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是谁杀死了巨齿鲨？

The sharks that roam today’s oceans can be fearsome, but they don’t really compare to some of the species that dominated the seas millions of years ago.

如今游弋在海洋中的鲨鱼可能令人生畏，但它们与数百万年前主宰海洋的某些物种相比，实在是小巫见大巫。

The megalodon — a massive shark that is thought to have died out around 2.6 million years ago — has left plenty of fossils behind for researchers to find, but determining what exactly killed the species off has proven a big challenge.

巨齿鲨—一种被认为在260万年前灭绝的巨型鲨鱼，留下了大量化石供研究人员寻找究竟是什么杀死了它，如今这却被证明是一个巨大的挑战。

As LiveScience reports, new research was presented recently at the annual American Geophysical Union conference that suggests the shark could regulate its body temperature similar to some species of modern sharks. However, the ancient shark’s much higher body temperature may have been its downfall.

据生命科学网站报道，最近美国地球物理联合会的年度会议上一项新的研究表明，这种鲨鱼可以像某些种类的现代鲨鱼一样调节体温。然而，这种古老鲨鱼体温要高得多，这可能是它灭绝的原因。 　　Determining the body temperature of an animal that hasn’t existed for millions of years is tough but not impossible. Clues to the shark’s body temperature were found in its teeth. Isotope bonds form differently depending on the temperature and the teeth of the megalodon suggest its body temperature was very high.

确定一种已经灭绝数百万年的动物的体温是困难的，但并非不可能。这种鲨鱼的牙齿中有它的体温线索。不同同位素键的形成取决于温度，巨齿鲨的牙齿表明它的体温非常高。 　　The shark’s size was the key to its dominance, but it was so large that its body temperature may have rivaled that of whales.

这种鲨鱼的体型是其称霸海洋的关键，但它的体型如此之大，以至于它的体温可能可以与鲸鱼相匹敌。 　　If the creature was keeping its body temperature as high as 104 degrees Fahrenheit, its metabolism would likely have demanded that it consume a huge amount, and as global temperatures change, it’s likely that the sharks just couldn’t keep up.

如果这种生物的体温一直保持在104华氏度这么高，那么它的新陈代谢很可能需要消耗大量的热量，而随着全球气温的变化，这种鲨鱼很可能没法保持体温。

As the shark’s prey moved to new, cooler areas, the massive predators would have felt a serious pinch. It’s also likely that new predators began to out-hunt the large sharks, putting even more strain on the species.

当这种鲨鱼的猎物转移到新的、较冷的地区时，作为大型掠食者，它会感到严重的生存压力。也有可能是有新的捕食者开始捕杀这种大型鲨鱼，给这个物种带来更大的生存压力。