scholarly journals Tiny, ornamented eggs and eggshell from the Upper Cretaceous of Utah represent a new ootaxon with theropod affinities

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sara E. Oser ◽  
Karen Chin ◽  
Joseph J. W. Sertich ◽  
David J. Varricchio ◽  
Seung Choi ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Egg Size ◽  
Upper Cretaceous ◽  
Specific Combination ◽  
Continuous Layer ◽  
National Monument ◽  
Pore Canals

AbstractA new Cretaceous ootaxon (eggshell type) from the Kaiparowits Formation of Grand Staircase-Escalante National Monument is among a growing number of very small eggs described from the Mesozoic. Analyses of two partial eggs (~ 17.7 mm in diameter) and 29 eggshell fragments reveal that this new ootaxon exhibits nodose ornamentation with distinctive branching pore canals that open atop the nodes. Its two-layered microstructure consists of a mammillary layer and a continuous layer with rugged grain boundaries between calcite grains. Although the exact identity of the egg producer is unknown, the eggshell microstructure and small size is consistent with a small-bodied avian or non-avian theropod. The specific combination of small egg size, branching pores, two-layered microstructure, and dispersituberculate ornamentation preserved in this new ootaxon is unique among theropod eggs. This underscores that both eggshell and skeletal fossils of Cretaceous theropods can display a mosaic of transitional morphological and behavioural features characteristic of both avian and non-avian taxa. As such, this new ootaxon increases the diversity of Cretaceous eggs and informs our understanding of the evolution of theropod eggshell microstructure and morphology.

The Structure and Deposition of the Cuticle in the Adult Mealworm, Tenebrio Molitor L. (Coleoptera)

1948 ◽  
Vol s3-89 (6) ◽  
pp. 197-216
Author(s):  
V. B. WIGGLESWORTH
Keyword(s):  
The Other ◽  
Secretory Cycle ◽  
Continuous Layer ◽  
Cement Layer ◽  
Dermal Glands ◽  
Basic Layer ◽  
Insoluble Form ◽  
The One ◽  
Pore Canals ◽  
Ammoniacal Silver

The conclusions on the structure of the cuticle in Tenebrio have been summarized on p. 204. Observations on the deposition of the cuticle are in general agreement with those made on Rhodnius. Mitosis and chromatolysis precede the formation of the definitive epidermis. The basic layer of the epicuticle, ‘cuticulin’, is then laid down. It consists of condensed lipoproteins (subsequently tanned, it is supposed, by quinones) and its deposition is immediately preceded by the peak in the secretory cycle of the subepidermal oenocytes. Pore canals from the epidermal cells penetrate the cuticulin layer and pour out silver-reducing material (believed to be dihydroxyphenols in insoluble form) upon its surface. This material is confined to the areas overlying the cell bodies during all but the last stages in its formation, when it fuses to give a more or less continuous layer. During the last few hours before moulting a wax layer appears to be laid down over this polyphenol layer. By the time moulting occurs the polyphenol layer is almost covered and the insect is nearly waterproof. During the first day after moulting, while the secretion of the wax is being completed, the loss of water by transpiration is about four to six times the normal. Very soon after moulting the dermal glands discharge the cement layer over the surface of the wax. The substance of this layer and the contents of the dermal glands reduce ammoniacal silver after extraction with boiling chloroform. It is suggested that it consists of polyphenol-containing material associated with protein and lipides. (It is shown that in Rhodnius the cement layer is formed by the admixture of secretion from the two types of dermal gland previously described. The one produces a solution of protein, the secretion of the other agrees in properties with that here described in Tenebrio. The similarity of this arrangement to that discovered by Pryor in the colleterial glands of the cockroach is pointed out.) In addition to these cement glands there are glands of unknown function opening into the floor of the pits in the cuticle. These are highly developed in the sternites of the male, small and inconspicuous in the female.

scholarly journals A diverse Late Cretaceous vertebrate tracksite from the Winton Formation of Queensland, Australia

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11544
Author(s):  
Stephen F. Poropat ◽  
Matt A. White ◽  
Tim Ziegler ◽  
Adele H. Pentland ◽  
Samantha L. Rigby ◽  
...  
Keyword(s):  
Natural History ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Upper Cretaceous ◽  
National Monument ◽  
Eastern Australia ◽  
Sauropod Tracks ◽  
Dinosaur Tracks ◽  
Conservation Park ◽  
Body Fossil

The Upper Cretaceous ‘upper’ Winton Formation of Queensland, Australia is world famous for hosting Dinosaur Stampede National Monument at Lark Quarry Conservation Park, a somewhat controversial tracksite that preserves thousands of tridactyl dinosaur tracks attributed to ornithopods and theropods. Herein, we describe the Snake Creek Tracksite, a new vertebrate ichnoassemblage from the ‘upper’ Winton Formation, originally situated on Karoola Station but now relocated to the Australian Age of Dinosaurs Museum of Natural History. This site preserves the first sauropod tracks reported from eastern Australia, a small number of theropod and ornithopod tracks, the first fossilised crocodyliform and ?turtle tracks reported from Australia, and possible lungfish and actinopterygian feeding traces. The sauropod trackways are wide-gauge, with manus tracks bearing an ungual impression on digit I, and anteriorly tapered pes tracks with straight or concave forward posterior margins. These tracks support the hypothesis that at least one sauropod taxon from the ‘upper’ Winton Formation retained a pollex claw (previously hypothesised for Diamantinasaurus matildae based on body fossils). Many of the crocodyliform trackways indicate underwater walking. The Snake Creek Tracksite reconciles the sauropod-, crocodyliform-, turtle-, and lungfish-dominated body fossil record of the ‘upper’ Winton Formation with its heretofore ornithopod- and theropod-dominated ichnofossil record.

scholarly journals Dinosaur ichnology and sedimentology of the Chignik Formation (Upper Cretaceous), Aniakchak National Monument, southwestern Alaska; Further insights on habitat preferences of high-latitude hadrosaurs

PLoS ONE ◽  
2019 ◽  
Vol 14 (10) ◽  
pp. e0223471 ◽  
Author(s):  
Anthony R. Fiorillo ◽  
Yoshitsugu Kobayashi ◽  
Paul J. McCarthy ◽  
Tomonori Tanaka ◽  
Ronald S. Tykoski ◽  
...  
Keyword(s):  
High Latitude ◽  
Upper Cretaceous ◽  
Habitat Preferences ◽  
National Monument ◽  
Southwestern Alaska

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

Measurement of the Displacement Across a Coincidence Grain Boundary

1977 ◽  
Vol 35 ◽  
pp. 124-125
Author(s):  
J. W. Matthews ◽  
W. M. Stobbs
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Fault ◽  
The Other ◽  
Measuring Technique ◽  
High Angle ◽  
Twin Boundaries ◽  
Rigid Displacement ◽  
Cubic Crystals ◽  
Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

The Effect of Specimen Thickness and Probe Size on Aem Analysis of Cr-Depletion Profiles in Sensitized Stainless Steel

1982 ◽  
Vol 40 ◽  
pp. 518-519
Author(s):  
E. L. Hall
Keyword(s):  
Grain Boundaries ◽  
Boundary Region ◽  
Chromium Concentration ◽  
Foil Thickness ◽  
Specimen Thickness ◽  
Probe Size ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Sensitization Process ◽  
Compositional Gradients

Sensitization in stainless steels is caused by the formation of chromium-rich M23C6 carbides at grain boundaries, which depletes the adjacent matrix and boundary region of chromium, and hence leads to rapid intergranular attack. To fully understand the sensitization process, and to test the accuracy of theories proposed to model this process, it is necessary to obtain very accurate measurements of the chromium concentration at grain boundaries in sensitized specimens. Quantitative X-ray spectroscopy in the analytical electron microscope (AEM) enables the chromium concentration profile across these boundaries to be studied directly; however, it has been shown that a strong effect of foil thickness and electron probe size may be present in the analysis of rapidly-changing compositional gradients. The goal of this work is to examine these effects.

Electrolytic Isolation of Twin-Type Shock Deformation Structures

1967 ◽  
Vol 25 ◽  
pp. 318-319
Author(s):  
F. I. Grace ◽  
L. E. Murr
Keyword(s):  
Grain Boundaries ◽  
Thin Foil ◽  
Electrolyte Composition ◽  
Experimental Conditions ◽  
Average Current Density ◽  
Electron Transmission ◽  
Deformation Structures ◽  
The Matrix ◽  
Average Current ◽  
Specimen Edge

During the course of electron transmission investigations of the deformation structures associated with shock-loaded thin foil specimens of 70/30 brass, it was observed that in a number of instances preferential etching occurred along grain boundaries; and that the degree of etching appeared to depend upon the various experimental conditions prevailing during electropolishing. These included the electrolyte composition, the average current density, and the temperature in the vicinity of the specimen. In the specific case of 70/30 brass shock-loaded at pressures in the range 200-400 kilobars, the predominant mode of deformation was observed to be twin-type faults which in several cases exhibited preferential etching similar to that observed along grain boundaries. A novel feature of this particular phenomenon was that in certain cases, especially for twins located in the vicinity of the specimen edge, the etching or preferential electropolishing literally isolated these structures from the matrix.

Sign in / Sign up

Export Citation Format

Share Document