The helmeted muskox was the most common and widespread muskox in North America during the last glaciation. (This conclusion is based upon the number of fossils found). The species inhabited steppe and alpine grasslands as well as woodlands, ranging from Alaska and Yukon to southern Texas, and from the Pacific to the Atlantic coasts.
The helmeted muskox was taller and had a more slender build than the living muskox. Its skull is longer and deeper than that of living muskoxen, and it supported horns that were situated higher and that flared more than those of the latter.
Hair and pellet-like droppings associated with a well-preserved skeleton from Alaska indicate that the helmeted muskox had a dark brown coat, and fed on grasses, sedges and occasionally shrubs.
Although the helmeted muskox reached eastern Beringia (unglaciated areas of Alaska, Yukon and Northwest Territories) it was confined to North America (fossils not having been reported from Siberia and other parts of Eurasia). It died out toward the close of the last glaciation, about 11 000 years ago—perhaps in part because of increasing competition in the north with the muskox and medium-horned bison farther south.