Proboscidea (Elephants)

Abstract

Proboscidea – the living elephants and their fossil relatives – are of ungulate origin, dating to the late Palaeocene of northeast Africa and spread to all continents except Australia and Antarctica. The earliest proboscideans were characterized by the presence of a prominent and hooked coracoid process on the scapula (shoulder blade), and a medial process on the astragalus (ankle bone). Advanced proboscideans have pneumatized bones in the cranium, a developed proboscis (trunk), horizontal (rather than the usual vertical) tooth displacement, tusks that exhibit Schreger pattern in a cross‐section, and possess a temporal gland. The estimated number of fossil and living species and subspecies of proboscideans is 165, of which only three are alive today.

Keywords: elephant; proboscis (trunk); proboscidea; horizontal tooth displacement; schreger pattern; temporal gland; diploe; graviportal

Figure 1.

Astragali (heel bones) of a condylarth ((a) and (a2)) and anthracobunid ((b) and (b2)) depicting the Tuberculum mediale, a process on the medial side of the bone. This process is one of two proboscidean characters discussed in the text (condylarths are of ungulate stock, believed to have given rise to Proboscidea; anthracobunid are believed by some authors to belong with Proboscidea). Figures (a) and (b) dorsal views, Figures (a2) and (b2) plantar views. Redrawn with permission from Shoshani and Tassy, 1996.

Figure 2.

Tooth replacement. Figure . Top figures (a), on left are depicted cross sections of a single lamella (plate) of an African elephant. To the right, plates are stacked to form a tooth. Far right figure shows left hemimandible with teeth in place and arrows indicating direction of movements of teeth in the jaw, a feature common to advanced proboscideans. Bottom figures (b) portray five stages of tooth displacement in lower jaws of African elephant. Teeth move on the mandible as if they were on a slow‐moving conveyor belt; through time younger teeth are displaced by older ones from behind. As the animal grows older successive cheek teeth become larger and contain more plates. By the time an elephant is about 60 years old, the last molar is worn out. There will be no new tooth to displace it, and the animal is not able to chew its food. It is most likely that it will then die from starvation if not killed by a predator. Redrawn with permission from Shoshani and Tassy, 1996.

Figure 3.

Trunk muscles, fascicles, and their functions. Note that there are approximately 150 000 muscle fascicles (portions of muscles) that make up the 16 muscles, 8 on each side. Research by J. Shoshani and G. H. Marchant, artwork by Utako Kikutani; courtesy of Natural History Magazine.

Figure 4.

Phylogeny of the Proboscidea. Major trends observed are; increase in size, increase in trunk length, increase in tusk size, and a shift from four (upper and lower) to two tusks, upper only. Research by J. Shoshani, artwork by G. H. Marchant.

Figure 5.

A bull African elephant in Amboseli National Park, Kenya. Note the cattle egret by the hind feet; depicting a common sight of egrets following large game in anticipation of insects disturbed by them (photograph by J. Shoshani, courtesy of the American Society of Mammalogists).

Figure 6.

Suggested world dispersal patterns and current distribution of the living African and Asian elephants. Note that proboscideans inhabited all the continents except Australia and Antarctica. The figurines on this map are the same as depicted in Figure , it is possible therefore to superimpose the scale onto the map. Research by J. Shoshani, artwork by G. H. Marchant.

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Further Reading

Benedict FG (1936) The Physiology of the Elephant. Washington, DC: Carnegie Institution of Washington.

Delort R (1990) Les éléphant piliers du monde. Evreux: Découvertes Gallimard, Histoire Naturalles.

Deraniyagala PEP (1955) Some Extinct Elephants, Their Relatives and the Two Living Species. Colombo: Ceylon National Museums Administration.

Douglas‐Hamilton I and Douglas‐Hamilton O (1975) Among the Elephants. New York: Viking Press.

Eltringham SK and Ward D (consultant eds) (1997) The Illustrated Encyclopedia of Elephants. New York: Smithmark Publishers.

Gheerbrant E, Sudre J and Cappetta H (1996) A Palaeocene proboscidean from Morocco. Nature 383(6595): 68–70.

Grubb P, Groves CP, Dudley JP and Shoshani J (2000) Living African elephants belong to two species: Loxodonta africana (Blumenbach, 1797) and Loxodonta cyclotis (Matschie, 1900). Elephant 2(4): 1–4.

Laws RM (1966) Age criteria for the African elephant (Loxodonta a. africana). East African Wildlife Journal 4: 1–37.

Maglio VJ (1973) Origin and evolution of the Elephantidae. Transactions of the American Philosophical Society of Philadelphia, New Series 63(3): 1–149.

McKenna MC, Bell SK, Simpson GG et al. (1997) A Classification of Mammals Above the Species Level. New York: Columbia University Press.

Osborn HF (1936 and 1942) Proboscidea, vol. I (1936), vol. I (1942). New York: The American Museum Press.

Shoshani J (1997) What can make a four‐ton mammal a most sensitive beast? Natural History 106(10): 36–45.

Shoshani J (1998) Understanding proboscidean evolution: a formidable task. Trends in Ecology and Evolution 13(12): 480–487.

Shoshani J (consultant ed.) (2000) Elephants: Majestic Creatures of the Wild (revised edn). New York: Checkmark Books (an imprint of Facts on File, Inc.).

Shoshani J and Tassy P (eds) (1996) The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives. New York: Oxford University Press.

Shoshani J, Goldenberg EM and Yang H (1998) Elephantidae phylogeny: morphological versus molecular results. Acta Theriologica, Supplement 5: 89–122.

Sikes SK (1971) The Natural History of the African Elephant. London: Weidenfeld and Nicolson.

Sukumar R (1989) The Asian Elephant: Ecology and Management. Cambridge: Cambridge University Press.

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How to Cite close
Shoshani, Jeheskel(Jul 2001) Proboscidea (Elephants). In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001575]