中国早白垩世翼龙动物群及其多样性对比

Comparison of biodiversity of the Early Cretaceous pterosaur faunas of China

中国西北和东北地区发育中生代河湖相沉积的陆相盆地,其中赋存丰富的脊椎动物化石群,包括天山北部准噶尔盆地的乌尔禾翼龙动物群、天山南部吐哈盆地的哈密翼龙动物群和辽西热河生物群富含翼龙化石。乌尔禾和哈密翼龙动物群都发现于下白垩统吐谷鲁群中,两者的繁盛时间大致相当,这两个动物群的翼龙个体数量巨大,但是物种多样性很低。乌尔禾翼龙动物群的化石多保存在半深湖环境沉积的细砂岩和粉砂岩中,化石保存较为完整,主要为正常死亡;哈密翼龙动物群的化石富集保存在滨浅湖环境事件沉积的风暴岩中,大都经过了大型风暴的短距离搬运和快速埋藏,骨架分散,但几乎所有单个骨骼完整。东北地区的热河生物群翼龙种类众多,共生包括鱼类、两栖类、恐龙等其他爬行类、鸟类和哺乳类等脊椎动物,生物多样性极为丰富,大多保存在半深湖深湖环境形成的页岩中,骨架多为完整保存,是火山爆发事件导致其集群死亡,并被火山灰快速埋藏,与新疆的动物群面貌明显不同。根据天山南北的翼龙动物群初步对比,乌尔禾翼龙动物群的主要优势类群准噶尔翼龙类,在天山北部的准噶尔盆地及相邻的蒙古西部地区都有分布,与天山南部的哈密翼龙动物群中已知唯一翼龙类群哈密翼龙完全不同,两者亲缘关系很远。因此认为在中生代,天山的隆升就已经达到了一定的高度,并对翼龙的南北迁徙交流形成了有效的地理阻隔。依据中国东北和西北地区早白垩世翼龙动物群对比,认为辽西及相邻周边地区由于华北克拉通破坏,导致大量火山活动,造成了生态环境的多样性和生物种类的快速更替,从而形成了热河生物群独有的极高的生物多样性,而缺少火山活动、环境相对单一的西北陆相盆地,虽然翼龙类具有数以千万计的庞大居群,但是物种多样性很低。华北克拉通破坏导致的辽西地区频繁而强烈的火山活动,是形成中国西北和东北早白垩世生物多样性差异的重要原因。

A large number of continental basins in northeastern and northwestern China contain abundant vertebrate fossils in lacustrine deposits.Among them,the Wuerho Pterosaur Fauna from the Junggar Basin on the north side of the Tian Shan Mountains,the Hami Pterosaur Fauna from the Turpan-Hami Basin on the south side of the Tian Shan Mountains,and the Jehol Biota of western Liaoning,all bear rich pterosaur fossils.The former two faunas of northwestern China shared similar prosperous time and were both discovered in the Lower Cretaceous Tugulu Group.Pterosaur diversity of these two faunas is low but the faunas included abundant individuals.Fossils of the Wuerho Pterosaur Fauna,preserved mostly in the finesandstones and siltstones of the semi-deep lacustrine deposits,were relatively complete and formed by normal death.The fossils of the Hami Pterosaur Fauna were largely preserved in the tempestites of the event deposits of a shore-shallow lake.The disarticulated bones were complete after the short-distance transport by storms and a fast burial.By contrast,the pterosaurs of the Jehol Biota of northeastern China have high diversity as well as an association with fishes,amphibians,dinosaurs and other reptiles,and birdsand mammals,They were mainly preserved in the semi-deep to deep lacustrine shales.The skeletons are relatively complete,as a volcanic eruption caused massive death and fast burial(by volcanic ashes)creating a very different outlook from that of the two northwestern faunas.Based on the preliminary comparison of the pterosaur faunas from the south and north sides of the Tian Shan Mountains,we inter that the dominant pterosaurs on the north side,dsungaripterids,are distributed in the Junggar Basin and neighboring western Mongolia,that they have a distant relationship with the only known taxon,Hamipterus,from the faunas from the south side.Hence,we have proposed that the Tian Shan Mountains rose to a relatively high level in the Mesozoic,blocking the migration of the faunas from both sides of the mountains.In western Liaoning and its neighboring regions,the destruction of the North China Craton caused abundant volcanic eruptions,which created a highly diversified ecological environment with rapid replacements of creatures thus resulting in unique biodiversity in the Jehol Biota.However,the continental basins in northwestern China,which experienced no volcanic eruption,have low diversity but high abundancy of pterosaurs.Therefore,we proposed that the frequent and intense volcanic eruptions caused by the destruction of the North China Craton played an essential role in the varying diversity between the pterosaur faunas of northeastern and northwestern China.