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迄今为止,中国已知的中生代哺乳动物共有26属29种(包括3个未定种),时代分布从早侏罗世至晚白垩世。在中国新近发现的中生代哺乳动物中,除少数几种材料比较零星之外,大多数都有保存很好的头骨和骨架为代表。它们提供了认识哺乳动物高阶元之间的系统发育关系以及早期演化过程中特征转变的重要信息。过去几年中发现的中生代哺乳动物多数产于热河生物群中。这些化石代表了不同的哺乳动物大类,同时显示了在个体大小、运动姿态以及食性方面的较高的分异。多方面的分异确保了它们在同一个生态系统中能够占据不同的生态位。频繁的火山活动被认为是辽宁西部地区动物大量死亡的主要原因。像巨爬兽(Repenomamus giganticus)一样以睡眠姿势保存的标本,很可能意味着随火山喷发释放出的有毒气体参与造成了这样的灾难。
So far, there are 26 genera and 29 species (including 3 undetermined species) of known Mesozoic mammals in China, with age distribution from Early Jurassic to Late Cretaceous. Most of the Mesozoic mammals recently discovered in China are represented by well-preserved skulls and skeletons, except for a few sporadic materials. They provide important information for understanding the phylogenetic relationships among mammalian higher-order elements and for the characterization of the early evolutionary processes. The Mesozoic mammals found in the last few years are mostly found in the Jehol Biota. These fossils represent different mammalian groups and show a high degree of differentiation in individual size, locomotor behavior, and diet. The many divisions ensure that they occupy different niches in the same ecosystem. Frequent volcanic activity is believed to be the main cause of mass deaths in western Liaoning. Specimens preserved in a sleeping position like a Repenomamus giganticus probably mean that such a disaster was caused by the involvement of toxic gases emanating from volcanoes.