The taphonomy of vertebrate melanosomes

Rossi, Valentina

The taphonomy of vertebrate melanosomes

dc.availability.bitstream	controlled
dc.check.date	2023-08-31
dc.contributor.advisor	McNamara, Maria	en
dc.contributor.author	Rossi, Valentina
dc.contributor.funder	European Research Council	en
dc.date.accessioned	2020-09-23T08:54:08Z
dc.date.available	2020-09-23T08:54:08Z
dc.date.issued	2020-08-31
dc.date.submitted	2020-08-31
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.description.status	Not peer reviewed	en
dc.description.version	Accepted Version	en
dc.format.mimetype	application/pdf	en
dc.identifier.citation	Rossi, V. 2020. The taphonomy of vertebrate melanosomes. PhD Thesis, University College Cork.	en
dc.identifier.endpage	273	en
dc.identifier.uri	https://hdl.handle.net/10468/10566
dc.language.iso	en	en
dc.publisher	University College Cork	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.rights	© 2020, Valentina Rossi.	en
dc.rights.uri	https://creativecommons.org/licenses/by-nc-nd/4.0/	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