The cutting-edge morphology of the mole snake’s dental apparatus

The mole snake (Pseudaspis cana) is capable of inflicting unusual bites in defence and during male combat that present as two parallel lacerations. We investigated the dental morphology of the mole snake by making SEM images, and by CT-scanning and digitally reconstructing the skulls of 14 specimens comprising both sexes. The lengths, volumes, shapes and positions of maxillary and dentary teeth were compared within individuals, between individuals, and between sexes. CT reconstructions show the occurrence of large, flat triangular teeth at the posterior end of the maxilla that are angled to point towards the posterior of the skull. SEM imagery highlights the presence of sharp ridges (carinae) on the posterior edges of the posterior dentary and maxillary teeth. Males have greater dental specialization, maxillary tooth variation, enlargement of the posterior-most maxillary teeth, and dentary teeth with posterior carinae. We hypothesize that mole snake dental specializations are adaptations for their particular form of male combat and possibly for subduing prey in the confines of underground burrows. Our findings reveal a complex dental morphology in mole snakes and provide impetus for further studies on the functional morphology of snake teeth.

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Micro-CT scanning provides insight into the functional morphology of millipede genitalia

Journal of Zoology ◽

10.1111/j.1469-7998.2011.00892.x ◽

2012 ◽

Vol 287 (2) ◽

pp. 91-95 ◽

Cited By ~ 22

Author(s):

J. M. Wojcieszek ◽

P. Austin ◽

M. S. Harvey ◽

L. W. Simmons

Keyword(s):

Functional Morphology ◽

Ct Scanning ◽

Micro Ct ◽

Insight Into

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Tylosaurine mosasaurs (Squamata) from the Late Cretaceous of northern Germany

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/njg.2014.31 ◽

2014 ◽

Vol 94 (1) ◽

pp. 55-71 ◽

Cited By ~ 10

Author(s):

J.J. Hornung ◽

M. Reich

Keyword(s):

Western Europe ◽

Democratic Republic ◽

Democratic Republic Of Congo ◽

Short Review ◽

Dental Morphology ◽

Significant Modification ◽

Northern Germany ◽

The Usa ◽

Dental Apparatus ◽

First Time

AbstractTwo genera of tylosaurine mosasaurs, Tylosaurus and Hainosaurus, are recorded for the first time from Germany. Tylosaurus sp. is represented by two isolated tooth crowns, originally described as Mosasaurus? alseni (here considered a nomen dubium) from the latest Santonian–Early Campanian, which are very similar to T. ivoensis and T. gaudryi. The material of Hainosaurus sp. comprises a maxillary with associated postorbitofrontal, two pterygoid teeth and several indeterminate cranial fragments. The specimen from the Late Campanian is slightly less derived than H. bernardi from the Maastrichtian in retaining labiolingually less compressed anterior maxillary teeth and unserrated pterygoid teeth with only very weak carinae. Despite only minor skeletal differences, the genus Hainosaurus is considered to be distinct from Tylosaurus because of its significant modification of the dental apparatus compared to the plesiomorphic condition in the latter. This dental morphology suggests a phylogenetic trend from a generalised-piercing marginal dentition in Tylosaurus towards the increasingly labiolingually compressed, symmetrical, strongly bicarinate cutting marginal teeth in Hainosaurus spp. from the Early through Late Campanian and Maastrichtian. A similar trend is also present in pterygoid teeth with very indistinct unserrated carinae in the Campanian Hainosaurus sp. towards serrated ones in the Maastrichtian H. bernardi. A short review indicates the presence of Hainosaurus in northern, central and western Europe (Sweden to Spain) since the Early Campanian, and the occurrence of Tylosaurus spp. in the same area until the Late Campanian. Hainosaurus persisted until the end of the Maastrichtian; outside Europe it may have been present in the Late Campanian of the USA and the Maastrichtian of the Democratic Republic of Congo. Judging from a simple, uni- to bicarinate, stoutly conical tooth morphology in aigialosaurs and very basal mosasaurs as well as phylogenetic patterns, the development of blade-like cutting tooth crowns appears to have been convergent in several clades of large-bodied Campanian–Maastrichtian mosasaurids. These include both mosasaurines ('Leiodon' mosasauroides, Prognathodon? sectorius, Prognathodon? kianda, Eremiasaurus heterodontus) and tylosaurines (Hainosaurus spp.).

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Functional significance of preserved color patterns of mollusks from the Gosport Sand (Eocene) of Alabama

Journal of Paleontology ◽

10.1017/s0022336000058911 ◽

1988 ◽

Vol 62 (01) ◽

pp. 83-87 ◽

Cited By ~ 4

Author(s):

Patricia H. Kelley ◽

Charles T. Swann

Keyword(s):

Functional Morphology ◽

Functional Significance ◽

Intraspecific Variability ◽

Color Pattern ◽

Color Patterns ◽

Historical Factors ◽

Life Mode ◽

Molluscan Fauna ◽

Excellent Preservation ◽

Architectural Constraints

The excellent preservation of the molluscan fauna from the Gosport Sand (Eocene) at Little Stave Creek, Alabama, has made it possible to describe the preserved color patterns of 15 species. In this study the functional significance of these color patterns is tested in the context of the current adaptationist controversy. The pigment of the color pattern is thought to be a result of metabolic waste disposal. Therefore, the presence of the pigment is functional, although the patterns formed by the pigment may or may not have been adaptive. In this investigation the criteria proposed by Seilacher (1972) for testing the functionality of color patterns were applied to the Gosport fauna and the results compared with life mode as interpreted from knowledge of extant relatives and functional morphology. Using Seilacher's criteria of little ontogenetic and intraspecific variability, the color patterns appear to have been functional. However, the functional morphology studies indicate an infaunal life mode which would preclude functional color patterns. Particular color patterns are instead interpreted to be the result of historical factors, such as multiple adaptive peaks or random fixation of alleles, or of architectural constraints including possibly pleiotropy or allometry. The low variability of color patterns, which was noted within species and genera, suggests that color patterns may also serve a useful taxonomic purpose.

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Plastic Deformation in Microtomed Sections

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066346 ◽

1971 ◽

Vol 29 ◽

pp. 458-459

Author(s):

J. Temple Black

Keyword(s):

Plastic Deformation ◽

Plastic Strain ◽

Applied Stress ◽

Elastic Strain ◽

High Strain ◽

Tool Material ◽

Cutting Edge ◽

Material Structure ◽

Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

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Analysis of Contrast Reversal in SEM Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009525x ◽

1972 ◽

Vol 30 ◽

pp. 398-399

Author(s):

M. D. Coutts ◽

E. R. Levin

Keyword(s):

Incident Beam ◽

Normal Incidence ◽

Beam Current ◽

Secondary Emission ◽

Image Contrast ◽

Sem Images ◽

Secondary Electrons ◽

Image Position

On tilting samples in an SEM, the image contrast between two elements, x and y often decreases to zero at θε, which we call the no-contrast angle. At angles above θε the contrast is reversed, θ being the angle between the specimen normal and the incident beam. The available contrast between two elements, x and y, in the SEM can be defined as,(1)where ix and iy are the total number of reflected and secondary electrons, leaving x and y respectively. It can easily be shown that for the element x,(2)where ib is the beam current, isp the specimen absorbed current, δo the secondary emission at normal incidence, k is a constant, and m the reflected electron coefficient.

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Mosaic Mapping: A Means of Tiling Images to Shorten Acquisition Speed for Lower - Magnification SEM Images and Wavelength Dispersive Spectrometers (WDS) X-Ray Maps

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164659 ◽

1996 ◽

Vol 54 ◽

pp. 438-439

Author(s):

J.D. Geller ◽

C.R. Herrington

Keyword(s):

Limiting Factors ◽

X Rays ◽

Angular Range ◽

Acceptance Angle ◽

Sem Images ◽

Worst Case ◽

X Ray ◽

Focusing Distance ◽

Layered Crystals ◽

Working Distance

The minimum magnification for which an image can be acquired is determined by the design and implementation of the electron optical column and the scanning and display electronics. It is also a function of the working distance and, possibly, the accelerating voltage. For secondary and backscattered electron images there are usually no other limiting factors. However, for x-ray maps there are further considerations. The energy-dispersive x-ray spectrometers (EDS) have a much larger solid angle of detection that for WDS. They also do not suffer from Bragg’s Law focusing effects which limit the angular range and focusing distance from the diffracting crystal. In practical terms EDS maps can be acquired at the lowest magnification of the SEM, assuming the collimator does not cutoff the x-ray signal. For WDS the focusing properties of the crystal limits the angular range of acceptance of the incident x-radiation. The range is dependent upon the 2d spacing of the crystal, with the acceptance angle increasing with 2d spacing. The natural line width of the x-ray also plays a role. For the metal layered crystals used to diffract soft x-rays, such as Be - O, the minimum magnification is approximately 100X. In the worst case, for the LEF crystal which diffracts Ti - Zn, ˜1000X is the minimum.

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vitreal cells and specialized phagocytes in the chick embryo retina: A TEM and SEM study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159205 ◽

1990 ◽

Vol 48 (3) ◽

pp. 330-331

Author(s):

M.A. Cuadros ◽

M.J. Martinez-Guerrero ◽

A. Rios

Keyword(s):

Cell Death ◽

Plasma Membrane ◽

Acid Phosphatase ◽

Chick Embryo ◽

Basement Membrane ◽

Sem Images ◽

Intimate Contact ◽

Cellular Processes ◽

Sem Study ◽

Free Cells

In the chick embryo retina (days 3-4 of incubation), coinciding with an increase in cell death, specialized phagocytes characterized by intense acid phosphatase activity have been described. In these preparations, all free cells in the vitreal humor (vitreal cells) were strongly labeled. Conventional TEM and SEM techniques were used to characterize them and attempt to determine their relationship with retinal phagocytes.Two types of vitreal cells were distinguished. The first are located at some distance from the basement membrane of the neuroepithelium, and are rounded, with numerous vacuoles and thin cytoplasmic prolongations. Images of exo- and or endocytosis were frequent; the cells showed a well-developed Golgi apparatus (Fig. 1) In SEM images, the cells was covered with short cellular processes (Fig. 3). Cells lying parallel to or alongside the basement membrane are elongated. The plasma membrane is frequently in intimate contact with the basement membrane. These cells have generally a large cytoplasmic expansion (Fig. 5).

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Correlation of Pore Structure and Permeability by SEM-Image Analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180896 ◽

1990 ◽

Vol 48 (1) ◽

pp. 428-429

Author(s):

C. A. Callender ◽

Wm. C. Dawson ◽

J. J. Funk

Keyword(s):

Image Analysis ◽

Pore Structure ◽

Imaging System ◽

Pore Space ◽

Simulation Models ◽

Image Analyzer ◽

Imaging Data ◽

Sem Images ◽

Thin Sections ◽

Rock Types

The geometric structure of pore space in some carbonate rocks can be correlated with petrophysical measurements by quantitatively analyzing binaries generated from SEM images. Reservoirs with similar porosities can have markedly different permeabilities. Image analysis identifies which characteristics of a rock are responsible for the permeability differences. Imaging data can explain unusual fluid flow patterns which, in turn, can improve production simulation models.Analytical SchemeOur sample suite consists of 30 Middle East carbonates having porosities ranging from 21 to 28% and permeabilities from 92 to 2153 md. Engineering tests reveal the lack of a consistent (predictable) relationship between porosity and permeability (Fig. 1). Finely polished thin sections were studied petrographically to determine rock texture. The studied thin sections represent four petrographically distinct carbonate rock types ranging from compacted, poorly-sorted, dolomitized, intraclastic grainstones to well-sorted, foraminiferal,ooid, peloidal grainstones. The samples were analyzed for pore structure by a Tracor Northern 5500 IPP 5B/80 image analyzer and a 80386 microprocessor-based imaging system. Between 30 and 50 SEM-generated backscattered electron images (frames) were collected per thin section. Binaries were created from the gray level that represents the pore space. Calculated values were averaged and the data analyzed to determine which geological pore structure characteristics actually affect permeability.

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