Zelenitsky Darla K, Therrien François, Kobayashi Yoshitsugu
Department of Geoscience, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
Proc Biol Sci. 2009 Feb 22;276(1657):667-73. doi: 10.1098/rspb.2008.1075.
This research presents the first quantitative evaluation of the olfactory acuity in extinct theropod dinosaurs. Olfactory ratios (i.e. the ratio of the greatest diameter of the olfactory bulb to the greatest diameter of the cerebral hemisphere) are analysed in order to infer the olfactory acuity and behavioural traits in theropods, as well as to identify phylogenetic trends in olfaction within Theropoda. A phylogenetically corrected regression of olfactory ratio to body mass reveals that, relative to predicted values, the olfactory bulbs of (i) tyrannosaurids and dromaeosaurids are significantly larger, (ii) ornithomimosaurs and oviraptorids are significantly smaller, and (iii) ceratosaurians, allosauroids, basal tyrannosauroids, troodontids and basal birds are within the 95% CI. Relative to other theropods, olfactory acuity was high in tyrannosaurids and dromaeosaurids and therefore olfaction would have played an important role in their ecology, possibly for activities in low-light conditions, locating food, or for navigation within large home ranges. Olfactory acuity was the lowest in ornithomimosaurs and oviraptorids, suggesting a reduced reliance on olfaction and perhaps an omnivorous diet in these theropods. Phylogenetic trends in olfaction among theropods reveal that olfactory acuity did not decrease in the ancestry of birds, as troodontids, dromaeosaurids and primitive birds possessed typical or high olfactory acuity. Thus, the sense of smell must have remained important in primitive birds and its presumed decrease associated with the increased importance of sight did not occur until later among more derived birds.
本研究首次对已灭绝兽脚亚目恐龙的嗅觉敏锐度进行了定量评估。通过分析嗅觉比率（即嗅球最大直径与大脑半球最大直径之比），以推断兽脚亚目恐龙的嗅觉敏锐度和行为特征，同时确定兽脚亚目内部嗅觉的系统发育趋势。对嗅觉比率与体重进行系统发育校正回归分析后发现，相对于预测值，（i）暴龙科和驰龙科的嗅球显著更大；（ii）似鸟龙科和窃蛋龙科的嗅球显著更小；（iii）角鼻龙类、异特龙类、基础暴龙类、伤齿龙科和基础鸟类的嗅球在95%置信区间内。相对于其他兽脚亚目恐龙，暴龙科和驰龙科具有较高的嗅觉敏锐度，因此嗅觉在它们的生态中可能发挥了重要作用，可能用于弱光条件下的活动、寻找食物或在大的活动范围内导航。似鸟龙科和窃蛋龙科的嗅觉敏锐度最低，这表明这些兽脚亚目恐龙对嗅觉的依赖程度降低，可能是杂食性。兽脚亚目恐龙嗅觉的系统发育趋势表明，鸟类祖先的嗅觉敏锐度并未降低，因为伤齿龙科、驰龙科和原始鸟类具有典型或较高的嗅觉敏锐度。因此，嗅觉在原始鸟类中一定仍然很重要，其假定的与视觉重要性增加相关的降低直到后来在更进化的鸟类中才出现。
