Using four paddle-like limbs to propel its bulky body through the water, the pliosaur made easy work of passing prey such as dolphin-like ichthyosaurs.
上龙用四根桨状的四肢推动它庞大的身体在水里游来游去，轻而易举地就能掠食形似海豚的鱼龙。
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So, it's a trivial matter, by looking at what is the weight and how far does it drop, to say OK, how much work is done by the paddle wheel.