Final answer:
Paranthropus robustus predominantly ate coarse and fibrous vegetation, evidenced by their dental wear and robust jaws adapted for grinding tough plant materials.
Step-by-step explanation:
Paranthropus robustus, a species of ancient hominids, primarily consumed coarse and fibrous vegetation. Unlike their relatives, the australopiths who had a partially carnivorous diet, Paranthropus robustus had large grinding teeth indicating heavy wear from a diet rich in hard nuts and seeds as well as other tough plant materials. Their robust physique and dental adaptations, including a sagittal crest for the attachment of strong jaw muscles, suggest that their diet was vastly different from other hominins that consumed softer foods and leaned more towards meat consumption. Though some Paranthropus may have had varied diets, the predominant evidence points to a reliance on plants in their habitat, which could vary from woody plants to fibrous grasses and seeds found in African savannas.