Body cavity size in fossil chewing herbivores, non-chewing herbivores, and carnivores: Implications for GIT volume and gigantism.

在食草动物中，共生肠道微生物对植物材料的消化是摄食物保留（可用于发酵的时间）和颗粒大小的函数。由于较小的颗粒尺寸加速了消解速率，因此保留时间和颗粒尺寸减小可以相互补偿。因此，缺乏颗粒尺寸减小机制的动物（非咀嚼恐龙，如蜥脚类恐龙，剑龙，甲龙）应该采用较长的摄食保留时间，由相对较大的（体积大）肠道促进。虽然体型已被建议作为体腔体积的指标，因此肠道，定量研究缺乏。通过对已灭绝的食草动物和活体动物骨骼的数字捕获、体型重建和体积计算，我们将检验以下假设：a）食肉恐龙、爬行动物和哺乳动物的体腔/腹腔体积小于食草动物，特别是B）非-咀嚼食草恐龙和更原始的爬行动物化石比咀嚼食草恐龙和哺乳动物有更大的体腔。我们预测，体腔的体积是一个重要的变量，在草食动物的消化形态生理适应，与恐龙-咀嚼和非咀嚼形式存在-是理想的模式生物为这一原则，显示更多的可变性，在这个参数比哺乳动物。特别是，我们预测，不成比例的大体腔是蜥脚类动物的决定性特征（尽管缺乏咀嚼，但有助于高食物摄入和代谢）。

In herbivores, digestion of plant material by symbiotic gut microbes is a function of both ingesta retention (time available for fermentation) and particle size. Because smaller particle size accelerates digestion rate, retention time and particle size reduction can compensate for each other. Thus, animals lacking a particle size reduction mechanism (non-chewing dinosaurs such as sauropods, stegosaurs, ankylosaurs) should have adopted long ingesta retention times, facilitated by comparatively large (voluminous) guts. Although body shape has been suggested as an indicator for the volume of the coelomic cavity and hence the gut, quantitative investigations are lacking. Using digital capture of mounted skeletons of extinct herbivores and live animals, body shape reconstructions and volume calculations, we will test the hypotheses that a) carnivorous dinosaurs, reptiles, and mammals have a less voluminous coelomic/abdominal cavity than their herbivore counterparts, and in particular that b) non-chewing herbivorous dinosaurs and more primitve fossil reptiles have a more voluminous coelomic cavity than chewing herbivorous dinosaurs and mammals. We predict that the volume of the body cavity is an important variate in herbivore digestive morphophysiological adaptation, with dinosaurs – where both chewing and non-chewing forms exist – being the ideal model organisms for this principle, displaying more variability in this parameter than mammals. In particular, we predict that a disproportionately large body cavity is a decisive characteristic of sauropods (that facilitated a high food intake and metabolism in spite of a lack of mastication).