A nearly metre-long front flipper from a giant Jurassic ichthyosaur preserves unusually detailed soft-tissue anatomy, including a fleshy tip and a serrated trailing edge. In a 2025 study, researchers proposed that these features may have helped the animal swim more quietly while hunting in dim water. The fossil provides evidence for a possible adaptation—not direct proof of how the animal behaved—and it is not the first ichthyosaur fossil with preserved soft tissue.
What did the giant ichthyosaur flipper fossil reveal?
The specimen is an isolated front flipper attributed to Temnodontosaurus, a large marine reptile that lived during the Jurassic. The 2025 paper describes skin ornamentations and a prolonged fleshy tip. A University of Manchester account of the study also reports a scalloped or serrated trailing edge and mineralized, rod-like structures the researchers call “chondroderms.”
Those are anatomical observations. The proposal that they reduced swimming noise is a functional interpretation based on the flipper’s structure and modeling, not something the fossil directly records. Lead researcher Johan Lindgren said the flipper’s wing-like shape, lack of bones at its distal end and serrated trailing edge together indicate that the animal had evolved ways to minimize sound while swimming.
What was found, and how large was it?
The fossil consists of part and counterpart preserving almost the entire front flipper, although its top portion is missing. No other remains were found with it. The University of Manchester account places the animal at about 183 million years ago, estimates that it exceeded 10 metres in length, and describes the flipper as one metre long. These are approximate figures reported for this specimen, not population-wide measurements.
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Georg Göltz, a fossil collector, found the specimen in a temporary road-cutting exposure at Dotternhausen, Germany, and brought it to paleontologist Sven Sachs’s attention, according to the university account. The researchers speculated that a larger ichthyosaur might have torn off the flipper, but the isolated fossil does not establish how it became separated.
How might a flipper help an ichthyosaur swim quietly?
The researchers used the flipper’s shape and trailing-edge structures to investigate how it may have moved through water. The University of Manchester report says the team used synchrotron X-ray microtomography, time-of-flight secondary-ion mass spectrometry, infrared microspectroscopy and computational fluid-dynamics modeling. Their interpretation is that the fleshy, serrated edge may have helped limit sound as water moved around the flipper.
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If the flipper did reduce swimming noise, that could have helped a large predator approach prey without alerting it. The study links that possibility to hunting in low light. But neither stealth nor a particular hunting event is preserved in the fossil: both are inferences about what the anatomy may have enabled.
Was this the first ichthyosaur fossil with soft tissue?
No. The 2025 find is notable for preserving detailed soft-tissue anatomy in a large ichthyosaur’s flipper, but soft tissue had been reported in ichthyosaurs before. A 2018 study of Stenopterygius described preserved skin layers, blubber, pigment-bearing cells and molecular remnants. The authors used those findings to discuss body insulation and coloration. A 2022 review surveyed the wider record of ichthyosaur soft-tissue evidence.
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| Study | Preserved evidence | Research question |
|---|---|---|
| 2018 Stenopterygius study | Skin layers, blubber, pigment-bearing cells and molecular remnants | Body covering, possible insulation and coloration |
| 2025 Temnodontosaurus study | Flipper skin ornamentations, a fleshy distal tip and trailing-edge structures | Flipper anatomy and a possible role in reducing swimming noise |
The two discoveries address different parts of ichthyosaur biology; the later flipper fossil does not replace or invalidate the earlier evidence.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What does the find change about prehistoric predators?
Ichthyosaurs were extinct marine reptiles, not dinosaurs. This specimen adds detailed evidence about the construction of a large ichthyosaur’s flipper and supports a testable proposal about how that shape may have affected swimming. It does not preserve a whole animal, a complete set of soft organs or a witnessed attack. The evidence supports a more specific discussion of possible hunting adaptations—not the claim that one fossil changes everything known about prehistoric predators.
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