Family
Rhinocerotidae
Rhinoceroses |
 |
The name "rhinoceros" translates directly from Greek as "nose-horn" -
an apt name, as all five extant species of rhinos possess at least one horn
(sometimes two) growing from the top side of the nose. Unlike the horns
of bovid artiodactyls, the "horns" of the rhinoceroses lack a bony core and
are comprised of compressed hair. The horns have purported medicinal
properties and are also used to make traditional ornaments -as a result,
all rhinoceros species have been hunted to the brink of extinction. The
Javan rhino (Rhinoceros sondaicus) is one of the most endangered species
of mammals on earth today, with an estimated population of 60 individuals.
The northern white rhino (Ceratotherium simum cottoni) is critically
endangered with fewer than 30 wild individuals remaining.
The Rhinocerotidae arose during the Eocene, likely from tapir-like ancestors.
Rapidly colonizing Eurasia and North America, and then invading Africa
during the Miocene, rhinos became a highly successful group: at least 30
genera are known in the fossil record. Modern rhinoceroses are restricted
to tropical and subtropical climates, but several cold-adapted species
once existed, including the woolly rhinoceros (Coelodonta) from the
Pleistocene. Today, rhinos are found in eastern and southern Africa
and to southeast Asia. African rhinoceroses tend to inhabit more open
terrain than the forest-dwelling Asian species.
The skin is tough and thick, falling into plate-like folds; in most species
it is bare or sparsely haired, but the Sumatran rhinoceros (Dicerorhinus
sumatrensis) has long hair on the back and sides. The nasal bones
of the skull are expanded forward to support the (anterior) horn. The
posterior horn (when present) is on the frontal bones. The dental formula
is I 0-1/0-2, C 0/0-1, P 3-4/3-4, M 3/3 x 2 = 24-36. |
The Rhinoceros Family
Tree
(branch lengths are not proportional to
time)
Click on the species above to learn
more,
or jump to the Rhinocerotidae
Species List
|
Literature Cited
Estes, R. D. 1991. The Behavior Guide to African Mammals: including
hoofed mammals, carnivores, primates. Los Angeles: University of California
Press.
Martin, R. E., R. H. Pine, and A. F. DeBlase. 2001. A Manual
of Mammalogy, Third Edition. Boston: McGraw-Hill Publishing.
Nowak, R. M. [Editor]. 1991. Walker's Mammals of the World. Fifth Edition.
Johns Hopkins University Press, Baltimore.
Tougard, C., T. Delefosse, C. Hänni, and C. Montgelard. 2001.
Phylogenetic relationships of the five extant rhinoceros species
(Rhinocerotidae, Perissodactyla) based on Mitochondrial Cytochrome b and
12S rRNA genes. Molecular Phylogenetics and Evolution; 19(1): 34–44.
Vaughan, T. A., J. M. Ryan, and N. J. Czaplewski. 2000. Mammalogy. Fourth
Edition. Saunders College Publishing, Philadelphia.
|
|
