98 results found
Liang C, Marghoub A, Kever L, et al., 2021, Lizard osteoderms - morphological characterisation, biomimetic design and manufacturing based on three species., Bioinspir Biomim
Osteoderms (OD) are mineralised dermal structures consisting mainly of calcium phosphate and collagen. The sheer diversity of OD morphologies and their distribution within the skin of lizards makes these reptiles an ideal group in which to study ODs. Nonetheless, our understanding of the structure, development, and function of lizard ODs remains limited. The specific aims of this study were: (1) to carry out a detailed morphological characterisation of ODs in three lizard species; (2) to design and manufacture biomimetic sheets of ODs corresponding to the OD arrangement in each species; and (3) to evaluate the impact resistance of the manufactured biomimetic sheets under a drop weight test. Skin samples of the anguimorphs Heloderma suspectum and Ophisaurus ventralis, and the skink Corucia zebrata were obtained from frozen lab specimens. Following a series of imaging and image characterisations, 3D biomimetic models of the ODs were developed. 3D models were then printed using additive manufacturing techniques and subjected to drop weight impact tests. The results suggest that a 3D printed compound of overlapping ODs as observed in Corucia can potentially offer a higher energy absorption by comparison with the overlapping ODs of Ophisaurus and the non-overlapping ODs of Heloderma. Compound overlapping ODs need to be further tested and explored as a biomimetic concept to increase the shock absorption capabilities of devices and structures.
Williams C, Kirby A, Marghoub A, et al., 2021, A review of the osteoderms of lizards (Reptilia: Squamata), BIOLOGICAL REVIEWS, ISSN: 1464-7931
Morris Z, Abzhanov A, Pierce S, 2021, Embryonic origins of the flattened skull table and snout in Crocodylia, Publisher: WILEY, ISSN: 0892-6638
Dobreva MP, Lynton-Jenkins JG, Chaves JA, et al., 2021, Sex identification in embryos and adults of Darwin's finches, PLOS ONE, Vol: 16, ISSN: 1932-6203
Abzhanov A, 2021, The many faces of evolution: heterochronic developmental mechanisms for adaptive radiations, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E2-E3, ISSN: 1540-7063
Morris ZS, Abzhanov A, 2021, Heading for higher ground: Developmental origins and evolutionary diversification of the amniote face., Curr Top Dev Biol, Vol: 141, Pages: 241-277
Amniotes, a clade of terrestrial vertebrates, which includes all of the descendants of the last common ancestor of the reptiles (including dinosaurs and birds) and mammals, is one of the most successful group of animals on our planet. In addition to having an egg equipped with an amnion, an adaptation to lay eggs on land, amniotes possess a number of other major morphological characteristics. Chief among them is the amniote skull, which can be classified into several major types distinguished by the presence and number of temporal fenestrae (windows) in the posterior part. Amniotes evolved from ancestors who possessed a skull composed of a complex mosaic of small bones separated by sutures. Changes in skull composition underlie much of the large-scale evolution of amniotes with many lineages showing a trend in reduction of cranial elements known as the "Williston's Law." The skull of amniotes is also arranged into a set of modules of closely co-evolving bones as revealed by modularity and integration tests. One of the most consistently recovered and at the same time most versatile modules is the "face," anatomically defined as the anterior portion of the head. The faces of amniotes display extraordinary amount of variation, with many adaptive radiations showing parallel tendencies in facial scaling, e.g., changes in length or width. This review explores the natural history of the amniote face and discusses how a better understanding of its anatomy and developmental biology helps to explain the outstanding scale of adaptive facial diversity. We propose a model for facial evolution in the amniotes, based on the differential rate of cranial neural crest cell proliferation and the timing of their skeletal differentiation.
Reaney AM, BouchenakKhelladi Y, Tobias JA, et al., 2020, Ecological and morphological determinants of evolutionary diversification in Darwin's finches and their relatives, Ecology and Evolution, Vol: 10, Pages: 14020-14032, ISSN: 2045-7758
Darwin's finches are a classic example of adaptive radiation, a process by which multiple ecologically distinct species rapidly evolve from a single ancestor. Such evolutionary diversification is typically explained by adaptation to new ecological opportunities. However, the ecological diversification of Darwin's finches following their dispersal to Galápagos was not matched on the same archipelago by other lineages of colonizing land birds, which diversified very little in terms of both species number and morphology. To better understand the causes underlying the extraordinary variation in Darwin's finches, we analyze the evolutionary dynamics of speciation and trait diversification in Thraupidae, including Coerebinae (Darwin's finches and relatives) and, their closely related clade, Sporophilinae. For all traits, we observe an early pulse of speciation and morphological diversification followed by prolonged periods of slower steady‐state rates of change. The primary exception is the apparent recent increase in diversification rate in Darwin's finches coupled with highly variable beak morphology, a potential key factor explaining this adaptive radiation. Our observations illustrate how the exploitation of ecological opportunity by contrasting means can produce clades with similarly high diversification rate yet strikingly different degrees of ecological and morphological differentiation.
Lee HW, Esteve-Altava B, Abzhanov A, 2020, Evolutionary and ontogenetic changes of the anatomical organization and modularity in the skull of archosaurs, SCIENTIFIC REPORTS, Vol: 10, ISSN: 2045-2322
Camacho J, Moon R, Smith SK, et al., 2020, Differential cellular proliferation underlies heterochronic generation of cranial diversity in phyllostomid bats, EvoDevo, Vol: 11, ISSN: 2041-9139
BackgroundSkull diversity in the neotropical leaf-nosed bats (Phyllostomidae) evolved through a heterochronic process called peramorphosis, with underlying causes varying by subfamily. The nectar-eating (subfamily Glossophaginae) and blood-eating (subfamily Desmondontinae) groups originate from insect-eating ancestors and generate their uniquely shaped faces and skulls by extending the ancestral ontogenetic program, appending new developmental stages and demonstrating peramorphosis by hypermorphosis. However, the fruit-eating phyllostomids (subfamilies Carollinae and Stenodermatinae) adjust their craniofacial development by speeding up certain developmental processes, displaying peramorphosis by acceleration. We hypothesized that these two forms of peramorphosis detected by our morphometric studies could be explained by differential growth and investigated cell proliferation during craniofacial morphogenesis.ResultsWe obtained cranial tissues from four wild-caught bat species representing a range of facial diversity and labeled mitotic cells using immunohistochemistry. During craniofacial development, all bats display a conserved spatiotemporal distribution of proliferative cells with distinguishable zones of elevated mitosis. These areas were identified as modules by the spatial distribution analysis. Ancestral state reconstruction of proliferation rates and patterns in the facial module between species provided support, and a degree of explanation, for the developmental mechanisms underlying the two models of peramorphosis. In the long-faced species, Glossophaga soricina, whose facial shape evolved by hypermorphosis, cell proliferation rate is maintained at lower levels and for a longer period of time compared to the outgroup species Miniopterus natalensis. In both species of studied short-faced fruit bats, Carollia perspicillata and Artibeus jamaicensis, which evolved under the acceleration model, cell proliferation rate is increased compared to the outgroup.Conc
Morris ZS, Pierce SE, Abzhanov A, 2020, Developmental mechanisms shaping crocodylian snouts, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E166-E166, ISSN: 1540-7063
Camacho J, Heyde A, Bhullar B-AS, et al., 2019, Peramorphosis, an evolutionary developmental mechanism in neotropical bat skull diversity, Developmental Dynamics, Vol: 248, Pages: 1129-1143, ISSN: 1058-8388
BackgroundThe neotropical leaf‐nosed bats (Chiroptera, Phyllostomidae) are an ecologically diverse group of mammals with distinctive morphological adaptations associated with specialized modes of feeding. The dramatic skull shape changes between related species result from changes in the craniofacial development process, which brings into focus the nature of the underlying evolutionary developmental processes.ResultsIn this study, we use three‐dimensional geometric morphometrics to describe, quantify, and compare morphological modifications unfolding during evolution and development of phyllostomid bats. We examine how changes in development of the cranium may contribute to the evolution of the bat craniofacial skeleton. Comparisons of ontogenetic trajectories to evolutionary trajectories reveal two separate evolutionary developmental growth processes contributing to modifications in skull morphogenesis: acceleration and hypermorphosis.ConclusionThese findings are consistent with a role for peramorphosis, a form of heterochrony, in the evolution of bat dietary specialists.
Abzhanov A, 2019, Phylogenetic principles and morphogenetic mechanisms for evolvability in avian adaptive radiations., Society for Comparative and Integrative Biology (SICB)
Abzhanov A, 2019, Use it or lose it: integration of cranial skeleton and musculature from plasticity to genetic assimilation, ”Morphometrics: Geometry and Statistics” workshop
Morris ZS, Abzhanov A, Pierce SE, 2019, Correlations between Developmental, Ecological, and Evolutionary Axes of Cranial Shape Variation in Extant Crocodylians and the Pseudosuchian Fossil Record, Publisher: WILEY, Pages: S186-S187, ISSN: 0362-2525
Abzhanov A, 2019, Phylogenetic principles and morphogenetic mechanisms for evolvability and biological shape change, ” Morphogenesis: Geometry and Physics” workshop
Camacho J, Moon R, Seetahal J, et al., 2019, Origins of Craniofacial Diversity in New World Leaf-Nosed Bats at the Developmental, Cellular and Genetic level, Publisher: WILEY, Pages: S93-S93, ISSN: 0362-2525
Abzhanov A, 2019, Shaping the beaks of Darwin's finches: developmental mechanisms of the famous adaptive radiation, UK Evo-Devo Symposium
Morris ZS, Pierce SE, Abzhanov A, 2019, The role of craniofacial growth zones in shaping crocodylian snouts, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E162-E162, ISSN: 1540-7063
Morris ZS, Vliet KA, Abzhanov A, et al., 2019, Heterochronic shifts and conserved embryonic shape underlie crocodylian craniofacial disparity and convergence, PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 286, ISSN: 0962-8452
Abzhanov A, 2018, Shaping the beaks of Darwin's finches: developmental mechanisms of the famous adaptive radiation, Darwin's Day
Abzhanov A, 2018, Shaping the faces of Darwin's finches and phyllostomid bats: developmental mechanisms of two famous adaptive radiations., “Growth, patterning and scaling during development”
Camacho J, Tabin CJ, Abzhanov A, 2018, Exploring adaptive and novel traits of bat faces through morphometrics and developmental genetics, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E28-E28, ISSN: 1540-7063
Abzhanov A, 2018, Phylogenetic evidence and ontogenetic mechanisms for evolvability in avian adaptive radiations, Avian Models 10
Abzhanov A, 2018, Morphogenetic mechanisms for evolvability in avian adaptive radiations, First European Regional Meeting on Vertebrate Morphology, Society for Integrative & Comparative Biology
Abzhanov A, 2017, The old and new faces of morphology: the legacy of D'Arcy Thompson's 'theory of transformations' and 'laws of growth', Development, Vol: 144, Pages: 4284-4297, ISSN: 0950-1991
In 1917, the publication of On Growth and Form by D'Arcy Wentworth Thompson challenged both mathematicians and naturalists to think about biological shapes and diversity as more than a confusion of chaotic forms generated at random, but rather as geometric shapes that could be described by principles of physics and mathematics. Thompson's work was based on the ideas of Galileo and Goethe on morphology and of Russell on functionalism, but he was first to postulate that physical forces and internal growth parameters regulate biological forms and could be revealed via geometric transformations in morphological space. Such precise mathematical structure suggested a unifying generative process, as reflected in the title of the book. To Thompson it was growth that could explain the generation of any particular biological form, and changes in ontogeny, rather than natural selection, could then explain the diversity of biological shapes. Whereas adaptationism, widely accepted in evolutionary biology, gives primacy to extrinsic factors in producing morphological variation, Thompson's ‘laws of growth' provide intrinsic directives and constraints for the generation of individual shapes, helping to explain the ‘profusion of forms, colours, and other modifications' observed in the living world.
Fabbri M, Koch NM, Pritchard AC, et al., 2017, The skull roof tracks the brain during the evolution and development of reptiles including birds, Nature Ecology and Evolution, Vol: 1, Pages: 1543-1550, ISSN: 2397-334X
Major transformations in brain size and proportions, such as the enlargement of the brain during the evolution of birds, are accompanied by profound modifications to the skull roof. However, the hypothesis of concerted evolution of shape between brain and skull roof over major phylogenetic transitions, and in particular of an ontogenetic relationship between specific regions of the brain and the skull roof, has never been formally tested. We performed 3D morphometric analyses to examine the deep history of brain and skull-roof morphology in Reptilia, focusing on changes during the well-documented transition from early reptiles through archosauromorphs, including nonavian dinosaurs, to birds. Non-avialan taxa cluster tightly together in morphospace, whereas Archaeopteryx and crown birds occupy a separate region. There is a one-to-one correspondence between the forebrain and frontal bone and the midbrain and parietal bone. Furthermore, the position of the forebrain–midbrain boundary correlates significantly with the position of the frontoparietal suture across the phylogenetic breadth of Reptilia and during the ontogeny of individual taxa. Conservation of position and identity in the skull roof is apparent, and there is no support for previous hypotheses that the avian parietal is a transformed postparietal. The correlation and apparent developmental link between regions of the brain and bony skull elements are likely to be ancestral to Tetrapoda and may be fundamental to all of Osteichthyes, coeval with the origin of the dermatocranium.
Abzhanov A, 2017, Phylogenetic principles and morphogenetic mechanisms for evolvability in avian adaptive radiations, EMBO conference
Abzhanov A, 2017, Phylogenetic evidence and ontogenetic mechanisms for evolvability in avian adaptive radiations, Joint Congress 2017
Morris ZS, Pierce SE, Abzhanov A, 2017, Craniofacial growth zones and modularity in Amniota: insight from the model crocodylian, Alligator mississippiensis., Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E355-E355, ISSN: 1540-7063
Abzhanov A, 2017, Developmental evolution of the animal face: insights into the origins of adaptive radiations, UK Evo-Devo Conference
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