Computer Simulations Imply Forelimb-Dominated Underwater Flight in Plesiosaurs

Abstract

Plesiosaurians are an extinct group of highly derived Mesozoic marine reptiles with a global distribution that spans 135 million years from the Early Jurassic to the Late Cretaceous. During their long evolutionary history they maintained a unique body plan with two pairs of large wing-like flippers, but their locomotion has been a topic of debate for almost 200 years. Key areas of controversy have concerned the most efficient biologically possible limb stroke, e.g. whether it consisted of rowing, underwater flight, or modified underwater flight, and how the four limbs moved in relation to each other: did they move in or out of phase? Previous studies have investigated plesiosaur swimming using a variety of methods, including skeletal analysis, human swimmers, and robotics. We adopt a novel approach using a digital, three-dimensional, articulated, free-swimming plesiosaur in a simulated fluid. We generated a large number of simulations under various joint degrees of freedom to investigate how the locomotory repertoire changes under different parameters. Within the biologically possible range of limb motion, the simulated plesiosaur swims primarily with its forelimbs using an unmodified underwater flight stroke, essentially the same as turtles and penguins. In contrast, the hindlimbs provide relatively weak thrust in all simulations. We conclude that plesiosaurs were forelimb-dominated swimmers that used their hind limbs mainly for maneuverability and stability.

New insights on the systematics, palaeoecology and palaeobiology of a plesiosaurian with soft tissue preservation from the Toarcian of Holzmaden, Germany

“…These mineralized soft tissues could thus bring limited but crucial constraints when determining the efficiency and manoeuvrability of the propulsive organs. Indeed, several studies have explored the buoyancy, swimming ability and velocity of plesiosaurians (e.g., Long et al 2006;Massare 1988;Motani 2002;O'Keefe 2001;Henderson 2006;Liu et al 2015), and the evidence presented here would thus support the idea that wing area in plesiosaurians was much larger than that suggested by skeletal remains alone.…”

Evidence for survival in a Middle Jurassic plesiosaur with a humeral pathology: What can we infer of plesiosaur behaviour?

“…This is analogous to that of penguins (Clark and Bemis, 1979;Liu et al, 2015), sea turtles (Gaillard et al, 2003;Liu et al, 2015;Walker, 1971), and sea lions (English, 1976;Liu et al, 2015). Halstead (1989) suggested that the plesiosaur body morphotype resembles that of turtles, noting the disparate size of fore and hind limbs.…”

“…Multiple authors (Godfrey, 1984;LinghamSoliar, 2000;Liu et al, 2015;Smith, 2013) suggested that plesiosaur propulsion was dependent on the forelimbs providing the power strokes (as confirmed by modeling), with hindlimbs providing directionality. This is analogous to that of penguins (Clark and Bemis, 1979;Liu et al, 2015), sea turtles (Gaillard et al, 2003;Liu et al, 2015;Walker, 1971), and sea lions (English, 1976;Liu et al, 2015).…”

“…The extensive loss of articular surface, however, suggests that the bones were not in direct contact, but flailed without control. Plesiosaur forelimb paddles have only one movable joint, that between the shoulder girdle and the humerus (Liu et al, 2015), so its function is critical to use of that limb. As to the muscles affected by the injury, function of the supracoracoideus, clavodeltoideus, and coracobrachialis were likely impaired, but the major muscle function impairment was that of the triceps and latissimus dorsi (Figure 7).…”

Computational fluid dynamics as a tool for testing functional and ecological hypotheses in fossil taxa

“…() compared the hydrodynamic performance of the fossil fish Saurichthys to a range of extant taxa; and Liu et al . () carried out simulations of water flow around an articulated, free‐swimming plesiosaur model.…”