Ventral structure and ontogeny of the late Furongian (Cambrian) trilobite Guangxiaspis guangxiensis Zhou, 1977 and the diphyletic origin of the median suture

2010 ◽  
Vol 84 (3) ◽  
pp. 493-504 ◽  
Author(s):  
Xue-Jian Zhu ◽  
Nigel C. Hughes ◽  
Shan-Chi Peng
Keyword(s):  
Morphological Change ◽  
Early Ontogeny ◽  
Guangxi Province ◽  
New Information ◽  
Cambrian Trilobite ◽  
Degree Of Convergence ◽  
Marked Morphological Change

Articulated meraspid and holaspid exoskeletons of Guangxiaspis guangxiensis from the Guole Township, Jingxi County, Guangxi Province, China, are preserved in mudstone deposited during an obrution event. The species has a short dorsal pre-cranidial median suture that splits ventrally into a pair of posteriorly divergent connective sutures. The rostral plate of G. guangxiensis is thus triangular in outline, as in the co-occurrent Shergoldia laevigata, which also bore a conterminant hypostome. These two taxa appear to be closely related. The cephalic venter of Shergoldia laevigata has recently been interpreted to suggest a diphyletic origin of the median suture within the order Asaphida, but Guangxiaspis guangxiensis, Shergoldia laevigata and other tsinaniid trilobites display several characters reminiscent of members of the non-asaphide suborder Leiostegiina. These include swellings adjacent to the margins of the L1 glabellar lobe, the shape and furrows of the glabella, a semi-circular pygidium with a long and thin axis, and macrospinous first opisthopleurae of the holaspid pygidium. Based on these characters and on other new information on the early ontogeny of other tsinaniids, all these taxa likely belong within Leiostegiina. This suggests that the median suture arose independently in corynexochide and asaphide trilobites. The degree of convergence between S. laevigata and members of the derived asaphide family Asaphidae was remarkable. Guangxiaspis guangxiensis shows marked morphological change during both meraspid and holaspid ontogeny and might include more than a single morphotype.

scholarly journals A Major Soybean QTL,qPDH1, Controls Pod Dehiscence without Marked Morphological Change

2009 ◽  
Vol 12 (2) ◽  
pp. 217-223 ◽  
Author(s):  
Masaya Suzuki ◽  
Kaien Fujino ◽  
Hideyuki Funatsuki
Keyword(s):  
Morphological Change ◽  
Marked Morphological Change ◽  
Pod Dehiscence

Bone histology yields insights into the biology of the extinct elephant birds (Aepyornithidae) from Madagascar

2020 ◽  
Vol 130 (2) ◽  
pp. 268-295 ◽  
Author(s):  
Anusuya Chinsamy ◽  
Delphine Angst ◽  
Aurore Canoville ◽  
Ursula B Göhlich
Keyword(s):  
Life History ◽  
Comparative Analysis ◽  
Histological Study ◽  
Early Ontogeny ◽  
Bone Histology ◽  
New Information ◽  
History Of ◽  
Biomechanical Constraints

Abstract Given that the biology of the recently extinct aepyornithids is poorly understood, we undertook a histological study of 29 skeletal elements of adult and juvenile specimens of Aepyornithidae, i.e. Aepyornis maximus, Aepyornis hildebrandti and Vorombe titan, in addition to a group of taxonomically unidentifiable juvenile Aepyornithiformes. Comparative analysis of the histology of the different skeletal elements showed that although the femur retained a good record of growth during early ontogeny, the tibiotarsus provided the best record of growth. Our data showed that, like other insular birds and their extant relative, the kiwi, Aepyornithidae experienced protracted growth. We also found that intracortical remodelling began early in ontogeny and continued throughout their lives, becoming more extensive throughout the compacta with age, albeit more restricted to the perimedullary region in the femora. We also deduced that the different skeletal elements experienced variable amounts of intracortical remodelling, which was most likely to be related to biomechanical constraints, size of the element and ontogenetic age. Additionally, we documented the occurrence of an unusual endosteal tissue within the large perimedullary erosional spaces of a femur of A. maximus. Overall, our study provided a lot of new information about the life history of these giant, recently extinct ratites.

scholarly journals New early Cambrian sclerites ofLapworthella schodakensisfrom NE Greenland: advancements in knowledge of lapworthellid taxonomy, sclerite growth and scleritome organization

2016 ◽  
Vol 154 (5) ◽  
pp. 1061-1072 ◽  
Author(s):  
L. DEVAERE ◽  
C. B. SKOVSTED
Keyword(s):  
Early Ontogeny ◽  
Body Plan ◽  
Morphological Features ◽  
Early Cambrian ◽  
Shell Microstructure ◽  
Laminar Shell ◽  
Small Shelly Fossils ◽  
New Information ◽  
Stage 4 ◽  
Species Taxonomy

AbstractThe Cambrian Stage 4 upper Bastion Formation of Albert Heim Bjerge and CH Ostenfeld Nunatak, NE Greenland, yielded 34 excellently preserved sclerites ofLapworthella schodackensisamong other small shelly fossils. Lapworthellids have been interpreted as members of the camenellans, a basal tommotiid group. Little is known about this group although the morphological and ultrastructural features of their sclerites allow a potential reconstruction of a lophophorate body plan. The exquisite material from Greenland provides significant new data for the revision of the species taxonomy, but also for the comprehension of the scleritome structure of lapworthellids and the mode of formation of their sclerites. Two morphotypes ofL. schodackensissclerites are identified: one with a simple apex, occurring in sinistral and dextral forms; and one bilaterally symmetrical sclerite with two apices. All bear a similar ornamentation constructed of repeated growth sets consisting of a reticulate inter-rib groove with tubercles, a densely denticulate rib and a striated sub-rib area. The new data on the ornamentation and observations of the laminar shell microstructure ofL. schodackensisenable us to improve the reconstruction of growth in lapworthellids. Finally, the morphological features of the two types of sclerites provide new information for the reconstruction of the bilaterally symmetrical multi-component lapworthellid scleritome with evidence of the fusion of adjacent sclerites during early ontogeny.

scholarly journals Braincase redescription of Efraasia minor Huene, 1908 (Dinosauria: Sauropodomorpha) from the Late Triassic of Germany, with comments on the evolution of the sauropodomorph braincase

2018 ◽  
Author(s):  
Mario Bronzati ◽  
Oliver W M Rauhut
Keyword(s):  
Ct Scan ◽  
Morphological Change ◽  
Morphological Variation ◽  
Soft Tissues ◽  
Jugular Vein ◽  
Foramen Magnum ◽  
Late Triassic ◽  
New Information ◽  
Phylogenetic Perspective ◽  
Scan Data

The braincase anatomy of the sauropodomorph dinosaur Efraasia minor (Late Triassic, Norian, Löwenstein Formation of Germany) is redescribed in detail, adding new information based on CT-Scan data. We discuss the evolution of sauropodomorph braincases from a phylogenetic perspective, focusing on non-neosauropodan representatives. For this, we revised braincase characters used in data matrices focused on these assemblage of taxa. This led to the recognition of problems with some of the phylogenetic characters, which did not accurately reflect the morphological variation observed among taxa within the group. We also discuss the presence of a divided metotic foramen in members of the group. This has implications for the recognition of soft tissues associated with braincase foramina in non-sauropodan sauropodomorphs, and we propose that the the path for the jugular vein was either through the posterior foramen resulting from this division or through the foramen magnum. Finally, our study demonstrates a series of differences regarding braincase anatomy between “prosauropods” and sauropod taxa. However, it remains unclear if these differences might be due to a drastic morphological change at the basis of the Sauropoda or if they simply reflect the lack of braincase materials of non-neosauropodan sauropods, which might exhibit transitional morphologies.

Lattice Imaging of Twin, Lath and α/Martensite Boundaries in Duplex Low Carbon Steels

1977 ◽  
Vol 35 ◽  
pp. 118-119
Author(s):  
J. Y. Koo ◽  
G. Thomas
Keyword(s):  
High Resolution Electron Microscopy ◽  
Ferrite Matrix ◽  
Carbon Steels ◽  
Bright Field Image ◽  
Low Carbon ◽  
Lattice Imaging ◽  
Bright Field ◽  
Lattice Image ◽  
New Information ◽  
Resolution Electron

High resolution electron microscopy has been shown to give new information on defects(1) and phase transformations in solids (2,3). In a continuing program of lattice fringe imaging of alloys, we have applied this technique to the martensitic transformation in steels in order to characterize the atomic environments near twin, lath and αmartensite boundaries. This paper describes current progress in this program.Figures A and B show lattice image and conventional bright field image of the same area of a duplex Fe/2Si/0.1C steel described elsewhere(4). The microstructure consists of internally twinned martensite (M) embedded in a ferrite matrix (F). Use of the 2-beam tilted illumination technique incorporating a twin reflection produced {110} fringes across the microtwins.

Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas

1970 ◽  
Vol 28 ◽  
pp. 306-307
Author(s):  
L. Andrew Staehelin
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Resolution ◽  
Smooth Surfaces ◽  
Small Particles ◽  
Membrane Surfaces ◽  
Wide Acceptance ◽  
New Information ◽  
Number Of Particles ◽  
Small Holes

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.

Trial production of γ-type energy filtering TEM

1995 ◽  
Vol 53 ◽  
pp. 604-605
Author(s):  
Y. Taniguchi ◽  
E. Nakazawa ◽  
S. Taya
Keyword(s):  
Magnetic Energy ◽  
Electron Optics ◽  
Electron Microscopic ◽  
Mass Spectrometers ◽  
Ion Optics ◽  
Energy Filtering ◽  
New Information ◽  
New Type ◽  
Fringing Fields

Imaging energy filters can add new information to electron microscopic images with respect to energy-axis, so-called electron spectroscopic imaging (ESI). Recently, many good results have been reported using this imaging technique. ESI also allows high-contrast observation of unstained biological samples, becoming a trend of the field of morphology. We manufactured a new type of energy filter as a trial production. This energy filter consists of two magnets, and we call γ-filter since the trajectory of electrons shows ‘γ’-shape inside the filter. We evaluated the new energyγ-filter TEM with the γ-filter.Figure 1 shows schematic view of the electron optics of the γ-type energy filter. For the determination of the electron-optics of the γ-type energy filter, we used the TRIO (Third Order Ion Optics) program which has been developed for the design of high resolution mass spectrometers. The TRIO takes the extended fringing fields (EFF) into consideration. EFF makes it difficult to design magnetic energy filters with magnetic sector fields.

Principles of Low-Vacuum SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1304-1305
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
New Technologies ◽  
High Vacuum ◽  
Optical Microscope ◽  
Specimen Surface ◽  
Electrical Field ◽  
Gaseous Environment ◽  
New Information ◽  
Gas Molecules ◽  
New Interactions ◽  
Gas Pressures

Only recently it became possible to expand scanning electron microscopy to low vacuum and atmospheric pressure through the introduction of several new technologies. In principle, only the specimen is provided with a controlled gaseous environment while the optical microscope column is kept at high vacuum. In the specimen chamber, the gas can generate new interactions with i) the probe electrons, ii) the specimen surface, and iii) the specimen-specific signal electrons. The results of these interactions yield new information about specimen surfaces not accessible to conventional high vacuum SEM. Several microscope types are available differing from each other by the maximum available gas pressure and the types of signals which can be used for investigation of specimen properties.Electrical non-conductors can be easily imaged despite charge accumulations at and beneath their surface. At high gas pressures between 10-2 and 2 torr, gas molecules are ionized in the electrical field between the specimen surface and the surrounding microscope parts through signal electrons and, to a certain extent, probe electrons. The gas provides a stable ion flux for a surface charge equalization if sufficient gas ions are provided.

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