Elephants Elephants - Wildpro - Twycross Zoo

10
(Eisenberg 1981); E. m. maximus, E. m. indicus, the continental form and E. m.
sumatranus of Sumatra (Santiapillai and Jackson 1990) (Eisenberg 1981).
However recent sequencing work using mitochondrial DNA (Fleischer et al
2001) suggests that there are two clades, A and B, with clade A originating in
Indonesia and Malaysia, suggesting that these are an ESU (evolutionary
significant unit). Clade A has been distributed by the human trade in
elephants among Myanmar, India and Sri Lanka, resulting in mixes of Clad A
in with B. This work does not support an ESU status for Sri Lankan elephants.
However the Sumatran subspecies is diagnosable and it is suggested that they
be managed as a separate unit. E. m. sumatranus also has physical differences.
They tend to be paler and smaller, with larger ears and one extra pair of ribs
(20) (Shoshani 1991a). More recently there is a suggestion that the Bornean
elephant may also be significantly different from mainland forms (Sukumar
2003) 1
PHYLOGENY
The order contains one living family, Elephantidae, with two living genera.
Elephants are members of the broad evolutionary line leading to ungulates or
hoofed mammals. Early proto-ungulates showed extensive radiation in the
Eocene. These fossils show development towards the ungulate condition but
the limbs remained primitive and the nails had not evolved in to proper
hooves. These lines died out leaving the remnants of three: the sirenians (sea
cows), hyraxes and elephants. Numerous primitive features shared by these
groups show their common ancestry (Eltringham 1982). There are various
classifications of extinct proboscids, (Eltringham 1982) (Carrington 1962)
(Nowak 1991) (Shoshani 1991b); this section is intended simply as a guide to
the radiation which resulted in the extant elephants.
RELATIONSHIP BETWEEN EXTANT FORMS
The earliest definite proboscidean genus Moeritherium of the Gomphotheriidae
arose in Africa in the late Eocene. Moeritherium was about the size of a large
pig. It survived into the lower Oligocene. From this evolved the three
families: Elephantidae (living) and extinct Mastodontidae and Stegodontidae.
The first known members of the Elephantidae are from late Miocene or early
Pliocene deposits in Africa. Table I. shows the distribution of proboscids from
Eocene to Recent. Whereas Loxodonta was confined to Africa, species of
Elephas ranged over Africa, Europe and Asia but became restricted to Asia by
the late Pleistocene. Three species of Loxodonta and eleven of Elephas have
been recognised (Eltringham 1982). Remains of a pygmy species of Elephas
have been found on some Mediterranean islands; E. maximus is thought to
have evolved some 0.2 million years ago.
The mammoths of the genus Mammuthus originated in Africa, probably from
the Loxodonta lineage, but passed into North America along the land bridge,
splitting into two branches, one mainly European and the other American.
1 Taxonomic notes updated and referenced