Exceptional preservation of organic matrix and shell microstructure in a Late Cretaceous Pinna fossil revealed by photoemission electron spectromicroscopy

Geology ◽  
2018 ◽  
Vol 46 (8) ◽  
pp. 711-714 ◽  
Author(s):  
Corinne E. Myers ◽  
Kristin D. Bergmann ◽  
Chang-Yu Sun ◽  
Nicholas Boekelheide ◽  
Andrew H. Knoll ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Organic Matrix ◽  
Shell Microstructure ◽  
Exceptional Preservation ◽  
Photoemission Electron

Toward a chronology of Haliotis fulgens, with a review of abalone shell microstructure

1995 ◽  
Vol 46 (3) ◽  
pp. 607 ◽  
Author(s):  
SA Shepherd ◽  
M Avalos-Borja ◽  
MO Quintanilla
Keyword(s):  
Organic Matrix ◽  
Spawning Season ◽  
First Year ◽  
Shell Microstructure ◽  
Sea Temperature ◽  
Abalone Shell

The microstructure of the shell of the abalone Haliotis fulgens consists of alternate layers of aragonite and prismatic calcium with darker organic matrix (conchiolin) that are visible as rings when the shell is ground down at the spire. This abalone deposits about four prismatic layers in the first year and three layers each year thereafter at the site studied. Prismatic layers are laid down in about April, August and November, corresponding with sea temperature minima and maxima and with the spawning season. After about 3 years of age, prismatic layers at the spire of the shell begin to be lost through erosion of the outer layers of the shell. The first prismatic layers deposited are 5-10 �m across, and later layers successively increase in thickness to a maximum of about 80 �m. This property is used to estimate the rate of erosion of layers, which is about one per annum. When the rate of deposition and the rate of erosion are known for a locality, an estimate of the true age can be made. The findings are considered in relation to the microstructure of the abalone shell.

Structure Characteristics of the Hemifusus tuba Conch Shell

2011 ◽  
Vol 675-677 ◽  
pp. 365-368
Author(s):  
Yan Liang ◽  
Jie Zhao ◽  
Cheng Wei Wu ◽  
Chen Xiao Mu
Keyword(s):  
Organic Molecules ◽  
Lamellar Microstructure ◽  
Organic Matrix ◽  
The Body ◽  
Functional Adaptation ◽  
Shell Microstructure ◽  
Body Shell ◽  
Sea Area ◽  
Conch Shell ◽  
Mollusk Shell

The mollusk shell mobilizes calcium from environment for skeletal mineralization. This occurs through synthesizing solids in solution in the presence of organic molecules of specific interior regions of the conch shell. The ultrastructure of the Hemifusus tuba conch shell living in the Huang/Bo sea area is investigated in the paper. It is shown that the composition and microstructure of the mollusk shell vary in different positions. The prodissoconch shell consists only of aragonite with the crossed-lamellar microstructure. While the spiral shell and the body shell of the Hemifusus tuba conch shell are composed of one calcite layer and several aragonite layers. The calcite layer consists of cylindrical grains, but the aragonite layers are crossed-lamellar ultrastructure. The margin of shell aperture is only composed of calcite with cylindrical grains. This natural optimization of the shell microstructure is intimately due to the growth of the organic matrix. The process of growth allows a constant renewal of the material, thus enabling the functional adaptation of the shells.

Shell microstructure of late Cretaceous (Maastrichtian) oysters from Ariyalur, Tamil Nadu

2014 ◽  
Vol 84 (1) ◽  
pp. 41-54
Author(s):  
Anand K. Jaitly ◽  
Sanjay K. Mishra ◽  
Shrinjana Sen
Keyword(s):  
Late Cretaceous ◽  
Tamil Nadu ◽  
Shell Microstructure

scholarly journals A new fossil marine lizard with soft tissues from the Late Cretaceous of southern Italy

2018 ◽  
Vol 5 (6) ◽  
pp. 172411 ◽  
Author(s):  
Ilaria Paparella ◽  
Alessandro Palci ◽  
Umberto Nicosia ◽  
Michael W. Caldwell
Keyword(s):  
Late Cretaceous ◽  
Soft Tissues ◽  
Carbonate Platform ◽  
Sister Group ◽  
New Taxon ◽  
Sources Of Information ◽  
Exceptional Preservation ◽  
Limb Reduction ◽  
The Mediterranean ◽  
Extinct Group

A new marine lizard showing exceptional soft tissue preservation was found in Late Cretaceous deposits of the Apulian Platform (Puglia, Italy). Primitivus manduriensis gen. et sp. nov. is not only the first evidence of the presence of dolichosaurs in a southern Italian Carbonate Platform, filling a palaeogeographic gap in the Mediterranean Tethys, but also extends the range of this group to the upper Campanian–lower Maastrichtian. Our parsimony analysis recovers a monophyletic non-ophidian pythonomorph clade, including Tetrapodophis amplectus at the stem of Mosasauroidea + Dolichosauridae, which together represent the sister group of Ophidia (modern and fossil snakes). Based on Bayesian inference instead, Pythonomorpha is monophyletic, with Ophidia representing the more deeply nested clade, and the new taxon as basal to all other pythonomorphs. Primitivus displays a fairly conservative morphology in terms of both axial elongation of the trunk and limb reduction, and the coexistence of aquatic adaptations with features hinting at the retention of the ability to move on land suggests a semi-aquatic lifestyle. The exceptional preservation of mineralized muscles, portions of the integument, cartilages and gut content provides unique sources of information about this extinct group of lizards. The new specimen may represent local persistence of a relict dolichosaur population until almost the end of the Cretaceous in the Mediterranean Tethys, and demonstrates the incompleteness of our knowledge of dolichosaur temporal and spatial distributions.

scholarly journals Preservation of latest Cretaceous (Maastrichtian)—Paleocene frogs (Eorubeta nevadensis) of the Sheep Pass Formation of east-central Nevada and implications for paleogeography of the Nevadaplano

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9455
Author(s):  
Joshua W. Bonde ◽  
Peter A. Druschke ◽  
Richard P. Hilton ◽  
Amy C. Henrici ◽  
Stephen M. Rowland
Keyword(s):  
Late Cretaceous ◽  
Microbial Mats ◽  
High Elevation ◽  
Lake Basin ◽  
Storm Activity ◽  
East Central ◽  
Temperate Lake ◽  
Exceptional Preservation ◽  
Bedding Planes ◽  
Mode 3

Here we report on exceptional preservation of remains of the frog Eorubeta nevadensis in deposits of the Sheep Pass Formation, ranging from Late Cretaceous to Eocene, in the south Egan Range, Nevada. This formation represents a lacustrine basin within the Sevier retroarc hinterland. The formation is subdivided into six members (A–F); of interest here are members B and C. The base of member B is ?uppermost Cretaceous-Paleocene, while member C is Paleocene. Member B frogs are preserved in three taphonomic modes. Mode 1 frogs are nearly complete and accumulated under attritional processes, with frogs settling on microbial mats, as evidenced by crenulated fabric of entombing limestone. Mode 2 involves accumulation of frogs as a result of attritional processes. These frogs are mostly complete with some showing evidence of invertebrate scavenging. Possible scavengers are gastropods, ostracods, and decapods. Mode 3 is represented by isolated, reworked remains of frogs as a result of storm activity, supported by the association of elements with disarticulated bivalves and mud rip-up clasts. Member C preserves frogs in two taphonomic modes. Mode 4 are nearly complete frogs that accumulated during discrete mass mortality events. Numerous individuals are preserved along bedding planes in identical preservational states. Mode 5 is beds of frog bone hash, which represent increased energy to the depositional system (likely tempestites) and reworking of previously buried frog remains. Taphonomy of the frogs, along with the associated fauna and flora, are consistent with preservation in a cool, temperate lake basin, supporting previous interpretations that the Nevadaplano was an elevated plateau during the late Cretaceous through the Eocene. This is a period of time coincident with a climatic thermal optimum, thus the most parsimonious explanation for a temperate lake at the latitude of east-central Nevada is to invoke high elevation, which is consistent with independent structural and clumped stable isotope studies.

A Protozoan Model for Golgi-Associated Calcification

1971 ◽  
Vol 29 ◽  
pp. 332-333
Author(s):  
D. C. Williams ◽  
D. E. Outka
Keyword(s):  
Golgi Apparatus ◽  
Organic Matrix ◽  
Model System ◽  
Sequential Formation

Many studies have shown that the Golgi apparatus is involved in a variety of synthetic activities, and probably no Golgi product is more elaborate than the scales produced by various kinds of phytoflagellates. The formation of calcified scales (coccoliths, Fig. 1,2) of the coccolithophorid phytoflagellates provides a particularly interesting model system for the study of biological mineralization, and the sequential formation of Golgi products.The coccoliths of Hymenomonas carterae consist of a scale-like base (Fig. 2 and 4, b) with a highly structured calcified (CaCO3) rim composed of two distinct elements which alternate about the base periphery (Fig. 1 and 3, A, B). Each element is enveloped by a sheath-like organic matrix (Fig. 3; Fig. 4, m).

Resolution in photoelectron microscopy

1991 ◽  
Vol 49 ◽  
pp. 458-459
Author(s):  
G. F. Rempfer
Keyword(s):  
Electron Microscopy ◽  
Electric Field ◽  
Ultraviolet Light ◽  
Uniform Field ◽  
Virtual Image ◽  
Lens System ◽  
Photoemission Electron Microscopy ◽  
Planar Electrode ◽  
Electron Lens ◽  
Photoemission Electron

In photoelectron microscopy (PEM), also called photoemission electron microscopy (PEEM), the image is formed by electrons which have been liberated from the specimen by ultraviolet light. The electrons are accelerated by an electric field before being imaged by an electron lens system. The specimen is supported on a planar electrode (or the electrode itself may be the specimen), and the accelerating field is applied between the specimen, which serves as the cathode, and an anode. The accelerating field is essentially uniform except for microfields near the surface of the specimen and a diverging field near the anode aperture. The uniform field forms a virtual image of the specimen (virtual specimen) at unit lateral magnification, approximately twice as far from the anode as is the specimen. The diverging field at the anode aperture in turn forms a virtual image of the virtual specimen at magnification 2/3, at a distance from the anode of 4/3 the specimen distance. This demagnified virtual image is the object for the objective stage of the lens system.

Human Enamel Replication

1976 ◽  
Vol 34 ◽  
pp. 180-181
Author(s):  
Norman L. Dockum ◽  
John G. Dockum
Keyword(s):  
Organic Matrix ◽  
Human Teeth ◽  
Human Enamel ◽  
Straight Line ◽  
Ultrastructural Characteristics

Ultrastructural characteristics of fractured human enamel and acid-etched enamel were compared using acetate replicas shadowed with platinum and palladium. Shadowed replications of acid-etched surfaces were also obtained by the same method.Enamel from human teeth has a rod structure within which there are crystals of hydroxyapatite contained within a structureless organic matrix composed of keratin. The rods which run at right angles from the dentino-enamel junction are considered to run in a straight line perpendicular to the perimeter of the enamel, however, in many areas these enamel rods overlap, interlacing and intertwining with one another.

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