Adaptations for stealth in the wing-like flippers of a large ichthyosaur

Summary, in English

With their superficially shark-like appearance, the Mesozoic ichthyosaurs provide a classic illustration of major morphological adaptations in an ancestrally terrestrial tetrapod lineage following the invasion of marine habitats^{1, 2–3}. Much of what is known about ichthyosaur soft tissues derives from specimens with body outlines^{4, 5–6}. However, despite offering insights into aspects of biology that are otherwise difficult to envisage from skeletal evidence alone (such as the presence of a crescentic fluke), information on their soft parts has hitherto been limited to a taxonomically narrow sample of small- to dolphin-sized animals^{2,4, 5–6}. Here we report the discovery of a metre-long front flipper of the large-bodied Jurassic ichthyosaur Temnodontosaurus, including unique details of its soft-tissue anatomy. In addition to revealing a wing-like planform, the fossil preserves a serrated trailing edge that is reinforced by novel cartilaginous integumental elements, herein denominated chondroderms. We also document chordwise-parallel skin ornamentations and a protracted fleshy distal tip that presumably acted like a flexible winglet in life. By integrating morphological and numerical data, we show that the observed features probably provided hydroacoustic benefits, and conclude that the visually guided^7,8Temnodontosaurus relied on stealth while hunting in dim-lit pelagic environments. This unexpected combination of control surface modifications represents a previously unrecognized mode of concealment, and underscores the importance of soft-tissue fossils when inferring aspects of palaeoethology and predator–prey palaeoecology.

• Author: Johan Lindgren; Dean R. Lomax; Robert Zoltán Szász; Miguel Marx; Johan Revstedt; Georg Göltz; Sven Sachs; Randolph G. De La Garza; Miriam Heingård; Martin Jarenmark; Kristina Ydström; Peter Sjövall; Frank Osbæck; Stephen A. Hall; Michiel Op de Beeck; Mats E. Eriksson; Carl Alwmark; Federica Marone; Alexander Liptak; Robert Atwood; Genoveva Burca; Per Uvdal; Per Persson; Dan Eric Nilsson
• Department/s: Department of Geology; LTH Profile Area: The Energy Transition; Department of Energy Sciences; eSSENCE: The e-Science Collaboration; Medical Radiation Physics, Lund; Solid Mechanics; Centre for Environmental and Climate Science (CEC); LU Profile Area: Light and Materials; LTH Profile Area: Photon Science and Technology; Chemical Physics; Sensory Biology; LU Profile Area: Natural and Artificial Cognition; Lund Vision Group
• Publishing year: 2025-08-28
• Language: English
• Pages: 976-983
• Publication/Series: Nature
• Volume: 644
• Issue: 8078
• Links: http://dx.doi.org/10.1038/s41586-025-09271-w
• Document type: Journal article
• Publisher: Nature Publishing Group
• Topic: Palaeontology and Palaeoecology
• Status: Published
• Research group: Lund Vision Group
• ISBN/ISSN/Other: ISSN: 0028-0836