica, and Avalonia assembled in the large Laurussian contintent at equatorial latitudes (modified from Cocks and Torsvik 2002). The figure shows locations where previous studies have presented firm evidence for anomalies either in stable isotopes, biodiversity, or facies during the Ireviken Event. Stars with white dot indicate that the...

Late Silurian Lau Event

The figure shows locations where previous studies have presented firm evidence for anomalies either in stable isotopes, biodiversity, or facies during the Lau Event. Stars with white dot indicate that the cited study does not include stable isotope data. AU - Austria (Sch nlaub 1986 Wenzel 1997) CR - Czech Republic (Lehnert et al. 2003, 2007b), EB - East Baltic Area (Kaljo et al. 2003), NE - Nevada (Saltzman 2001), NSW - New South Wales (Talent et al. 1993), OK - Oklahoma (Saltzman...

Introduction

Mass extinction events affect a wide breadth of ecosystems and are one of the major driving mechanisms behind evolution, origination, and diversification of taxa. Such dramatic turnovers have therefore played a significant role in the history of life. The 'major five' mass extinctions (Raup and Sepkoski 1982) have received intense attention over the last 25 years, starting with the K-Pg impact hypothesis launched by Luis Alvarez and others in Science in 1980. By comparison, few studies have...

Geological History

The Southeast Asian continental block is largely composed of elements, which had broken off from the southern super-continent Gondwanaland (Gatinsky and Hutchinson 1987 Metcalf 1990, 1996). Much of the modern geographical aspects of Southeast Asia occurred as a result of the fusion between the Sinoburmalaya and Cathaysia plates, in an event known as the Late Triassic Indosinian Orogeny (Hutchinson 2005). More plate collisions followed, including the collision of the Burma plate with Shan...

Types of current insect extinctions

While it is accepted that current insect extinction are basically a human induced process various authors emphasize individual causative factors. These isolated factors are usually global warming (Thomas et al. 2004) elevated carbon dioxide (Penuelas and Estiarte, 1998), co-extinctions (Dunn 2005 Koh et al. 2004), habitat Zschokke et al. 2000 (Tscharntke and Kruess 1999 Steffan-Dewenter and Tscharntke 2002 Londre and Schnitzer 2006) and habitat loss (Seabloom et al. 2002 Pimm and Raven 2000) or...

Late Ordovician mass extinction

Geology Department, Faculty of Science, Minia University, Minia 61519, Egypt, aelewa link.net The Ordovician period was an era of extensive diversification and expansion of numerous marine clades. Although organisms also present in the Cambrian were numerous in the Ordovician, a variety of new types including cephalopods, corals (including rugose and tabulate forms), bryozoans, crinoids, graptolites, gastropods, and bivalves flourished. Ordovican communities typically displayed a higher...

The Middle Silurian Mulde Event

The Middle Silurian Mulde Event refers to a faunal overturn and crisis at the top of the Lower Homerian stage. A spectacular mass extinction among the graptolites characterizes the event. The mass mortality is locally expressed by extremely dense bedding plane accumulations of a few single survivor species, sometimes literally blackening the bedding planes (Lenz et al. 2006). Contemporaneous formation of organic-rich shale, alum shale, and not least the formation of the so-called 'boundary coal...

Conserving insect biodiversity in city parks and road verges

Among the human structures that fragment in a definite way the habitat of many species are the roads (Saarinen et al. 2005). Many animals attempting to cross this barrier are being killed by traffic. For the United States it is estimated that the daily rate of road-killed vertebrates is one million (Ries et al. 2001). No similar rates for invertebrates have been estimated but this source of mortality is of minor importance compared to other mortality sources. When Ries et al. (2001) followed...

References Global Environment Humanrole

Anshari G, Kershaw AP, van der Kaars S (2001) A Late Pleistocene and Holocene pollen and charcoal record from peat swamp forest, Lake Sentarum Wildlife Reserve, West Kalimantan, Indonesia. Palaeogeogr Palaeoclimat Palaeoecol 171 213-228 Batchelor BC (1979) Discontinuous rising Late Cainozoic eustatic sea-levels, with special reference to Sundaland, southeast Asia. Geologie en Mijnbouw 58 120 Batchelor DAF (1988) Dating of Malaysian fluvial tin placers. Journal of Southeast Asian Earth Sciences...

The Silurian marine scene

During the Silurian the continents were still largely unsettled which means that weathering processes, and the processes of erosion and transport of sediments from the continents to the shallow shelves must have differed substantially from post-Silurian times. The marine realm stood in sharp contrast to the silent land masses and yielded abundant and diverse life forms. The preceding Great Ordovician Biodiversification Event had resulted in a tremendous array of adaptive radiations among marine...

Reef builders

The scleractinian corals, important reef builders during the Triassic, suffered a marked decline at the end of the Triassic that was followed by a reef gap during part of the Early Jurassic (Hettangian-early Sinemurian), after which corals re-diversified to become the dominant reef builders (Stanley 1988). Stanley (2001, p. 26) viewed this as a rapid collapse of reefs at the TJB, concluded it was the result of a first-order mass extinction and noted that Jurassic recovery was slow. i< ji...

Temporal and spatial development and biodiversity

To be regarded a mass extinction an event should be (1) 'confined to a short interval of geological time, it should (2) affect a wide variety of clades occupying a wide spectrum of habitats and (3) it should eradicate a high proportion of species' (Brenchley and Harper 1998, p. 322 numbers added by the current author). These three prerequisites are only partly fulfilled by the Silurian global events, the minor amount of taxonomic loss during the Silurian global events being the main difference....

The Silurian events and carbonate platforms

Todays carbonate platforms - such as the Bahamas platform or the Great Barrier Reef - are major marine ecosystems that respond to a wide variety of changes in the contemporaneous oceans. They have a life cycle and a carbonate production rate that depends on the interaction of climate, relative sea-level, and biotic factors such as diversification rate. For this reason, environmental changes in coastal marine waters are reflected in the type of carbonate production and thus in the sediment...

Insect extinctions from climate change

It is well known that the climate of the earth becomes warmer (Parmesan 1996 Schmitt 2003) and this is going to continue for the next 50-100 years (Parmesan et al. 1999). This situation triggered various associated processes such as the decline of plants, which are important hosts for herbivorous insects (Barber et al. 2000 Scott et al. 2002 Petrakis and Legakis 2005). In this sense global warming cannot be separated from other sources of extinction such as habitat loss and co-extinctions. The...

Human overhunting in Southeast Asia

Synchrony of colonisation and extinctions in Southeast Asia is particularly difficult to establish, and is exacerbated by questions of human evolution and poor chronology of sites (Louys et al. 2007). Unlike North America and Australia, the earliest colonisers in Southeast Asia were not modern humans but Homo erectus. Evidence as to whether Homo erectus in Asia subsisted predominantly on a scavenging or hunting diet is still equivocal, although current evidence is suggestive that the former...

Insect mass extinctions in the past

It is known that insects are very different from other organisms at least in the distinction of background and mass extinction. The difference lies in the fact that insects are always dependent on other organisms and usually are important parts of local ecological communities. Labandeira and Philips (1996) record the late Carboniferous (Middle-Late Pennsylvanian stage - Fig. 1) extinction and consider that this is the first major insect extinction. At the same time an extinction of extensive...