what are the names of their extinct relatives?
"Euceratherium",  "Soergelia",  "Praeovibos", etc.
Muskox
The first well known muskox, the "shrub-ox" "Euceratherium", crossed to North America over an early version of the Bering Land Bridge two million years ago and prospered in the American southwest and Mexico.
where did the polar bear live with her family In the Arctic Circle, encompassing the Arctic Ocean what do they eat? ringed and bearded seals are they very strict about their diet? No. in what way? They consume a wide variety of other wild foods, including muskox birds, eggs, rodents, crabs, other crustaceans and other polar bears. did these birds exist since prehistoric days? UNANSWERABLE does the first animal has any links to prehistoric period? Yes, during the Pleistocene period, muskoxen were much more widespread.
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Muskox [SEP] Fossil history and extinct relatives
The first well known muskox, the "shrub-ox" "Euceratherium", crossed to North America over an early version of the Bering Land Bridge two million years ago and prospered in the American southwest and Mexico. "Euceratherium" was larger yet more lightly built than modern muskoxen, resembling a giant sheep with massive horns, and preferred hilly grasslands. A genus with intermediate horns, "Soergelia", inhabited Eurasia in the early Pleistocene, from Spain to Siberia, and crossed to North America during the Irvingtonian (1.8 million years to 240,000 years ago), soon after "Euceratherium". Unlike "Euceratherium", which survived in America until the Pleistocene-Holocene extinction event, "Soergelia" was a lowland dweller that disappeared fairly early, displaced by more advanced ungulates, such as the "giant muskox" "Praeovibos" (literally "before "Ovibos"").