Interpreting melanin-based coloration through deep time: a critical review.
Colour, derived primarily from melanin and/or carotenoid pigments, is integral to many aspects of behaviour in living vertebrates, including social signalling, sexual display and crypsis. Thus, identifying biochromes in extinct animals can shed light on the acquisition and evolution of these biological traits. Both eumelanin and melanin-containing cellular organelles (melanosomes) are preserved in fossils, but recognizing traces of ancient melanin-based coloration is fraught with interpretative ambiguity, especially when observations are based on morphological evidence alone. Assigning microbodies (or, more often reported, their 'mouldic impressions') as melanosome traces without adequately excluding a bacterial origin is also problematic because microbes are pervasive and intimately involved in organismal degradation. Additionally, some forms synthesize melanin. In this review, we survey both vertebrate and microbial melanization, and explore the conflicts influencing assessment of microbodies preserved in association with ancient animal soft tissues. We discuss the types of data used to interpret fossil melanosomes and evaluate whether these are sufficient for definitive diagnosis. Finally, we outline an integrated morphological and geochemical approach for detecting endogenous pigment remains and associated microstructures in multimillion-year-old fossils.
Department of Geology, Lund University, 223 62 Lund, Sweden johan.lindgren@geol.lu.se.
Johan
J
Lindgren
Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA.
Alison
A
Moyer
Department of Geology, Lund University, 223 62 Lund, Sweden Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA.
Mary H
MH
Schweitzer
SP Technical Research Institute of Sweden, Chemistry, Materials and Surfaces, 501 15 Borås, Sweden.
Peter
P
Sjövall
MAX-IV laboratory, Lund University, 221 00 Lund, Sweden Chemical Physics, Department of Chemistry, Lund University, 221 00 Lund, Sweden.
Per
P
Uvdal
Department of Biology, Lund University, 223 62 Lund, Sweden.
Dan E
DE
Nilsson
MAX-IV laboratory, Lund University, 221 00 Lund, Sweden.
Jimmy
J
Heimdal
MAX-IV laboratory, Lund University, 221 00 Lund, Sweden.
Anders
A
Engdahl
Department of Geology, Lund University, 223 62 Lund, Sweden.
Johan A
JA
Gren
MUSERUM, Natural History Division, 7800 Skive, Denmark.
Bo Pagh
BP
Schultz
Museum of Evolution, Uppsala University, 752 36 Uppsala, Sweden Palaeobiology Programme, Department of Earth Sciences, Uppsala University, 752 36 Uppsala, Sweden.
Benjamin P
BP
Kear
D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D008543:Melanins / Q000737:chemistry*; D020460:Melanosomes / Q000502:physiology; D008830:Microbodies / Q000737:chemistry*; D010858:Pigmentation; D014714:Vertebrates / Q000502:physiology*
D008543:Melanins; C041877:eumelanin
bacteria; eumelanin; melanosome; pheomelanin; pyomelanin; vertebrate