华北地区二迭纪、三迭纪陆生四足类的性质及其时代探讨

有关华北陆相二迭纪、三迭纪地层里的四足类化石,过去除了二马营上部的中国肯氏兽动物群以外,在其他层位里很少或根本没有记载。近年来,收集到不少这方面的资料,足以对该地区这一段时期内脊椎动物的面貌有一个梗概的了解。本文介绍了晚二迭世到早、中三迭世的四个含骨化石层位,即石千峰组和石盒子组顶部;和尚沟组;二马营底部和二马营上部,对各层位的动物化石进行了初步的分析,并与我国新疆及其他大陆上的有关动物群进行了对比。

LATE PERMIAN AND TRIASSIC TERRESTRIAL TETRAPODS OF NORTH CHINA

In China,the continental sediments of late Permian and early,middle Triassicspreads mainly over two areas,Sinkiang and North China,the latter includes the pro-vinces of Shansi,Shensi,Inner Mongolia and Honan.Before liberation,only few specimens of large dicynodonts were discovered fromShansi.It was known as Sinokannemeyeria.In the years of 1955 and 1956,this regionwas surveyed by the field teams of IVPP and a series of expectant results was obtainedfrom the Upper-Er-Ma-Ying formation:This collection was studied and the paperswere published in the last decade.Sinokannemeyeria fauna was considered as related to that of Cynognathus fauna ofSouth Africa at that time.But does lystrosaurs exist in North China?What kind of fauna will appearbelow the Upper-Er-Ma-Ying?Owing to the paucity of Vertebrate fossils,the problemwas waiting to be solved.Twenty years ago,two fragments of small jaws were found from the Lower-Er-Ma-Ying of Shansi and were sent to us by the geological team.One of them was identi-fied as a procolophonid-Paoteodon,represented by a part of upper jaw with threeacrodont teeth.The other was recognized as a cynodont——Ordosiodon.During the past years,a team of the Geological Academy worked in Shensi andInner Mongolia and excavated a rather large collection of vertebrate fossils from latePermian and Triassic beds.Among them,apart from those from Upper-Er-Ma-Ying,acomplete skull of kannemeyerid was discovered at the base of Lower-Er-Ma-Ying.Another skull of proterosuchian was excavated from the Ho-Shan-Kou beds lying belowthe Er-Ma-Ying,In the years of 1976 and 1977,field groups of IVPP went to the same region witha hope to get more materials from the horizons below the Upper-Er-Ma-Ying.Theresult was rather ideal.The collection has not been fully described yet,but severalgroups of reptiles could be recognized as shown in table 1(p.102).Up to the present,four layers of bone beds were known.1.The top layer,Upper-Er-Ma-Ying,contains the Sinokannemeyeria fauna.Thepresence of traversodonts and the comparison of kannemeyerids,together with the geological evidences indicated the geological age of this layer might be of middleTriassic,so as to be comparable to the Yerrapalli of India and the Dongus of USSR,probably Manda and N'tawere as well,that is,a little later than that of Cynognathuszone of South Africa.2.Four groups of reptiles were identified from the base of Lower-Er-Ma-Ying,they are:large dicynodonts,procolophonids,scaloposaurs and primitive thecodonts.Apart from Parakannemeyeria,there is an another genus of kannemeyerid with along and elevated parietal crest,much similar to Kannemeyeria.It is named asShanbeikannemeyeria by Chin(in press).Scaloposaurs are firstly known in China.Two skulls discovered from this layer and the Ho-Shan-Kou respectively are very similar.The skulls are related to those scaloposaurs from the Lystrosaurus zone of SouthAfrica,such as Ericiolacerta and Regisaurus in certain respects,but are distinguishedby the strong canine,the structure of the postcanine and the peculiar reflected laminaof angular.Our specimens are also not so specialized as Bauria,Sesamodon andWatsoniella of Cynognathus zone.Among the materials of thecodonts,there are severalvertebrae very peculiar in shape,most probably they are of protorosaurs.3.Ho-Shan-Kou is the third layer.The striking fact is that no dicynodont werefound from here.Proportionally,procolophonids appear in larger quantity than inthe Er-Ma-Ying beds.Scaloposaurs exist as well as in the above layer.The proterosu-chian skull studied by Chin is named as Fugusuchus(in press).This is a differentgenus from Chasmatosaurus and a little generalized than Erythrosuchus of the Cyno-gnathus zone.Isolated materials of labyrinthodonts were also discovered.4.Shih-Tien-Feng is the lowermost layer in this group of sediments.The maingroup of tetrapods obtained here is that of pareiasaurs,together with several amphi-bian specimens.No other group of reptiles has been found yet,and no dicynododontsas well.However,a small collection of isolated bones and teeth were obtained fromHonan,at the top of Shih-Ho-Tze formation.According to Young,besides the pareia-saurs,there are representatives of tapinocephalians,procynosuchids,perhaps gorgo-nopsians as well.But as the materials are fragmentary and the fossil bearing horizonis still not certain,it is better to put both these two horizons into one fossil layer atpresent,and represent the only Permian tetrapod complex in North China.To sum up,there is a comparable kannemeyerid fauna of middle Triassic in agefrom both regions of North China and Sinkiang.Owing to the incomplete sequence offossiliferous beds,the tetrapod complex appeared in both regions are somewhat different.In Sinkiang,the layer between those of kannemeyerid fauna and lystrosaur one isbarren.And in North China,the layer between Ho-Shan-Kou and Shih-Tien-Feng isbarren too.The present fossil record indicates that the late Permian tetrapods of bothregions are different,as one contains dicynodonts only and the other pareiasaursmainly.