题目内容：

英语翻译
【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.
【】里句子结构比较乱,请教高手分析句子结构,然后再标准翻译,

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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 ...