The palaeoecology of the non-mammalian cynodonts Diademodon and Cynognathus from the Karoo Basin of South Africa, using stable light isotope analysis
The palaeoecology of the non-mammalian cynodonts Diademodon and Cynognathus from the Karoo Basin of South Africa, using stable light isotope analysis
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DOI：
10.1016/j.palaeo.2005.04.016
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发表时间：
2005-08-01
影响因子：
3
通讯作者：
Chinsamy, A
中科院分区：
文献类型：
--
作者：
Botha, J;Lee-Thorp, J;Chinsamy, A
同时代的中三叠世非哺乳类犬齿类、双齿类和猫科动物的古肿瘤学至今仍知之甚少，尽管它们的大体形态已经得到了深入的研究。它们生长模式的显著差异表明，尽管它们生活在相似的环境中，但存在内在的生物学差异。本研究利用牙釉质碳酸盐稳定碳、氧同位素分析方法，对天鹅和双齿石牙标本的古生态进行了研究。所得的稳定同位素图谱与鳄鱼和已发表的哺乳动物牙釉质数据进行了比较。可以预见的是，非哺乳动物猫头鹰的C-13值落在C-3植物性饮食的预期范围内。Diademodon的Delta O-18和Delta C-13值都明显比Cynognapus的耗竭程度更大，这表明前者在阴凉、潮湿的地区觅食，是夜间活动的和/或更直接地依赖环境水。天鹅座牙齿所反映的季节幅度相对较低。然而，在Diademodon牙齿中观察到的高幅度、方向性的6180牙齿内变异与来自半干旱季节性地区的现存哺乳动物和C niloticus牙齿的变异相当或更高。这表明，卡鲁盆地在中三叠世存在明显的季节性，而Diademodon对这种变化很敏感。Diademodon和Cynognatus之间的这些同位素差异表明，它们对气候波动的反应不同，并揭示了对非哺乳动物犬齿动物古生态的新见解。(C)2005爱思唯尔B.V.保留所有权利。
The palaeoccology of the coeval Middle Triassic non-mammalian cynodonts, Diademodon and Cynognathus (Therapsida) remains poorly understood although their gross morphology has been studied intensively. Significant differences in their growth patterns suggest inherent biological differences, despite having inhabited similar environments. In this study, the palaeoecology of Cynognathus and Diademodon specimens were examined using intra-tooth stable carbon and oxygen isotope analyses of enamel carbonate. The resulting stable isotope patterns of Cynognathus and Diademodon were compared with that of Crocodylus niloticus and published mammalian tooth enamel data. Predictably, the non-marnmalian cynodont delta C-13 values fall within the expected range for C-3 plant diets. Both delta O-18 and delta C-13 values of Diademodon are markedly more depleted than those of Cynognathus, suggesting that the former fed in shadier, damper areas, was nocturnal and/or depended more directly on environmental water. The seasonal amplitude reflected in the Cynognathus teeth is relatively low. However, high amplitude, directional 6180 intra-tooth variations in the Diademodon teeth are comparable to, or higher than, those observed for extant mammalian and C niloticus teeth from semi-arid, seasonal regions. This suggests that marked seasonality prevailed in the Karoo Basin during the Middle Triassic, and that Diademodon was sensitive to these variations. These isotopic differences between Diademodon and Cynognathus indicate differing responses to climatic fluctuations and reveal new insights into the palaeoecology of non-mammalian cynodonts. (c) 2005 Elsevier B.V All rights reserved.