14 Bossies and Blowholes
Thundering Hooves
We live in a world where most of the attention gets grabbed by the carnivores—and
mammals are no exception. We have TV shows entitled “Fangs” but none (alas) called
“Molars,” and the hoofed mammals are often regarded as little more than fodder.
—Christine Janis, 2003After rodents and bats, the third-largest group of placental mammals is the ungulates,
or hoofed mammals. Hoofed mammals make up about a third of the genera of living and
extinct mammals, and nearly all large-bodied herbivorous mammals are ungulates. Most
people are familiar with the common domesticated animals that provide us with food and
services, such as horses, donkeys, cows, sheep, goats, pigs, as well as camels and alpacas,
and know of more exotic hoofed mammals in the zoo or wild, such as rhinos, giraffes, ante-
lopes, and hippos. (If elephants are members of Afrotheria, they may not be ungulates, but
we will discuss these large hoofed mammals in this chapter anyway).
But the diversity of hoofed mammals of the past is much greater than the limited selec-
tion that survives today, with twice as many extinct families and genera. These include a wide
array of hornless rhinoceroses, including the indricotheres, which towered over elephants as
the largest land mammals that ever lived; bizarre chalicotheres, which were related to tapirs
but looked like horses, except that they had claws like a ground sloth and knuckle-walked
on their long forelimbs like gorillas; a great variety of North American camels, none of which
had humps, but some of which did great impersonations of gazelles and giraffes; a num-
ber of extinct giraffes, none with long necks; pigs with horns; elephants without tusks that
looked more like tapirs; and last but not least, an incredible array of transitional fossils that
show how whales evolved from terrestrial hoofed mammals. All of this is well preserved
in the fossil record because most ungulates are large-bodied and heavy-boned animals that
tend to fossilize well.
Until recently, most of their history was not well understood or well documented. Part of
the problem was logistical: the huge collection of fossil ungulates in the American Museum
of Natural History in New York has still not been fully published since it became available
for study in the 1970s. This collection occupies a separate wing of the museum, with 10 floors
of storage and labs and offices and includes a whole storage floor of mastodonts and mam-
moths, a whole floor of North American rhinos, a whole floor of North American camels, a
whole floor of horses, and three other floors of all the rest of the mammals. I was fortunate to
arrive there as a graduate student in 1976 and got to work on many different groups of mam-
mals. Many of these new collections contain cabinet after cabinet of undescribed complete
skulls and skeletons of many species that had previously been known only from isolated
teeth and jaws. For example, I did a lot of research on horses, peccaries, and camels (which
is still ongoing), but my major task was documenting the long history of North American