Origin and function of the yolk sac in primate embryogenesis | Nature Communications
What is a gibbon? — Gibbon SSP
How quirk of primate evolution gave humans the voice apes lack | Evolution | The Guardian
Gibbon (Hylobatidae) Species Identification Recommended for Rescue or Breeding Centers
Monkey Mania: Frogs are not the only ones with a striking vocal sac - CGTN
Primate - Wikipedia
Siamang – Wisconsin National Primate Research Center – UW–Madison
Siamang | Smithsonian's National Zoo
Principal functions of the primate hypoblast and yolk sac. Graphical... | Download Scientific Diagram
File:PrimateAirSacs Schematic.png - Wikimedia Commons
Siamangs have large gular sac (throat pouch) that can be inflated to the size of its head, allowing it to make loud, resonating calls or songs : r/Awwducational
A male proboscis monkey's nut-sack is located on their face : r/ShittyAnimalFacts
Siamang | Smithsonian's National Zoo
Siamang | Smithsonian's National Zoo
Siamang (Symphalangus syndactylus) | about animals
Siamang | San Diego Zoo Animals & Plants
A "singing swinging" lesser ape: the Siamang
Happy International Primate Day! - Sacramento Zoo
Monkey Haven - Siamangs have a throat sac (also called a gular sac) which they can inflate to be about the size of their head. This sac makes their calls louder! Both
Monkey Mania: Frogs are not the only ones with a striking vocal sac - CGTN
