Tubulidentataaardvark

Aard­varks are pig-sized mam­mals (up to 82 kg) that spe­cial­ize in in­sec­tivory, es­pe­cially in cap­tur­ing and con­sum­ing ter­mites. Their limbs are mod­i­fied for dig­ging into the very hard ter­mite mounds found in African sa­van­nahs. The nails are ac­tu­ally some­where be­tween true nail and hoof in form. They are strongly con­structed, shovel-like, and ob­vi­ously adapted for dig­ging. Aard­vark skin is thick and sparsely haired. The thick­ness of the skin pro­tects these an­i­mals from bit­ing ants, and aard­varks may sleep in the ant nests they have re­cently ex­ca­vated for feed­ing.

The skulls of aard­varks are elon­gate and con­i­cal, and aard­varks have a more elab­o­rate set of turbinal bones than any other mam­mal. The zy­go­matic arch is com­plete. The palate ends at the pos­te­rior end of the pala­tine bones; it is not ex­tended pos­te­ri­orly by the ptery­goids (as is the case in pan­golins).

While aard­varks have teeth (un­like other anteaters), they lack in­cisors and ca­nines ( den­tal for­mula 0/0 0/0 2-3/2 3/3 = 20-22). No enamel is pre­sent on their cheek teeth, which are made up of hexag­o­nal prisms of den­tine that can be seen under a dis­sect­ing mi­cro­scope. These teeth are, how­ever, sur­rounded by a layer of ce­men­tum. They are root­less and con­tin­u­ously grow­ing. The den­ti­tion of aard­varks is also un­usual be­cause, while they are di­phy­o­dont, the milk teeth are small, vari­able in num­ber, and shed be­fore the an­i­mal is born.

Like pan­golins, aard­varks have a long, pro­trusile tongue and a giz­zard-like stom­ach. They seem to rely pri­mar­ily on their sense of smell for lo­cat­ing prey. Their nos­trils have pe­cu­liar fleshy ten­ta­cles and dense hairs; these serve to seal the nos­trils when the an­i­mal is dig­ging.

Aard­varks were once thought to be closely re­lated to pan­golins and xe­narthrans. We now think that their re­sem­blance to mem­bers of those groups is a re­sult of con­ver­gent adap­ta­tion for eat­ing ants, and that their real affini­ties lie with the Sire­nia, Hyra­coidea, and Pro­boscidea. Their fos­sil record is scanty; it be­gins in the early Miocene (a few older fos­sils have been ques­tion­ably as­so­ci­ated with this group).

There is one Fam­ily (Oryc­teropo­di­dae) and one species ( Oryc­tero­pus afer) in this order. Aard­varks are found in Africa south of the Sa­hara.

Lit­er­a­ture and ref­er­ences 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.

Jones, C. 1984. Tubu­li­den­tates, pro­boscideans, and hyra­coideans. Pp. 523-535 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.

Sav­age, R. J. G. and M. R. Long. 1986. Mam­mal Evo­lu­tion, an Il­lus­trated Guide. Facts of File Pub­li­ca­tions, New York. 259 pp.

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

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

Con­trib­u­tors

Phil Myers (au­thor), Mu­seum of Zo­ol­ogy, Uni­ver­sity of Michi­gan-Ann Arbor.

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