A revision of the dubois crocodylians, gavialis bengawanicus and crocodylus ossifragus, from the pleistocene homo erectus beds of java

Abstract

Revision of the two extinct Javanese crocodylian species Gavialis bengawanicus Dubois, 1908, and Crocodylus ossifragus Dubois, 1908, indicates that only the former is valid and that the latter is a junior subjective synonym of the extant C. siamensis Schneider, 1801. Gavialis bengawanicus is diagnosed by a relatively small number of maxillary and dentary teeth, a modest maxillary process developed into the lacrimal, a W-shaped maxillo-palatine suture, a planar skull table, occlusal pits present exclusively on the dentaries, and relatively small and subcircular supratemporal fossae at maturity. It is the best-known extinct Gavialis, and it probably represents the only valid extinct Gavialis species known outside the Indian subcontinent. Both crocodylians from Java have been found exclusively along with the Stegodon-Homo erectus fauna, which is considered to be largely the result of an Early Pleistocene dispersal from the Siwaliks Hills via the so-called Siva-Malayan route. It is not clear if the dispersal of Gavialis from the Indian subcontinent to Java necessarily required the crossing of salt water barriers, but the possible occurrence of Gavialis remains in Sulawesi and Woodlark, two islands located east of the Huxley and Wallace lines that were never connected to the mainland, can be explained by inferring a marine dispersal. According to the present knowledge of the past distribution of Gavialis, this genus originated in the Indo-Pakistani area in the early Miocene and during the Quaternary dispersed to the Sunda region, possibly reaching western-most Oceania. © 2010 by the Society of Vertebrate Paleontology.