Abstract The image of the highly intelligent, pack-hunting raptor has become engrained in scientific literature and popular works alike. First proposed to explain the relatively common co-occurrence of the large-bodied iguanodontian Tenontosaurus tilletti and the wolf-sized Deinonychus antirrhopus from the Lower Cretaceous of North America, a canid-like social hunting structure has become the standard depiction of dromaeosaurs in popular works over the last three decades. This reconstruction is, however, problematic largely due to the fact that highly coordinated hunting strategies are rarely observed in modern archosaurs. This has led to the alternative hypothesis that D. antirrhopus was more analogous to agonistic reptilian carnivores, like the Komodo dragon (Varanus komodoensis). Among the many differences between these two analogs is how social and asocial organisms rear their young, producing a diagnostic pattern based on the presence or absence of ontogenetic dietary changes. In order to test for dietary changes through growth, stable carbon and oxygen isotope (δ13C, δ18O) analysis was performed on tooth carbonate from small ( 9 mm crown height) D. antirrhopus specimens from two microsites from the Lower Cretaceous Cloverly (Montana) and Antlers (Oklahoma) formations. Teeth from goniopholidid crocodylians and Tenontosaurus tilletti from the Cloverly Formation were also tested for comparison. The results show that the Cloverly goniopholidids, like their modern counterparts, went through a distinct transition in diet as they grew. The smallest teeth were the relatively most enriched in 13C (mean = −9.32‰; n = 5), the medium-sized teeth were the most-depleted in 13C (mean = −10.56‰; n = 5), and the largest teeth were intermediate (mean = −10.12‰; n = 6). These factors are characteristic of the dietary shifts seen in modern asocial reptiles. D. antirrhopus showed this same pattern in tooth samples collected from both rock units, with small teeth being the more enriched in 13C (mean = −8.99‰; n = 10) and the large teeth being more depleted in 13C (mean = −10.38‰; n = 10). These differences suggest that juvenile and adult D. antirrhopus from both formations likely consumed different prey. Hypothetical food sources, such as T. tilletti, are close to the 13C isotopic signal of adult D. antirrhopus, consistent with the hypothesized trophic relationship (predator-prey) between these two species. Juvenile D. antirrhopus had a diet more enriched in 13C, likely composed of smaller-bodied, but trophically-higher species. Taken together, these data add to the growing evidence that D. antirrhopus was not a complex social hunter by modern mammalian standards.

中文翻译：

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Deinonychus antirrhopus (Theropoda; Dromaeosauridae) 的个体发生饮食变化：通过稳定同位素分析洞察猛禽恐龙的生态和社会行为

摘要 高度智能的猎杀猛禽的形象已经在科学文献和流行作品中根深蒂固。首次提出来解释北美下白垩统的大型禽齿类腱龙和狼大小的恐爪龙相对常见的共生现象，犬类社会狩猎结构已成为流行作品中驰龙类的标准描述在过去的三个十年中。然而，这种重建是有问题的，主要是因为在现代主龙中很少观察到高度协调的狩猎策略。这导致了另一种假设，即 D. antirrhopus 更类似于激动的爬行动物食肉动物，如科莫多巨蜥 (Varanus komodoensis)。这两个类似物之间的许多差异之一是社会和非社会生物如何抚养他们的年轻人，根据个体遗传饮食变化的存在或不存在产生诊断模式。为了通过生长测试饮食变化，对来自下白垩纪三叶草（蒙大拿州）的两个微型站点的小（9 mm 冠高）D. antirrhopus 标本的牙齿碳酸盐进行了稳定的碳和氧同位素（δ13C、δ18O）分析。鹿角（俄克拉荷马州）队形。来自 Cloverly Formation 的 goniopholid crocodylians 和 Tenontosaurustiletti 的牙齿也进行了测试以进行比较。结果表明，Cloverly goniopholids 和现代同类一样，在成长过程中经历了明显的饮食转变。最小的牙齿相对富含 13C（平均值 = -9.32‰；n = 5），中等大小的牙齿在 13C 中消耗最严重（平均值 = -10.56‰；n = 5），最大的牙齿是中间的（平均值 = -10.12‰；n = 6）。这些因素是现代非社会爬行动物饮食变化的特征。D. antirrhopus 在从两个岩石单元收集的牙齿样本中显示出相同的模式，小牙齿中 13C 的含量更高（平均值 = -8.99‰；n = 10），而大牙齿中 13C 的含量更多（平均值 = -10.38 ‰；n = 10)。这些差异表明来自两个地层的幼年和成年 D. antirrhopus 可能消耗了不同的猎物。假设的食物来源，如 T.tilletti，接近成虫 D. antirrhopus 的 13C 同位素信号，与这两个物种之间假设的营养关系（捕食者-猎物）一致。幼年 D. antirrhopus 的饮食中 13C 含量更高，可能由体型较小但营养较高的物种组成。综上所述，这些数据增加了越来越多的证据，即按照现代哺乳动物的标准，D. antirrhopus 并不是复杂的社会猎手。