Also known as Harlan’s muskox, woodox, woodland muskox, helmeted muskox, or bonnet-headed muskox. This extinct critter was from the bovid genus, and the middle to late Pleistocene of North America. During the pleistocene, Bootherium was one of the most widely distributed muskox species in North America. It is most closely related to the modern muskox.

Size and physical description
Bootherium were estimated to weigh around 423.5 kg (934 lb). They had a thicker skull and considerably longer snout. Hence the name helmeted muskox. The horns of were situated high on the skull, with a downward curve and were fused along the midline of the skull. Unlike tundra muskoxen whose horns are separated by a medial groove.
The helmeted muskox was taller and less robust than the tundra muskox. It had longer legs, a shorter, lighter, more gracile body, and less protruding eye orbits (Guthrie 1992). It had a long, deep skull, which, in males has a roughly pitted, basined surface between the horn cores.
The horn cores were located high on the skull and curved outwards and downwards.
Studies have concluded the ox beast had shorter, lighter coat with much shorter, finer guard hairs than are found in the living muskox. They had a significantly longer tail. Characteristics that indicate less emphasis on body heat conservation.

Did you know? helmeted muskox name derives from the helmet-like boney plate that covers the animal’s skull.

Habitat:
Recovered from a wide range of habitats, including grasslands, alpine meadows and woodlands. They have been found in association with a disperse range of animals, including tree squirrels, open-habitat voles, caribou, and extinct stag-moose (Cervalces). Bootherium probably moved between boreal forests and open areas. Compared with the barren, tundra habitats occupied by the extant species of muskox (Ovibos). Suported by the warmer interglacial periods in beringa. The nature of the presumed habitats utilized by Bootherium indicates that this animal was adapted to slightly warmer climates than the extant muskox.

Diet
The helmeted muskox appears to have been a generalist herbivore. A study of preserved plant materials recovered from the molars of six different Bootherium skulls in Alaska were studied. Combined with the examination of fecal pellets, both show the species consumed both grasses and woody plants (Guthrie 1992). In particular, this study revealed that these animals chowed down on woody plant bark, various upland grasses, willows, and large amounts of Vaccinium, an ericaceous shrub . Bootherium likely foraged for sedges in wetter lowland areas and browsed on lichens within open tundra habitats.

Behavior
The longer, more gracile legs of this animal, combined with their shorter pelage, suggest that it was more mobile than modern muskox. Higher mobility would suggest different social interactions, habitat use and responses to threats than their more sedentary cousins (Guthrie 1992). These animals may have been more migratory in their habitat use, seeking better protected landscapes. The structure of the male’s skull and horns suggest it established dominance during rut by running clashes, as with modern muskox, however that the force of the clash was confined to the horn bos. The flattened, boney plate across the top of the skull, between the horn cores. Morphology of the male horns suggests that they were used for clashing, rather than for defense from predators. Female horns, were likely used for antipredator defense.

Taxonomy
Fossils have been documented from as far north as Alaska to California, Utah, Texas, Missouri, Michigan, Oklahoma, Virginia, North Carolina and New Jersey. Remains of this animal have also been recovered from numerous sites throughout Indiana, Illinois, Michigan, and to a lesser extent, Missouri, Iowa, Minnesota, and Ohio.
It appears to have been the only ox to have evolved in and remain restricted to the North American continent.
The species became extinct approximately 11,000 years ago at the end of the last ice age.

Of the fours species of muskox that have inhabited North America, the helmeted muskox appears to have been the most abundant and widely distributed. Three other species of musk oxen co-inhabited North America during the Pleistocene era. Besides the surviving tundra muskox, the extinct shrub-ox (Euceratherium collinum) and Soergel’s ox (Soergelia mayfieldi) were also present.

Bibliography: Campos, P., Sher, A., Mead, J., Tikhonov, A., Buckley, M., Collins, M., Willerslev, E., Gilbert, M. T. P. 2010. Clarification of the taxonomic relationship of the extant and extinct ovibovids, Ovibos, Praeovibos, Euceratherium and Bootherium.

M. Mendoza, C., Janis, C. M., Palmqvist, P. 2006. Estimating the body mass of extinct ungulates: a study on the use of multiple regression. Journal of Zoology 270(1):90-101.

McDonald, J.N., Ray, C.E. 1989. The autochthonous North American musk oxen Bootherium, Symbos, and Gidleya (Mammalia: Artiodactyla: Bovidae). Smithsonian Contributions to Paleobiology, 66.