Hibernation may have a far more ancient history than previously thought. A new study suggests that 250 million years ago, a pig-size, ancient relative to mammals slowed its metabolism during harsh Antarctic winters, The New York Times reports. Lystrosaurus, which translates to “shovel lizard,” had short, stubby tusks that grew in layers similar to tree rings. When researchers compared cross-sections of six Lystrosaurus tusks from Antarctica with four from what is now South Africa, they found that the tusks from the Antarctic had closely spaced, thick rings, indicating a slowdown in metabolism, they report this week in Communications Biology. Such a slowdown likely resulted from stress. And given the regularity of the pattern—and its similarity to those in the teeth of modern-day hibernators—ancient hibernation is a likely cause.
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