Lithostratigraphic context for Kln-1993.05-SNJ, a fossil colobine maxilla from Jokotingkir, Sangiran Dome

Abstract

Jablonski and Tyler (1999) announced a new subspecies of colobine monkey based on a fossil partial maxilla from the Sangiran dome. The specimen is easily assigned to a living leaf monkey species—most extant Southeast Asian catarrhines differ only subspecifically from their Middle Pleistocene earliest local fossil ancestors. Yet Jablonski and Tyler (1999) reported an improbable provenance for the specimen; a mass-flow volcanic breccia generally considered late Pliocene in age. We show that the Lower Lahar was laid down amidst a range of paludal habitats and that its deposition predates the appearance of all-but-now extinct, water-tolerant mammals on emergent Java. No other catarrhine fossil has been ascribed to the Lower Lahar, not even hominins, which are the most gregarious members of the group. More probable provenance lies in the upper Sangiran or the lower Bapang formations. Either alternative would associate the specimen with other catarrhine fossils in more tenable Pleistocene environments. We also unravel errors and inconsistencies in the contextual report and in the discussion of dome geochronology. The various radiometric, paleomagnetic, and paleontologic studies cited show a discordance of about 300 Ka (thousand years) across the lithostratigraphic sequence. Plio-Pleistocene biogeographic hypotheses for Java must work with short and long chronologies.