A study of fossil tusk layers from Antartica suggests that a very widespread species resorted to hibernation back then:
Scientists discovered the hibernation-like state in a member of the genus Lystrosaurus, a distant relative of mammals. The stubby, pig-like animal first emerged in the fossil record not long before the end of the Permian Period, which was marked by a mass extinction event that wiped out 70 percent of land-based vertebrates…
Scientists were able to the discover the animal’s hibernation by studying its tusks, the cross sections of which contain records of metabolism, growth and stress.
Brooks Hays, “Fossil suggests animals have been hibernating for 250 million years” at UPI
Paper. (open access)