Maxillae are a special type of bones found in a variety of animals, particularly mammals—including humans. They are a pair of bones located in the upper jaw, and they have a variety of functions associated with the mouth, jaw and tongue. The presence of maxillae is what distinguishes mammals from other classes of animals, and they are often considered to be a key evolutionary step that allowed the development of more complex animals, such as humans. The primary function of maxillae is to support the structure of the mouth and facial muscles. This allows us to open and close our mouths, and they also provide a base for the lower teeth to rest on and hold them in place. Maxillae also help to keep food from entering the nasal cavity, and they are joined to other bones in the face, such as the zygomatic bone and the palatine bone in the roof of the mouth. In humans, maxillae also help form the area around the nose, which gives individuals their unique facial features and helps to provide structure to the face. They are involved with many of the complex facial expressions that humans are capable of, along with providing structural support to the muscles and bones in the face. Through the presence of maxillae, mammals are able to possess some of the most sophisticated facial expressions in the animal kingdom. Overall, maxillae are a key part of the structure of the mammalian jaw and face, and their presence helps to set mammals apart from other animals. Not only do they provide structural support, but they are also responsible for forming facial features and allowing for complex expressions. This is what makes them so special and helps to explain why maxillae are such an important part of human anatomy.