A multi-spectroscopic investigation into the diagenesis of avian polyene pigments: simulated maturation, chemical pathways and palaeontological implications

A multi-spectroscopic investigation into the diagenesis of avian polyene pigments: simulated maturation, chemical pathways and palaeontological implications | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article A multi-spectroscopic investigation into the diagenesis of avian polyene pigments: simulated maturation, chemical pathways and palaeontological implications Arindam Roy, Evan Thomas Saitta, Maya Musa, Sumaya Al-Kindi, Thomas G. Kaye, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7900994/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Bright plumage colours in birds such as yellow, orange, red, and green are predominantly produced by polyene-pigments (carotenoids and psittacofulvins). Carotenoids evolved independently in various passerine groups and may have been present in early archosaurs, while psittacofulvins are unique to parrots and evolved only once. In the context of animal integuments, while melanin has been well-studied due to its wide distribution and high fossilization potential, polyene preservation remains less understood. To test their preservation potential, we conducted sediment-encased pressure-temperature maturation experiments on modern feathers. Feather samples containing carotenoids and psittacofulvins were compacted in clay and subjected to 250 bars of pressure at temperatures from 40-200°C, simulating geological diagenesis. Using UV-Vis-NIR, Raman, and FTIR spectroscopy we tracked the pigments’ chemical transformations. Our results show carotenoids are extremely unstable, rapidly degrading and acting as pro-oxidants that accelerate the decay of the feather's protein matrix. In contrast, psittacofulvins demonstrate greater resilience, predictably transforming into a semi-stable polycyclic aromatic geopolymer, or ‘psittacofulvin-char’, at higher temperatures. This establishes a clear taphonomic hierarchy (Melanin, Psittacofulvins, Carotenoids, and Corneous β Proteins) that explains the fossil record’s melanin bias. We propose a framework for a narrow polyene preservation window, identifying ‘psittacofulvin-char’ as a potential geochemical fossil biomarker. Physical sciences/Chemistry Earth and environmental sciences/Solid earth sciences Full Text Additional Declarations No competing interests reported. Supplementary Files Royetal.2025SupplementaryInformationforCarotenoidsManuscript20251019.pdf Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 14 May, 2026 Reviewers agreed at journal 22 Apr, 2026 Reviews received at journal 24 Feb, 2026 Reviewers agreed at journal 12 Feb, 2026 Reviewers agreed at journal 05 Jan, 2026 Reviewers agreed at journal 08 Dec, 2025 Reviewers invited by journal 01 Dec, 2025 Editor assigned by journal 24 Oct, 2025 Submission checks completed at journal 22 Oct, 2025 First submitted to journal 21 Oct, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7900994","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":623141499,"identity":"774b61ae-4e89-4cf2-851b-d112da46fc0a","order_by":0,"name":"Arindam Roy","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzklEQVRIiWNgGAWjYPACGzkDCRibhzgtacYkazmcuIFoLfwNvA8f8zAwp2+Xbn66gaHGjsHgzAH8WiQOsBsb8zCw5e6cc8zsBsOxZAaDsw0ErDnAxibNw8CTu+FGAlAL2wEGg/MEdMhDtEikG9xI/3aD4R8RWgwgWgwSDG7kmN1gbDtA2GGGh9mYDecYJBjunJFTdiOxL5lHkpD35Y63MT54U/Ff3lwifduND9/s5PjOJBBwGTMDAxOPAZSTQGxEMv4gStkoGAWjYBSMWAAAkRc81dToGrUAAAAASUVORK5CYII=","orcid":"","institution":"University of Birmingham","correspondingAuthor":true,"prefix":"","firstName":"Arindam","middleName":"","lastName":"Roy","suffix":""},{"id":623141500,"identity":"4182ee59-9b2e-4ffc-a2a3-5b0be0a7f988","order_by":1,"name":"Evan Thomas Saitta","email":"","orcid":"","institution":"Field Museum of Natural History","correspondingAuthor":false,"prefix":"","firstName":"Evan","middleName":"Thomas","lastName":"Saitta","suffix":""},{"id":623141501,"identity":"95a8d178-0019-486d-81ea-dc1164b1afd3","order_by":2,"name":"Maya Musa","email":"","orcid":"","institution":"University of Pavia","correspondingAuthor":false,"prefix":"","firstName":"Maya","middleName":"","lastName":"Musa","suffix":""},{"id":623141502,"identity":"fca2f4cf-e25f-4b55-9f4a-0a039a943f29","order_by":3,"name":"Sumaya Al-Kindi","email":"","orcid":"","institution":"Minerals Development Oman SAOC","correspondingAuthor":false,"prefix":"","firstName":"Sumaya","middleName":"","lastName":"Al-Kindi","suffix":""},{"id":623141503,"identity":"57996fc6-7136-4ba2-a35b-6e580270df07","order_by":4,"name":"Thomas G. 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Carotenoids evolved independently in various passerine groups and may have been present in early archosaurs, while psittacofulvins are unique to parrots and evolved only once. In the context of animal integuments, while melanin has been well-studied due to its wide distribution and high fossilization potential, polyene preservation remains less understood. To test their preservation potential, we conducted sediment-encased pressure-temperature maturation experiments on modern feathers. Feather samples containing carotenoids and psittacofulvins were compacted in clay and subjected to 250 bars of pressure at temperatures from 40-200°C, simulating geological diagenesis. Using UV-Vis-NIR, Raman, and FTIR spectroscopy we tracked the pigments’ chemical transformations. Our results show carotenoids are extremely unstable, rapidly degrading and acting as pro-oxidants that accelerate the decay of the feather's protein matrix. In contrast, psittacofulvins demonstrate greater resilience, predictably transforming into a semi-stable polycyclic aromatic geopolymer, or ‘psittacofulvin-char’, at higher temperatures. This establishes a clear taphonomic hierarchy (Melanin, Psittacofulvins, Carotenoids, and Corneous β Proteins) that explains the fossil record’s melanin bias. 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