Gizzard vs. teeth, it’s a tie: food-processing efficiency in herbivorous birds and mammals and implications for dinosaur feeding strategies

Particle size reduction is a primary means of improving efficiency in herbivores. The mode of food particle size reduction is one of the main differences between herbivorous birds (gizzard) and mammals (teeth). For a quantitative comparison of the efficiency of food comminution, we investigated mean fecal particle sizes (MPS) in 14 herbivorous bird species and compared these with a data set of 111 non-ruminant herbivorous mammal species. In general MPS increased with body mass, but there was no significant difference between birds and mammals, suggesting a comparable efficiency of food processing by gizzards and chewing teeth. The results lead to the intriguing question of why gizzard systems have evolved comparatively rarely among amniote herbivores. Advantages linked to one of the two food comminution systems must, however, be sought in different effects other than size reduction itself. In paleoecological scenarios, the evolution of \"dental batteries,\" for example in ornithopod dinos...食物颗粒物粒径缩减是植食性动物提升消化效率的核心方式。食物颗粒物粒径缩减的方式，是植食性鸟类（砂囊，gizzard）与哺乳动物（牙齿，teeth）之间的核心差异之一。为定量比较食物粉碎效率，我们测定了14种植食性鸟类的平均粪便颗粒物粒径（mean fecal particle sizes, MPS），并将其与包含111种非反刍植食性哺乳动物（non-ruminant herbivorous mammal）的数据集开展对比分析。总体而言，MPS随体重增加而升高，但鸟类与哺乳动物之间未出现显著差异，这表明砂囊与咀嚼牙齿的食物处理效率相当。上述结果引出了一个耐人寻味的问题：为何砂囊消化系统在羊膜动物（amniote）植食类群中的演化频次相对较低？然而，两类食物粉碎系统各自的优势，应当从粒径缩减之外的其他效应中探寻。在古生态学（paleoecological）场景中，例如鸟脚类恐龙（ornithopod dinosaurs，原文缩写为dinos）的"齿列复合体（dental batteries）"演化……