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Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles

Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles
Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles
Throughout the animal kingdom, adaptive colouration serves critical functions ranging from inconspicuous camouflage to ostentatious sexual display, and can provide important information about the environment and biology of a particular organism1, 2. The most ubiquitous and abundant pigment, melanin, also has a diverse range of non-visual roles, including thermoregulation in ectotherms3, 4. However, little is known about the functional evolution of this important biochrome through deep time, owing to our limited ability to unambiguously identify traces of it in the fossil record2. Here we present direct chemical evidence of pigmentation in fossilized skin, from three distantly related marine reptiles: a leatherback turtle5, a mosasaur6 and an ichthyosaur7. We demonstrate that dark traces of soft tissue in these fossils are dominated by molecularly preserved eumelanin, in intimate association with fossilized melanosomes. In addition, we suggest that contrary to the countershading of many pelagic animals8, 9, at least some ichthyosaurs were uniformly dark-coloured in life. Our analyses expand current knowledge of pigmentation in fossil integument beyond that of feathers2, 10, allowing for the reconstruction of colour over much greater ranges of extinct taxa and anatomy. In turn, our results provide evidence of convergent melanism in three disparate lineages of secondarily aquatic tetrapods. Based on extant marine analogues, we propose that the benefits of thermoregulation and/or crypsis are likely to have contributed to this melanisation, with the former having implications for the ability of each group to exploit cold environments.
0028-0836
484-488
Lindgren, J.
73aad518-451a-4b75-8750-0ec44f68462e
Sjövall, P.
0d8726d9-46b1-43fa-9219-837ce0dd1942
Carney, R.
e77bb60a-2b4c-4ea6-949a-cb3ac62aee99
Uvdal, P.
8793735e-61b6-4be4-a559-81d9f5017991
Gren, J.
3f590dad-ea4b-463e-90f0-cc2b1a20a821
Dyke, G.
600ca61e-b40b-4c86-b8ae-13be4e331e94
Pagh Schultz, B.
100df1c7-2054-496e-94e7-92ea2aafbf4d
Shawkey, M.
7bf9c732-ef4b-4717-8d26-e2f6d37f54a3
Barnes, K.
16d4c700-62e1-49ba-83ea-84f0720f2405
Polcyn, M.
2ff3a0bd-75e0-4a60-9175-35557fdd63ef
Lindgren, J.
73aad518-451a-4b75-8750-0ec44f68462e
Sjövall, P.
0d8726d9-46b1-43fa-9219-837ce0dd1942
Carney, R.
e77bb60a-2b4c-4ea6-949a-cb3ac62aee99
Uvdal, P.
8793735e-61b6-4be4-a559-81d9f5017991
Gren, J.
3f590dad-ea4b-463e-90f0-cc2b1a20a821
Dyke, G.
600ca61e-b40b-4c86-b8ae-13be4e331e94
Pagh Schultz, B.
100df1c7-2054-496e-94e7-92ea2aafbf4d
Shawkey, M.
7bf9c732-ef4b-4717-8d26-e2f6d37f54a3
Barnes, K.
16d4c700-62e1-49ba-83ea-84f0720f2405
Polcyn, M.
2ff3a0bd-75e0-4a60-9175-35557fdd63ef

Lindgren, J., Sjövall, P., Carney, R., Uvdal, P., Gren, J., Dyke, G., Pagh Schultz, B., Shawkey, M., Barnes, K. and Polcyn, M. (2014) Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles. Nature, 506, 484-488. (doi:10.1038/nature12899).

Record type: Article

Abstract

Throughout the animal kingdom, adaptive colouration serves critical functions ranging from inconspicuous camouflage to ostentatious sexual display, and can provide important information about the environment and biology of a particular organism1, 2. The most ubiquitous and abundant pigment, melanin, also has a diverse range of non-visual roles, including thermoregulation in ectotherms3, 4. However, little is known about the functional evolution of this important biochrome through deep time, owing to our limited ability to unambiguously identify traces of it in the fossil record2. Here we present direct chemical evidence of pigmentation in fossilized skin, from three distantly related marine reptiles: a leatherback turtle5, a mosasaur6 and an ichthyosaur7. We demonstrate that dark traces of soft tissue in these fossils are dominated by molecularly preserved eumelanin, in intimate association with fossilized melanosomes. In addition, we suggest that contrary to the countershading of many pelagic animals8, 9, at least some ichthyosaurs were uniformly dark-coloured in life. Our analyses expand current knowledge of pigmentation in fossil integument beyond that of feathers2, 10, allowing for the reconstruction of colour over much greater ranges of extinct taxa and anatomy. In turn, our results provide evidence of convergent melanism in three disparate lineages of secondarily aquatic tetrapods. Based on extant marine analogues, we propose that the benefits of thermoregulation and/or crypsis are likely to have contributed to this melanisation, with the former having implications for the ability of each group to exploit cold environments.

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More information

e-pub ahead of print date: 8 January 2014
Published date: 25 February 2014
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 360992
URI: http://eprints.soton.ac.uk/id/eprint/360992
ISSN: 0028-0836
PURE UUID: db00bb64-0716-4f83-a56e-f3fea1242e22

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Date deposited: 09 Jan 2014 14:03
Last modified: 16 Jul 2019 21:14

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