Contributors

Lu, Hui-nan Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Pan, Hua-zhang Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Shen, Yan-bin Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Wang, Qi-fei Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Wang, Xiao-lin Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of

Sciences; No. 142, Xi-Zhi-Men-Wai Street, Beijing 100044, China Wang, Yuan Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of

Sciences; No. 142, Xi-Zhi-Men-Wai Street, Beijing 100044, China Wang, Yuan-qing Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of

Sciences; No. 142, Xi-Zhi-Men-Wai Street, Beijing 100044, China Wu, Shun-qing Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Xu, Xing Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of

Sciences; No. 142, Xi-Zhi-Men-Wai Street, Beijing 100044, China Yang, Jing-lin Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Zhang, Fu-cheng Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of

Sciences; No. 142, Xi-Zhi-Men-Wai Street, Beijing 100044, China Zhang, Hai-chun Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Zhang, Jiang-yong Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of

Sciences; No. 142, Xi-Zhi-Men-Wai Street, Beijing 100044, China Zhang, Jun-feng Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China Zhou, Zhong-he Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of

Sciences; No. 142, Xi-Zhi-Men-Wai Street, Beijing 100044, China Zhu, Xiang-gen Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences;

No. 39, East Beijing Road, Nanjing 210008, China

Mee-matm Chang

Sihetun Village Photo: Jie Zhang/ IVW

Last decade lias witnessed a renewed interest in the Jehol Biota both within the scientific community and among the genera! public worldwide. The numerous research papers on the Jehol Biota, published in the prestigious journals such as Nature and Selena , have generated heated controversies among scientists and gained a widespread media frenzy. Here is a perfect example of Stephen J. Gould meeting Thomas S. Kuhn: a sudden "scientific revolution" has punctuated a long period of "normal science," with John Ostrom's revival of Thomas H. Huxley's theory of dinosaurian origin of birds as the new (or more precisely, renewed) paradigm. The discoveries of "feathered" dinosaurs in the Jehol Biota appear to have provided the direct evidence in support of the paradigm and therefore aroused public's intrigue in the notion of dinosaurs still being with us. Scientifically even more important is the Jehol Biota's well-preserved ancient biodiversity, which contains enormous amount of information on the paleoecosysrem as well ¿is many evolutionary issues.

We Chinese paleontologists have also had our turn of the wheel not only in those fabulous fossil finds hut also in our poise to join our country's drive toward excellence in scientific research. To that end, I hope that this book bears some fruits. In the remainder of this chapter, I will present a brief history of the studies on the Jehol Biota, an outline of its main components, and a highlight of its scientific import.

"Jehol" is the transliteration of the two Chinese characters " ^¡"T in the Wade-Giles romanization system of the Chinese language, which was used until 1979 when the spelling of proper nouns were officially adopted using the Pinyin (Chinese phonetic alphabet) system of romanization in the mainland of China. In the Pinyin system, these two characters are transliterated to "Rehe". However, we must abide by the "International Stratigraphic Guide" (1976) to continue to use the terms of Jehol Group and Jehol Biota (or Fauna). The literal meaning of the two Chinese characters "J^;5]"" is "Hot River", derived from many hot springs in the area. What are now called western Liaoning, northern Hebei and southeastern Inner Mongolia were municipally included in Jehol Province (Fig. I ) before 1956, when the provincial name was abolished. At present, the only historical reminder of the

11 Map of the eastern China, the insel (taken from Ding. Weng Ki Zeng, eds.. ! 936. New Mop of Provinces of China) showing the comparable area of the "Jehol Province" (shaded area), after which the Biota was named.

ft

"Jehol" is the two characters engraved on a stone tablet in Rehe Hot Spring of the Chengde summer resort, originally built for the emperors of the Qing Dynasty to escape the midsummer heat in the Forbidden City (Fig. 2).

In his paper "Cretaceous Mollusca from North China" (1923), the American geologist Prof. Amadeus W. Grabau (Fig. 3) named the fossil-bearing strata in the vicinity of Lingyuan County (now Lingyuan city in western Liaoning Province) as "Jehol Series". And while studying the Mesozoic stratigraphy of China in 1928, he first used the name "Jehol Fauna". In 1962, after working on various deposits bearing the fossil fish Lycoptera from different areas of western Liaoning, Prof. Zhi-wei Gu (Fig. 4), a malacologist from the Nanjing Institute of Geology and Palaeontology, used the name "Jehol Group" for the strata containing the conchostracan Eosestheria middendorfii (previously known as Bairdestheria middendorfii), insect larva Ephemeropsis and fish Lycoptera. Accordingly, he called the biota "Jehol Biota" or, in short, the E.-E.-L. Biota (Fig. 5).

The late Mesozoic Jehol Biota and those comparable to it had a wide distribution over northern China, Mongolia, Transbaikalian region of Siberia, Korea, and Japan (Fig. 6). The size of this area almost approaches that of the present-day Europe. This late Mesozoic oasis provided favorable conditions for many ancient animals and plants to thrive. A series of NE/SW- oriented fault basins developed during the Yanshan Orogeny (mountain-building episode), and were filled with thick volcanic and fluvial-lacustrine deposits. It was probably because of the frequent volcanic eruptions that numerous plants and animals were rapidly buried and consequently, preserved as exquisite fossils. Their catastrophic misery has turned into our best luck today: we have collected not only complete skeletons but also soft parts , such as feathers, and featherlike structures preserved as impressions, and not only gizzard stones but also stomach contents, especially in Chaoyang and Beipiao regions of western Liaoning.

The earliest studied fossil from the Jehol Biota in western Liaoning is a small fish found in the vicinity of Lingyuan City. The material was collected by L'Abbé David, and named in 1880 by a French ichthyologist, H. E. Sauvage, as Prolebias davidi, then thought to be a Tertiary cyprinodont (pupfish). It was not until 1901 when the renowned British ichthyologist A. S. Woodward reassigned the fish to the Mesozoic Lycoptera, a genus endemic to Siberia, Mongolia, and northern China. To date, the described fossils of the Jehol Biota include over 60 species of plants, nearly 90 species of vertebrates,

Feathered Dinosaur Skeletons

and almost a thousand species of invertebrates. With the Jehol Biota being a hotbed of paleontological research at present, that number is increasing rapidly.

The Jehol Biota possesses the dual qualities that entice an unbridled enthusiasm from professionals and lay persons alike. The fossils are extremely well preserved, beautiful, and abundant. They have important implications on some key issues in evolution such as origin and early diversification of major groups like birds (Hou et al.,1995), mammals, and angiosperms (flowering plants), origin of avian flight, tempo and mode of evolution, paleobiogeography, paleoecology, and paleoenvironments.

The most notable among the recent fossil findings from western Liaoning are of course the "feathered" dinosaurs. Feathers had never been

2^,3 Amndeus W. Grabau (1870-1946), an American geologist who proposed the jeholFauna in 1928, (Courtesy; Yuan-tin Sun/ PKU)

KfcX. 4 Zhi-wei Cu (b. 19181. a Chinese mala-eulogist of" the NIGP who proposed the E.-t:.-L. Biota in 1962.

discovered previously in animals other than birds. Yet, feathers or Featherlike structures have been found abundantly associated with a number of dinosaurs from Liaoning such as Sittosauropteryx (Chen et al.,1998)i Cautffptefyx, Beipiaosattrus, Protarchawpttryx, Stnornithosaurus, and Mtcrorapror. If we only look at the skeletons of these creatures, dinosaur workers would say without hesitation that they are dinosaurs. Yet all of them bear feathers or featherlike structures. Though somewhat bewildered at first, many paleontologists soon realized how significant these discoveries were: the feathers and featherlike structures found in those dinosaurs betrayed the dinosaurs' affinity to birds!

In fact, about 130 years ago, Thomas H. Huxley thought the dinosaur was the direcr ancestor of birds. And a few daring scientists even predicted that fearhers would sooner or later be found on dinosaurs, but that point of view had nut received general acceptance. It was nor until 1973 when Prof. John Ostrom at die Yale University studied the small theropod Deirmlycbtts, and found that its skeleton was astonishingly similar to that of Afchaeopteryx, the earliest bird. And he suggested that small theropods might be the ancestors of birds. Despite the many skeletal characters that relate dinosaurs with birds, for most people, nothing can be more convincing than actually seeing the dinosaurs covered with feathers. To those who arc convinced that birds are direct descendants of dinosaurs, the feathered dinosaurs from western Liaoning are nothing but the "smoking gun". However, a vocal minority of leading palebraithologists still insists that birds came f rom a primitive group of reptiles called thecodonts. Besides, feathers and featherlike structures were found on dinosaurs that apparently could not fly. Then what are those feathers for/ Were they for insulation, for camouflage, for courtship, or for defense? And how did the avian flight originate? Did the proco-birds attain their flight capability by walking and running on the ground and then raising their wings to fly ("ground-up" theory), or by gliding from the tree to learn how to fly ("tree-down" theory)? We cannor expect that at! these questions, together with the origin of birds, be answered just with the discoveries of new materials. More careful and synthetic work has to be done before more persuasive hypotheses emerge on more solid ground. Admittedly, this kind of work is more tedious and less sensational, but it is truly exciting and intellectually stimulating. Contrariwise, clever argumentation and religious war are bound to be detrimental to the progress in science.

The fossil plants, especially angiosperms, from western liaoning are also very interesting. The records of angiosperms can be traced back to the works oi H. Yabe and S. Endo in 1930s. They described Potumogeton jeholensis. Due to the poor preservation of the material, little attention was paid to their work. Later, S. Miki (1964) questioned the identification of Potamogeton, and considered the plant as Ranunculus instead. More recently, Zheng-yao Cao and others (1997) and Shu-ying Duan (1997) reported monocots and fructification with carpels. Cao et al.'s Lianxia chenii (Gyperaceae) and Eragrosites cbangii (Gramineae) were later designated as gnetales, a group of gymnosperm, by Shun-qing Wu (1999) and Shuang-xing Guo and Xiang-wu Wu (2000) while Duan's Chaoyangia liangii is probably also a gnetalean, not an angiosperm. Similar forms have been found in the Lower Cretaceous strata of Mongolia and were described by V. A. Krassilov (1982) under other names; Cyperacites sp., Polamugeton-\ike spike, and Gurvanella dictyptera.

Archaefructus liaoningensis was described by Ge Sun, D. L. Dilcher and others (1998) as an angiosperm although this is not yet unquestionably accepted by most paleobotanists. Its age, however, may not be the Late Jurassic, as these authors suggested, but is more likely to be the same, i.e., the Early Cretaceous, as that of the early angiosperms previously discovered from Europe, Mongolia and western North America. A more definite angiosperm Sinocarpus decussatus was described recently by Qin Leng and E. M. Friis (2003). Another significant plant from the Jehol Biota is a gymnosperm Sequoia jeholensis. And it is regarded as the oldest record of the genus. The genus is at present surviving only in California. For lacking cone and the leaf cuticular structure, it must be treated with caution at present. More recently, Zhi-yan Zhou and Shao-lin Zheng (2003) reported that the ovulate organs of Ginkgo from the Yixian Formation show striking similarities to those of the extant species Ginkgo biloba, indicating a morphological stasis in Ginkgo's reproductive structure for over 100 million years. With ever increased and better-preserved specimens, we anticipate more thorough paleobotanical research of the Jehol

Jehol Biota Fish
5 Three representatives of the Jehol Biota in the early studies, the conchostracan Eosestheria (Upper left), insect larva h'phemeropsis (Upper Right) and fish Lycoptera (Lower). (Photo: IVPP)

Biota in the near future as well.

The diversity, abundance, and exquisite preservation of the Jehol Biota make it one of a handful of extraordinary "Fossil-Lagerstätten" (strata containing abundant and well preserved fossils) in the world. Recently described vertebrate fossils include bony fishes, archaic frogs, salamanders, aquatic reptiles, lizards, turtles, dinosaurs, early mammals, etc. There are also abundant invertebrates: mollusks, ostracods, conchostracans, insects and

3000fcm

■ 6 Distribution of the Jehol Biota (green area) at its peak period.

Cretaceous Paleogeography Photos

wb 7 Paleogeographic map of the world in the Early Cretaceous. (Modified from Kenton. Rich & Rich, 1989)

■ 6 Distribution of the Jehol Biota (green area) at its peak period.

wb 7 Paleogeographic map of the world in the Early Cretaceous. (Modified from Kenton. Rich & Rich, 1989)

others. Although this faunal list is far from complete, it catches a glimpse at the vast panorama of the Jehol Biota, which awaits further exploration.

The Jehol Biota also has significant bearings on reconstructing the relationships among the ancient landmasses, i.e., paleobiogeography. During the lifetime of the Jehol Biota, the eastern part of Eurasia was an isolated area. It was separated from the western part of Eurasia by the Turgai Strait, and from North America by the comparatively wide Bering Strait (Fig. 7). Paleo-Qinling and Dabie Mountains on the southern border of this area must have acted as some kind of barrier that prevented the exchange of organisms between the north and south. Owing to this isolation, the Jehol Biota consists of many endemic forms, not seen on other continents, and not even seen in the southern part of China. For example, Lycoptera is a fish never found in any other places out of the distribution area of the Jehol Biota. Fishes such as polyodontid Protopsephurus and Yanosteus as well as amiiformes Sinamia were never found in their contemporaneous deposits anywhere else. In Late Cretaceous, however, when the Asian-Alaskan Land Bridge came into existence, many forms related to the aforementioned fishes started to appear and develop in North America (Fig. 8). Some of their close relatives still survive in North America as relics even today. For instance, Hiodon (mooneye) is related to Lycoptera, Amia (bowfin) to Sinamia, Polyodon (paddlefish) to Protopsephurus and Yanosteus\ and a few other fishes seem to adopt the North American freshwater system as their present day refugium. You can find them nowhere else nowadays, and you can hardly find their ancient relatives in other parts of the world, either. Yet they occurred in the Jehol Biota. This is another aspect showing the Jehol Biota's scientific importance.

As for the age of the Jehol Biota, the debate has lasted for several decades. There are mainly two different opinions about the age: the Late Jurassic (ca. 145 millions years before present, or 145 Ma) versus the Early Cretaceous (ca. 125 Ma). Recently, C. C. Swisher III et al. (1999, 2002) and Ching-hua Lo et al. (1999) dated the Yixian Formation respectively. The former suggested an age of around 125 Ma (Early Cretaceous) using single sanidine crystal 40Ar/39Ar dating. And the latter used biotite for the 40Ar/39Ar laser single-grain fusion method and came up with an age of around 147 Ma (Late Jurassic). Many workers from various institutions are interested in the dating, and the work is still underway. The debate would probably go on for some time. But we can expect better results with more refined dating techniques and careful sampling and laboratory work in the near future.

This book provides the Biota's temporal and spatial relationships, showcases some of its most wonderful fossils, and summarizes our preliminary understandings of them. In a book that involves many authors and covers many taxonomic groups, it is almost inevitable that inconsistencies in age assignments and stratigraphic correlations exist. In most chapters, the Jehol Group includes the Yixian and Jiufotang Formations only, whereas in a few other chapters the scope of the Group varies to include certain strata either overlying or underlying those formations. We cannot overstate scientific impacts of the Jehol Biota on recent progress in paleontology. We hope that our readers will find the following pages visually pleasing, scientifically interesting, and intellectually rewarding.

It is worth noting that the Chinese names have, over the years, confused our overseas colleagues and bibliographers alike. To ease the situation, we decide to list the Chinese names according to the English convention, i.e., the first name first — a reversal of the Chinese custom with surname first. To further ease the pronunciation and potential confusion, we hyphenate the first name with two characters, e.g., Shu-an Ji. Without the hyphen, "Shuan" could be misconstrued as a single syllable, i.e., a first name with only one character.

ACKNOWLEDGMENTS: Needless to say, in a project as vast as this, there are numerous unsung heroes behind the contributors to this volume. I would like to name just a few whose assistances are particularly appreciated: E. M. Friis for her help with Chapter 19 and her willingness in joining in to add Chapter 20, Zhi-yan Zhou for his generosity in providing much-needed consultation on fossil plants, Er-mi Zhao, Zhe-xi Luo, and Ke-qin Gao for helping with figures for amphibian, mammal, and choristodere chapter, respectively, Dong Ren for supplying information and providing figures on insects, and Shu-an Ji for offering figures for some of the Jehol lizards. We express our heartfelt appreciation to Xiao-lian Zeng and Anderson Yang for their elegant artwork. We would also like to express our gratitude to the Chaoyang City Government and Land and Resources Bureau of Liaoning Province for their support in facilitating our fieldwork, and to the Museum of Natural Science (Taiwan) for supporting and participating in our research work (Fig. 9). This project is financed by the grants from the Chinese Academy of Sciences, the National Natural Science Foundation of China, the Ministry of Science and Technology of China, and the National Geographic Society of the US.

Asian-Alaskan Land Bridge

Asian-Alaskan Land Bridge

Subduction Zone

■n 8 Paleogeographic map of the world in [he Late Cretaceous. (From: http://www.scoEese.com)

■n 8 Paleogeographic map of the world in [he Late Cretaceous. (From: http://www.scoEese.com)

un 9 The IVPP field team joined by Prof. Yen-nian Cheng lhack row, 2nd from the right) and his crew from the Museum of Natural History (Taiwan) in an excavation at Jianshangou. western Liaoning in May. 1999, when the vice president of the CAS, Prof. Yi-yu Chen (back row, 6th from the right) and the deputy mayor of the Chaoyang City. Mr. Xiao-kun Chen (back row, 7th from the light) visited the fossil site.

Living Ecosystem For Dinosaurs

mi n u mmi

Xi(io-!in Wang, Zhong-he Zhou

The eruption of Mount Vesuvius in 79 AI) not only destroyed the historical city Pompeii but also caused the death of many people.When the lost city was rediscovered in 17-iS, the people and animals were still found lying in the thick ashes of the volcanic eruptions. Just as Pompeii's residents were victimized by the volcanic eruptions of 79 AD, so were the members of the Jehol Biota in the Early Cretaceous. This "Mesozoic Pompeii" has provided us a window through which we can observe the wonderful life that lived over one hundred million years ago.

Geologically speaking, the Jehol Biota developed in a relatively short time and quickly radiated in a large area in East Asia. It represents one of the largest radiations of terrestrial vertebrates during the Cretaceous period. The Jehol Biota has produced numerous beautifully preserved fossils, and thus revealed many evolutionary events of the terrestrial life.

The discoveries of birds and feathered dinosaurs in the western part of Liaoning Province in late 1980s and 1990s attracted enormous attention of paleontologists worldwide. In the last decade, several dozens of major bird and dinosaur localities have been found in this region by workers mainly from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) and the Nanjing Institute of Geology and Palaeontology (NIG P), Chinese Academy of Sciences. In the neighboring areas of northern Hebei Province and the southeastern Inner Mongolia (Nei Mongol Autonomous Region), there were also important discoveries similar to those from Liaoning. Since 1997, the field crews of the IVPP have launched about half a dozen large-scale excavations in Beipiao, Chaoyang, Fuxin in Liaoning, Fengning in Hebei and Ningcheng in Inner Mongolia, and collected hundreds of significant vertebrate specimens including fishes, amphibians, turtles, aquatic reptiles, lizards, pterosaurs, dinosaurs, birds, and mammals. Western Liaoning has since hosted hundreds of visitors each year worldwide and paleontologists and laypersons alike.

The Jehol Biota emerged at a time when the climate in the area was warm, with ample rainfall for most of the seasons. Such climatic background provided an ideal environment for animals and plants to thrive and differentiate. Lakes were widespread. Some of the water bodies were probably wide and deep. The plants were flourishing along the margins of the lakes. Volcanic eruptions were frequent at that time. Most vertebrates were preserved in rather deep lake deposits.

Throughout the Early Cretaceous, the Jehol Biota witnessed the increased volcanic activities. At least three major eruptions occurred during the deposition of the Yixian Formation and were responsible for the four significant lake deposit-volcanic eruption cycles. The volcanic rocks of the Yixian Formation mainly consist of basalts and andesites. The lake deposits of the Yixian Formation were mainly formed at the intervals between the major intermediate-basic eruptions although small-sized intermediate-acid volcanic eruptions occurred occasionally. The volcanic activities were less frequent and relatively weak at the time of the Jiufotang Formation.

The volcanic eruptions had long-lasting impact on the development and evolution of the Jehol Biota. With the intermediate-acid eruptions, a lot of poisonous gases were spread to the air, which could have caused the deterioration of the whole ecological system. For instance, at the Sihetun locality, several highly fossiliferous layers with exquisitely preserved fossils indicated some major mass mortality events of birds and feathered dinosaurs. The vertebrate fossils are mainly preserved in grayish black lacustrine shale and mudstone. They are frequently covered by a layer of volcanic ashes (tuff) (Fig. 10). Nearly all fossils are preserved in articulation; birds and dinosaurs often with feathers, skins and other soft tissues in the form of impression or

10 Stratigrapliic section at the Sihetun locality, showing lacustrine deposits (gray layers) with intercalated tuffs (yellow layers).

imprint with organic traces. Some specimens of dinosaurs were found with eggs, gastroliths and the stomach contents with remains identifiable as plant seeds, lizard and mammal skeletons. It is most likely that the environmental changes resulted from the volcanic eruptions caused the mass mortality of birds and other vertebrates. After a brief floating transportation on the surface of the lakes, the dead bodies quickly descended into, and were buried in, the deep water. The abundant volcanic ashes speeded up the deposition process; therefore the dead bodies were preserved rapidly and completely. In a sense, this is no different from the great burial of Pompeii.

Among the famous vertebrate fossil localities of the Jehol Biota are: Sihetun and Lujiatun localities in Beipiao; Fanzhangzi and Shanzui (Dawangzhangzi) localities in Lingyuan; Wanfotang, Hejiaxin, Wujiatun and Xierhuqiao localities in Yixian, Jinzhou; Shangheshou, Dapingfang, Lianhe and Dongdadao localities in Chaoyang, western Liaoning Province; Sichakou and Senjitu localities in Fengning, northern Hebei Province; and Daohugou and Xitaizi localities in Ningcheng, southeastern Inner Mongolia (Fig. 11).

Jilin

Siping

Shenyang

Jilin

60 km

Siping

Shenyang eo»11 Distribution of major fossil vertebrate localities in western Liaoning and the neighboring areas. I.Tertiary basins; 2. Cretaceous basins; 3. Jurassic-Cretaceous basins; 4, faults (F); 5, Provincial boundary; 6. Vertebrate sites. A.Jingangshan, Yixian: B, Sihetun. Beipiao; C. Dawujiazi. Fuxin; D. Boluochi, Chaoyang; I:. Fanzhangzi, Lingyuan; F, Daoluigou, Ningcheng; G, Shangheshou, Chaoyang; i . Liaohe Basin; . Fuxin-Yixian Basin; ( ■ .Jinlingsi-Yangshan Basin; J , Beipiao-Chaoyang Basin; 5 . Jianchang-Kazuo Basin; Q . I.ingyuan-Sanshijiazi Basin; (T), Pingzhuang-Ningcheng Basin; !; , Chifeng-Yuanbaoshan Basin. (Geologic information of basins partly from Liaohe Petroleum Administration Bureau)

In sum, after over half a century's study of the Jehol Biota and especially the unusual discoveries of the past ten years, our knowledge of the Jehol Biota has increased greatly compared with what was known in the past as represented by the Eosestberia-Ephemeropsis-Lycoptera assemblage (E.-E.-L. fauna as traditionally defined). The recent finds of the vertebrate fossils in western Liaoning have shed new light on the study of the origin of birds and their flight, the origin of feathers, early radiation of birds, mammals and angiosperms, and also furthered our understanding of the Early Cretaceous continental ecosystem.

Like the meticulous grid system at archaeological excavation sites, the rock layers have to be systematically studied in order to determine where the fossils are and decipher the geological age of the fossils embedded in them. Long before the recent discoveries of birds and feathered dinosaurs, the rocks producing them have been studied by several generations of paleontologists and geologists. It was the American geologist Amadeus W. Grabau who first proposed the "Jehol Series" and "Jehol Fauna" in 1920s. In 1962, Prof. Zhi-wei Gu introduced the Jehol Group into the literature. The Jehol Group is o

110 Ma

Jlnankhthy* k hthyofnunu

Jinanu hthy.* longicephiilux Longdeit'hthys hiqjitiTiaenna Peipiaosteus sp. Protopsephuru.1 sp Yunitfiteti\ sp. Smamio sp.

110 Ma

Jlnankhthy* k hthyofnunu

Jinanu hthy.* longicephiilux Longdeit'hthys hiqjitiTiaenna Peipiaosteus sp. Protopsephuru.1 sp Yunitfiteti\ sp. Smamio sp.

MlMcmum lugna

Liaoxitriton xhongfiani Sinopterm dunff Chunyaitgiiptenei zhmgi Ltaoningtiplrrvs gui l'\tllact>*uuru\ mungotiensi *

P\itutamuuru.\ meilryingensis Saurnpoda indel. Microraptor zhaoia/iwi Murorapior gui

200-}0fl m

60-inn m

"S

1S0-i00m

80-120m

1S0-i00m

80-120m

128.4 Ma

139.4 Ma

Lyeoptera IchthYufuuna

I Lyeoptera muroii

Lyeoptera davidi Lyeoptera mkuntigai Peipiaosteus fingfftngmsis - Protopsephurwi liui 4M Yaitostws longidttrftilis

Lyeoptera sinensis Lyeoptera JuxinensLs PeipwiHttvs punt Yanosteus longidursalis ^ Protopsephurwi liui Si nam in sp.

128.4 Ma

139.4 Ma

Manchumchetys manchoukuoensis Monjurosuchus splendent Yabeinosaurus tenuis Pterodactyloidca

Marnhumchelys sp. Monjuwsuihus splendens Iiyphalosaurus Ungyuanensis Hyphahsaurus. sp. Yabt'inosaurus tenuis Plcrodaclyloidea Psittacosaurus sp. Liaoningosaurus paradoxus Jinihousaurits yangi Sinosmnwpteryx sp. Sinornithasaurus sp. Ttxianosaurus hngimanus Sinobaatar Ungyuanensis Eomaia SCOUSOliO

fjaobatrathus graham CaUobatrachux sunyanensix Xfesophnve beipiaoenstx Manchurttchelys liaaxiensis Xfonjumsuchw: splendens Yabeinoxaurus tenuis Emipterw yangi liattpterus gracilis Oendmrhynckoidtx < itrvidenlatm Pxitlatosuurus sp. Sinoxuuwpteryx prima Protarxhaeopteryx ntbuxta Caudipteryx zoui Caudipteryx dongi fieipiaoxttunts inexpet tus Sinornithosuurus mil I e nit ¿hangheotherium yuimjuecuxpidens Jeholodens jenbnsi

Anura indel.

Psittacoxaurus sp. Jeholnsaurus shangyuanensix Liaoceratopx yanzigouenxis Inasivosaurus gauthieri Sinovenator changii Repennmamm robustux Gobiconodon zofiae

Calhayornis-Chaoyangia Avifauna

Sinornis xantensis Bolmnhiu zhengi Caihayornix yandita Caihayornix t.audaiu.\ fuK Uthaynrnis wulktri Longchengamis sunwnensis ('uxpiroxlrixitrnix ht/ui Largirostmrnis sexdentorix Chaoyangia beishmensix Snnglwgarnix linghensis Longiptenx cfuwyangensis Yanttrms martini YLxianornis grubaui Conjuciusornis sp. Sapeornis chaoyangensis Jeholornis prima

Confuciusornis Avifauna

Liaoxiomis delicatus Lianxutrnis sp. Jibeinia luanhvra Pmiopwryx fengningensi* Confuciusornis sp.

Confuciusornis xanctux Confuciu\orni \uniae Confuausorm chuonzhttus Confuciusomis dui C hangchengornix hengdattziensts Liutmingarnix Umgidilris Ettenanriomis buhleri t s i r

1, basalt and andesite with volcanic breccia (lava); 2. conglomerate with volcanic breccia: 3, sandstone and conglomerate; 4. tufiaceous sandstone and tuff; 5. shale and tuff: 6, silt and silty mudstone; 7. subvolcanic rock a set of late Mesozoie rocks consisting of intercalated volcanic and lacustrine deposits rich in tuffaceous materials. The group comprises the Yixian Formation and the overlying Jiufotang Formation.

Thejehol Group is mainly distributed in northern Hebei Province, western l.iaoning Province and southeastern Inner Mongolia in Northeast China. The deposits were formed in a series of northeast faulting basins in the late Mesozoie of northeastern Asia. Among the major basins are the Fuxin-Yixian Basin, Jinlingsi-Yangshan Basin, Beipiao-Chaoyang Basin, Jianchang-Kazuo Basin, Lingyuan-Sanshijiazi Basin, Pingzhuang-Ningcheng Basin, and Chifeng-Yuanbaoshan Basin. The vigorous collisions of plates in the western rim of the Pacific have resulted in the intensive tectonic activities in the eastern margin of the Eurasian continent at that time. Consequently, tectonic activities and frequent volcanic eruptions Complicated the depositional history in different basins; hence the correlation of the deposits in these basins often becomes difficult.

The traditional Jehol Group, chronologically from old to new, comprises the Yixian Formation, Jiufotang Formation, Shahai Formation and Fuxin Formation. Recent studies show that the lithographic characteristics and the fossil assemblages of the Shahai and Fuxin Formations are much different from those of the Yixian and Jiufotang Formations. The Yixian Formation mainly comprises basalts and andesires, with interbedding lacustrine sediments (tuffaceous sandstones, gray and gray-black shales, mudstone and tuffs). Four fossil-bearing beds can now be recognized from the Yixian Formation. The Jiufotang Formation mainly comprises lacustrine sediments (grayish, gray-yellow, and gray-black sandstones,

112 Biostratigraphic sequences of thejehol Croup.

siltstones, shales and mudstones, with intercalated tuffs). The Shahai and Fuxin Formations are mainly composed of coal deposits and clastics, seldom with volcanic contents. The typical Jehol elements such as the Eosestheria-Ephemeropsis-Lycoptera assemblage as well as the feathered dinosaurs, early birds and some other distinctive vertebrates are only found in the Yixian and

Jiufotang Formations. Their appearance in the Yixian Formation or slightly earlier deposits represents a major biological radiation event in the Early Cretaceous, and most of them existed until the Jiufotang time. Therefore, the Yixian and Jiufotang Formations record a complete history of the Jehol Biota. Currently, the Jehol Group is generally accepted as only to comprise these two

13 Lujiatun locality (basal part ot Yixian Formation) in Shangyuan, Beipiao, Liaoning. showing tuffaceous sandstones, mudstones and overlying basalts (Lava, 128.4Ma).

mus 14 Danhugou locality (basal part ofVixian Formation, but also arguably as Middle Jurassic Jiulongshan Formation by some other researchersl in Shantou. Ningcheng, Inner Mongolia, showing IVI'I1 excavation sites of the year 2003.

formations.

Recently, we have recognized five fossil-bearing beds (or "members") of different age, with distinctive vertebrate assemblages (Fig. 12). They are, from the bottom to top: Lujiatun Bed of the lowest Yixian Formation (Jeholosaurus-Repenomamus assemblage), Jianshangou Bed of the lower Yixian Formation (Lycoptera sinensis-Confuciusornis avian fauna assemblage), Dawangzhangzi Bed of the middle Yixian Formation (Lycoptera davidi-Hyphalosaurus assemblage), Jingangshan Bed of the upper Yixian Formation

(Lycoptera muroii-Manchurochelys manchoukuoensis assemblage), and the Boluochi Bed of the Jiufotang Formation (Jinanichthys-Cathayornis avian fauna assemblage). Most of the fossil localities of the Jehol Group can be referred to one of the above five beds.

Lujiatun Bed (Member) of the lowest Yixian Formation This bed is mainly distributed in the Sihetun and neighboring areas of the Jinlingsi-Yangshan Basin, representing a newly recognized fossil-bearing horizon of the Yixian Formation. It corresponds to the lowest bed (Member 1) in the composite stratigraphie section at the Sihetun area. The main localities where the Lujiatun Bed is exposed include Lujiatun, Xiaobeigou, Shuiquan and Sihetun of Beipiao City and Liutai of Yixian County, Jinzhou City. It is best represented in the Lujiatun locality.

The Lujiatun alluvial deposits were formed in the margin of early developing stages of the basins. They mainly comprise tuffaceous conglomerate, sandstones and silty mudstones about 20—40 meters thick (Fig. 13). This bed represents a nearly simultaneous mass mortality event that wiped out numerous adult and juvenile individuals of vertebrates, including the small-sized ornithischians such as Jeholosaurus, Psittacosaurus and Liaoceratops, the small-sized theropods like Sinovenator and Incisivosaurus, the primitive mammals Repenomamus and Gobiconodon, and frogs. No invertebrate fossil has been recognized. A few plant fragments and spore-pollen samples have been collected. Most of the Lujiatun fossils were collected in 2000 and 2001.

Since the fall of 1998, the Daohugou locality (Fig. 14) in Ningcheng County, Chifeng City, Inner Mongolia, adjacent and north to Lingyuan City, Liaoning, has produced abundant salamanders such as Jeholotriton paradoxus and Cbunerpeton tianyiensis, the haired pterosaur Jeholopterus ningchengensis and feathered theropods such as the arboreal maniraptoran Epidendrosaurus ningchengensis and other vertebrates. It is noteworthy that thousands of beautifully preserved insects and plants have also been collected from this locality, yet the age of this deposit is still controversial, ranging from the Middle Jurassic to the Early Cretaceous according to different workers. We now regard the bed at Daohugou comparable to the Dabeigou Formation in northern Hebei, and it might be comparable to or slightly lower than the Lujiatun Bed in western Liaoning. At the neighboring Xitaizi locality (Fig. 15) with its statra overlying the Daohugou fossil horizon, abundant acipenseriform fishes Protopsephurus and Yanosteus, bird Confuciusornis and dinosaur Psittacosaurus have been collected, and this horizon is clearly comparable to the lower part of the Yixian Formation.

Jianshangou Bed (Member) of the lower Yixian Formation The Jianshangou Bed is mainly distributed in Sihetun and the neighboring areas, corresponding to Member 3 of the Sihetun composite section (Fig. 16). It is best represented in the Sihetun and Jianshangou localities. Around 20 localities in Sihetun and the neighboring areas are mainly distributed in an area about 12 — 14 km from north to south and 4~5 km from east to west.

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