Dinosaur Diversity During the Transition Between the Middle and Late Parts

Article Geology December 2013 Vol.58 No.36: 46634669 doi: 10.1007/s11434-013-6059-9 Dinosaur diversity during the transition between the middle and late parts of the Late Cretaceous in eastern Shandong Province, China: Evidence from dinosaur eggshells ZHAO ZiKui*, ZHANG ShuKang, WANG Qiang & WANG XiaoLin Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China Received March 22, 2013; accepted July 1, 2013 The record of dinosaur eggs from the Upper Cretaceous Wangshi Group in eastern Shandong Province, China shows that the dinosaur species represented by elongatoolithids were present from the middle to the late Late Cretaceous, whereas those represented by the dictyoolithids and spheroolithids became extinct in the middle Late Cretaceous and the new species represented by ovaloolithids appeared in the late Late Cretaceous. Estimated eggshell conductance of water vapor is over 4 to over 115 times higher in spheroolithids and the dictyoolithids than in elongatoolithids and ovaloolithids, indicating that eggs of the first two oo- 18 families required higher humidity during incubation. Based on the O record as preserved in eggshell, a change from relatively humid to relatively dry climatic conditions can be assumed to have taken place during the transition between the middle and late parts of the Late Cretaceous. It is reasonable to suggest that the change in climate was the cause of the dinosaur diversity. dinosaur eggshell, gas conductance, dinosaur diversity, middle-late Late Cretaceous, eastern Shandong Province Citation: Zhao Z K, Zhang S K, Wang Q, et al. Dinosaur diversity during the transition between the middle and late parts of the Late Cretaceous in eastern Shan- dong Province, China: Evidence from dinosaur eggshells. Chin Sci Bull, 2013, 58: 46634669, doi: 10.1007/s11434-013-6059-9 Since the 1980s, there has been considerable progress in India [10] and the Nanxiong Basin, Guangdong Province, research into regional and global biological events. A huge China [11–14] in Asia, but evidence from continental set- mass of data from the marine strata of Americas, Europe, tings regarding other biological events that took place in the northern Africa and India indicate that ten major marine Cretaceous is very limited. biological events took place in the Cretaceous [1], including Upper Cretaceous Wangshi Group in Laiyang-Zhucheng, the Cenomanian-Turonian boundary mass extinction, the eastern Shandong Province, yields abundant dinosaur eggs Turonian-Coniacian stage boundary bio-events, the Coni- [15–18]. Changes in this dinosaur egg fauna may represent acian-Santonian stage boundary bio-events, the Santonian- important ecological changes during the transition between Campanian stage boundary bio-events, the middle Maas- the middle and late portions of the Late Cretaceous [17,19,20]. trichtian extinction interval, and finally the Cretaceous- Previous studies published since 1992, and especially Paleogene boundary mass extinction at the conclusion of the since 2010, led us to travel to Laiyang, Jiaozhou and Zhu- Late Cretaceous. However, the fossil record preserved in cheng to investigate the Upper Cretaceous Wangshi Group, Cretaceous continental strata is less complete than its ma- which yields dinosaur eggs. We collected specimens, and rine counterpart. The Cretaceous-Paleogene dinosaur extinc- studied the water vapor conductance of different kinds of tion is well documented in inland western North America dinosaur egg from the Wangshi Group using biomechanical [2–7], the Mediterranean coast of Europe [8,9], western methods. In this paper we present the results of this research, and discuss the processes and causes underlying dinosaur *Corresponding author (email: [email protected]) diversity patterns in the middle-late Late Cretaceous. © The Author(s) 2013. This article is published with open access at Springerlink.com csb.scichina.com www.springer.com/scp 4664 Zhao Z K, et al. Chin Sci Bull December (2013) Vol.58 No.36 1 Geological setting and confirmation of the saurs from the Jiangjunding and Jingangkou Formations in position of the boundary between the middle and the Wangshi Group were distinctive derived forms, and that late parts of the Late Cretaceous they indicated a Late Cretaceous age for the Wangshi Group. Hu et al. [25] suggested that the dinosaurian fauna domi- nated by Shantungosaurus giganteus from the Xingezhuang The Upper Cretaceous Wangshi Group exposed in eastern Formation was early Late Cretaceous (corresponding to Shandong Province is a set of continental clastic deposits Cenomanian-Turonian) in age, whereas the dinosaur fauna composed of red conglomerate, sandstone and silty mud- represented by Tanius sinensis from the Jiangjunding For- stone. The Wangshi Group directly overlies the Lower Cre- mation was middle Late Cretaceous (corresponding to Co- taceous Qingshan Group, and crops out widely in areas in- niacian-Santonian) and the dinosaur fauna represented by cluding Laiyang, Jiaozhou and Zhucheng (Figure 1). In the Tsintaosaurus spinorhinus from the Jingangkou Formation 1920s, Tan [21] investigated in the area around Jiangjund- was late Late Cretaceous (corresponding to Campanian). ing and Jingangkou in Laiyang County and established the Recently, Wang et al. [27] compared and discussed the di- ‘Wangshi Series’. In the 1950s, dinosaur eggs [22,23] and nosaur egg faunas and strata of the major Chinese basins in some complete dinosaur skeletons including the holotype of which dinosaur eggs had been found, and also suggested the the famous Tsintaosaurus spinorhinus [24] began to be re- Jiangjunding and Jingangkou Formations of the Wangshi covered from the middle and upper parts of the ‘Wangshi Group were middle and late Late Cretaceous respectively Series’, catching the attention of government agencies whose (corresponding to Coniacian-Campanian). In addition, the responsibilities included aspects of geology or paleontology. Jingangkou Formation has also been interpreted as late Late Subsequently, some of these agencies initiated extensive Cretaceous based on gastropod and ostracod biostratigraphy research on the lithostratigraphy and biostratigraphy of the [28,29]. “Wangshi Series”. Shantungosaurus giganteus and other In modern stratigraphy, boundaries between different dinosaur remains were found in Zhucheng [25]. In 1995, units are defined on the basis of two elements: recognizable Cheng et al. [26] revised the lithostratigraphic divisions of geological events, and the time equivalence of a given event the “Wangshi Series”. The Wangshi Series was described as in different places. The dinosaur egg faunas from the Wangshi Group and divided into, in ascending order, the Jiangjunding and Jingangkou Formations can be distin- Xingezhuang, Jiangjunding and Jingangkou Formations in guished from one another with remarkable clarity [12]: the the Laiyang area. major egg type seen in the Jiangjunding Formation is sphe- The Wangshi Group has yielded abundant hadrosaurid roolithid, and that seen in the overlying Jingangkou For- dinosaur specimens. Young [24] considered that the hadro- mation is ovaloolithid. Furthermore, the δ18O signatures of Figure 1 Distribution of the Wangshi Group in eastern Shandong Province. Zhao Z K, et al. Chin Sci Bull December (2013) Vol.58 No.36 4665 dinosaur eggshell preserved in the two formations are also Protodictyoolithus jiangi very different [20]. Therefore, the stratigraphic boundary Spheroolithidae between the middle and late parts of the Late Cretaceous in Spheroolithus spheroides eastern Shandong should correspond to the boundary be- S. chiangchiungtingensis tween the Jiangjunding and Jingangkou Formations. S. megadermus Paraspheroolithus irenensis (2) In total, seven oospecies representing three oogenera 2 Dinosaur diversity in the middle-late Late have been recovered from the upper Upper Cretaceous Cretaceous in Shandong Jingangkou Formation: Elongatoolithidae The dinosaur egg fauna of the Wangshi Group in eastern Elongatoolithus elongatus Shandong occurs mainly in the Jiangjunding and Jingang- Spheroolithidae kou Formations of Laiyang, Jiaozhou and Zhucheng, and is Paraspheroolithus irenensis especially abundant in the Wangshi Group of Laiyang. Ovaloolithidae More than one hundred and twenty complete or nearly com- Ovaloolithus chinkangkouensis plete dinosaur eggs, and numerous eggshell fragments, have O. monostriatus been found to date. Eleven oospecies representing five oogen- O. tristriatus era and four oofamilies (Elongatoolithidae, Spheroolithidae, O. mixtistriatus Ovaloolithidae and Dictyoolithidae) have been erected O. laminadermus [18,19,30,31]. Other specimens, especially some that have Comparisons of eggshell microstructure among the afore- been collected in the past twenty years, include new types mentioned oospecies (Figure 2) show that Protodictyoo- that remained undescribed but can be assigned to Elonga- lithus jiangi, Spheroolithus spheroides and S. chiangchiung- toolithidae, Ovaloolithidae or Prismatoolithidae based on tingensis have loosely arranged eggshell units and a well preliminary observations. Since more time will be needed developed pore canal system. These oospecies have been before a formal report can be published, these specimens are found only in the middle Upper Cretaceous Jiangjunding not discussed further in this paper. Formation and never in the overlying Jingangkou Formation (1) In total,

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