The Late Neogene elephantoid-bearing faunas of Indonesia and their palaeozoogeographic implications

The stratigraphic framework of the Neogene fossil vertebrate bearing formations of the Indonesianislands Sulawesi and Flores is established and the sediments are dated by means of marinemicropalaeontological and/or palaeomagnetic methods. The results allow comparison of the faunaevolution on these islands with the better known fauna succession of Java. On both Sulawesi and Floresremains of large mammals and reptiles were excavated from fossil-rich layers, documenting thecomposition of large vertebrate faunas fairly well. For Sulawesi this procedure allows distinction ofseparate fauna units which formerly had been lumped together. Both on South-Sulawesi and Flores 3successive faunas can be distinguished. The oldest terrestrial faunas have recorded ages of 2.5 Ma and0.9 Ma, respectively. On both islands intermediate faunas have a Middle Pleistocene age, while theyoungest faunas are subrecent to Recent.Elephantoids (Stegodon and Elephas) showing various degrees of dwarfing are important constituentsin all non-subrecent/Recent faunas. Their dental, cranial and postcranial remains are described indetail and their taxonomic positions are discussed. A new species (Stegodon sondaari sp. nov.) isdescribed from Flores. Geological/tectonic data and the nature of the impoverished and highlyendemic faunas from Sulawesi and Flores both indicate longlasting isolation from the southeast Asianmainland and from Java.On Flores and probably also on South Sulawesi fauna turnovers with extinction and immigration ofelephantoids occurred around the Early to Middle Pleistocene transition. On both islands the totaldisappearance of elephantoids presumably took place before the onset of the Holocene. On Flores theMiddle Pleistocene faunal assemblage is associated with a palaeolithic industry, which is tentativelyascribed to Homo erectus. Early hominids appear to have been able to cross water barriers and successfullycolonize Flores as far back as 0.6 Ma ago. They may have been in part responsible for theobserved faunal turnover on the island, but alternatively, extinctions may have been caused by a volcaniccatastrophe.The existing biostratigraphic framework of Java is discussed and some additions concerning elephantoidtaxa are given. Following the emergence of Java above sea-level from the Late Pliocene until c. 1.5Ma, mammalian dispersal to the island was limited. This is illustrated by impoverished faunal assemblagesand the occurrence of various dwarfed elephantoids in this time in