The one anatomical character that separates Anserimimus from the ornithomimids is the manus. The fossils of the hand are fragmentary, just like the remainder of the animal's discovered remains. The known bones of the hand are flattened enough that their shape was significant enough that the shape was the basis of the specific epithet. The problem with an assumption that the bones are flatter than others in the family is that we run into all kinds of "what if" scenarios. The most hopeful situation is one in which there is nothing at all incorrect with the bones and that the flatness of the hand is exactly what it is, a flattened hand. Given the idea of accepting that it is the correct shape of the hand, what would a dinosaur need a flattened hand for? Swimming comes to mind, but there is no note of webbing on the hand or anything that would aid in swimming. A terrestrial animal with a flattened hand could most definitely use that hand for the purpose of digging. Many ornithomimids have been proposed to have enjoyed omnivorous diets. A specialized insectivorous diet, not merely the diet of an omnivore, could use a flattened hand to dig into crevices and tear plants apart and get at all those Mesozoic insects. Other uses are certainly possible. This use is definitely a bit more interesting. It is an adaptation than we do not regularly see in insect eating dinosaurs, but if anyone can think of one, make sure it gets shared!