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If a diver surfaces too quickly, he may suffer the bends. Nitrogen dissolved in his blood is suddenly liberated by the reduction of pressure. The consequence, if the bubbles accumulate in a joint, is sharp pain and a bent body—thus the name. If the bubbles form in his lungs or his brain, the consequence can be death.
如果潜水员浮出水面太快，他可能会身体弯曲。血液中溶解的氮由于压力的降低而突然释放出来。如果气泡积聚在关节中，其后果是剧烈疼痛和身体弯曲。如果气泡在他的肺部或大脑中形成，后果可能是死亡。
Other air-breathing animals also suffer this decompression sickness if they surface too fast: whales, for example. And so, long ago, did ichthyosaurs. That these ancient sea animals got the bends can be seen from their bones. If bubbles of nitrogen form inside the bone they can cut off its blood supply. This kills the cells in the bone, and consequently weakens it, sometimes to the point of collapse. Fossil bones that have caved in on themselves are thus a sign that the animal once had the bends.
其他呼吸空气的动物如果浮出水面太快也会遭受这种减压病：例如鲸鱼。很久以前，鱼龙也是如此。从它们的骨骼中可以看出这些古代海洋动物弯曲了。如果骨骼内形成氮气泡，就会切断骨骼的血液供应。这会杀死骨骼中的细胞，从而削弱骨骼，有时甚至到崩溃的地步。因此，化石骨骼本身已经塌陷，这是这种动物曾经弯曲的迹象。
Bruce Rothschild of the University of Kansas knew all this when he began a study of ichthyosaur bones to find out how widespread the problem was in the past. What he particularly wanted to investigate was how ichthyosaurs adapted to the problem of decompression over the 150 million years. To this end, he and his colleagues traveled the world's natural-history museums, looking at hundreds of ichthyosaurs from the Triassic period and from the later Jurassic and Cretaceous periods.
堪萨斯大学的布鲁斯·罗斯柴尔德在开始对鱼龙骨骼进行研究时就知道了这一切，以了解这个问题在过去有多普遍。他特别想研究的是，在1.5亿年的时间里，鱼龙是如何适应减压问题的。为此，他和同事们参观了世界自然历史博物馆，观察了数百种三叠纪以及侏罗纪和白垩纪晚期的鱼龙。
When he started, he assumed that signs of the bends would be rarer in younger fossils, reflecting their gradual evolution of measures to deal with decompression. Instead, he was astonished to discover the opposite. More than 15% of Jurassic and Cretaceous ichthyosaurs had suffered the bends before they died, but not a single Triassic specimen showed evidence of that sort of injury.
当他开始研究时，他认为年轻化石中弯曲的迹象会更罕见，这反映了它们处理减压措施的逐渐演变。相反，他惊讶地发现了相反的情况。超过15%的侏罗纪和白垩纪鱼龙在死亡前曾遭受过弯曲，但没有一个三叠纪的标本显示这种伤害的证据。
If ichthyosaurs did evolve an anti-decompression means, they clearly did so quickly—and, most strangely, they lost it afterwards. But that is not what Dr Rothschild thinks happened. He suspects it was evolution in other animals that caused the change.
如果鱼龙确实进化出了一种抗减压手段，那么它们显然进化得如此之快，而且最奇怪的是，它们后来失去了这种能力。但罗斯柴尔德博士并不是这么认为的。他怀疑是其他动物的进化导致了这种变化。
Whales that suffer the bends often do so because they have surfaced to escape a predator such as a large shark. One of the features of Jurassic oceans was an abundance of large sharks and crocodiles, both of which were fond of ichthyosaur lunches. Triassic oceans, by contrast, were mercifully shark- and crocodile-free. In the Triassic, then, ichthyosaurs were top of the food chain. In the Jurassic and Cretaceous, they were prey as well as predator—and often had to make a speedy exit as a result.
遭受弯曲的鲸鱼经常这样做，因为它们浮出水面是为了躲避大型鲨鱼等捕食者。侏罗纪海洋的特征之一是有大量的大鲨鱼和鳄鱼，它们都喜欢以鱼龙作为午餐。相比之下，三叠纪的海洋幸运地没有鲨鱼和鳄鱼。在三叠纪，鱼龙是食物链的顶端。在侏罗纪和白垩纪，它们既是猎物也是捕食者，因此经常不得不迅速离开。
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