scholarly journals A unique late Eocene coleoid cephalopod Mississaepia from Mississippi, USA: New data on cuttlebone morphology, ultrastructure, chemical composition, and their phylogenetic implications

2012 ◽  
Author(s):  
Larisa Doguzhaeva
Keyword(s):  
Chemical Composition ◽  
Late Eocene ◽  
Phylogenetic Implications ◽  
Coleoid Cephalopod

A new genus of coleoid cephalopod from the Jackson Group (Late Eocene), Hinds County, Mississippi

2010 ◽  
Vol 292 (1-3) ◽  
pp. 53-63 ◽  
Author(s):  
Patricia G. Weaver ◽  
David T. Dockery III ◽  
Charles N. Ciampaglio
Keyword(s):  
New Genus ◽  
Late Eocene ◽  
Coleoid Cephalopod

scholarly journals Reconstruction of Tertiary palaeoenvironments using a combination of molecular and conventional palaeobiology

1992 ◽  
Vol 6 ◽  
pp. 134-134
Author(s):  
Jerry J. Hooker ◽  
Pim F. Van Bergen ◽  
Ros L. Singer ◽  
Margaret E. Collinson ◽  
Jan W. De Leeuw ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Fresh Water ◽  
Plant Macrofossils ◽  
Late Eocene ◽  
Marsh Vegetation ◽  
Pyrolysis Gas ◽  
Organic Input ◽  
Multidisciplinary Study ◽  
Early Oligocene

The Bembridge Limestone Formation (BLF), Late Eocene of Headon Hill, Isle of Wight, England, contains a diverse array of mammals (around 50 spp.) distributed through 10 levels. Its lower part (“lower fauna”) marks the appearance of a significant number of species, genera and one family unknown from earlier English Late Eocene strata. Towards the top of the BLF there is a reversion to faunas (“upper fauna”) more typical of the underlying Headon Hill Formation. This represents their last appearance in England. The succeeding Bembridge Marls Member fauna is similar to that in the lower part of the BLF. These changes are provincial in scale and may be climate induced (reflecting a slight warming followed by terminal Eocene cooling). Superimposed on these changes are smaller-scale more frequent fluctuations linked to alternating marl and black mud lithologies which may represent local habitat changes. In order to obtain overall understanding of the environment of deposition and taphonomic bias influencing these mammalian assemblages an integrated multidisciplinary study is being undertaken.Plant macrofossils are unfortunately extremely rare in this sequence. Those few which are present typify the fresh-water marsh vegetation widespread in the Late Eocene/Early Oligocene of England. In contrast mammalian faunas indicate more wooded conditions. Seeds like those of the modern free-floating fresh-water plant Stratiotes occur in three levels. However, they are poorly-preserved. The chemical composition of the seed coat as revealed by flash pyrolysis gas chromatography indicates a very simple polyphenol macromolecule probably resulting from transformations of more complex polyphenols in well-preserved Stratiotes seeds.Determinable palynomorphs are very rare and largely restricted to the part of the sequence which contains the “upper fauna”. They suggest a tranquil fresh-water depositional setting as do several molluscs and charophytes. Palynomorphs also include fungal remains, fern spores and a few tree pollen, the latter possibly from regional vegetation. However, the bulk of the palynological organic matter consists of brown structureless organic matter (SOM), resin-like particles and “platy kerogen”. In the lower beds, pale shelly muds with potamidids and corbiculids lack mammals and contain palynological organic matter dominated by resin-like particles and with abundant pyrite. These beds probably reflect brackish influence, the loss of which largely coincides with the reappearance of abundant mammals (“lower fauna”), occurrence of Stratiotes and of charophytes. Resin-like particles remain dominant in the palynological organic matter. “Platy kerogen” dominates three units including that containing the first occurrence of the “upper fauna”. Subsequently resin-like particles again dominate. Brown SOM is scattered throughout but is well represented in two units one of which contains “lower fauna” the other “upper fauna”.Variations in palynological organic matter are reflected in the chemical composition of residues studied. Results from five black muds show that samples which mainly contain resin-like particles are dominated by n-alkanes and n-alk-1-enes in their pyrolysates. However, there is no indication of known resin chemical signatures. This indicates that the organic matter in these residues is mainly derived from cuticles (cutan) and/or cell wall remains (algaenan) of fresh-water algae. Samples containing “platy kerogen” and brown SOM are dominated by aromatics and phenols in their pyrolysates indicating an origin from woody materials. Work in progress on stable isotope analyses of the residues may further clarify the nature of the organic input.

scholarly journals Comparative mitogenome analyses uncover mitogenome features and phylogenetic implications of the subfamily Cobitinae

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Peng Yu ◽  
Li Zhou ◽  
Wen-Tao Yang ◽  
Li-jun Miao ◽  
Zhi Li ◽  
...  
Keyword(s):  
Phylogenetic Analyses ◽  
Purifying Selection ◽  
Late Eocene ◽  
Protein Coding ◽  
Ancestral Species ◽  
Intergenic Spacers ◽  
Trna Secondary Structure ◽  
Phylogenetic Implications ◽  
Scientific Value ◽  
Mtdna Introgression

Abstract Background Loaches of Cobitinae, widely distributed in Eurasian continent, have high economic, ornamental and scientific value. However, the phylogeny of Cobitinae fishes within genera or family level remains complex and controversial. Up to now, about 60 Cobitinae mitogenomes had been deposited in GenBank, but their integrated characteristics were not elaborated. Results In this study, we sequenced and analyzed the complete mitogenomes of a female Cobits macrostigma. Then we conducted a comparative mitogenome analysis and revealed the conserved and unique characteristics of 58 Cobitinae mitogenomes, including C. macrostigma. Cobitinae mitogenomes display highly conserved tRNA secondary structure, overlaps and non-coding intergenic spacers. In addition, distinct base compositions were observed among different genus and significantly negative linear correlation between AT% and AT-skew were found among Cobitinae, genus Cobitis and Pangio mitogenomes, respectively. A specific 3 bp insertion (GCA) in the atp8-atp6 overlap was identified as a unique feature of loaches, compared to other Cypriniformes fish. Additionally, all protein coding genes underwent a strong purifying selection. Phylogenetic analysis strongly supported the paraphyly of Cobitis and polyphyly of Misgurnus. The strict molecular clock predicted that Cobitinae might have split into northern and southern lineages in the late Eocene (42.11 Ma), furthermore, mtDNA introgression might occur (14.40 Ma) between ancestral species of Cobitis and ancestral species of Misgurnus. Conclusions The current study represents the first comparative mitogenomic and phylogenetic analyses within Cobitinae and provides new insights into the mitogenome features and evolution of fishes belonging to the cobitinae family.

A calcaneus attributable to the primitive late eocene anthropoidProteopithecus sylviae: Phenetic affinities and phylogenetic implications

2013 ◽  
Vol 151 (3) ◽  
pp. 372-397 ◽  
Author(s):  
Justin T. Gladman ◽  
Doug M. Boyer ◽  
Elwyn L. Simons ◽  
Erik R. Seiffert
Keyword(s):  
Late Eocene ◽  
Phylogenetic Implications

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

On the Inhomogeneity of Chemical Composition over the Surface of 21 Per

1976 ◽  
Vol 32 ◽  
pp. 343-349
Author(s):  
Yu.V. Glagolevsky ◽  
K.I. Kozlova ◽  
V.S. Lebedev ◽  
N.S. Polosukhina
Keyword(s):  
Chemical Composition ◽  
Spectral Line ◽  
Variable Star ◽  
Radial Velocities ◽  
Crimean Astrophysical Observatory ◽  
Line Intensities ◽  
Magnetic Variable

SummaryThe magnetic variable star 21 Per has been studied from 4 and 8 Å/mm spectra obtained with the 2.6 - meter reflector of the Crimean Astrophysical Observatory. Spectral line intensities (Wλ) and radial velocities (Vr) have been measured.

Structural Studies on Mitotic Spindle Fibres

1978 ◽  
Vol 36 (3) ◽  
pp. 615-626
Author(s):  
J.R. Mcintosh
Keyword(s):  
Chemical Composition ◽  
Mitotic Spindle ◽  
Structural Studies ◽  
Mitotic Apparatus ◽  
Chemical Studies ◽  
Medical Interest ◽  
Spindle Fibres

The mitotic apparatus is a structure of obvious biological and medical interest, but it has proved to be a difficult cellular machine to understand. The chemical composition of the spindle is only slightly elucidated, largely because of the difficulties in preparing useful isolates of the structure. Chemical studies of the mitotic spindle have been reviewed elsewhere (Mcintosh, 1977), and will not be discussed further here. One would think that structural studies on the mitotic apparatus (MA) in situ would be straightforward, but even with this approach there is some disagreement in the results obtained with various methods and by different investigators. In this paper I will review briefly the approaches which have been used in structural studies of the MA, pointing out the strengths and problems of each approach. I will summarize the principal findings of the different methods, and identify what seem to be fruitful avenues for further work.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

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