Ecomorphology of plesiosaur flipper geometry

Abstract

The Plesiosauria is an extinct group of marine reptiles once common in mesozoic seas. Previous work on plesiosaur hunting styles has suggested that short-necked, large-headed animals were pursuit predators, whereas long-necked, small-headed animals were ambush predators. This study presents new data on the aspect ratios (ARs) of plesiosaur flippers, and interprets these data via comparison with AR in birds, bats and aircraft. Performance trade-offs implicit in AR variation are well-understood in the context of aircraft design, and these trade-offs have direct ecomorphological analogues in birds and bats. Knowledge of these trade-offs allows interpretation of variation in plesiosaur AR. By analogy, short-necked taxa were specialized for manoeuvrability and pursuit, whereas long-necked taxa were generally specialized for efficiency and cruising. These interpretations agree with previous assessments of maximum swimming speed

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).…”

The Evolution of Marine Reptiles

“…Some of them were giants, reaching 20 meters in total length (Nicholls and Manabe 2004), whereas the others were small, reaching only about 40 centimeters . Some were adapted to cruising long distances (Motani 2002a, b), whereas the others were more suitable for ambushing (Massare 1988;O'Keefe 2001).…”

Evolution of hyperphalangy and digit reduction in the cetacean manus

“…In many lineages of aquatic tetrapods including marine mammals (e.g., pinnipeds, sirenians, and cetaceans), fossils document the evolutionary changes from a weight-bearing forelimb, to a limb encased in a soft tissue flipper used in aquatic locomotion. In mosasaurs, the large and broad flipper allowed at least partial lift-based propulsion and the ability to swim quickly with high maneuverability (O'Keefe, 2001). However, in cetaceans (whales, dolphins, and porpoises) the flippers are streamlined and elongated, a shape that functions in lift, breaking, turning, and to stabilize and maintain equilibrium while swimming (Fish and Rohr, 1999).…”