“…The anatomical data was evaluated using three additional data sets reflecting the natural diet, and the digestive physiology. The natural diet is typically described as the percentage of grass in the natural diet (%grass; Clauss, Kaiser, & Hummel, ) and was available for all species investigated (Akbari, Moradi, Rezaie, & Baghestani, ; Clauss et al, ; Clauss, Hofmann, et al, ; Dittmann, Hummel, et al, ; Gagnon & Chew, ; Meier et al, ; Müller et al, ; Rduch, ; Serbent, Periago, & Leynaud, ; Zerbe et al, ). In order to achieve more convenient parameter estimates for the natural diet, we expressed %grass in this study as the proportion of grass (i.e., ranging from 0 to 1 rather than from 0 to 100).…”