The taphonomy of vertebrate melanosomes

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dc.contributor.advisor McNamara, Maria en Rossi, Valentina 2020-09-23T08:54:08Z 2020-09-23T08:54:08Z 2020-08-31 2020-08-31
dc.identifier.citation Rossi, V. 2020. The taphonomy of vertebrate melanosomes. PhD Thesis, University College Cork. en
dc.identifier.endpage 273 en
dc.description.abstract The field of fossil colour is emerging rapidly as a new focus of palaeobiological research. Evidence of melanosomes, micron-sized organelles containing melanin, found in skin, feathers and hair of exceptionally preserved fossil vertebrates has been used to infer melanin-based integumentary colouration of extinct animals. Although melanosomes from the integument are well studied, less attention has been given to melanosomes from non-integumentary tissues; the impact of non-integumentary melanosomes on inferences of fossil colour is unknown. The correct identification of integumentary melanosomes requires a mechanism, or multiple mechanisms, to distinguish these from non-integumentary melanosomes. Identification of integumentary melanosomes in fossils is therefore critical to studies of fossil colour. In this thesis the spatial distribution, geometry and chemistry of melanosomes in a taxonomically broad set of extant higher vertebrate tissues were analysed using histology, scanning electron microscopy, synchrotron rapid-scanning X-ray fluorescence and synchrotron X-ray absorption near edge spectroscopy. Data from extant taxa were compared with data from fossil vertebrates from nine Konservat-Lagerstätten. Spatial distribution, geometry and chemistry of fossil melanosomes were analysed using scanning electron microscopy and synchrotron rapid-scanning X-ray fluorescence. Taphonomic experiments simulated the impact of high pressure and temperature and the presence of metal-rich fluids on the morphology and chemistry of melanosomes from the skin and liver of extant amphibians. Histological analysis of tissues in extant taxa shows that internal melanosomes are abundant in all extant taxa and tissues. Moreover, different tissues can be discriminated using melanosome geometry and metal associations. Critically, non-integumentary melanosomes are preserved in fossils and can be identified from the skin using melanosome morphology and chemistry. Nevertheless, in fossils, melanosome geometry and chemistry are altered, and in some case, these indices cannot discriminate between the skin and other organs. Taphonomic experiments show that during maturation, the chemistry of melanosomes from the skin and the liver converges, with melanosomes losing their characteristic tissue-specific chemical signals. This result suggests that the metals-melanin association is unstable during diagenesis. Collectively, these data provide new fundamental knowledge on the taphonomy of melanosomes, including a new tool for inferring the internal anatomy of fossils using the geometry and chemistry of preserved melanosomes. Moreover, this thesis reveals that, although in some case tissue-specific chemical signals can preserve in fossil melanosomes, the chemistry is unlikely to be fully biological in origin. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2020, Valentina Rossi. en
dc.rights.uri en
dc.subject Fossil colour en
dc.subject Organic chemistry en
dc.subject Synchrotron XRF en
dc.subject Melanosomes en
dc.subject Metals en
dc.subject Experimental taphonomy en
dc.title The taphonomy of vertebrate melanosomes en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD - Doctor of Philosophy en
dc.internal.availability Full text not available en
dc.description.version Accepted Version en
dc.contributor.funder European Research Council en
dc.description.status Not peer reviewed en Biological, Earth and Environmental Sciences en
dc.internal.conferring Autumn 2020 en
dc.relation.project info:eu-repo/grantAgreement/EC/H2020::ERC::ERC-STG/637691/EU/Animal coloration through deep time: evolutionary novelty, homology and taphonomy/ANICOLEVO en
dc.availability.bitstream controlled 2023-08-31

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© 2020, Valentina Rossi. Except where otherwise noted, this item's license is described as © 2020, Valentina Rossi.
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