Final answer:
The horizontal forward-projecting incisors of the lower jaw in prosimians are specialized for grooming and obtaining food resources like sap or gum from trees, and are a key part of their dental structure and adaptation.
Step-by-step explanation:
The structure formed by the incisors of the lower jaw projecting forward almost horizontally, which is found in prosimians and used for grooming fur and scraping sap/gum from trees, is part of their dental morphology particularly adapted for such functions. The incisors are one of eight (four upper and four lower) blade-like teeth at the front of the mouth used to slice off pieces of food. In prosimians, these incisors can be specialized to carry out additional tasks such as grooming or obtaining food resources like sap or gum, which varies from the typical use of incisors in other primates primarily for biting into food.
While not specifically named in this context, this dental structure is a distinctive feature in the prosimians' oral anatomy and is crucial for understanding their ecological interactions and behaviors.