Giraffidaegiraffes and okapis

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This family includes only two living species, the giraffe and the okapi. These two very different animals are restricted to subSaharan Africa.

Giraffids are large (okapis) to huge (giraffes); weights range from around 250 kg to over 1500 kg. They have long and narrow heads, thin lips, and long, seemingly prehensile tongues. Okapis lack, however, the extraordinary long neck and legs of giraffes. Both species have long, narrow, fully unguligrade feet that lack lateral digits. Third and fourth metapodials fuse to form cannon bones. The tarsals of giraffes consist of only four bones: calcaneum, astragulus, fused navicular and cuboid, fused cuneiforms. Okapi tarsals are even more specialized, consisting of just three bones.

Giraffids have short horns that project from the parietals and frontals. These are unique among mammals, consisting of bony cores ( ossicones) covered by furred skin.

In addition to having unusual horns, giraffid skulls lack sagittal crests, and they may have rough, thickened areas near the junction of the nasals and frontals which in some populations develops into a third horn. A postorbital bar is present. The mandibles are very long and slender. The skull of the giraffe contains extensive pneumatized areas and is remarkably light for its size. These pneumatized areas are much less well developed in the okapi.

The cheekteeth of giraffids are selenodont and brachydont. Upper incisors and canines are absent. The lower incisors and incisor-like canines are separated from the cheek teeth by a very long diastema. The dental formula is 0/3, 0/1, 3/3, 3/3 = 32.

Giraffids have a complex four-chambered, ruminating stomach.

Okapis and giraffes are very different in their ecology and behavior. Okapis inhabit the deep forests of central Africa. They are solitary animals with relatively small home ranges. Their diet includes mostly browse, but they also graze on grasses. Giraffes are gregarious, living in herds of up to 25 animals, which occupy large home ranges usually in relatively open savannahs. Their eyesight is excellent (in contrast to that of okapis). They are exclusively browsers, using their long necks to reach into the crowns of trees to feed.

Giraffids first appeared in the fossil record in the early Miocene.

Technical characters:

References and literature cited:

Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. 1999. Mammalogy. Adaptation, Diversity, and Ecology. WCB McGraw-Hill, Boston. xii+563pp.

Nowak, R.M. and J.L. Paradiso. 1983. Walker's Mammals of the World, 4th edition . John Hopkins University Press, Baltimore, MD.

Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution: An Illustrated Guide. Facts on File Publications, UK. 251 pp.

Simpson, C. D. 1984. Artiodactyls. Pp. 563-587 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, N.Y. vii+576 pp.

Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. Fourth Edition. Saunders College Publishing, Philadelphia. vii+565pp.

Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate