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132 results for “eggshell”
FIGURE 3 in Identification of fossilized eggshells from the Taung hominin locality, Taung, Northwest Province, South Afric
FIGURE 3. All specimens, both extant eggs and fossil eggshells, showing surface morphology at 12.5X magnification.
Fig. 2 in The eggshell of the Eocene bird Lithornis
Fig. 2. SEM micrograph images of eggshells. A. Lithornis celetius, YPM PU 16961, Bagtail Quarry, Montana, Fort Union Formation (Paleocene). A1. Circular pore orifice on the eggshell outer surface (arrow). A2. Even though it is hard to see, the entire thickness of the eggshell consists of three aprismatic structural layers (layers, 1 and 3 are also relatively thin comparatively to layer 2; see text). A3. Detail of layers 1 and 2 (note the acicular crystals at the base of the eggshell units). A4. Detail of layer 3. B. Tinamus tinamus (Tinamidae), AMNH 15478, Recent. B1. Layer 3. B2. Layer 1 with acicular calcite crystals at the base of eggshell units.
Fig. 1 in The eggshell of the Eocene bird Lithornis
Fig. 1. SEM micrograph images of eggshells. A. Lithornis vulturinus (Lithornithidae), NMING F 2005−1, Walton−on−the−Naze, Essex, UK, London Clay Formation (lower Eocene). A1. Circular pore orifice on the eggshell outer surface; A2. Three aprismatic structural layers (our layers 1–3; see text) compose the entire thickness of the same specimen. Layers, 1 and 3 are relatively thin comparatively to layer 2. A3. Details of layer 3. A4. Bladed calcite crystals at the base of eggshell. B. Rhynchotus rufescens (Tinamidae), AMNH 13376, Recent. B1. Layer 3 of the eggshell. B2. Structural layers with bladed calcite crystals at the base of eggshell units.
Fig. 2 in Earliest Laurasian sauropod eggshells
Fig. 2. UM2− LBA 2. Bajocian megaloolithid eggshells. A. SEM, outer ornamentation showing tightly packed nodes. B. SEM, radial view, note discretispherulitic shell units. La Balme, Cajarc Formation, Quercy Limestones, France.
Fig. 1 in Earliest Laurasian sauropod eggshells
Fig. 1. UM2−LBA 1. Thin section of Bajocian eggshell analyzed with cathodoluminescence. La Balme, Cajarc Formation, Quercy Limestones, France.
Fig. 3 in Earliest Laurasian sauropod eggshells
Fig. 3. Strict consensus of 10 equally most parsimonious trees, based on the analysis of 27 eggshell selected characters (see Appendix 1). Testudoflexoolithus and Krokolithes eggshells have been selected for an outgroup comparison. Each tree has a length of 60 steps, a Consistency Index (CI) of 0.583 and a Retention Index (RI) of 0.788. Phylogenetic reconstructions were performed by PAUP 3.1.1 (Swofford 1993). Heuristic searches using stepwise addition and a randomized input order of taxa (100 replications) have been executed. No differential character weights were used. Selected characters and data matrix are given in the Appendix 1. T, turtle; C, crocodile; A, avian; H, hadrosaur; Th, theropod. The cladistic analysis (see Table 2) is based on the analysis of 27 selected eggshell characters after Mikhailov (1997). This analysis supports a theropod dinosaur origin for birds, already demonstrated by Zeletnisky (2004) and Varrichio and Jackson (2004).
Figures 7–10 in Regional Comparisons of the Thickness of Moa Eggshell Fragments (Aves: Dinornithiformes)
Figures 7–10. Histograms of moa eggshell thicknesses for samples of (Fig. 7) 340 fragments from the Wairau Bar archaeological site, Marlborough; (Fig. 8) 595 fragments from the Oamaru archaeological site; (Fig. 9) 147 fragments from Chatto Creek, Central Otago; and (Fig. 10) 125 fragments from the Shag River archaeological site, Otago.
Figure 2 in Regional Comparisons of the Thickness of Moa Eggshell Fragments (Aves: Dinornithiformes)
Figure 2. Regressions of mean eggshell thickness on latitude for the eight geographic samples in this study (Table 3) and for the 20 whole moa eggs for which measurements of eggshell thickness are possible (Gill, 2007). For eggshell fragments (open circles), the four North Island data-points are at bottom left and the four South Island ones at middle right. The regression lines and correlation coefficients are: y = 0.028x + 0.027, r = 0.75 (fragments; lower line); y = 0.034x–0.17, r = 0.44 (whole eggs; upper line).
Figure 1 in Regional Comparisons of the Thickness of Moa Eggshell Fragments (Aves: Dinornithiformes)
Figure 1. Locality map of New Zealand showing eight sites (four from each of North and South Islands) for which samples of moa eggshell fragments were measured in this study. Archaeological sites are marked with an asterisk (*).
Figures 3–6 in Regional Comparisons of the Thickness of Moa Eggshell Fragments (Aves: Dinornithiformes)
Figures 3–6. Histograms of moa eggshell thicknesses for samples of (Fig. 3) 612 fragments from North Cape, Northland; (Fig. 4) 1042 fragments from Tokerau Beach, Northland; (Fig. 5) 273 fragments from Puketitiri, Hawke's Bay; and (Fig. 6) 431 fragments from Castle Point, Wairarapa.
Data for: Novel quantification of eggshell surfaces in Dromaius novaehollandiae with implications for the fossil eggshells of Oviraptorosauria (Dinosauria)
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Eggshell colour differences in a classic example of coevolved eggshell mimicry
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Data from: Unscrambling variation in avian eggshell colour and patterning in a continent-wide study
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Data from: Comparative crystallography suggests maniraptoran theropod affinities for latest Cretaceous European ‘geckoid’ eggshell
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Data from: The shape of avian eggs: assessment of a novel metric for quantifying eggshell conicality
<p>Studying avian egg shape and other aspects of its morphology has recently undergone a renaissance. Yet, most studies rely solely on two metrics for the quantification of egg shape: elongation and asymmetry. The difficulty of additionally quantifying the curvature of an eggshell has yielded many attempts including those with complex equations and spatial modeling techniques based on digitized images. These have lacked an independent single-variable metric, hampering comparative studies. We propose a metric for one common quality of egg shape, conicality, which is notably variable in diverse species' calcareous shells including shorebirds and non-avian theropods. This metric utilizes multiple measurements of the slope along an eggs profile to produce a distribution of angular measurements, which can be analyzed with a Kurtosis (K) value. This metric was tested with sets of computer modeled and 3D printed egg forms, where elongation, the percentage of conicality, and the relative curvature of the shell profile were controlled. For applicability to natural eggs and their diversity across taxa, the Kurtosis value was used to quantify the gradient of conicality across a focal avian family, Alcidae, where the Kurtosis value successfully identified the most conical eggs using qualitative descriptions from well-established literature. Given the significance of egg morphology and profile curvature to structural integrity, surface-area to volume ratio, egg mobility/stability, nesting behavior, and embryonic development, our proposed measure of conicality could prove a useful variable to the study of avian and non-avian egg-producing species. </p>
DNA sequence data generated using non-invasive feather and eggshell samples from the Grenada Dove for two gene regions: Cyt b and ND2
<p>As an island endemic with a decreasing population, the Critically Endangered Grenada Dove <em>Leptotila wellsi</em> is threatened by accelerated loss of genetic diversity resulting from ongoing habitat fragmentation. Small, threatened populations are difficult to sample directly but advances in molecular methods mean that non-invasive samples can be used. We performed the first assessment of genetic diversity of populations of Grenada Dove by a) assessing mtDNA genetic diversity in the only two areas of occupancy on Grenada, b) defining the number of haplotypes present at each site and c) evaluating evidence of isolation between sites. We used non-invasively collected samples from two locations: Mt Hartman (n=18) and Perseverance (n=12). DNA extraction and PCR were used to amplify 1,751 bps of mtDNA from two mitochondrial markers: NADH dehydrogenase 2 (<em>ND2</em>) and Cytochrome b (<em>Cyt b</em>). Haplotype diversity (<em>h</em>) of 0.4, a nucleotide diversity (π) of 0.00023 and two unique haplotypes were identified within the <em>ND2</em> sequences; a single haplotype was identified within the <em>Cyt b </em>sequences. Of the two haplotypes identified; the most common haplotype (haplotype A = 73.9%) was observed at both sites and the other (haplotype B = 26.1%) was unique to Perseverance. Our results show low mitochondrial genetic diversity and clear evidence for genetically isolated populations. The Grenada Dove needs urgent conservation action, including habitat protection and potential augmentation of gene flow by translocation in order to increase genetic resilience and diversity with the ultimate aim of securing the long-term survival of this Critically Endangered species. </p>
High within-clutch repeatability of eggshell phenotype in Barn Swallows (Hirundo rustica erythrogaster) despite less maculated last-laid eggs
<p>Ecological and life history variation and both interspecific and intraspecific brood parasitism contribute to diversity in egg phenotype within the same species. In this study, Barn Swallows (<em>Hirundo rustica erythrogaster</em>) laid eggs with high intraclutch repeatability in egg size, shape, and maculation. Despite this high intraclutch repeatability, last-laid eggs had consistently less of the eggshell covered in spots and fewer spots than earlier-laid eggs in the clutch. We examined sources of interclutch and intraclutch variation using both direct measurements and custom-software (SpotEgg, NaturePatternMatch) that provide detailed information on egg characteristics, especially maculation measures. In addition to our main findings, maculation on different sides of the egg was highly repeatable; however, only shape, proportion of the eggshell maculated, and average spot size were repeatable between first and replacement clutches. Low intraclutch variation in maculation could allow females to recognize their clutch and this may be adaptive for colonial nesting species, such as the Barn Swallow. Characterizing intraspecific variation in egg size, shape, and maculation is the first step in understanding whether intraclutch variation is low enough - and interclutch variation high enough – such that eggs could serve as identity signals.</p>
FIGURE 7 in Identification of fossilized eggshells from the Taung hominin locality, Taung, Northwest Province, South Afric
FIGURE 7. Representative SEM results from one (TDES 3) of the fossil eggshells.
FIGURE 1. Fossil eggs from Taung, T92-88 in Identification of fossilized eggshells from the Taung hominin locality, Taung, Northwest Province, South Afric
FIGURE 1. Fossil eggs from Taung, T92-88 on the right and T93-17 on the left.
Microstructural and crystallographic evolution of palaeognath (Aves) eggshells
<p>The avian palaeognath phylogeny has been recently revised significantly due to the advancement of genome-wide comparative analyses and provides the opportunity to trace the evolution of the microstructure and crystallography of modern dinosaur eggshells. Here, eggshells of all major clades of Palaeognathae (including extinct taxa) and selected eggshells of Neognathae and non-avian dinosaurs are analysed with electron backscatter diffraction. Our results show the detailed microstructures and crystallographies of (previously) loosely categorized ostrich-, rhea-, and tinamou-style morphotypes of palaeognath eggshells. All rhea-style eggshell appears homologous, while respective ostrich-style and tinamou-style morphotypes are best interpreted as homoplastic morphologies (independently acquired).</p> <p>Ancestral state reconstruction and parsimony analysis additionally show that rhea-style eggshell represents the ancestral state of palaeognath eggshells both in microstructure and crystallography. The ornithological and palaeontological implications of the current study are not only helpful for the understanding of evolution of modern and extinct dinosaur eggshells, but also aid other disciplines where palaeognath eggshells provide a useful archive for comparative contrasts (e.g. palaeoenvironmental reconstructions, geochronology, and zooarchaeology).</p>
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