Final answer:
No monkey species is specialized exclusively in eating grasses as they are generally omnivorous. Some primates consume grass as part of their diet, but they are not considered grass-eating specialists. Different monkey species have various dietary adaptations but are primarily frugivorous.
Step-by-step explanation:
Among the various monkey species, none are specialized exclusively in eating grasses, as most monkeys are generally omnivorous, preferring a varied diet that predominantly consists of fruits along with occasional plants and animal material. Monkeys are not ruminants like some mammals that specialize in grass diets; rather, their digestive systems are more suited to the handling of diverse foods available in their arboreal and terrestrial habitats. While some primates, such as baboons, might consume grass as part of their diets, it is incorrect to consider them as specialists in grass eating.
Monkey species exhibit various dietary adaptations. For instance, spider monkeys possess prehensile tails which are very handy for life in the trees where they typically consume fruit. Other species like the proboscis monkey or Allen's swamp monkey have developed webbed fingers to assist with their aquatic lifestyles, but this does not directly relate to a specialization in eating grasses.