SEARCH · PubMed Health

Results for “FOSSILS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,261 records · Page 70Linked to original sources

PubMed2005

Paleontology. Shaking the earliest branches of anthropoid primate evolution.

Primates living today are believed to share a common ancestor that originated in either Africa or Asia. Fossil examples of such anthropoid ancestors have been found in both continents, so pushing back the origins to a single location has been controversial. In their Perspective, Jaeger and Marivaux discuss results reported in the same issue by Seiffert et al. that may put part of the controversy to rest. Seiffert et al. describe the earliest and most complete African anthropoid fossils from the Fayum desert region of Egypt. Cranial and dental fossils of two different small species were found, and their character, especially the features of the fossil teeth, suggests an ancient evolutionary history in Africa. At the same time, the phylogenetic analysis of Seiffert et al. is consistent with the view that African anthropoids immigrated from Asia at a very early date, probably before the late Paleocene (60 million years ago), possibly followed by later waves of immigration.

Africa↗

PubMed1999

Evolutionary and preservational constraints on origins of biologic groups: divergence times of eutherian mammals.

Some molecular clock estimates of divergence times of taxonomic groups undergoing evolutionary radiation are much older than the groups' first observed fossil record. Mathematical models of branching evolution are used to estimate the maximal rate of fossil preservation consistent with a postulated missing history, given the sum of species durations implied by early origins under a range of species origination and extinction rates. The plausibility of postulated divergence times depends on origination, extinction, and preservation rates estimated from the fossil record. For eutherian mammals, this approach suggests that it is unlikely that many modern orders arose much earlier than their oldest fossil records.

Animals↗

PubMed2000

Earliest Pleistocene hominid cranial remains from Dmanisi, Republic of Georgia: taxonomy, geological setting, and age.

Archaeological excavations at the site of Dmanisi in the Republic of Georgia have uncovered two partial early Pleistocene hominid crania. The new fossils consist of a relatively complete cranium and a second relatively complete calvaria from the same site and stratigraphic unit that yielded a hominid mandible in 1991. In contrast with the uncertain taxonomic affinity of the mandible, the new fossils are comparable in size and morphology with Homo ergaster from Koobi Fora, Kenya. Paleontological, archaeological, geochronological, and paleomagnetic data from Dmanisi all indicate an earliest Pleistocene age of about 1.7 million years ago, supporting correlation of the new specimens with the Koobi Fora fossils. The Dmanisi fossils, in contrast with Pleistocene hominids from Western Europe and Eastern Asia, show clear African affinity and may represent the species that first migrated out of Africa.

Africa↗

PubMed2005

Quality control of waste to incineration--waste composition analysis in Lidköping, Sweden.

In order to decrease environmental impacts in waste management the choice of treatment method must be based on the characteristics of the waste. Present sampling procedures do not provide statistically representative samples of solid waste and this provides difficulties in characterization. The objective of this study was to develop a procedure for waste component analysis and sampling of waste after collection and at plant level. A further objective was to characterize the waste delivered to an incineration plant for physical and chemical properties and to determine the amounts of delivered waste that could be classified as biofuels and fossil fuels. The proportions of recyclables and hazardous waste were also examined. Samples were taken randomly from waste trucks and divided by square implementation. Statistical analysis of the results showed that the number of sub-samples could be decreased with only a moderate increase in the confidence interval. This means that future waste composition analyses could be made more efficient and thereby less expensive. The analysis of the waste delivered to the Lidköping incineration plant (Central Sweden) showed that 66.4% of the household waste was composed of biofuels and 21.3% of non-renewable combustibles, of which 40.3% were recyclables. In addition, 11.6% of the household waste was non-combustible and 0.6% hazardous waste. The heat value for the biofuels was 18.0-19.7 MJ kg(-1) dry mass (DM) and for the fossil fuels 28.2-33.9 MJ kg(-1) DM. The industrial waste consisted of 35.9% biofuels, 62.0% fossil fuels, 1.6% non-combustible and 0.5% hazardous waste. The heat value was 19.5 MJ kg(-1) DM for the biofuels and 31.4 MJ kg(-1) DM for the fossil fuels.

Bioelectric Energy Sources↗

PubMed2006

State of energy consumption and CO2 emission in Bangladesh.

Carbon dioxide (CO2) is one of the most important gases in the atmosphere, and is necessary for sustaining life on Earth. It is also considered to be a major greenhouse gas contributing to global warming and climate change. In this article, energy consumption in Bangladesh is analyzed and estimates are made of CO2 emission from combustion of fossil fuel (coal, gas, petroleum products) for the period 1977 to 1995. International Panel for Climate Change guidelines for national greenhouse gas inventories were used in estimating CO2 emission. An analysis of energy data shows that the consumption of fossil fuels in Bangladesh is growing by more than 5% per year. The proportion of natural gas in total energy consumption is increasing, while that of petroleum products and coal is decreasing. The estimated total CO2 release from all primary fossil fuels used in Bangladesh amounted to 5072 Gigagram (Gg) in 1977, and 14 423 Gg in 1995. The total amounts of CO2 released from petroleum products, natural gas, and coal in the period 1977-1995 were 83 026 Gg (50% of CO2 emission), 72 541 Gg (44% of CO2 emission), and 9545 Gg (6% CO2 emission), respectively. A trend in CO2 emission with projections to 2070 is generated. In 2070, total estimated CO2 emission will be 293 260 Gg with a current growth rate of 6.34% y . CO2 emission from fossil fuels is increasing. Petroleum products contribute the majority of CO2 emission load, and although the use of natural gas is increasing rapidly, its contribution to CO2 emission is less than that of petroleum products. The use of coal as well as CO2 emission from coal is expected to gradually decrease.

Bangladesh↗

PubMedDate not supplied

Disparity, decimation and the Cambrian "explosion": comparison of early Cambrian and present faunal communities with emphasis on velvet worms (Onychophora).

The controversy about a Cambrian "explosion" of morphological disparity (followed by decimation), cladogenesis and fossilization is of central importance for the history of life. This paper revisits the controversy (with emphasis in onychophorans, which include emblematic organisms such as Hallucigenia), presents new data about the Chengjiang (Cambrian of China) faunal community and compares it and the Burgess Shale (Cambrian of Canada) with an ecologically similar but modern tropical marine site where onychophorans are absent, and with a modern neotropical terrestrial onychophoran community. Biovolume was estimated from material collected in Costa Rica and morphometric measurements were made on enlarged images of fossils. Cambrian tropical mudflats were characterized by the adaptive radiation of two contrasting groups: the vagile arthropods and the sessile poriferans. Arthropods were later replaced as the dominant benthic taxon by polychaetes. Vagility and the exoskeleton may explain the success of arthropods from the Cambrian to the modern marine and terrestrial communities, both in population and biovolume. Food ecological displacement was apparent in the B. Shale, but not in Chengjiang or the terrestrial community. When only hard parts were preserved, marine and terrestrial fossil deposits of tropical origin are even less representative than deposits produced by temperate taxa, Chengjiang being an exception. Nutrient limitations might explain why deposit feeding is less important in terrestrial onychophoran communities, where carnivory, scavenging and omnivory (associated with high motility and life over the substrate) became more important. Fossil morphometry supports the interpretation of "lobopod animals" as onychophorans, whose abundance in Chengjiang was equal to their abundance in modern communities. The extinction of marine onychophorans may reflect domination of the infaunal habitat by polychaetes. We conclude that (1) a mature ecological community structure was generalized during the Cambrian, and even biodiversity and equitability indices were surprisingly close to modern values; (2) the morphological diversity and geographic distribution of onychophorans indicate a significant pre-Cambrian evolutionary history which does not support the "explosion" hypothesis; (3) disparity among phyla was not as important as the explosion-decimation model predicts, but in the case of onychophorans, disparity within the phylum was greater than it is today and its reduction may have been associated with migration into the sediment when large predators evolved.

Animals↗

PubMed1975

Distal humerus in hominoid evolution.

Multivariate analysis of 16 measurements of the distal humerus in samples of hominoids, cercopithecoids, Tertiary hominoid fossils, and early hominids shows the following results: (1) there is a substantial and functionally interpretable difference between the distal humerus of cercopithecoids and hominoids (excluding Hylobates); (2) the Tertiary hominoid fossils resemble the cercopithecoids more than the hominoids although they are in some ways intermediate; (3) the hominid fossil from Kanapoi resembles Homo sapiens very closely; (4) the Kromdraai humerus is intermediate in shape between Pan and other hominoids; and (5) the large fossil hominid from East Rudolf (KNM-ER 739) is unique among the hominoids.

Animals↗

PubMed2002

Evolutionary significance of cranial variation in Asian Homo erectus.

Homo erectus inhabited a wide geographic area of Asia, ranging from 40 degrees north latitude in China to 8 degrees south latitude in island Southeast Asia. Yet variation within Asian H. erectus and its relation to ecological and temporal parameters have been little studied. I synthesize the revised radiometric chronologies for hominid sites in Asia and their relation to new oxygen isotope curves (proxies for climatic fluctuations and landbridge connections). These data suggest substantial opportunities in the later Pleistocene for both regional isolation and gene flow between hominids in mainland and Southeast Asia. They also suggest that the most northerly located Chinese sites (Zhoukoudian and Nanjing) may have been occupied during sequential, interglacial periods. Probably reflecting these periods of isolation, nonmetric features and principal components analysis (PCA) of calvarial shape suggest regional differentiation between northern Asian and Southeast Asian H. erectus. The most recent Southeast Asian fossils (e.g., Ngandong) conform to the Southeast Asian pattern. Except perhaps in brain size, there is no evidence that the temporally intermediate Chinese fossils are intermediate in morphology between older and younger Indonesian fossils. In fact, northern Chinese calvaria are easier to exclude from the larger Asian H. erectus hypodigm than are the Ngandong fossils. The Chinese specimens differ from the others based on their narrower occipitals and frontals for their cranial size. The Chinese sample from Zhoukoudian alone is thus not a good proxy for the morphology and variation seen within Asian H. erectus. Both the Chinese and late Indonesian samples exhibit less variation than does the early Indonesian sample; this along with their shared morphological bauplan suggests a common origin and no more than subspecific differentiation. This shared morphology, despite regional differences, was likely maintained by the increasing intensity of multiple glaciations (and longer-lasting land bridge connections) between mainland and island Southeast Asia during the last million years.

Animals↗

PubMed1986

The first rib of hominoids.

Homo sapiens is unique among extant hominoids in displaying a univertebral articular pattern for the first rib; that is, the head of the first rib articulates only with the body of the first thoracic vertebra. All other hominoids, indeed virtually all other mammals, display a bivertebral pattern; that is, the head of the first rib articulates with the bodies of both the seventh cervical and the first thoracic vertebrae, as well as the intervening disk. Two fossil hominid partial first ribs, A.L. 288-lax and A.L. 333-118, show that the univertebral pattern was fully established in the hominid lineage by the appearance of Australopithecus afarensis. Four hypotheses, based in functional anatomy, can be postulated for the evolution of the univertebral pattern: (1), it increases the volume (via increased length) of the neck, which could, in turn, compensate for the functional loss of the laryngeal sac systems in hominid vocalization; (2), it is a consequence of the more barrel-shaped thorax in hominids; (3), it is a consequence of functional modifications in the hominid shoulder girdle; and/or (4), it is a consequence of modifications in hominid first rib motion while breathing in an upright stance. Fossil evidence supports all but the first hypothesis, and most strongly supports the third. However, evidence for the first hypothesis does suggest that the evolution of descent of the upper respiratory system in the hominid lineage may have been permitted by the presence of the univertebral pattern, while the reverse is probably not true. Furthermore, fossil evidence for the third hypothesis shows that, by the appearance of A. afarensis, the hominid upper limb had been freed from locomotor constraints, which concomitantly confirms full adaptation to upright posture. Thus, because of their potential relationship with upright posture, the two remaining hypotheses (i.e., "thoracic shape" and "first rib movement during breathing") also have support from the fossil evidence.

Animals↗

PubMed1995

New characters for the functional interpretation of primate scapulae and proximal humeri.

The study of muscle function in nonhuman primates through the technique of electromyography (EMG) has facilitated the identification of specific functional roles for muscles in particular behaviors. This has led to a more complete understanding of the biomechanics of certain regions of the musculoskeletal system, and should facilitate our ability to identify morphological features useful in the functional interpretation of fossil material. The current paper represents one such investigation of a new set of morphometric characters of the scapula and proximal humerus suggested by EMG analyses of shoulder muscle function. A set of new metric variables were examined on the scapulae and proximal humeri of 25 species of extant anthropoid primates, as well as on casts of scapulae and humeri of three fossil primate taxa. The variables are primarily related to the line of action and attachments of the rotator cuff muscles. The position of the scapular spine, the degree of lateral expansion of the subscapular fossa, the size and shape of the subscapularis insertion facet on the lesser tubercle, and the orientation of the infraspinatus insertion facet on the greater tubercle all appear to successfully sort the extant taxa into locomotor groups. Their appearance on the fossil specimens generally supports previous functional interpretations of each taxon's locomotor abilities based on a variety of other characters, suggesting that these traits are equally applicable to fossil material.

Animals↗

PubMed2001

Virtual anthropology (VA): a call for glasnost in paleoanthropology.

The adventurous scientist, with a hat protecting him from the fierce sun as he travels from one remote place to another, hunting for fossils of our ancestors, has been a part of the romantic imagination associated with anthropological research in the 20th Century. This picture of the paleoanthropologist still retains a grain of truth. Indeed, many new sites were discovered under troublesome conditions in the recent past and have added substantial information about our origins. But on another front, probably less sensational but no less important, are contributions stemming from the analysis of the already discovered fossils. With the latter, a rapid evolution in anthropologic research took place concurrently with advances in computer technology. After ambitious activities by a handful of researchers in some specialized laboratories, a methodologic inventory evolved to extract critical information about fossilized specimens, most of it preserved in the largely inaccessible interior as unrevealed anatomic structures. Many methodologies have become established but, for various reasons, access to both the actual and the digitized fossils is still limited. It is time for more transparency, for a glasnost in paleoanthropology. Herein are presented some answers to the question of how a high-tech approach to anthropology can be integrated into a predominantly conservative field of research, and what are the main challenges for development in the future.

Animals↗

PubMed2002

Bone microstructure and developmental plasticity in birds and other dinosaurs.

Patterns of bone microstructure have frequently been used to deduce dynamics and processes of growth in extant and fossil tetrapods. Often, the various types of primary bone tissue have been associated with different bone deposition rates and more recently such deductions have extended to patterns observed in dinosaur bone microstructure. These previous studies are challenged by the findings of the current research, which integrates an experimental neontological approach and a paleontological comparison. We use tetracycline labeling and morphometry to study the variability of bone deposition rates in Japanese quail (Coturnix japonica) growing under different experimental conditions. We compare resulting patterns in bone microstructure with those found in fossil birds and other dinosaurs. We found that a single type of primary bone varies significantly in rates of growth in response to environmental conditions. Ranging between 10-50 microm per day, rates of growth overlap with the full range of bone deposition rates that were previously associated with different patterns of bone histology. Bone formation rate was significantly affected by environmental/experimental conditions, skeletal element, and age. In the quail, the experimental conditions did not result in formation of lines of arrested growth (LAGs). Because of the observed variation of bone deposition rates in response to variation in environmental conditions, we conclude that bone deposition rates measured in extant birds cannot simply be extrapolated to their fossil relatives. Additionally, we observe the variable incidence of LAGs and annuli among several dinosaur species, including fossil birds, extant sauropsids, as well as nonmammalian synapsids, and some extant mammals. This suggests that the ancestral condition of the response of bone to environmental conditions was variable. We propose that such developmental plasticity in modern birds may be reduced in association with the shortened developmental time during the later evolution of the ornithurine birds.

Animals↗

PubMed2006

Identifying the morphological signatures of hybridization in primate and human evolution.

Recent studies point to contact and possible admixture among contemporaneous hominin species during the Plio-Pleistocene. However, detection of hybridization in fossils-and especially fossil hominins-is contentious, and it is hindered in large part by our lack of understanding about how morphological hybridity is manifested in the primate skeleton. Here, we report on a study of known-pedigree, purebred yellow and olive baboons (n = 112) and their hybrids (n = 57), derived from the baboon colony of the Southwest Foundation for Biomedical Research. The hybrids were analyzed in two different groups: (1) F1 = olive x yellow first-generation hybrids; (2) B1 = olive x F1 backcross hybrids. Thirty-nine metric variables were tested for heterosis and dysgenesis. Nonmetric data were also collected from the crania. Results show that these primate hybrids are somewhat heterotic relative to their parental populations, are highly variable, and display novel phenotypes. These effects are most evident in the dentition and probably indicate the mixing of two separately coadapted genomes and the breakdown in the coordination of early development, despite the fact that these populations diverged fairly recently. Similar variation is also observed in museum samples drawn from natural hybrid zones. The results offer a strategy for detecting hybrid zones in the fossil record; implications for interpreting the hominin fossil record are discussed.

Analysis of Variance↗

PubMed2000

Leaves of Berberidaceae (Berberis and Mahonia) from Oligocene sediments, near Tepexi de Rodríguez, Puebla.

From the Oligocene Los Ahuehuetes locality, near Tepexi de Rodríguez, Puebla, Mexico, five new plant species are described based on their leaf architecture. The presence of brochidodromous or acrodromous venation, and secondary veins forming angular (versus rounded) arcs, are well defined characters in the fossil material that relate it to Berberidaceae. Comparison with the leaves and leaflets of extant and fossil plants allow the recognition of one Mahonia and four Berberis new species. The lack of detailed information on leaf architecture in Berberidaceae limits the evaluation of the taxonomic relationships that can be suggested between fossil and extant plants. However, from a biogeographic point of view the presence of these new fossil plants supports the hypothesis of a North American origin of the Orientalis Groups of Mahonia, to which a lineage of Berberis may be added. Furthermore, two of the new species suggest the dispersal, some time during the Tertiary, of a lineage that today forms the Australis Group of Berberis from low latitude North America to South America. The movement of the Chortis Block is proposed as an alternative to explain the dispersal of a growing list of plants from north to south in the Americas. Only through future geological and palaeobotanical work can this hypothesis be corroborated.

Journal Article↗

PubMed2001

An Early Permian plant assemblage from the Taiyuan Formation of northern China with compression/impression and permineralized preservation.

A small but diverse fossil flora is described from the Early Permian Taiyuan Formation occurring at the Yangshuling mine in Pingquan district of Hebei Province, northern China. Fossils occur as compression/impressions within mudrocks and fine-grained sandstones and also as carbonate permineralizations within volcaniclastic tuffs. All are fragmentary and contain lycopsids, sphenopsids, ferns and seed plants, and include several new species. In the compression assemblage sphenopsid and pteridosperm foliage accounts for the majority of the fossils recognised with only a few other kinds of plant organs present. In contrast, the permineralized assemblage is dominated by cordaitaleans with a composition similar to that occurring in coal-ball assemblages elsewhere in the Taiyuan Formation. From the taxonomic synthesis presented it is apparent that the Yangshuling permineralized assemblage contains many of the plant taxa diagnostic of the northern realm of the Early Permian Cathaysian flora, and preserves a representative sample of the wetland coal-swamp vegetation of this time. The permineralized assemblage at Yangshuling represents the first example of anatomically preserved plants from volcaniclastic lithologies from the Palaeozoic of China, raising the possibility of similarly preserved plant-fossil assemblages elsewhere in the Cathaysian realm.

Journal Article↗

PubMedDate not supplied

Comparative life-cycle assessments for biomass-to-ethanol production from different regional feedstocks.

This study compares life-cycle (cradle-to-gate) energy consumption and environmental impacts for producing ethanol via fermentation-based processes starting with two lignocellulosic feedstocks: virgin timber resources or recycled newsprint from an urban area. The life-cycle assessment in this study employed a novel combination of computer-aided tools. These tools include fermentation process simulation coupled with an impact assessment software tool for the manufacturing process life-cycle stage impacts. The process simulation file was provided by the National Renewable Energy Laboratory (NREL) and was modified slightly to accommodate these different feedstocks. For the premanufacturing process life-cycle stage impacts, such as the fuels and process chemicals used, transportation, and some preparatory steps (wood chipping, etc.), a life-cycle inventory database (the Boustead Model) coupled with an impact assessment software tool were used (the Environmental Fate and Risk Assessment Tool). The Newsprint process has a slightly lower overall composite environmental index (created from eight impact categories) compared to the Timber process. However, the Timber process consumes less electricity, produces fewer emissions in total, and has less of a human health impact. The amount of life-cycle fossil energy required to produce ethanol is 14% of the energy content of the product, making the overall efficiency 86%. Process improvement strategies were evaluated for both feedstock processes, including recycle of reactor vent air and heat integration. Heat integration has the greatest potential to reduce fossil-derived energy consumption, to an extent that fossil-derived energy over the life cycle is actually saved per unit of ethanol produced. These energy efficiency values are superior to those observed in conventional fossil-based transportation fuels.

Biotechnology↗

PubMed2005

Contribution of biomass burning to atmospheric polycyclic aromatic hydrocarbons at three European background sites.

Radiocarbon analysis of atmospheric polycyclic aromatic hydrocarbons (PAHs) from three background areas in Sweden, Croatia, and Greece was performed to apportion their origin between fossil and biomass combustion. Diagnostic ratios of PAHs implied that wood and coal combustion was relatively more important in the northern European site, while combustion of fossil fuels was the dominant source of PAHs to the two central-southern European background sites. The radiocarbon content (delta14C) of atmospheric PAHs in Sweden ranged between -388 per thousand and -381 per thousand, while more depleted values were observed for Greece (-914 per thousand) and Croatia (-888 per thousand). Using a 14C isotopic mass balance model it was calculated that biomass burning contributes nearly 10% of the total PAH burden in the studied southern European atmosphere with fossil fuel combustion making up the 90% balance. In contrast, biomass burning contributes about 50% of total PAHs in the atmosphere at the Swedish site. Our results suggest that the relative contributions of biomass burning and fossil fuels to atmospheric PAHs may differ considerably between countries, and therefore, different national control strategies might be needed if a further reduction of these pollutants is to be achieved on a continental-global scale.

Air Pollutants↗

PubMed2005

Molecular characteristics of urban organic aerosols from Nanjing: a case study of A mega-city in China.

Over 90 organic species have been determined in fine aerosols (PM2.5) collected during the summer and winter in Nanjing, a typical mega-city in China, using gas chromatography-mass spectrometry. The organic compounds detected were apportioned to four emission sources (i.e., plant emission, fossil fuel combustion, biomass burning, and soil resuspension) and secondary oxidation products. The most abundant classes of compounds are fatty acids, followed by sugars, dicarboxylic acids excluding oxalic and malonic acids, and n-alkanes, while alcohols, polyols/polyacids and lignin/sterols are less abundant. Total amounts of the seven classes of compounds were on average 938 ng m(-3) in the summer and 1301 ng m(-3) in the winter, respectively, contributing 0.26-1.96% of particle mass (PM2.5). In the summer, n-alkanes were heavily enhanced by vegetation emissions with a maximum carbon number (Cmax) at C29, whereas they were dominated by emissions from fossil fuels combustion with a Cmax at C22/ C23 in the winter. Concentrations of unsaturated fatty acids were lower in the summer than in the winter, being consistent with enhanced photooxidation of unsaturated fatty acids in the summer. Concentrations of dicarboxylic acids for the summer aerosols were much higher in the daytime than in the nighttime, indicating increased photochemical production in the daytime. In the summer, plant emissions were the most significant source of organic aerosols, contributing more than 33% of total compound mass (TCM), followed by fossil fuel combustion or secondary oxidation. In contrast, fossil fuel combustion was the dominant source of winter organic aerosols, contributing more than 51% of TCM, followed by plant emissions and secondary oxidation products. The quantitative results on sugars and lignin pyrolysis products further suggested that biomass burning and soil resuspension are also significant sources of urban organic aerosols.

Aerosols↗