Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur
Journal article, 2018
Ichthyosaurs are extinct marine reptiles that display a notable external similarity to modern toothed whales. Here we show that this resemblance is more than skin deep. We apply a multidisciplinary experimental approach to characterize the cellular and molecular composition of integumental tissues in an exceptionally preserved specimen of the Early Jurassic ichthyosaur Stenopterygius. Our analyses recovered still-flexible remnants of the original scaleless skin, which comprises morphologically distinct epidermal and dermal layers. These are underlain by insulating blubber that would have augmented streamlining, buoyancy and homeothermy. Additionally, we identify endogenous proteinaceous and lipid constituents, together with keratinocytes and branched melanophores that contain eumelanin pigment. Distributional variation of melanophores across the body suggests countershading, possibly enhanced by physiological adjustments of colour to enable photoprotection, concealment and/or thermoregulation. Convergence of ichthyosaurs with extant marine amniotes thus extends to the ultrastructural and molecular levels, reflecting the omnipresent constraints of their shared adaptation to pelagic life.
Author
Johan Lindgren
Lund University
Peter Sjövall
RISE Research Institutes of Sweden
Volker Thiel
University of Göttingen
Wenxia Zheng
North Carolina State University
Shosuke Ito
Fujita Health University
Kazumasa Wakamatsu
Fujita Health University
Rolf Hauff
Urwelt-Museum Hauff
Benjamin P. Kear
Uppsala University
Anders Engdahl
Lund University
Carl Alwmark
Lund University
Mats E. Eriksson
Lund University
M. Jarenmark
Lund University
Sven Sachs
Naturkundemuseum Bielefeld
Per E. Ahlberg
Uppsala University
Federica Marone
Paul Scherrer Institut
Takeo Kuriyama
Wildlife Management Research Center
University of Hyogo
Ola Gustafsson
Lund University
Per Malmberg
Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry
Aurélien Thomen
University of Gothenburg
Irene Rodríguez-Meizoso
Lund University
P. Uvdal
Lund University
Makoto Ojika
Nagoya University
Mary H. Schweitzer
Lund University
North Carolina State University
North Carolina Museum of Natural Sciences
Nature
0028-0836 (ISSN) 1476-4687 (eISSN)
Vol. 564 7736 359-365Subject Categories
Evolutionary Biology
Other Earth and Related Environmental Sciences
Zoology
Infrastructure
Chalmers Infrastructure for Mass spectrometry
DOI
10.1038/s41586-018-0775-x
PubMed
30518862