Species: Hylobates syndactylus
Common Name: Siamang
Siamangs are part of a group called the lesser apes. They are native to Malaysia and Sumatra and are sympatric with the white-handed gibbon (H. lar).
The gibbons and the siamang are a strange mix. Anatomically they are both the most primitive (i. e. cattaqrhine like – they have ischial callosities) and the bost derived (in limb proportions – interestingly, they often group with the Atelines in analysis of skeletal anatomy). They are the smallest of the apes (although the Siamangs are the largest of the genus) and do not display sexual dimorphism. While gibbons prefer primary forests, the siamang tends to be found at high elevations and in mountainous regions. They are monogamous and highly territorial, with each territory covering up to 95 acres. Territory size is largely dependent on food resources – the siamag feeds on ripe fruit some of which is widely dispersed in scattered clumps.
Sinanthropus has an interesting discusion of some possible ancestors.
Below are some pictures of the skull of the siamang in side and front views and a picture of the skeleton. Note the large canines, which are pretty much equally sized in both males and females. Also note the short snouts, shallow faces and large orbits.
Also note the lack of nuchal and sagittal crests (although some do develop sagittal crests). Here is a side view of a gorilla skull for comparison.
Finally, here is the siamang skeleton.