Harlan's Musk Ox (Bootherium bombifrons)
In 1809, Caspar Wistar and his fellow members at the American Philosophical Society puzzled over a skull fragment collected from Big Bone Lick by William Clark (1). The skull, which was missing teeth and the snout, had a pair of boney horn cores, which indicated it was related to cows, oxen, sheep and bison (family Bovidae).
Caspar Wistar's illustration of the
Big Bone Lick skull (three-quarter
front view on top, rear view on
bottom). (after Wistar, 1818)
These horn were situated on the side of the head rather than on the top, so it could not have belonged to a sheep or a goat. Comparisons with an ox and a bison indicated that this animal was neither. The horns were located further from the back of the skull and they curved downwards and forwards rather than upwards and backwards. Nonetheless, he felt that it most closely resembled the bison. Wistar never named the fossil, but Ricard Harlan named it Bos bombifrons (2) in 1825.
In 1828, James E. De Kay reported on a partial skull from Missouri. He realized it was more like the extant (still living) tundra musk ox (Ovibos moschatus) than a bison, but he also realized it was a different species. He then identified it as belonging to the same species as an extinct fossil musk ox from Siberia. Unaware that the Siberian animal was named Ovibos pallantis one year earlier, De Kay named both it and the Missouri fossil Bos pallasii.
Bootherium bombifrons (top) and
Bootherium cavifrons (bottom)
(after Leidy (1852)
In 1852, Joseph Leidy (3) described a skull fragment collected from the banks of the Arkansas River (present day Oklahoma). Leidy realized that this fragment, which also lacked teeth and the snout, was related to the tundra musk ox and named it Bootherium cavifrons; Leidy included De Kay's Missouri specimen with B. cavifrons. He also realized the Big Bone Lick specimen was closely allied with the new animal so he reassigned it as Bootherium bombifrons. Sixty years later (1912), Oliver Hay reassigned B. cavifrons to a new genus, Symbos. In 1989, Jerry McDonald and Clayton Ray demonstrated that Symbos cavifrons and Bootherium bombifrons were actually male and female versions, respectively, of the same species. Given the priority of the Big Bone Lick specimen, the species is now known as Bootherium bombifrons.
Bootherium bombifrons, known variously as Harlan's musk ox, helmeted musk ox and woodland musk ox, appears to have been the most abundant and widely distributed musk ox in North America. Its fossils have been collected from Alaska to Texas and from California to the continental shelf off New Jersey (4). Remains date from about 500,000 to 11,100 years ago.
Habitat preferences are unclear, since its fossils have been recovered from a variety of grasslands, alpine meadows and woodland sites. An analysis of fossilized dung from Alaska indicates that it grazed on grasses and sedges, at least during the winter. Its close relative, the tundra musk ox, is both a grazer and a browser.
Harlan's musk ox appears to have been adapted to less frigid climates that the tundra musk ox. It was taller and less stocky and its hair was shorter and finer. Its skull is deeper and the snout is considerably longer. The horns, which are situated higher on the skull, curve down, forward and out from the body. The horns in males of both species are substantially more massive than those of the female, but those of Harlan's musk ox are fused along the midline, whereas those of the tundra musk ox are separated by a medial groove.
Harlan's musk ox was one of at least four species of musk ox to inhabit North America. However, it appears to have been the only one to have evolved in and remain restricted to the continent. The shrub ox (Euceratherium collinum) and the Soergel's ox (Soergelia mayfieldi) apparently emigrated from Eurasia sometime during the Irvingtonian Land Mammal Age (1.9 million to 300,000 years ago). Both species extended as far south as Kansas or Oklahoma. The shrub ox persisted until about 11,500 years ago, while the rarely collected Soergel's ox may have died out earlier. The tundra musk ox (Ovibos mochatus) is the only living representative in North America. It's a more recent Eurasian immigrant, arriving sometime between 187,000 and 129,000 years ago. The tundra musk ox extended as far south as Iowa, Indiana and New York. Current populations are found in Greenland and the Canadian Arctic. Once extirpated from Alaska, it has since been successfully reintroduced. Eurasian populations became extinct about 3,000 years ago.
Musk oxen belong to the tribe Ovibonini, of which only the tundra musk ox and the takin (Budorcas taxicolor) of central Asia survive today. Their closest living relatives are the saiga (Saiga tatarica), goats and sheep.
Web Pages:
- Animal Diversity Web's web page on the Tundra Musk Ox:
animaldiversity.ummz.umich.edu/site/accounts/
information/Ovibos_moschatus.html - Animal Diversity Web's web page on the Tankin:
animaldiversity.ummz.umich.edu/site/accounts/
information/Budorcas_taxicolor.html - Explore North's web page on the tundra Musk Ox:
www.explorenorth.com/library/weekly/aa020101a.htm - Illinois State Museum's web page on Musk Oxen:
www.museum.state.il.us/exhibits/larson/muskox.html - Yukon Beringia's web page on the Helmeted Muskox:
www.beringia.com/02/02maina13.html
Print Resources:
- Bedini, S.A. 1981. "Jefferson: Man of Science". Frontiers: Annual of the Academy of Natural Sciences of Philadelphia 3: 10-24.
- De Kay, James, E. 1828. "Notes on a fossil skull in the Cabinet of the Lyceum, of the genus Bos, from the banks of the Mississipi; with observations on the American species of the genus." Annals of the Lyceum of Natural History of New-York. 2: 280-291.
- Harlan, Richard. 1825. Fauna Americana: being a description of the mammiferous animals inhabiting North America. Philadelphia: Anthony Finley.
- Hay, O.P. 1912. "The Pleistocene period and its Vertebrata." In Edward Barrett. Thirty-sixth Annual Report of Department of Geology and Natural Resources; Indiana; 1911. Indianapolis: William M. Burford.
- Kurtén, B. and E. Anderson. 1980. Pleistocene Mammals of North America. New York: Columbia University Press.
- Lang, I.A. 2002. Ice Age Mammals of North America: A Guide to the Big, the Hairy, and the Bizarre. Missoula: Mountain Press. Missoula.
- Leidy, Joseph. 1852. "Memoir on the extict species of American ox." Smithsonian Contributions to Knowledge, 5(3).
- McDonald, J.N., and C.E. Ray. 1989. "The autochthonous North American musk oxen Bootherium , Symbos, and Gidleya (Mammalia: Artiodactyla: Bovidae)." Smithsonian Contributions to Paleobiology, 66.
- Wistar, Caspar. 1818. "An account of two heads found in the morass, called the Big Bone Lick, and presented to the Society, by Mr. Jefferson". Transactions of the American Philosophical Society, new series, 1: 375-380
Notes:
- In 1807, William Clark (of Lewis and Clark fame) led an expedition to Big Bone Lick, Kentucky to retrieve fossils of the "Mammoth" (American mastodon). Almost all of the specimens in the Thomas Jefferson Fossil Collection came from this expedition. See Discovering the Mastodon: Fossils in the White House for more information.
The publication of Wistar's presentation in Transactions of the American Philosophical Society was scheduled soon after he gave the talk in February of 1809. Unfortunately, the manuscript was lost by the committee of referees. After much delay, Wistar rewrote his observations from memory. Some of what he wrote was published in the Transactions in 1818. Regrettably, Wistar died before it was published.
Another skull that Wistar was presenting to the American Philosophical Society in 1809 belonged to an extinct deer, the stag moose (Cervalces scotti). [go back] - Bos is the generic name for oxen and their relatives. Examples include cattle (Bos primigenius or Bos taurus), guar (Bos gaurus) and yak (Bos mutus or Bos grunniens). Scientists during Harlan's time commonly assigned a variety of related forms, including bison to this genus. [go back]
- Joseph Leidy (1823-1891) was one of leading paleontologists, zoologists and anatomists of the United States during the 19th century. See The Academy's Joseph Leidy Online Exhibit for more information. [go back]
- The trapping of water by the vast continental glaciers dramatically lowered sea levels during the Pleistocene Ice Age. Consequently, large areas of the continental shelf were exposed. Fossils from a variety of terrestrial animals, including mammoths, mastodons and musk oxen have been accidentally collected by commercial fishermen trawling along the shelf floor. [go back]