Abstract
Background:
The islands of Sumatra and Java in Indonesia are home to slow lorises, and the long-standing biogeographical separation between the Sunda and Javan species contributes to morphological divergence. However, morphological identification and body size prediction remain limited due to insufficient anatomical data.

Aim:
This study aimed to investigate the anatomical characteristics of the thoracic and pelvic limbs in relation to the total body length (TBL) and pelvic breadth (PB) of the Sunda and Javan slow lorises, which are relevant to distinct biogeographic pressures.

Methods:
Morphometric data were collected from 43 adult slow lorises in a rehabilitation and conservation area under the supervision of Yayasan Inisiasi Alam Rehabilitasi Indonesia, Bogor. Measurements comprised the upper arm length, that considered the bony landmark of the humerus (HL), thigh length referring to the femur bone landmarks (FL), TBL, and PB. Measurements were taken during routine medical check-ups within a week. Statistical analyses, including correlation and regression, were conducted using the established methodologies.

Results:
The results showed that HL, FL, TBL, and PB of Javan slow lorises were significantly higher than those of Sunda, but there was no statistically significant difference between males and females. Both HL and FL were moderately correlated with TBL in both species, contributing to TBL prediction. HL and FL showed no significant correlation with PB.

Conclusion:
The body measurements of Sunda slow lorises were significantly smaller than those of the Javan species. These results provided useful morphometric data that improved species identification and helped estimate body length, but did not serve as reliable indicators of sexual dimorphism. The data obtained could help in comparative anatomy and forensic applications in conservation efforts, such as fur color pattern and body size identification. In line with genetic and ecological behavior data, the results are expected to serve as an important reference in conservation programs.

Key words: Javan slow lorises; Morphometric; Nycticebus coucang; Nycticebus javanicus; Sunda slow loris.