Scientists have created a biotechnology-based control system to simulate plesiosaur swimming by solving the long-debated “four-wing problem.” A research team may have solved the mystery of how a plesiosaur, an ancient marine reptile, moved by developing a biotechnology-inspired control system that mimics its locomotion settings.

Extinct animals have significantly different body shapes than extant animals; therefore, it is difficult to determine how they move when comparing them to living species. In addition, fossils rarely preserve the soft tissue of limbs that scientists need to study movement and obtain important information about lifestyles.

Plesiosaurs roamed Earth’s prehistoric oceans thanks to their unique body structure, which included four large, equal-sized fins. But how plesiosaurs used these fins to swim has long puzzled paleontologists. This so-called “four-wing problem” has been hotly debated for many years.

But now a research team consisting of researchers from Tohoku University, Kanagawa University and the University of Manchester has developed a new approach to solve this mystery.

“Instead of focusing solely on how water interacted with plesiosaur bodies, that is, the hydrodynamics of swimming, we decided to investigate how these animals controlled their movements,” says Akio Ishiguro, a professor at Tohoku University’s Telecommunications Research Institute (RIEC). “This was because plesiosaurs could swim at different speeds and in different conditions.”

Inspiration from living things

Akio and his colleagues were inspired by the coordination mechanisms between limbs that underlie the flexible gait used by other quadrupedal vertebrates such as dogs and cats. They developed an autonomous, decentralized control system for a plesiosaur-like robot.

Experimental results showed that the control system successfully generated coordinated patterns between the anterior and posterior fins in response to changes in the oscillatory cycle and morphology.

“Our new approach reconstructs the way extinct animals can regulate their movement patterns in a flexible and situation-dependent manner,” says Akira Fukuhara, associate professor at RIEC and lead/first author of the paper. “This also means we can start exploring the movement repertoire of other extinct animals and learn more about their lifestyles.”

Details of the results were recently published in the journal. Scientific Reports.

Also participating in the research were two former RIEC graduate students, Mtsutoshi Sato and Hisayuki Ogawa; With Kanagawa University professor Tamaki Sato; and William Sellers, professor at the University of Manchester.

Looking ahead, the research team hopes to produce a movement reconstruction that takes other aspects of plesiosaur bodies into account. “Plesiosaurs are known to have long necks, but this length varied greatly from creature to creature,” Ishiguro adds. “We hope to create models that include the role of the neck, head and torso in controlling the movements of these ancient creatures.”