The four-flipper swimming method of plesiosaurs enabled efficient and effective locomotion

Abstract

The extinct ocean-going plesiosaurs were unique within vertebrates because they used two flipper pairs identical in morphology for propulsion. Although fossils of these Mesozoic marine reptiles have been known for more than two centuries, the function and dynamics of their tandem-flipper propulsion system has always been unclear and controversial. We address this question quantitatively for the first time in this study, reporting a series of precisely controlled water tank experiments that use reconstructed plesiosaur flippers scaled from well-preserved fossils. Our aim was to determine which limb movements would have resulted in the most efficient and effective propulsion. We show that plesiosaur hind flippers generated up to 60% more thrust and 40% higher efficiency when operating in harmony with their forward counterparts, when compared with operating alone, and the spacing and relative motion between the flippers was critical in governing these increases. The results of our analyses show that this phenomenon was probably present across the whole range of plesiosaur flipper motion and resolves the centuries-old debate about the propulsion style of these marine reptiles, as well as indicating why they retained two pairs of flippers for more than 100 million years.

Estimating the evolutionary rates in mosasauroids and plesiosaurs: discussion of niche occupation in Late Cretaceous seas

“…Swimming modes and abilities of Mesozoic aquatic vertebrates are tightly connected with their physiology, behavior, and other aspects of their biology and, thus, constitute an important research area (e.g., Massare, 1988;Massare, 1994;Motani, 2002). A number of studies have thoroughly assessed the swimming abilities in plesiosaurs and discussed the differences in the two main plesiosaur 'body plans' -the 'long-' and 'short-necked' forms (e.g., Frey & Riess, 1982;Tarsitano & Riess, 1982;Godfrey, 1984;Halstead, 1989;Nicholls & Russell, 1991;Lingham-Soliar, 2000;O'Keefe, 2001;Carpenter et al, 2010;Liu et al, 2015;Muscutt et al, 2017;Noè, Taylor & Gómez-Pérez, 2017;Troelsen et al, 2019). The same applies to mosasauroids whose swimming abilities and especially their origin have been assessed through detailed studies of various aspects of their anatomy (see, e.g., Lindgren, Jagt & Caldwell, 2007;Lindgren et al, 2010;Lindgren, Polcyn & Young, 2011;Konishi et al, 2012;LeBlanc, Caldwell & Lindgren, 2013;Lindgren, Kaddumi & Polcyn, 2013;Houssaye & Bardet, 2013;Cuthbertson et al, 2015;D'Emic, Smith & Ansley, 2015).…”

Deflected wake interaction of tandem flapping foils

“…To improve the propulsive performance of a flapping system, various researchers have proposed the use of multiple foil configurations. In particular, tandem flapping foils are shown to improve thrust generation via wake recapture both numerically (Akhtar et al 2007;Broering & Lian 2012;Muscutt, Weymouth & Ganapathisubramani 2017b) and experimentally (Warkentin & DeLaurier 2007;Usherwood & Lehmann 2008;Muscutt et al 2017a). More specifically, thrust and efficiency augmentation can be achieved when the hind foil is weaving within the incoming vortices shed by the front one, determined by the inter-foil spacing and phase lag.…”

“…Moreover, tandem flapping configurations, e.g. insect wings (Alexander 1984;Thomas et al 2004), plesiosaur flippers (Muscutt et al 2017a), etc., are shown to outperform single flappers under certain wake-to-wake interactions.…”

3D Printing: Applications in evolution and ecology

“…As we have seen 3D printing allows the production highly complex and detailed models that can be used for research. Printed models of extinct organisms, for example, can be used to measure efficiency of flight or swimming, helping us to understand behavior and function of prehistoric creatures (e.g., swimming methods of plesiosaurs, Muscutt et al, ).…”