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At least 433 records · Page 24Linked to original sources
PubMed1998

Cope's rule and the dynamics of body mass evolution in North American fossil mammals.

Body mass estimates for 1534 North American fossil mammal species show that new species are on average 9.1% larger than older species in the same genera. This within-lineage effect is not a sampling bias. It persists throughout the Cenozoic, accounting for the gradual overall increase in average mass (Cope's rule). The effect is stronger for larger mammals, being near zero for small mammals. This variation partially explains the unwavering lower size limit and the gradually expanding mid-sized gap, but not the sudden large increase in the upper size limit, at the Cretaceous-Tertiary boundary.

Animals↗
PubMed1999

The future of the fossil record.

The fossil record provides a powerful basis for analyzing the controlling factors and impact of biological evolution over a wide range of temporal and spatial scales and in the context of an evolving Earth. An increasingly interdisciplinary paleontology has begun to formulate the next generation of questions, drawing on a wealth of new data, and on methodological advances ranging from high-resolution geochronology to simulation of morphological evolution. Key issues related to evolutionary biology include the biotic and physical factors that govern biodiversity dynamics, the developmental and ecological basis for the nonrandom introduction of evolutionary innovations in time and space, rules of biotic response to environmental perturbations, and the dynamic feedbacks between life and the Earth's surface processes. The sensitivity of evolutionary processes to rates, magnitudes, and spatial scales of change in the physical and biotic environment will be important in all these areas.

Animals↗
PubMed2000

Society of Vertebrate Paleontology. Fossils come to life in Mexico.

New insights into ancient life came by land and sea at the 60th annual meeting of the Society of Vertebrate Paleontology, held here from 25 to 28 October. Stunningly preserved fossils from Mongolia gave contrasting views of dinosaur family life, while biomechanical models clocked the swimming speed of cruising ichthyosaurs.

Animals↗
PubMed1988

Genetic and fossil evidence for the origin of modern humans.

The origin of living Homo sapiens has once again been the subject of much debate. Genetic data on present human population relationships and data from the Pleistocene fossil hominid record are used to compare two contrasting models for the origin of modern humans. Both genetics and paleontology support a recent African origin for modern humans rather than a long period of multiregional evolution accompanied by gene flow.

Africa↗
PubMed1977

Beef production options and requirements for fossil fuel.

A large percentage of the feed resources used in beef production cannot be used by man or most other animals. These noncompetitive feeds could be used in different ways to increase beef production, but fossil fuel consumption by the beef industry would not be greatly reduced.

Animal Feed↗
PubMed1995

Paleomagnetic age for hominid fossils at Atapuerca archaeological site, Spain.

A paleomagnetic investigation at the Gran Dolina site excavation (Atapuerca, Spain) shows that the sediments containing the recently discovered human occupation were deposited more than 780,000 years ago, near the time of the Matuyama-Brunhes boundary. Forty-one oriented samples were obtained from 22 sites along an 18-meter section of the Gran Dolina karst filling. The lower 16 sites displayed reversed-polarity magnetizations whereas the upper six sites were normal. The reversal spans the hominid finds at stratigraphic level TD6 (the Aurora stratum), and these hominid fossils are therefore the oldest in southern Europe.

Animals↗
PubMed1994

Fossil evidence for early hominid tool use.

Although several Plio-Pleistocene hominids are found in association with stone and bone tools, it has been generally assumed that at any one time the hominid with the largest brain was the toolmaker. Fossils recovered over the last decade suggest that early hominids subsequent to 2.5 million years ago all might have used tools and occupied "cultural" niches. A test for humanlike precision grasping (the enhanced ability to manipulate tools) is proposed and applied to australopithecines and early Homo. The results indicate that tools were likely to have been used by all early hominids at around 2.0 million years ago. The earliest australopithecines, which predate the appearance of stone tools in the archaeological record, do not show signs of advanced precision grasping.

Animals↗
PubMed2004

Reduction of brain and sense organs in the fossil insular bovid Myotragus.

Our study of the fossil rupicaprine bovid Myotragus [Bate, 1909] from the Mediterranean island Majorca (Spain) provides evidence that this animal underwent significant changes (reduction) in the relative size of brain and sense organs after geographic isolation at the end of the Messinian Salinity Crisis (Miocene-Pliocene boundary, 5.2 Mya). The changes in the central nervous system of Myotragus parallel the pattern reported for domesticated animals, in which decrease in relative brain size is accompanied by a decrease in the relative size of their sense organs. We interpret the important size reduction of brain and sense organs in Myotragus as an adaptive strategy for more efficient energy use under the special environmental conditions of the insular ecosystem, characterized by absence of predation and limitation of trophic resources.

Animals↗
PubMedDate not supplied

New fossil platyrrhine from Argentina.

A new fossil primate was found in the Pinturas Formation, south-western Patagonia, at the type locality of the rare Soriacebus ameghinorum. It is a mandibular fragment with two molars that strongly resemble those of S. ameghinorum in their high and closed trigonid, distal expansion of the talonid, small hypoconulid, buccal expansion of the enamel and similar cusp development. But the type of S. ameghinorum differs by having mesiodistally longer trigonids, long premetacristids and more oblique distal trigonid walls, with the metaconid more lingually placed and the postmetacristid distolingually oriented and with the talonid being buccolingually smaller than the trigonid with a more restricted basin. M2 is slightly smaller than in the new specimen, and the buccal enamel is less flared. Although it is difficult to determine if this new specimen represents an individual variation of S. ameghinorum or a new species of Soriacebus, its morphology appears to be less derived than that of the type mandible, and it is, therefore, of systematic significance.

Animals↗
PubMed2006

Malagasy primate origins: phylogenies, fossils, and biogeographic reconstructions.

The geographic origin of Malagasy primates is a rich source of debate, providing a useful context for understanding effects of differing phylogenetic interpretations upon area of origin reconstructions. This study has evaluated the biogeographic implications of competing primate phylogenies in order to reconstruct the area of origin of Malagasy strepsirhines. The robusticity of biogeographic inference is examined based on sensitivity to tree topology. The results demonstrate extreme vulnerability to both out-group choice and internal tree topology, suggesting caution for area of origin interpretations from phylogenies that exclude fossil taxa. Moreover, even a single taxon can have a powerful effect upon biogeographic interpretations. Perhaps not surprisingly, it is only with greater phylogenetic resolution that a clearer understanding of the biogeographic origins of Malagasy primates will emerge.

Animals↗
PubMed1996

Ontogeny of the knee joint in humans, great apes and fossil hominids: pelvi-femoral relationships during postnatal growth in humans.

Results of a study of the femoral bicondylar angle in adult and juvenile humans and great apes are presented. These results raise the question of whether or not the measurement reference of this angle is valid. This is because humans and great apes have a very different growth process of the distal epiphyseal suture of the femur during the period between birth and adulthood. The approximately 3 million years old juvenile femoral diaphyses attributed to Australopithecus afarensis (AL 333-110 and AL 333-111) were also studied. These specimens show an insertion of the diaphysis into the epiphysis of the simplified type typical of modern humans. This region is more convoluted in nonhuman anthropoids. Pelvifemoral interrelations are investigated through both longitudinal and cross-sectional radiographic studies of 23 human children. Growth changes in bicondylar and collo-diaphyseal angles, total femoral and femoral neck lengths, and interacetabular distance are correlated with age and to each other. These results are used to demonstrate the distinctive features of the Australopithecus afarensis fossil, AL 288-1.

Adult↗
PubMed2006

In vivo cranial suture function and suture morphology in the extant fish Polypterus: implications for inferring skull function in living and fossil fish.

This study describes the mechanical role that cranial sutures play in fish during feeding. The long-term goal of our work is to establish relationships between suture form and function, so that functional inferences can be made from suture morphology in fossil taxa. To this end, strain gauges were surgically implanted across selected sutures in the skull roof of four individuals of Polypterus endlicherii. After surgery, bone and suture strains during feeding were recorded along with high-speed video of the feeding events. Each trial was designated as a suction feeding or biting on prey trial, and neurocranial elevation, hyoid position and gape were quantified to aid in interpreting the strain data. The strains due to suction feeding are different from those observed during biting. Suction feeding results in a fairly stereotyped strain pattern, with the interfrontal and frontoparietal sutures experiencing tension, while the interparietal suture is compressed. Biting causes much more variable strain patterns. However, both suction and biting result in compression in the back of the skull, and tension between the frontals. Peak strains, and the time at which they occur in the feeding cycle, were compared between suction and biting. In general, peak suture strains are higher during suction than during biting, but not all of these differences are significant. Peak suture and bone strains occur at or near maximum gape during both suction and biting, suggesting that these strains are caused by muscle contraction involved in mouth opening and closing. Micro-computed tomography (microCT) scans of the experimental specimens indicate that the interfrontal and frontoparietal sutures, typically loaded in tension, are less interdigitated in cross section than the interparietal suture, which experiences compression. This is consistent with published correlations of suture form and function in mammals, where interdigitated sutures indicate compression and lack of interdigitation is associated with tension.

Animals↗
PubMed1978

Potentially carcinogenic species emitted to the atmosphere by fossil-fueled power plants.

The identities and physicochemical characteristics of potentially carcinogenic species emitted to the atmosphere by fossil-fueled power plants are presented and discussed. It is pointed out that many so-called carcinogens are preferentially concentrated on the surface of respirable fly ash particles thus enabling them to come into intimate contact with lung tissues when inhaled. Relatively little information is available about the identities of particulate polycyclic organic compounds whose emission from coal fired power plants may well be substantially greater than hitherto supposed. The importance of chemical changes, which several species may undergo following emission (but prior to inhalation) in determining their potential carcinogenic impact, is stressed.

Air Pollutants↗
PubMed1993

Bacterial and human cell mutagenicity study of some C18H10 cyclopenta-fused polycyclic aromatic hydrocarbons associated with fossil fuels combustion.

A number of isomeric C18H10 polycyclic aromatic hydrocarbons (PAHs), thought to be primarily cyclopenta-fused PAHs, are produced during the combustion and pyrolysis of fossil fuels. To determine the importance of their contributions to the total mutagenic activity of combustion and pyrolysis samples in which they are found, we characterized reference quantities of four C18H10 CP-PAHs: benzo[ghi]fluoranthene (BF), cyclopenta[cd]pyrene (CPP), cyclopent[hi]acephenanthrylene (CPAP), and cyclopent[hi]aceanthrylene (CPAA). Synthesis of CPAA and CPAP is described. The availability of reference samples of these isomers also proved to be an essential aid in the identification of the C18H10 species often found in combustion and pyrolysis samples. Chemical analysis of selected combustion and pyrolysis samples showed that CPP was generally the most abundant C18H10 isomer, followed by CPAP and BF. CPAA was detected only in pyrolysis products from pure PAHs. We tested the four C18H10 PAHs for mutagenicity in a forward mutation assay using S. typhimurium. CPP, BF, and CPAA were roughly twice as mutagenic as benzo[a]pyrene (BaP), whereas CPAP was only slightly active. These PAHs were also tested for mutagenic activity in human cells. In this assay, CPP and CPAA were strongly mutagenic but less active than BaP, whereas CPAP and BF were inactive at the dose levels tested. Also, the bacterial and human cell mutagenicity of CPAA and CPAP were compared with the mutagenicity of their monocyclopenta-fused analogs, aceanthrylene and acephenanthyrlene. Although the mutagenicities of CPAP and acephenanthrylene are similar, the mutagenic activity of CPAA is an order of magnitude greater than that of aceanthyrlene.

Cell Line↗
PubMed1995

Fossil fuel biodegradation: laboratory studies.

Biodegradation of the polycyclic aromatic hydrocarbons of creosote by undefined bacterial cultures was shown to be accompanied by the accumulation of neutral and acidic oxidation products. Formation of a number of identified neutral products is accounted for by demonstration of anomalous actions of an arene dioxygenase on the benzylic methylene and methylene carbons of napthenoaromatic hydrocarbons. Both neutral and acidic water-soluble fractions are also formed when various mixed bacterial cultures degrade weathered crude oil. While constituents of these fractions are not yet identified, the neutral materials have been shown to be toxic to developing embryos of invertebrates. These observations are discussed in relation to chemical and toxicological assessments of biodegradation of the complex chemical mixtures of fossil fuels.

Biodegradation, Environmental↗
PubMed2006

In situ infrared microspectroscopy of approximately 850 million-year-old prokaryotic fossils.

In situ infrared (IR) and Raman microspectroscopy have been conducted on Neoproterozoic, organic-walled microfossils (prokaryotic fossils) in doubly polished, petrographic thin sections in order to detect their spectral signatures. The microfossils are very well preserved and occur in black chert from the approximately 850 million-year-old Bitter Springs Formation, Northern Territory, Australia. Raman microspectroscopy on two species of microfossils, one a filament and the other a coccoid, shows disordered peaks (D peak, 1340 cm(-1)) and graphite peaks (G peak, 1600 cm(-1)), indicating that they consist of disordered carbonaceous materials. IR micro-mapping results of the filament reveal that the distributions of peak heights at 2920 cm(-1) (aliphatic CH(2)), 1585 cm(-1) (aromatic C-C), and 1370 cm(-1) (aliphatic CH(3)) match the shape of the filamentous microfossil. These results suggest that IR microspectroscopy can be used for in situ characterization of organic polar signatures that morphologically indicate microfossils embedded in chert by using doubly-polished rock (petrographic) thin section samples. Further, these methods can be applied to controversial microfossil-like structures to test their biogenic nature.

Fossils↗
PubMed2006

Dinosaur fossils predict body temperatures.

Perhaps the greatest mystery surrounding dinosaurs concerns whether they were endotherms, ectotherms, or some unique intermediate form. Here we present a model that yields estimates of dinosaur body temperature based on ontogenetic growth trajectories obtained from fossil bones. The model predicts that dinosaur body temperatures increased with body mass from approximately 25 degrees C at 12 kg to approximately 41 degrees C at 13,000 kg. The model also successfully predicts observed increases in body temperature with body mass for extant crocodiles. These results provide direct evidence that dinosaurs were reptiles that exhibited inertial homeothermy.

Alligators and Crocodiles↗