Temporal range: Late Pliocene - Early Pleistocene
The Sulawesi dwarf elephant (Stegoloxodon celebensis or Elephas celebensis) was about half the size of Archidiskodon (=Mammuthus) planifrons to which it was initially considered to be related by Dirk Albert Hooijer in 1949. The most evident difference with the latter is the presence of functional lower tusks in some individuals. This was considered as paedomorphosis, a retention of juvenile characters in the adult stage, by Vincent Maglio in his revision of the proboscideans in 1973. He based his conclusion on the presence of vestigial incisive germs in mandibles of Mammuthus planifrons. This idea was followed by Hooijer in 1974.
Ancestry and taxonomy
The retention of functional lower tusks is, however, not seen in juveniles of otherwise single paired tuskers, so cannot be considered a paedomorphic feature proper. It is simply a retention of a primitive character, as seen in the African elephantid genera Primelephas and Stegotetrabelodon, and possibly the earliest forms of Elephas planifrons. Between the late 1980s and early 1990s, an Indonesian-Dutch team excavated more material, including a fairly complete but rather distorted skull. All material, new as well as old, is described and revised in Van den Bergh’s thesis of 1999 on the Indonesian elephantoids, with a discussion on taxonomy. He puts question marks, “Elephas”, to indicate the uncertain taxonomical position, following Paul Sondaar’s approach of 1984. Van den Bergh accepts a possible relation with “Elephas” indonesicus from Ci Pangglosoran near Bumiayu on Java, dated to the same geological period. Also this specimen was originally assigned to Elephas (= Mammuthus) planifrons, but was later renamed Stegoloxodon indonesicus by Kretzoi in 1950. Recently, Georgi Markov and Haruo Saegusa made a further step and synonymized “Elephas” with Stegoloxodon in 2008.
Fossils of the Sulawesi dwarf elephant are found in the Walanea Formation, dated to the Late Pliocene - Early Pleistocene. The single fossil of the Javanese species was found at Ci Pangglosoran near Bumiayu on Java, dated to the same geological period.
- Hooijer, D.A .(1949). Pleistocene Vertebrates from Celebes. IV. - Archidiskodon celebensis nov spec. Zoologische Mededelingen, Museum Leiden 30: 205–226.
- Maglio, V.J. (1973). Origin and evolution of the Elephantidae. Transactions of the American Philosophical Society Philadelphia Volume 63. American Philosophical Society, Philadelphia. Pp. 149
- Hooijer, D.A. (1974). Elephas celebensis (Hooijer) from the Pleistocene of Java. Zoologische Mededelingen, Museum Leiden, 48: 85–93.
- Bergh, G.D. van den, 1999. The Late Neogene elephantoid-bearing faunas of [Indonesia and their palaeozoogeographic implications; A study of the terrestrial faunal succession of Sulawesi, Flores and Java, including evidence for early hominid dispersal east of Wallace's line, Scripta Geologica 117: 1-419 
- Sondaar, P.Y., 1984. Faunal evolution and the mammalian biostratigraphy of Java. Courier Forschungsinstitut Senckenberg 69: 219-235.
- Kretzoi, M., 1950. Stegoloxodon nov. gen., a loxodonta elefantok esetleges azsiai ose (Stegoloxodon nov. gen., a possible Asiatic ancestor of true loxodonts). Foldtani Kozlony 80: 405-408 [In Hungarian and English].
- Markov, G.N. and Saegusa, H., 2008. On the validity of Stegoloxodon Kretzoi, 1950 (Mammalia: Proboscidea). Zootaxa 1861: 55-56.
- Van der Maarel, F.H., 1932. Contributions to the knowledge of the fossil mammalian fauna of Java. Wetenschappelijke Mededelingen Dienst van den Mijnbouw in Nederlandsch-Indie 15: 1-208.