“燕子去了，有再来的时候”，这个描写候鸟迁徙的句子如果放到一亿多年前的侏罗纪，也许要改成“恐龙去了，有再来的时候”，因为研究人员最近发现了恐龙也会进行季节性迁徙的有力证据。
英国《自然》杂志网站10月26日刊登一份报告说，包括恐龙在内的脊椎动物牙齿生长时，都会带有当时所在地区氧同位素比例特征。美国科罗拉多学院的研究人员对蜥脚类恐龙牙齿化石进行相关分析后发现，这种恐龙很可能会进行季节性迁徙。研究人员推测，这些恐龙经常到谷地肥沃的冲积平原中觅食，但当谷地遭受季节性干旱时，就迁徙到高地，等旱季过后再回到谷地。
研究人员亨利·弗里克说，这个结果是意料之中的，因为蜥脚类恐龙体型巨大，又是食草动物，如果长期在一个地方居住，当地植被难以承受。
蜥脚类恐龙是已知陆地上曾有过的最大的脊椎动物之一，据化石推测其体长可达30多米，估计体重可达上百吨。这种恐龙的季节性迁徙为了解它们的生活习性提供了线索。研究人员说，今后将尝试用类似技术手段来研究其他种类恐龙的生活习性。(生物谷 Bioon.com)
doi:10.1038/nature10570
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Lowland–upland migration of sauropod dinosaurs during the Late Jurassic epoch
Henry C. Fricke, Justin Hencecroth1 & Marie E. Hoerner
Sauropod dinosaurs were the largest vertebrates ever to walk the Earth, and as mega-herbivores they were important parts of terrestrial ecosystems. In the Late Jurassic-aged Morrison depositional basin of western North America, these animals occupied lowland river-floodplain settings characterized by a seasonally dry climate. Massive herbivores with high nutritional and water needs could periodically experience nutritional and water stress under these conditions, and thus the common occurrence of sauropods in this basin has remained a paradox. Energetic arguments and mammalian analogues have been used to suggest that migration allowed sauropods access to food and water resources over a wide region or during times of drought or both, but there has been no direct support for these hypotheses. Here we compare oxygen isotope ratios (δ18O) of tooth-enamel carbonate from the sauropod Camarasaurus with those of ancient soil, lake and wetland (that is, ‘authigenic’) carbonates that formed in lowland settings. We demonstrate that certain populations of these animals did in fact undertake seasonal migrations of several hundred kilometres from lowland to upland environments. This ability to describe patterns of sauropod movement will help to elucidate the role that migration played in the ecology and evolution of gigantism of these and associated dinosaurs.
