A new extinct primate among the Pleistocene megafauna of Bahia, Brazil.

A nearly complete skeleton of a robust-bodied New World monkey that resembles living spider monkeys was recovered from undisturbed Pleistocene deposits in the Brazilian state of Bahia. The skeleton displays the highly specialized postcranial pattern typical of spider and woolly spider monkeys and shares cranial similarities to the spider monkey exclusively. It is generically distinct on the basis of its robustness (>20 kg) and on the shape of its braincase. This new genus indicates that New World monkeys nearly twice the size of those living today were part of the mammalian biomass of southern Amazonia in the late Pleistocene. The discovery of this specimen expands the known adaptive diversity of New World monkeys and demonstrates that they underwent body size expansion in the terminal Pleistocene, as did many other types of mammals.

Unusual dynamics of extinction in a simple ecological model.

Studies on natural populations and harvesting biological resources have led to the view, commonly held, that (i) populations exhibiting chaotic oscillations run a high risk of extinction; and (ii) a decrease in emigration/exploitation may reduce the risk of extinction. Here we describe a simple ecological model with emigration/depletion that shows behavior in contrast to this. This model displays unusual dynamics of extinction and survival, where populations growing beyond a critical rate can persist within a band of high depletion rates, whereas extinction occurs for lower depletion rates. Though prior to extinction at lower depletion rates the population exhibits chaotic dynamics with large amplitudes of variation and very low minima, at higher depletion rates the population persists at chaos but with reduced variation and increased minima. For still higher values, within the band of persistence, the dynamics show period reversal leading to stability. These results illustrate that chaos does not necessarily lead to population extinction. In addition, the persistence of populations at high depletion rates has important implications in the considerations of strategies for the management of biological resources.

Avoiding Extinction: An Evaluation of Short-Term Recovery Recommendations for the Endangered Rio Grande Silvery Minnow

The endangered Rio Grande silvery minnow (Hybognathus amarus; RGSM) is nearing extinction and requires immediate recovery actions. In a draft report to the Middle Rio Grande Program, a Program Advisory Panel (PAP) recommended 34 short-term recovery measures to be implemented within the next five years, and 21 long-term recovery actions. However, these recommendations need further analysis to determine if and how the actions could be implemented. This project evaluated short-term recommendations provided by the PAP to identify the most effective and rank the relative importance of the actions. These recommendations were divided into 7 recovery categories: population augmentation (5 recommendations); hydrologic regimen (4 recommendations); physical habitat (3 recommendations); biological component of habitat (2 recommendations); population monitoring (6 recommendations); monitoring, analysis, and modeling (12 recommendations); and information and planning (2 recommendations). Each recommendation was evaluated for its potential to produce anticipated recovery progress for the RGSM based on assessments of the degree of feasibility, cost effectiveness, and associated potential consequences if fully implemented. In addition, other alternatives in a range of options were also considered where applicable. In each case, recommendations were evaluated from on-site visits, interviews with researchers and resource managers, and literature review. Based on the research findings, three major groupings of the recovery categories were identified: natural aspects of recovery, program aspects of recovery, and emergency measures. At least one recovery category within each major grouping was considered important by the respondents, which indicates that each grouping is of high importance in relation to the situation at hand. However, actions within each grouping have varying priorities given constraints on available resources, time, and budget. An integrated approach that accounts for the complexity of the river system and the species itself was considered the best approach to avoid extinction while ensuring long-term sustainability. Results of these analyses were provided directly to the PAP for their review, and it is anticipated that project results could advance implementation of the most appropriate immediate recovery actions needed to prevent extinction of the RGSM.

Extinction trends of threatened invertebrates in peninsular Spain

Using information from two recently published atlases of threatened invertebrate species in peninsular Spain, we examined the climatic, land use and geographic characteristics of the 100 km2 UTM cells with most likelihood of suffering extinctions (extinction cells), as well as the attributes of the species prone to population extinctions. Extinction cells have had significantly (1) lower precipitation values, (2) higher temperatures, (3) higher percentages of anthropic land uses or (4) higher rates of anthropization during the last 20 years than the remaining cells. Nevertheless, probable extinctions may occur under a wide range of climatic and anthropization change rates and these variables can only explain a low proportion (~5 %) of variability in the occurrence or number of extinction cells. Aquatic species seem to suffer higher local extinction rates than terrestrial species. Interestingly, many invertebrate species with approximately 25 or less occurrence cells are on a clear trajectory towards extinction. These results outline the difficulties and uncertainties in relating probable population extinctions with climatic and land use changes in the case of invertebrate data. However, they also suggest that a third of the considered Spanish threatened species could have lost some of their populations, and that current conservation efforts are insufficient to reverse this tendency.

Evolution of the last koninckinids (Athyridida, Koninckinidae), a precursor signal of the early Toarcian mass extinction event in the Western Tethys

Koninckinids are a suitable group to shed light on the biotic crisis suffered by brachiopod fauna in the Early Jurassic. Koninckinid fauna recorded in the late Pliensbachian–early Toarcian from the easternmost Subbetic basin is analyzed and identified as a precursor signal for one of the most conspicuous mass extinction events of the Phylum Brachiopoda, a multi-phased interval with episodes of changing environmental conditions, whose onset can be detected from the Elisa–Mirabile subzones up to the early Toarcian extinction boundary in the lowermost Serpentinum Zone (T-OAE). The koninckinid fauna had a previously well-established migration pattern from the intra-Tethyan to the NW-European basins but a first phase with a progressive warming episode in the Pliensbachian–Toarcian transition triggered a koninckinid fauna exodus from the eastern/central Tethys toward the westernmost Mediterranean margins. A second stage shows an adaptive response to more adverse conditions in the westernmost Tethyan margins and finally, an escape and extinction phase is detected in the Atlantic areas from the mid-Polymorphum Zone onwards up to their global extinction in the lowermost Serpentinum Zone. This migration pattern is independent of the paleogeographic bioprovinciality and is unrelated to a facies-controlled pattern. The anoxic/suboxic environmental conditions should only be considered as a minor factor of partial control since well-oxygenated habitats are noted in the intra-Tethyan basins and this factor is noticeable only in the second westward migratory stage (with dwarf taxa and oligotypical assemblages). The analysis of cold-seep proxies in the Subbetic deposits suggests a radiation that is independent of methane releases in the Subbetic basin.

The fauna from the terminal Pleistocene of Palegawra Cave, a Zarzian occupation site in northeastern Iraq / Priscilla F. Turnbull -- and Charles A. Reed --.

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(Table 3) Textural and bulk mineralogy of Pliocene and Pleistocene sediments from ODP Hole 161-976B

The Pliocene and Pleistocene deposits recovered at Site 976 from the northwestern Alboran Sea at the Málaga base-of-slope include five main sedimentary facies: hemipelagic, turbidite, homogeneous gravity-flow, contourite, and debris-flow facies. The thickness and vertical distribution of these facies into lithostratigraphic Units I, II, and III show that the turbidites and hemipelagic facies are the dominant associations. The Pliocene and Pleistocene depositional history has been divided into three sedimentary stages: Stage I of early Pliocene age, in which hemipelagic and low-energy turbidites were the dominant processes; Stage II of early Pleistocene/late Pliocene age, in which the dominant processes were the turbidity currents interrupted by short episodes of other gravity flows (debris-flows and homogeneous gravity-flow facies) and bottom currents; and Stage III of Pleistocene age, in which both hemipelagic and low-energy gravity-flow processes occurred. The sedimentation during these three stages was controlled mainly by sea-level changes and also by the sediment supply that caused rapid terrigenous sedimentation variations from a proximal source represented by the Fuengirola Canyon.

Petrology and geochemistry of sideromelane glass shards from Pleistocene as layers north and south of Gran Canaria

Major elements, S, F, Cl concentrations and relative proportions of S6+ to total S were analyzed with electron microprobe in sideromelane glass shards from Pleistocene volcaniclastic sediments drilled during ODP Leg 157. Glasses are moderately to strongly evolved and represent a spectrum from alkali basalt, basanite and nephelinite through hawaiite, mugearite and tephrite to phonolitic tephrite. Measured S6+/SumS (0.03±0.98) and calculated Fe2+/Fe3+ (2.5±5.8) ratios in the melt yield preeruptive redox conditions ranging from NNO-1.4 to NNO+2.1. The morphology of the glass shards, variations of S and Cl concentrations (0.010±0.127 wt% S, 0.018±0.129 wt% Cl), calculated preeruptive temperatures (1030±1200 °C) and oxygen fugacities suggest that glasses deposited even within the same ash layers have diverse origin and may have resulted from both submarine and subaerial eruptions. Most vesicle-free glasses are characterized by high concentrations of S and represent undegassed or slightly degassed submarine lavas, whereas vesiculated glasses with low concentrations of S and Cl are strongly degassed and can be ascribed to the eruptions in shallow water or on land. Sideromelane glass shards at Sites 953 are thought to have resulted from submarine eruptions northeast of Gran Canaria, glasses at Site 954 represent mostly volcaniclastic material of shallow water submarine and subaerial eruptions on Gran Canaria and Tenerife, and glasses deposited at Site 956 resulted from submarine or explosive eruptions on Tenerife.

Planktonic foraminiferal preservation in Plio/Pleistocene sediments from the western equatorial Atlantic and Caribbean

Records of mean sortable silt and planktonic foraminiferal preservation from the Ceará Rise (western equatorial Atlantic) and from the Caribbean are presented to analyze the Pliocene (3.5-2.2 Ma) to Pleistocene (1.6-0.3 Ma) evolution of near-bottom current strength and the carbonate corrosiveness of deep water. During the mid-Pleistocene climate transition (~1 Ma) a drastic decrease in glacial bottom current strength and an increase in carbonate corrosiveness is registered, demonstrating a substantial decrease in the glacial contribution of the Lower North Atlantic Deep Water (LNADW) to the Atlantic Ocean. Also, an increased sensitivity to eccentricity orbital forcing is registered after the MPT. By contrast, carbonate preservation increases considerably in the deep Caribbean in response to a strong and persistent stable contribution of Upper North Atlantic Deep Water (UNADW). We found evidence for the strongest and most stable circulation within the LNADW cell during the Northern Hemisphere cooling period between ~3.2 and 2.75 Ma. This is in agreement with the 'superconveyor model' which postulates that the highest NADW production took place prior to ~2.7 Ma. A considerable decrease in bottom current strength and planktonic foraminiferal preservation is observed synchronous with the first occurrence of large-scale continental ice sheets in the Northern Hemisphere. This documents the final termination of the 'superconveyor' at ca. 2.75 Ma. However, our data do not support a 'superconveyor' in the interval between 3.5 and 3.2 Ma when high-amplitude fluctuations in bottom current flow and preservation in planktonic foraminifera are observed. Because of the great sensitivity of NADW production to changes in surface water salinity, we assume that the high-amplitude fluctuations of LNADW circulation prior to ~3.2 Ma are linked to changes in the Atlantic salinity budget. After 2.75 Ma they are primarily controlled by ice-sheet forcing. In contrast to the stepwise deterioration of planktonic foraminiferal preservation in the western deep Atlantic, a trend toward better preservation from the Pliocene to Pleistocene is observed in the deep Caribbean. This indicates a long-term increase in the contribution of UNADW to the Atlantic Ocean.

Pliocene-Pleistocene stack of globally distributed benthic stable oxygen isotope records

We present a 5.3-Myr stack (the ''LR04'' stack) of benthic d18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first benthic delta18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the delta18O stack to a simple ice model based on 21 June insolation at 65 N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly more variance in benthic delta18O than previously published stacks of the late Pleistocene as the result of higher resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of delta18O from 2.7-1.6 Ma is primarily a deep-water temperature signal and that the phase of d18O precession response changed suddenly at 1.6 Ma.