The Holocene record of the slow loris (Nycticebus sp.) in Java (Indonesia)

(Sub)fossil lorises are rare in Southeast Asia. Their taxonomic relationship with extant populations, and the extent to which their distribution and morphology are influenced by changing environmental conditions, remains poorly understood. This study provides a synthesis of Nycticebus occurrences in Holocene Java. A morphometric analysis of a sample of craniodental remains aims to improve our understanding of their taxonomic status. Morphometrics were also used to explore potential size changes during the Holocene.

Based on the literature and a review of museum catalogs, a synthesis was compiled of (sub)fossil slow loris occurrences in Java. Morphometric data on the mandible and maxilla of 10 (sub)fossil lorises were compared with a dataset of extant specimens to assess variation in size and shape.

Five Holocene Nycticebus occurrences were identified in eastern Java. All specimens fall in the range of N. javanicus and N. coucang. The specimens from Hoekgrot, Gua Jimbe, and Sampung suggest an affinity to N. javanicus. The remains from Gua Jimbe and Hoekgrot gave values close to the largest N. javanicus specimens, but the (presumably older) Song Terus specimen was of average size.

The distribution of Nycticebus suggests that it originally occurred throughout the island. The remains are probably best identified as N. javanicus or N. coucang, but the Neolithic finds from Hoekgrot and Gua Jimbe are presumably N. javanicus. Size variation in Nycticebus was clinal, but although some large specimens were present, no evidence was found for size diminution during the Holocene.