Musk-oxen are More Closely Related to Goats than They are to Cows

In one of the first articles I ever wrote for this blog, I speculated there were 3 species of Pleistocene bovines roaming the area known today as Georgia.  Bison antiquus, a late Pleistocene species of bison, is thought to have evolved from Bison latifrons about 24,000 years BP, yet  a specimen of the latter found in Clark Quarry near Brunswick, Georgia suggested there was a temporal overlap between these 2 species. This specimen  was originally dated to 14,000 BP.  Since I wrote that article, scientists have resubmitted this specimen to radiocarbon dating. and this time it produced a date of 24,000 BP–within the accepted time span this species is thought to have existed.  It’s still one of the more recent specimens of this species, but it is not evidence of temporal  overlap with B. antiquus. There was never more than 1 species of bison living in the region at the same time.

About a month ago, a reader also alerted me to an error I made by classifying the helmeted musk-ox (Bootherium bombifrons) as a bovine.  I wrongly assumed because of its appearance, and the common name ox, that it was closely related to cows. An oxen is a word used for a castrated cow. I should have paid closer attention to my mammalogy books.  Musk-oxen are more closely related to goats and sheep than they are to cattle.  Many laymen likely share my misconception, so I’ve reviewed the literature and will now sort out the bovids.

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Woolly musk-oxen are like a really large goat and are not close kin to cattle.  A species of musk-oxen adapted to temperate climates  lived as far south as Louisiana during the Iice Age.  It was taller, had shorter hair, and a different horn structure than the species  still extant.

Mountain goats are in the same subfamily as muskoxen.

Saiga antelope are also in the same subfamily as musk-oxen.  During the Ice Age saiga antelope lived as far east as Alaska.

The Bovidae family is divided into 2 subfamilies: the caprinae and the bovinae.  Bovids originated in Africa and most species are adapted to warmer climates, but during the Pleistocene a number of species became adapted to the cooler climates of the Ice Ages, and they spread throughout northern Eurasia and across the Bering Landbridge to North America.  None ever made it to South America.

Pleistocene and modern American species in the caprinae subfamily include saiga antelope (Saiga tatarica), shrub oxen (Eucatherium sp.), mountain goats (Oreamnos americanus), Harrington’s mountain goat (Oreamnos harringtoni), bighorn sheep (Ovis Canadensis), dall sheep (Ovis dalli), woolly musk-oxen (Ovibos moschantus), and the helmeted musk-oxen (Bootherium bombifrons)..  The  bovinae species that colonized North America were bison (Bison sp.), and the yak (Bos grunniens), the latter having been restricted to mountains in Alaska during some climate stages of the Pleistocene.

Saiga antelopes still occur on central Asian steppes, but they expanded their range to the grassy mammoth steppe of Alaska during the Last Glacial Maximum.  Shrub oxen were probably the first bovids to colonize North America early during the Pleistocene, and they didn’t become extinct til about 11,000 BP.  Shrub oxen are not known to have occurred east of Iowa.  Harrington’s mountain goat was a sister species of the modern day mountain goat and is also now extinct.

The only species of caprinae that ever colonized southeastern North America was the helmeted musk-ox.  Fossils of this species have been found in Texas, Lousiana, Mississippi, western Tennessee, and Virginia; but notably not in the abundant fossil deposits of Florida. (See https://markgelbart.wordpress.com/2011/07/27/the-south-central-salient-of-the-helmeted-musk-ox-ovibos-cavifrons-or-bootherium-bombifrons/ )  This suggests the southeasternmost range limit was in north or central Georgia or possibly South Carolina’s piedmont.  The helmeted musk-ox expanded its range during the Last Glacial Maximum when grassy desert scrub habitat became a widespread type of environment throughout North America.  Fossil coprolites, originally excreted by helmeted musk-oxen, show these tough animals fed upon green vegetation during summer but could subsist on dry twigs during the long cold Ice Age winters.  Like their goat cousins, they could absorb nutritional value from dead plant material, reminding one of the cartoon stereotype of goats eating the wrappers off tin cans. This amazing animal was able to extract nutrition from cellulose.

Because helmeted musk-oxen were able to survive on dry twigs, I do not believe climate change could have caused their extinction.  There has never been a shortage of dry twigs in North America during any climate phase.  I do believe the replacement of their favored habitat of desert scrub and grassland with forests and woodlands following the end of the Ice Age did cause the range of this species to contract.  This range contraction made them more vulnerable to human overhunting.  Like wooly musk-oxen, the helmeted musk-ox formed defensive circles when confronted with predators.  This was effective against wolves or saber-tooth cats but disastrous against spear-wielding humans who could slaughter an entire herd at once from a safe distance.  R. Dale Guthrie speculated competition with bison caused the extinction of helmeted  musk-oxen, but I reject this hypothesis because these 2 species co-existed for 300,000 years.  I believe bison avoided extinction because they run away from people and migrate long distances and perchance found regions where the population of humans was too low to eat them faster than they could reproduce.

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Tags: Bootherium bombifrons, bovids, bovines, caprines, helmeted musk ox