Scientists in Germany have brought Jurassic Park to life by building a working model plesiosaur from replica bones.
Plesiosaurs, who lived about 210 million years ago, adapted to life underwater in a unique way: their front and hind legs evolved in the course of evolution to form four uniform, wing-like flippers.
Dr Anna Krahl has investigated how they used these to move through the water. By reconstructing their bones and from that, muscles via digital model, she was able to show that it was necessary to twist the flippers in order to travel forwards.
Researchers in vertebrate palaeontology have puzzled for 120 years about how plesiosaurs swam - but Dr Krahl believes she has finally found the answer.
"Having the front legs transformed into wing-like flippers is relatively common in evolution, for instance, in sea turtles. Never again, however, did the hind legs evolve into an almost identical-looking airfoil-like wing," explains Anna.
She tested out their mobility options, which meant working out whether they moved like modern ducks, turtles, or sea lions. The question remained how plesiosaurs could ultimately twist their flippers to place them in a hydrodynamically favourable position and produce lift without rotating the upper arm and thigh around the longitudinal axis. A reconstruction of the muscles of the fore, and hind flippers for Cryptoclidus using reptiles alive today, showed that plesiosaurs could actively enable such flipper twisting.
In addition to classical models, the researchers also used digital ones.
"These digital models were the basis for calculating the forces using a method we borrowed from engineering: the finite element method, or FE," she notes. "Analysis comparing them to modern-day sea turtles, and based on what is known about their swimming process, indicated that plesiosaurs were probably not able to rotate their flippers as much as would be necessary for rowing."