Features of herbivorous animals
There are features shared by many existing or extinct herbivores that we will have to spread throughout the carnivore and omnivore populations.
- high-crowned teeth for grazers (with some exceptions like the hippo and llama)
- the ability to acquire and maintain colonies of cellulytic endosymbionts (microorganisms that release endogenous enzymes that hydrolyze the compounds forming the cell walls of plant tissues)
“Dental features suggestive or indicative of high-fiber herbivory include dentitions adapted for crushing and grinding, or marginal teeth with labiolingually compressed, leaf-shaped, and cuspidate crowns suitable for puncturing and shredding plant fodder. Features of the skull and mandible variously associated with feeding on plants, especially in mammals, include short tooth rows (along with foreshortening of the snout and mandible), elevation/depression of the jaw joint relative to the occlusal plane for increased mechanical advantage of the adductor jaw muscles, enlargement of the adductor chambers and temporal openings as well as deepening of the zygomatic arches and mandibular rami for the origin and insertion of substantial adductor jaw muscles, and jaw joints suitable for complex mandibular motion. Finally, plant-eating tetrapods typically have longer and/or bulkier digestive tracts, and a longer and/or bulkier trunk region, than related faunivorous forms because part of the gut is modified to form a reservoir housing and crating suitable pH conditions for the endosymbiotic micro-organisms involved in the fermentative breakdown of the cellulose from the ingested plant fodder. Passage of food through longer intestinal tracts also allows for longer periods of time for processing of resistant materials. Thus the rib cages of many herbivorous tetrapods are either much wider and more capacious (‘barrel-shaped’) than those of their closest faunivorous relatives, or the trunk region is elongated to accommodate a longer digestive tract. This is reflected in overall body proportions as well as in the structure of the vertebral column.” (Sues 4)