Researchers have found evidence of a hibernation-like state in a 250m-year-old fossil of a creature that lived in Antarctica.
A creature that may look strange to our eyes – but was a distant relative of modern mammals – has helped uncover an important palaeontological discovery. Writing in Communications Biology, scientists at Harvard University and the University of Washington described the discovery of evidence of a hibernation-like state in an animal that lived in Antarctica during the Early Triassic period some 250m years ago.
This is the oldest evidence of a hibernation-like state in vertebrate animals and indicates that ‘torpor’ has been around a lot longer than we once thought. Torpor is a term used to describe hibernation and similar states when animals lower their metabolic rate and reduce activity to survive a harsh environment.
A member of the Lystrosaurus genus, the creature was common during this time and characterised by its turtle-like beak and ever-growing tusks. Around this time, Antarctica lay largely within the Antarctic Circle, which experienced extensive periods without sunlight in winter.
While hibernation in modern-day animals is well understood, scientists have found it difficult to study in fossilised remains.
“Animals that live at or near the poles have always had to cope with the more extreme environments present there,” said lead author Megan Whitney. “These preliminary findings indicate that entering into a hibernation-like state is not a relatively new type of adaptation. It is an ancient one.”
Finding ‘stress marks’
To make this discovery, Whitney and her fellow researchers compared cross-sections of tusks from six Antarctic Lystrosaurus to cross-sections of four found in South Africa. Much like elephants, the tusks of this creature grew continuously throughout its life, making it possible to study the rate of growth.
Both the Antarctic and South African tusks showed similar growth patterns with layers of dentine deposited in concentric circles like tree rings. However, the Antarctic tusks were slightly different in that they showed closely spaced, thick rings which indicate periods of less deposition due to prolonged stress, according to the researchers.
“The closest analogue we can find to the ‘stress marks’ that we observed in Antarctic Lystrosaurus tusks are stress marks in teeth associated with hibernation in certain modern animals,” said Whitney.
However, as this does not definitively prove hibernation occurred, the researchers hope to uncover and study more Lystrosaurus remains.
“What we observed in the Antarctic Lystrosaurus tusks fits a pattern of small metabolic ‘reactivation events’ during a period of stress, which is most similar to what we see in warm-blooded hibernators today,” Whitney said.