古生物学：獲物に忍び寄るための古代爬虫類の特殊なヒレ

Ichthyosaurs — marine reptiles from the Mesozoic era that resembled dolphins — may have had specialized fins that allowed them to sneak up on prey by reducing ambient noise, according to a paper published in Nature. The findings may offer insight into how modern noise pollution could be reduced using engineering that mimics the fin.

The ichthyosaurs were a group of reptiles that successfully transitioned from terrestrial to marine environments. In doing so, these creatures transformed their bodies from those that mimicked reptiles to those that more closely resemble sharks or dolphins. However, previous insights into the ichthyosaurs’ soft tissue anatomy have mostly been derived from the outlines of their bodies, as opposed to fossilized evidence.

John Lindgren and colleagues present fossil evidence of a unique front flipper from an ichthyosaur named Temnodontosaurus, which lived between 183 and 181 million years ago. The flipper fossil, excavated from the Pliensbachian–Toarcian Posidonia Shale in southwest Germany, is approximately one meter long and features a wing-like shape with a serrated edge and a flexible tip. Lindgren and colleagues suggest that the fin was used by the Temnodontosaurus during hunting. More specifically, through computer fluid dynamics simulations, the authors propose that the serrations on the fin likely helped reduce noise from the reptile as it hunted prey in dimly lit marine environments.

The authors note that hearing has long been a crucial sense amongst seafaring creatures, and in the modern day, that sense is disrupted by human activity, such as shipping activity and military sonar. Lindgren and colleagues suggest that the fin serrations and surface texture of Temnodontosaurus could serve as a blueprint to reduce noise pollution in the open ocean.