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At least 451 records · Page 25Linked to original sources
PubMed2006

Description of Pintomyia (Pifanomyia) brazilorum sp. nov. a new fossil species from the Dominican Republic (Diptera: Psychodidae: Phlebotominae).

A sand fly fossil was found in amber; a vegetal resin, which allows all the external phlebotomine structures to be seen. The piece that contains the new species is 14 mm long x 8 mm wide x 3 mm high. All the structures from the head, thorax, and abdomen were examined under the microscope and measured with a calibrated micrometric eyepiece. The morphological aspects of the new species suggest its inclusion in the Pintomyia genus, Pifanomyia subgenus though it is not possible to include it in any of the series known for this subgenus. The presence of two atrophied spines on the gonostyles and gonocoxites without tufts of setae permit the exclusion of the new species from the other species of the subgenus Pifanomyia. The new species is named Pintomyia (Pifanomyia) brazilorum sp. nov.

Amber↗
PubMed2000

Overgrowth competition between clades: implications for interpretation of the fossil record and overgrowth indices.

Overgrowth interactions (2693 in total) were observed among three major groups (arguably clades) of bryozoans--cheilostomatids (57 species), ctenostomatids (3 species), and cyclostomatids (14 species). The bryozoans studied here occur in shallow water at high-temperate polar latitudes where they encrust hard substrata such as rock piles. The main study site was the intertidal and infralittoral zones of Kodiak Island, Alaska, but observations were also made in similar zones of South Georgia Island and the Falkland Islands in the South Atlantic Ocean. Cheilostomatids dominated the number of species, individuals, and interactions at all depths. Intraclade interactions formed 73.7% of the encounters for cheilostomatids, 1.6% for ctenostomatids, and 5.7% for cyclostomatids. The competitive ranking of the three clades was broadly ctenostomatids > cyclostomatids > cheilostomatids. Significantly, these results contradict all previous quantitative studies of bryozoan overgrowth, in which cheilostomatids are reported to overgrow cyclostomatids at a higher rate. From these studies and the literature, we calculated win indices to vary from 0 to 0.42 for living cyclostomatids, from 0.08 to 0.9 for living cheilostomatids, and from 0.25 to 0.75 for living ctenostomatids. The win indices of cyclostomatid and cheilostomatid clades show significantly more variation in living assemblages than in fossil assemblages. This disparity may be due to differential preservation (polar and subpolar assemblages last less than 4 years). The diversity was very high in terms of both species richness and interaction types (outcomes between competitor pairs). Comparison with the literature suggests the possibility that nearshore diversity of bryozoans may be bimodal (have two peaks) between high arctic and antarctic latitudes. Indices of success in overgrowth competition have been constructed in various ways. For cheilostomatids, the method of calculation had little influence on the ranking of representatives. In contrast, the apparent success of ctenostomatids and cyclostomatids varied hugely with how the index was calculated. This inconsistency is due to the use of very different strategies in overgrowth competition; among the two latter groups, many interactions involve tied outcomes.

Animals↗
PubMedDate not supplied

Protoascon missouriensis, a complex fossil microfungus revisited.

The Carboniferous microfungus Protoascon missouriensis has been interpreted variously as an ascomycete, chytridiomycete, zygomycete and oomycete. We offer a more complete interpretation based on a re-examination of the type material that suggests the fossil represents an (a)zygosporangium-suspensor complex of a zygomycete comparable to some modern members of the Mucorales.

Fossils↗
PubMed1999

Ultrastructural study of fossil human tooth tissue.

The preservation of fossil human soft tooth tissue from extinct populations which inhabited the northeast of Argentina (fourteenth and fifteenth centuries) is described. Studies were performed using both Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The preservation of the surface structure in Tomes fibrils and in odontoblastic processes was determined by SEM; whereas by TEM we could observe the dentin ducts occupied by acellular material, being the inner structure of the odontoblastic processes poorly preserved. It is suggested that such preservation is due to an "instantaneous phosphatization" occurring immediately after death as a result of the presence of calcium phosphate deposits.

Archaeology↗
PubMed2000

[Molecular genetic analysis for taxonomic determination of fossil skull fragments of Warendorf-Neuwarendorf].

The isolation and examination DNA segments from prehistoric and fossil bone samples has become one of the biggest challenges in anthropology within the past years. By using specially developed and/or adapted genetic methods, it is possible under laboratory conditions to amplify portions of DNA from bone remains in states of good preservation by the polymerase chain reaction (PCR). DNA sequence data can provide far more specific answers to palaeanthropological questions than one would expect solely by morphologic comparison. Here we introduce an alternative approach for the classification of total ancient DNA by means of Southern hybridisation techniques.

Anthropology, Physical↗
PubMed1992

A compendium of fossil marine animal families, 2nd edition.

A comprehensive listing of 4075 taxonomic families of marine animals known from the fossil record is presented. This listing covers invertebrates, vertebrates, and animal-like protists, gives time intervals of apparent origination and extinction, and provides literature sources for these data. The time intervals are mostly 81 internationally recognized stratigraphic stages; more than half of the data are resolved to one of 145 substage divisions, providing more highly resolved data for studies of taxic macroevolution. Families are classified by order, class, and phylum, reflecting current classifications in the published literature. This compendium is a new edition of the 1982 publication, correcting errors and presenting greater stratigraphic resolution and more current ideas about acceptable families and their classification.

Animals↗
PubMed1975

Studies of the fossil dinosaur bone in the scanning electron microscope.

A fossil dinosaur bone, 80 million years old, was subjected to investigation in the scanning microscope. The bone surfaces to be examined were prepared with appropritely modified methods used in the technique of replication in transmission electron microscopy. In the scanning microscope pictures of vascular canals were obtained. The walls of these canals were shown to be formed of collagen fibrils. Moreover, it was demonstrated that the internal surface of the canal wall is made up of bundles of collagen fibrils which run obliquely, corkscrewwise, and in the form of plexus to the long axis of tke canal; Besides, osteocytes of the dinosaur bone were isolated and pictures of their spatial structure together with characteristic points of departure of processes from the cell body were obtained.

Animals↗
PubMed2006

Conserved phenotypic variation patterns, evolution along lines of least resistance, and departure due to selection in fossil rodents.

Within a group of organisms, some morphologies are more readily generated than others due to internal developmental constraints. Such constraints can channel evolutionary changes into directions corresponding to the greatest intraspecific variation. Long-term evolutionary outputs, however, depend on the stability of these intraspecific patterns of variation over time and from the interplay between internal constraints and selective regimes. To address these questions, the relationship between the structure of phenotypic variance covariance matrices and direction of morphological evolution was investigated using teeth of fossil rodents. One lineage considered here leads to Stephanomys, a highly specialized genus characterized by a dental pattern supposedly favoring grass eating. Stephanomys evolved in the context of directional selection related to the climatic trend of global cooling causing an increasing proportion of grasslands in southwestern Europe. The initial divergence (up to approximately 6.5 mya) was channeled along the direction of greatest intraspecific variation, whereas after 6.5 mya, morphological evolution departed from the direction favored by internal constraints. This departure from the "lines of least resistance" was likely the consequence of an environmental degradation causing a selective gradient strong enough to overwhelm the constraints to phenotypic evolution. However, in a context of stabilizing selection, these constraints actually channel evolution, as exemplified by the lineage of Apodemus. This lineage retained a primitive diet and dental pattern over the last 10 myr. Limited morphological changes occurred nevertheless in accordance with the main patterns of intraspecific variation. The importance of these lines of least resistance directing long-term morphological evolution may explain parallel evolution of some dental patterns in murine evolution.

Animals↗
PubMed1989

[The course of the mandibular canal in fossils and forensic material].

Authors have studied 220 fossil and 44 postmortem mandible-halves by measurements at identical points and in transverse slices cut in the plane of the teeth P2-M3. Parameters relevant to the course of the mandibular canal are summarized. Data add to the knowledge concerning the anatomy and topography of the mandible.

Cadaver↗
PubMed1986

The assessment of fluctuating odontometric asymmetry from incomplete hominid fossil data.

Problems of small sample size and incompleteness of fossil data in the evaluation of metric asymmetry may be overcome by the application of cluster sampling techniques together with factorial analyses of variance. Degrees of fluctuating odontometric asymmetry are reported in Australopithecus, Homo erectus and Homo neanderthalensis. In all three populations mesiodistal dimensions were shown to be more asymmetric than buccolingual dimensions, with maxillary teeth exhibiting significantly greater degrees of asymmetry than mandibular teeth. Neanderthal teeth were significantly more metrically asymmetric than those of either Australopithecus or H. erectus, with population differences in asymmetry centered in the maxillary teeth.

Animals↗
PubMed1987

Paleoanthropological applications of amino acid racemization dating of fossil bones and teeth.

The general principals of the amino acid racemization based dating technique are discussed. The results obtained at Olduvai Gorge (Tanzania) and Zhoukoudian (China) are presented as an illustration of the paleoanthropological application of racemization dating. Tooth enamel provides the best material for the racemization dating of Middle to Lower Pleistocene deposits, although in some cases bones also yield reliable ages. The racemization method provides a means of dating teeth and bones which are too old for radiocarbon dating. Only small samples are required and processing procedures are straightforward. The technique is particularly useful in paleoanthropological studies since hominid fossils can be directly dated.

Amino Acids↗
PubMed1987

Microbial lipids betrayed by their fossils.

Novel families of microbial lipids have been betrayed by their molecular fossils. They comprise the very widespread and varied hopanoids, and 'orphan' lipids. Membrane reinforcement appears to be universally achieved by these polyterpenoids; a hypothetical phylogenetic tree comprises the above, some postulated intermediates, bacterial carotenoids, cycloartenol, and finally cholesterol.

Bacteria↗
PubMedDate not supplied

Interpretation of the results of investigating molecular fossils.

The difficulties and possible errors in interpreting the results of investigating molecular fossils within the scope of the problem of chemical evolution and origin of life on the earth are examined. These difficulties can be largely overcome on the basis of modeling processes of the transformation of organic matter under different geological conditions.

Amino Acids↗
PubMed1984

Metabolic pathways of the fossil dinosaur bones Part II. Vascular canal in the communication system.

Examination was made on the fossil dinosaur bone 80 million years old. Samples to be examined were prepared by specially elaborated methods. The vascular canal of the dinosaur bone was the object of study. The microscopic and ultrastructural images of the canal revealed three zones therein: proper, perivascular, and vascular. The zone proper was formed by the mineralized wall of the canal, the perivascular zone was a space between the proper and the vascular zone, and the vascular zone was made up of the canal contents identified with blood vessels. The perivascular zone contained collagen fibres; moreover, histochemical examinations revealed in it mucopolysaccharides and lipids. In the wall of the vascular canal (zone proper) the outlets of the bone canaliculi departing from the osteocyte lacunae were detected. The endings of these canaliculi were of two kinds: they were either of the same diameter as the rest of the canaliculus (more numerous) or assumed a widening funnel form as the canaliculi reached the vascular canal (less numerous). By analogy with modern bone appropriate functions may be ascribed to particular zones distinguished in the vascular canal and to the varied endings of the bone canaliculi in the system of conveyance of nutrient and conservative elements as well as metabolites.

Animals↗
PubMed1984

Metabolic pathways of the fossil dinosaur bones. Part III. Intermediary and other osteocytes in the system of metabolic pathways of dinosaur bone.

The fossil dinosaur bone material, 80 million years old was studied. Samples for analysis were prepared with specially elaborated methods. Images obtained in the light, transmission electron, and scanning electron microscopes revealed the spatial distribution of the osteocytes lying near and far from the vascular canal. Osteocytes of particular kind were found to be present in the immediate vicinity of the canal. The characteristic morphological structure and the localization of this osteocytes between the vascular canal and the osteocytes lying farther from the canal, as well as the mediation of this cell in the system of connections between those elements, served as a basis for the separation of this cells as the intermediary osteocyte. Among the osteocytes situated farther from the vascular canal, three kinds were distinguished: mono-, bi-, and multipolar, according to the kinds of processes and their distribution in relation to the mother cell body. By analogy with modern bone, in dinosaur bone specific functions may be ascribed to the distinguished types of osteocytes and to their differentiated processes in the conduction of nutrient and building elements and metabolites from the vascular canal to the intermediary osteocytes and, with their participation, to other osteocytes lying farther from the canal. This should naturally be analysed as the two-way tract.

Animals↗
PubMed1984

Metabolic pathways of the fossil dinosaur bones. Part IV. Modes of linkage between osteocytes and a variety of nexuses of osteocytes processes.

Examinations were carried out on the fossil dinosaur bones 80 million years old. Samples for examination were prepared with specially elaborated methods. The light, transmission electron, and sanning electron microscopic images showed the spatial distribution of osteocytes with the system of processes as well as by thin and short ones. The axial processes, retaining the same diameter along their entire course, usually connected the polar parts of the osteocytes which frequently lay considerable distance apart. Such connections were of two kinds. In one case the link was attained by catoplasmic continuity. In the other, the processes belonging to one osteocyte came into contact with definite spot of plasmalemma of another osteocyte by means of a terminal, club-shaped widening, the so called contact body. This spot looked like a hollow or a conical protuberance. In this type of contact there were always tiny apertures between the contacting elements. Moreover, three types of contact, especially between thin processes, were distinguished, i.e. "end to end", "side to side", and "end to side". It seems that direct connections achieved through cytoplasmic continuity are utilized in rapid exchange, which may be indicated by the thickness of processes and the lack of a membranous barrier. The remaining, indirect links (with participation of membranes) though varied in the type of contact seem to fulfil identical functions.

Animals↗