Modifications required for transforming carnivores/omnivores/insectivores into herbivores:

There are certain species that are herbivorous but carnivorans (belonging to the order Carnivora). They have evolved away from carnivory and completely towards herbivory.

Our results demonstrate that skull shape correlates with feeding behaviour...with the only exception of the bushy-tailed olingo (B. gabbi) [herbivorous carnivorans] share a set of common traits in their craniodental anatomy...These features relate to the capacity to exert high bite forces.

There are certain evolutionary constraints in carnivorans that have restricted the ways in which they can acquire herbivorousness. We should seek to overcome those constraints opening up different and complementary pathways for the transition to herbivory.

Our results support the existence of a complex relationship taking place between ecology, biomechanics, and morphology that makes convergent evolution a rare phenomenon. Ecological equivalence was the only condition that produced convergence in more than one occasion for carnivorans.