Helmeted Muskox

Helmeted muskox, Bootherium bombifrons

The helmeted muskox, also known as Harlan's muskox or the woodland muskox, is an extinct species of muskox that lived in the U.S. Midwest during the late Pleistocene. This species was native to North America, and evolved at some point during the middle to late Pleistocene in the intermontane valleys of eastern Beringia (Campos et al. 2010). The scientific classification of Bootherium bombifrons has a long and complex history. Until recently, paleontologists thought that at least two different types of helmeted muskoxen were present in late Pleistocene North America. One type had smaller, more slender horns with a rounder cross-section; this form was originally classified as Bos bombifrons, and later as Bootherium bombifrons, based on a specimen recovered from Big Bone Lick, KY in 1809. The second type had larger, heavier horns with an oval cross-section, and it was originally classified as Bootherium cavifrons, and then later as Symbos cavifrons, based on a specimen recovered from Oklahoma in 1852.  More recently, it has been demonstrated that  these two forms represent the male and female of a single species (McDonald and Ray, 1989), and since Bootherium bombifrons was described first, this classification has been kept for the species. New aDNA research has demonstrated conclusively that the helmeted muskox was genetically different than the extant muskox, Ovibos moschatus (Campos et al. 2010). These findings agree with previous morphological studies, which highlight the differences in body shape and size of the two species as well as the distinct differences in the size and shape of their horns. 

Helmeted Muskox

Helmeted muskox (Bootherium bombifrons) skeleton on display at the Indiana State Museum in Indianapolis. 

Artiodactyla (Hoofed Mammals)
Bovidae (Muskoxen, Bison, Sheep, Goats)

Height: unknown

Weight: 423.5 kg (934 lb); Mendoza et al. 2006