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Fossil microbodies are melanosomes: evaluating and rejecting the ‘fossilised decay-associated microbes’ hypothesis

Citation

Roy, Arindam et al. (2020), Fossil microbodies are melanosomes: evaluating and rejecting the ‘fossilised decay-associated microbes’ hypothesis, Dryad, Dataset, https://doi.org/10.5061/dryad.xgxd254dj

Abstract

Melanosomes are membrane-bound organelles of varying geometry, commonly found within a range of vertebrate tissues, that contain the pigment melanin. Melanosomes have been identified in the fossil record in many exceptionally preserved fossils allowing reconstructions of the coloration of many extinct animals. However, these microstructures have also been interpreted as “microbial cells” or melanin producing bacteria based on their geometric similarities to melanosomes. Here we test these two conflicting hypotheses experimentally. Our results demonstrate multiple lines of evidence that these fossil microbodies are indeed melanosomes: the geometry of decay-associated microbes differs significantly from fossil microbodies; fossil microbodies are very strongly localized to in vivo melanized tissues and are absent in tissues typically unmelanized in vivo, in all fossils examined regardless of lithology or age. On the basis of these results, as well as a thorough review of existing literature on melanin like pigments, we are able to rule out a bacterial origin for fossil microbodies and demonstrate that fossil microbodies associated with exceptional vertebrate fossils are in fact preserved melanosomes.

Methods

This raw dataset has been collected by measuring modern melanosome samples, fossil microbodies in exceptionally preserved fossils and experimental decay microbial consortia from scanning electron micrographs. The variables measured and tabulated in this dataset are length, diameter and aspect ratio (length/diameter). Summary statistics of raw data are included in Sheet 9.

Usage Notes

Guide to Dataset Usage

File Name: DATA_Dryad_Roy et al. 2020

File organisation

|- Sheet 1: Fig 1 - Shape and size profiles of modern melanosomes, fossil microbodies and microbes from

decay experiments.

|- Sheet 2: Modern melanosome samples

|- Sheet 3: Microbodies from isolated fossil feathers

|- Sheet 4: Microbodies from fossil feathers attached to skeletal material

|- Sheet 5: Microbes from experimental decay of isolated feathers

|- Sheet 6: Microbes from experimental decay of bird carcasses (1 week of decay)

|- Sheet 7: Microbes from experimental decay of bird carcasses (2 weeks of decay)

|- Sheet 8: Microbes from experimental decay of tadpoles

|- Sheet 9: Summary statistics

There are missing values in Sheet 6 and Sheet 7 due to failure of microbial growth during the decay experiments.

Funding

Hong Kong Ph.D. Fellowship*, Award: PF16-09281

Bob Savage Memorial Fund, School of Earth Sciences, University of Bristol

Palaeontological Association Postgraduate Travel Fund (Grants-in- Aid scheme)

HKU MOOC course Dinosaur Ecosystems*

University of Bristol Alumni Foundation Travel Grant

Royal Society Research Grant, Award: RG15042

Hong Kong Ph.D. Fellowship, Award: PF16-09281

Bob Savage Memorial Fund, School of Earth Sciences, University of Bristol

Palaeontological Association Postgraduate Travel Fund (Grants-in- Aid scheme)

HKU MOOC course Dinosaur Ecosystems

University of Bristol Alumni Foundation Travel Grant

Royal Society Research Grant, Award: RG15042