Muscutt Luke E, Dyke Gareth, Weymouth Gabriel D, Naish Darren, Palmer Colin, Ganapathisubramani Bharathram
Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK
Evolutionary Zoology, University of Debrecen, 4032 Debrecen, Hungary.
Proc Biol Sci. 2017 Aug 30;284(1861). doi: 10.1098/rspb.2017.0951.
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.
已灭绝的海洋爬行生物plesiosaurs在脊椎动物中很独特，因为它们使用两对形态相同的鳍状肢来推进。尽管这些中生代海洋爬行动物的化石已经被发现了两个多世纪，但其串联鳍状肢推进系统的功能和动力学一直不明确且存在争议。在本研究中，我们首次对此问题进行了定量分析，报告了一系列精确控制的水箱实验，这些实验使用了根据保存完好的化石按比例重建的plesiosaur鳍状肢。我们的目的是确定哪种肢体运动会产生最有效和高效的推进力。我们发现，与单独使用相比，plesiosaur后鳍状肢与前鳍状肢协调运作时，产生的推力最多可增加60%，效率提高40%，鳍状肢之间的间距和相对运动对这些增加起着关键作用。我们的分析结果表明，这种现象可能在plesiosaur鳍状肢运动的整个范围内都存在，解决了关于这些海洋爬行动物推进方式的数百年争论，也说明了它们为何在一亿多年来一直保留着两对鳍状肢。
