Answer :
Final answer:
Hylobatidae, or gibbons and siamangs, are distinguished by their long arms that are used for brachiation, and thumb placement at the wrist which assists in swinging through trees. They have ischial callosities for sitting and are known for their loud, territorial vocalizations.
Explanation:
The family Hylobatidae, commonly referred to as gibbons and siamangs, are known for their physical characteristic of having extremely long arms relative to their legs, making them adept brachiators.
The thumb placement at the wrist, as opposed to the palm, enhances their ability to swing through trees with speed and agility.
This trait allows them to use their hands as hooks when moving from branch to branch. Hylobatidae also have ischial callosities, which are padded areas on their rear used for sitting, especially when sleeping, as they do not build nests.
Another significant feature is their vocalization; they can produce loud calls used for communication and territorial defense, with a distinctive morning and evening 'song' performed by monogamous pairs.
