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16 results for “ratite”
Fig. 3 in Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex
Fig. 3. Dinosaur and ratite MB. (A) MOR 1125, (B) emu, and (C) ostrich demineralized (14) MB. The coloration in (B) and (C) results from infiltration of tissues with blood sinuses. (D) MOR 1125, partially demineralized, showing enlarged, randomly arranged vascular openings surrounded by circumferential matrix fibers. Partially demineralized (E) emu and (F) ostrich medullary tissues show extensive vascular penetration, with randomly spaced and varyingly sized vessel openings. (G) Plane view of undemineralized dinosaur tissues shows fibrous matrix and an unusual pattern of vascular doublets or triplets within osteonlike structures (arrows). The inset shows variation in depth and diameter of vascular sinuses. (H) Undemineralized emu MB shows similar doublet pattern (arrows) and fibrous matrix. The greater depth of field makes focusing difficult. (I) Ostrich MB is denser closer to the cortex (inset), where the doublet/triplet pattern of vessels (arrows) is evident, but this becomes obscured by the increasing development of bony tubes and spicules as bone extends further into the medullary cavity. (J) Plane view of MOR 1125 shows the partially eroded, fibrous MB distributed across the cortex in a mazelike fashion. (K) Emu MB shows white (chloroform-altered) and cream-colored MB in the same mazelike pattern. (L) Thicker, randomly oriented tubular spicules of ostrich MB, showing deep penetration and intimate association of blood-containing sinuses.
(G) Higher magnification of dinosaur femur fragment in oblique view shows dense CB lined with newly described bone tissue, also seen in oblique view of emu (H) and ostrich (I) tibia. Ostrich MB is apparently unique in forming longitudinal tubules. in Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex
(G) Higher magnification of dinosaur femur fragment in oblique view shows dense CB lined with newly described bone tissue, also seen in oblique view of emu (H) and ostrich (I) tibia. Ostrich MB is apparently unique in forming longitudinal tubules.
Fig. 2 in Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex
Fig. 2. Dinosaur and ratite comparative views. (A) Freshly broken fragment of MOR 1125 shows laminar ELB separating CB and MB. Bone tissues decrease in density internal to the ELB, because of increased vascularity. (B) Emu tibia, midshaft section. Erosion rooms extending into ELB are secondarily filled by MB. (C) Ostrich bone, mid shaft. MB is distinct from CB, but no obvious ELB is visible and several large vascular sinuses are seen. (D) Higher magnification of MB region of MOR 1125, showing increased porosity and more random orientation of MB than CB or ELB. (E) Emu, stained (14) to distinguish bone from infiltrating marrow fat. MB is more vascular than overlying CB and exhibits a random, whorled pattern. (F) Ostrich MB, showing relationship of bony spicules to invading blood sinuses, colored red from remnant blood. (G) Ground section of MOR 1125. Dense cortical Haversian bone shows second- and third-generation remodeling. ELB separates Haversian bone from more vascular MB. (H) Similar orientation of emu femur shows dense CB, distinct ELB, and a thin layer of MB. (I) Ostrich MB appears more laminar than in (C) or (F) because of the longitudinal orientation of tubelike medullary spicules.
Data from: Testing gradual and speciational models of evolution in extant taxa: the example of ratites
Ever since Eldredge and Gould proposed their model of punctuated equilibria, evolutionary biologists have debated how often this model is the best description of nature and how important it is compared to the more gradual models of evolution expected from natural selection and the neo-Darwinian paradigm. Recently, Cubo proposed a method to test whether morphological data in extant ratites are more compatible with a gradual or with a speciational model (close to the punctuated equilibrium model). As shown by our simulations, a new method to test the mode of evolution of characters (involving regression of standardized contrasts on their expected standard deviation) is easier to implement and more powerful than the previously proposed method, but the Mesquite module CoMET (aimed at investigating evolutionary models using comparative data) performs better still. Uncertainties in branch length estimates are probably the largest source of potential error. Cubo hypothesized that heterochronic mechanisms may underlie morphological changes in bone shape during the evolution of ratites. He predicted that the outcome of these changes may be consistent with a speciational model of character evolution because heterochronic changes can be instantaneous in terms of geological time. Analysis of a more extensive dataset confirms his prediction despite branch length uncertainties: evolution in ratites has been mostly speciational for shape-related characters. However, it has been mostly gradual for size-related ones.
Data from: From ratites to rats: the size of fleshy fruits shapes species' distributions and continental rainforest assembly
Seed dispersal is a key process in plant spatial dynamics. However, consistently applicable generalisations about dispersal across scales are mostly absent because of the constraints on measuring propagule dispersal distances for many species. Here, we focus on fleshy-fruited taxa, specifically taxa with large fleshy fruits and their dispersers across an entire continental rainforest biome. We compare species-level results of whole-chloroplast DNA analyses in sister taxa with large and small fruits, to regional plot-based samples (310 plots), and whole of continent patterns for the distribution of woody species with either large (>30mm) or smaller fleshy fruits (1093 taxa). The pairwise genomic comparison found higher genetic distances between populations and between regions in the large-fruited species (Endiandra globosa), but higher overall diversity within the small-fruited species (Endiandra discolor). Floristic comparisons among plots confirmed lower numbers of large-fruited species in areas where more extreme rainforest contraction occurred, and re-colonisation by small-fruited species readily dispersed by the available fauna. Species distribution patterns showed that larger-fruited species had smaller geographic ranges than smaller-fruited species and locations with stable refugia (and high endemism) aligned with concentrations of large fleshy-fruited taxa, making them a potentially valuable conservation-planning indicator.
Data from: Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution
The evolution of the ratite birds has been widely attributed to vicariant speciation, driven by the Cretaceous breakup of the supercontinent Gondwana. The early isolation of Africa and Madagascar implies that the ostrich and extinct Madagascan elephant birds (Aepyornithidae) should be the oldest ratite lineages. We sequenced the mitochondrial genomes of two elephant birds and performed phylogenetic analyses, which revealed that these birds are the closest relatives of the New Zealand kiwi and are distant from the basal ratite lineage of ostriches. This unexpected result strongly contradicts continental vicariance and instead supports flighted dispersal in all major ratite lineages. We suggest that convergence toward gigantism and flightlessness was facilitated by early Tertiary expansion into the diurnal herbivory niche after the extinction of the dinosaurs.
Data from: Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution
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Data from: Testing gradual and speciational models of evolution in extant taxa: the example of ratites
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Data from: From ratites to rats: the size of fleshy fruits shapes species' distributions and continental rainforest assembly
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Data from: Ratite non-monophyly: independent evidence from 40 novel loci
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Data from: Genomic support for a moa-tinamou clade and adaptive morphological convergence in flightless ratites
One of the most startling discoveries in avian molecular phylogenetics is that the volant tinamous are embedded in the flightless ratites, but this topology remains controversial because recent morphological phylogenies place tinamous as the closest relative of a monophyletic ratite clade. Here, we integrate new phylogenomic sequences from 1,448 nuclear DNA loci totalling almost one million base pairs from the extinct little bush moa, Chilean tinamou and emu with available sequences from ostrich, elegant crested tinamou, four neognaths and the green anole. Phylogenetic analysis using standard homogeneous models and heterogeneous models robust to common topological artefacts recovered compelling support for ratite paraphyly with the little bush moa closest to tinamous within ratites. Ratite paraphyly was further corroborated by eight independent CR1 retroposon insertions. Analysis of morphological characters reinterpreted on a 27-gene paleognath topology indicates that many characters are convergent in the ratites, probably as the result of adaptation to a cursorial life style.
Data from: Genomic support for a moa-tinamou clade and adaptive morphological convergence in flightless ratites
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20 in Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex
20 um. Demineralized fragments of cortical bone from (E) MOR 1125, (F) chicken, (G) emu, and (H) ostrich are shown. A fibrous character dominates all samples. Scale bars for (E), (F), and (H), 30 mm; for (G), 10 mm. Higher magnification of demineralized CB from (I) MOR 1125, (J) emu, and (K) ostrich CB demonstrates the structural similarity between samples, although the MOR 1125 matrix is highly degraded. Scale bars for (I) and (K), 6 um; for (J), 5 um.
orientation of emu femur shows dense CB, distinct ELB, and a thin layer of MB. (I) Ostrich MB appears more laminar than in (C) or (F) because of the longitudinal orientation of tubelike medullary spicules. in Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex
orientation of emu femur shows dense CB, distinct ELB, and a thin layer of MB. (I) Ostrich MB appears more laminar than in (C) or (F) because of the longitudinal orientation of tubelike medullary spicules.
Fig. 1 in Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex
Fig. 1. Extant avian MB and homologous dinosaurian bone tissues. (A) Domestic laying hen, midshaft femur cross section showing the extension of spongy MB deep into the mar row cavity and surrounding preexisting trabeculae (T). (B) Laying emu, midshaft cross section, with a thin layer of MB on the endosteal bone surface, separated from overlying CB by ELB. (C) Ostrich MB arising from CB. Convoluted bony projections surround large cavities and form by continued deposition on hairlike spicules of calcified bone (S). (D) MB on endosteal surface of MOR 1125 femur fragment delineated from overlying CB by large vascular sinuses and change in color, texture, and density. (E) Emu and (F) ostrich bone taken at same aspect as (D), showing mor phological distinction between bone types. (G) Higher magnification of dinosaur femur fragment in oblique view shows dense CB lined with newly described bone tissue, also seen in oblique view of emu (H) and ostrich (I) tibia. Ostrich MB is apparently unique in forming longitudinal tubules.
Fig. 4 in Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex
Fig. 4. Scanning elec tron microscope images of demineralized MB [(A) to (D)] and CB [(E) to (K)]. Demineralized, aldehyde-fixed (14) MB tissues from (A) MOR 1125, (B) extant laying hen, (C) emu, and (D) ostrich show random, crumbly texture. Organized collagen fiber bundles are not distinct in any sample because of rapid deposition and woven character. Scale bars for (A) and (B), 40 um; for (C) and (D), 20 um. Demineralized fragments of cortical bone from (E) MOR 1125, (F) chicken, (G) emu, and (H) ostrich are shown. A fibrous character dominates all samples. Scale bars for (E), (F), and (H), 30 mm; for (G), 10 mm. Higher magnification of demineralized CB from (I) MOR 1125, (J) emu, and (K) ostrich CB demonstrates the structural similarity between samples, although the MOR 1125 matrix is highly degraded. Scale bars for (I) and (K), 6 um; for (J), 5 um.
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