Evrim Yazgin
Cosmos science journalist
Noise from ships play a harmful role in the lives of marine-dwellers including whales and dolphins which rely on sonar and echolocation for hunting, mating and social bonding.
A new study suggests that a possible solution might have been found more than 180 million years ago.
Palaeontologists propose, in a paper published in Nature, that modern ships could employ a similar system used by ancient marine reptiles which had specialised fins to sneak up on their prey.
Ichthyosaurs evolved at least 250 million years ago from early reptiles which returned from dry land to the seas. These dolphin-like creatures were the best adapted to life underwater of all the marine reptiles which lived during the time of the dinosaurs.
Some ichthyosaurs grew to be enormous and may even have rivalled the blue whale for size.
The ichthyosaur described in the Nature paper is a Temnodontosaurus which lived between 183 and 181 million years ago, during the Jurassic period. Temnodontosaurus could grow to about 9m long and had one of the largest eyes of any animal living or extinct.
The first Temnodontosaurus specimen was found by legendary palaeontologist Mary Anning and her brother Joseph in Dorset, England in the 1810s.
A new fossilised Temnodontosaurus flipper found in southwest Germany offers insight into how these ancient marine reptiles’ specially-adapted flippers made them silent but deadly hunters. The new fossil uniquely preserves impressions of soft tissue around the flipper bones.
The flipper is about 1m long, and has a wing-like shape with a serrated edge and flexible tip.
Computer simulations of the fluid dynamics showed that the serrated edge of the flipper provided the ancient marine reptile with stealth by suppressing hydrodynamic noise caused by the flipper.
They say this is the first time such an evolutionary tactic has been seen in ichthyosaurs and would have helped Temnodontosaurus hunt in dimly lit open ocean environments.
The authors say this ancient solution could solve modern problems.
“Auditory cues are important sensory stimuli to seagoing animals not only in the distant past but also today,” they write in their conclusion. “Increased ambient noise from shipping activity, military sonar and offshore wind farms is therefore a growing concern because of its negative impact on aquatic life.
“To reduce human-induced noise pollution (that is, anthropogenic masking of biotic sounds), the effectiveness of passive flow control devices, such as trailing edge serrations and surface treatments, on hydrofoils and aerofoils is currently being explored. Our findings show that such features already existed in at least one lineage of ichthyosaurs 183 million years ago.”