compelling and earliest evidence of the âCambrian explosionââ the event that ... The Early Cambrian Chengjiang fauna from Chengjiang County, Yunnan, is a.
Introduction to the Excursion One of the most complete and easily accessible Neoproterozoic and Cambrian successions on Earth is well exposed around Kunming of eastern Yunnan. Kunming, also nicknamed as Spring City, is located at an elevation of 1900 meters on the Yunn an-Guizhou Plateau with lower latitude and high elevation. It is the Capital City of Yunnan Province in southwestern China, famous for its diverse cultures of many minorities, mildest climate, widespread flowers, as well as yielding prolific paleontological fossils, such as dinosaurs, fishes and the famous Chengjiang fauna. The post-congress fieldtrip in eastern Yunnan has been scheduled as a 4-day excursion around the Dianchi Lake in Kunming. Key stops in the eastern side of Dianchi Lake and the highlighted localities to be visited include some of the most important Chengjiang soft-bodied fossil localities in Chengjiang County. Therein, you will visit the classic fossil site at Maotianshan Hill, which is the first discovery site of the Chengjiangf. The discovered locality has been now protected as the National Geopark of China and the world natural heritage. In addition, you will visit the fossil Museum in the field station of the Nanjing Institute of Geology and Paleontology (CAS) and the exceptionally well–preserved fossils hosted in Chengjiang County. Furthermore, we will visit another subsidiary section of the Chengjiang fauna, where you have access to collecting Chengjiang fossils, including brachiopods. Kunming is also famous for the Stone Forest (Shilin), a 5A-class tourist site and also a national Geopark, which is a notable set of overground Karst limestone formations located in Shilin Yi Autonomous County, about 120 km southeast of Kunming City. On the western bank of Dianchi Lake, we will visit the Meishucun Section that was once proposed as a candidate of the Stratotype Section for Precambrian-Cambrian boundary. Therein, we will visit the proposed Points A, B and C, based on the FADs of different fossils, such as small shelly fossils and trilobites. In addition, the important fossil localities of the Chengjiang fauna in Erjie area will be showed and collecting is allowed there.
ZHIFEI ZHANG Early Life Institute & Department of Geology, Northwest University, Xian, China GUOXIANG LI LPS, Nanjing Institute of Geology and Palaeontology, Nanjing, China 26-29 May, 2015
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Fig.1. Showing locations of the sections to be visited during the field trip (Modified from Hu et al., 2013)
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Table of Contents Contents Introduction to the Excursion
Day 1 (26 May)
Nanjing to Kunming in the early morning Registration and lunch Visiting of National Minorities Museum of Yunnan Province (afternoon)
Day 2 (27 May)
Kunming to Chengjiang County Stop 1. Maotianshan Hill, the discovery site of Chengjiang fauna. Stop 2. Fossil Museum at field station of the Nanjing Institute of Geology and Paleontology (CAS). Stop 3. Hongjiachong Section of the Chengjiang fauna, close to the bank of Fuxian Lake. Stop 4. Lunch and sightseeing around the bank of Fuxian Lake. Stop 5. Fossil Museum of Chengjiang County. Stop 6. Ediacaran fossils at the Luxishao Section (depending on time).
Day 3 (28 May)
Kunming to Meishucun Section, Jinning County Stop 1. Start point of the Meishucun Section. Stop 2. Point A proposed as the E-C boundary. Stop 3. Point B proposed as the E-C boundary. Stop 4. Point C proposed as the E-C boundary. You will see the earliest trilobites and brachiopods in the uppermost thin-bedded siltstone of the Shiyantou Member. Stop 5. The fossil quarry of Chengjiang fauna close to the Erjie Town. There you will visit the live fossil quarries, and will see the ongoing collecting campaign of Chengjiang fossils organized by the working group of Early Life Institute, Northwest University, Xi’an.
Day 4 (29 May)
Kunming to Shilin The Stone Forest (Shilin), a 5A-class tourist site and a national Geopark. The field trip will be finished with a dinner on the evening of Friday.
Day 5 (30 May)
Dismiss after breakfast
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Day 1 (26 May) —Nanjing to Kunming Registration and lunch The journey by airplane starts from Nanjing on 26 May at 8 o’clock in the early morning, expected to arrive in Kunming airport around 12 o’clock. There are approximately 3 hour for registration and lunch and short break in the hotel. Afternoon —Visiting of National Minorities Museum of Yunnan Province National Minorities Museum of Yunnan Province, adjacent to Yunnan Ethnic Village, is located near the Dianchi Lake, about 9 km away from the hotel. This is the most important exhibition and collection of Yunnan ethnic history and culture. National Minorities Museum of Yunnan Province not only is China's largest minority museum, but also is Southeast Asia's largest minority museum. Exhibition in more than 6000 square meters, including 8 thematic and 11 exhibition halls, reflects the spirit of Yunnan ethnic minorities, and vividly embodies the colorful Yunnan and the traditional culture of personality. It has the very high academic value and ornamental value.
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Fig.2. Geological map of Kunming region, Yunnan Province. (Modified from Luo et al., 1984)
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Fig.3. The paleogeography of Early Cambrian Qiongzhusian Stage of Eastern Yunnan. （Modified from Jiang et al., 2008) 6
Day 2 (27 May) —Kunming to Chengjiang County
Fig.4. Google map of Chengjiang county, showing the location of the three sections that we will visit
Stop 1
（40 minutes）
Maotianshan Hill, the first discovery site of Chengjiang fauna Maotianshan Hill is located 5 km east of Chengjiang County (102°57′30″， 24°39′30″). This site is of outstanding global value because it provides the most compelling and earliest evidence of the “Cambrian explosion”— the event that marks the first geological appearance of nearly all the major metazoan animal phyla in the fossil record. The geological structure at Maotianshan area is complex. In this area, the southern and northern sides are respectively cut by a fault extending approximately from east to west. On the other hand, there are two sets of faults extending north-west at the foot of eastern and western Maotianshan Hill. The exposed strata are mainly composed of the mudstone of the Yu’anshan Member in Heilinpu Formation. The section is situated on the western slope of Maotianshan. In ascending order, the section comprises a set of dark carbonaceous siltstone at the basal, and then greyish-white or greyish-yellow mudstone after weathering at the top. The grayish-yellow mudstone yields abundant fossils of bradoriids Hanchiangella, Nanchengella, as well as plenty of fragments of trilobites, and the trilobite Parabadiella co-exist in the western area of Yangtze platform, with several stable layers. Therefore, the top of dark carbonaceous siltstone should belong to the lowest part of the Chiungchussuan (recently Qiongzhusian) Yu’anshan Member of the Heilinpu Formation. The ending point of the section is the top of the Yu’anshan Member, and is cut by a fault, which makes a little loss of this Member. The Upper 7
Yu’anshan Member is mainly composed of mudstone, intercalated with thin to thick-bedded fossiliferous siltstone, which contains the Chengjiang Lagerstätte, including trilobites: Eoredlichia, Yunnanocephalus; bradoriids: Kunmingella, Kunyangella; other arthropods: Naraoia, Isoxys, Waptia, Fuxianhuia; worms: Maotianshania, Palaeoscolex; sponges, hyoliths, algae and brachiopods. Its middle and lower parts are dark carbonaceous mudstone and dark argillaceous siltstone. So far, there occurred 10 genera and species of brachiopods from 8 families of crown brachiopods and 2 stem groups (Mickwitziidae and Yuganotheciidae) revealed from the Chengjiang Könservat-Lagerstätten (Cambrian, Stage 3), such as Eoglossa chengjiangensis, Lingulellotreta malongensis, Diandongia pista, ?Xianshanella haikouensis, Kuangshanotreta malungensis, Kutorgina chengjiangensis, Alisina. sp, Longtancunella chengjiangensis, Heliomedusa orienta, Yuganotheca elegans.
Fig.5. The first discovery site of Chengjiang fauna. A. A picture taken in 2005; B. Taken in 2015.
Stop 2
（50 minutes）
Fossil Museum at field station of the Nanjing Institute of Geology and Paleontology (CAS) The Early Cambrian Chengjiang fauna from Chengjiang County, Yunnan, is a very unusual fossil Könservat-Lagerstätte. It contains extraordinarily well-preserved fossils in great abundance, vividly reflecting the true components and appearance of marine communities 520 million years ago. The discovery of the Chengjiang fauna extends the fossil records of most living animal phyla back to the beginning of the Cambrian, providing evidence for deciphering the mystery of the “Cambrian explosion” of animals. The Chengjiang fauna has been appraised as one of the most exciting discoveries of the 20th century. The Chengjiang Field Station of Palaeontology was established in 1998 to support field research, international academic exchange, and scientific promotion and education. Fossil Museum at field station of the Nanjing Institute of Geology and Paleontology (CAS) is situated on the southern slope of Hill Maotianshan. There exhibits the typical and exquisitely preserved fossils that were collected from the Maotianshan Section.
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Fig.6. Overview of the field station of the Nanjing Institute of Geology and Paleontology (CAS)
Stop 3
（30 minutes）
Hongjiachong Section The Hongjiachong village is the lowest place of Chengjiang Fauna National Geopark, close to Fuxian Lake in Chengjiang County. The section is located on the 30° northeast of the village margin, 9.5 km far from Chengjiang County. The outcrop is very good for the mining of phosphorite in the past, with successively exposed stratigraphic strata from Lower Cambrian Zhongyicun Member in Yuhucun Formation to the Hongjingshao Formation.
Fig.7. The start point and outcrop of the Hongjiachong section, close to the north bank of Fuxian Lake
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Stop 4
（50 minutes）
Lunch and sightseeing around the northern bank of Fuxian Lake Fuxian Lake (Chinese: 抚仙湖 ; pinyin: Fǔxiān Hú) stretches out through Chengjiang, Jiangchuan and Huaning counties in Yunnan Province, spanning an area of 212 square kilometers. The lake is ranked third largest in Yunnan, after Dianchi Lake and Erhai Lake. Also the deepest lake in Yunnan, it is 155 meters deep at its greatest depth. It is also the third deepest fresh water lake in China, after Tianchi and Kanas Lake. Fuxian Lake is known for its unique fauna, including many endemic species. However, its relative isolation makes it vulnerable to biological invasions and pollution. In 2001 it was reported that the earthenware and stonework covering an area of approximately 2.4–2.7 square kilometers had been discovered beneath the lake. It is thought that the remains may represent buildings from the ancient Dian Kingdom that slid in to the lake during an earthquake. In 2006, CCTV made an additional survey. Carbon dating in 2007 found relics to be roughly 1,750 years-old. In October 2014 additional research was made on the site by a multidisciplinary team. Portions were mapped and 42 handmade stone artifacts were recovered from a depth of seven meters. Fuxian Lake deserves to be mentioned for its Good water quality and charming surroundings. We’ll have a good time!
Fig.8. The distant view of the Fuxian Lake.
Stop 5
（40 minutes）
Fossil Museum of Chengjiang County It is located in the center of the Chengjiang County. There exhibit a great many kinds of Chengjiang Fossils and a very nice reconstruction of fossil communities.
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Stop 6
（50 minutes）
Ediacaran fossil at the Luxishao Section (depending on time) The late Ediacaran successions Jiucheng Member Yuhucun Formation, containing abundant exquisitely preserved problematic fossil Shanxilithes, is well developed here. Shaanxilithes is a cosmopolitan late Ediacaran potential index fossil species with the extensive biogeographical distribution in eastern Yunnan, southern Shaanxi, Northern Sichuan, Central Guizhou, Northwestern Qinghai, Northern Ningxia in China, and North-central part of Siberia, as well as the Lesser Himalaya of India. Although, it is difficult to refer Shaanxilithes to a living phylum with a certain phylogenetic affinity for the simple body, new research demonstrates that the fossils of Shaanxilithes are probably body fossils, characterized by a stable shape and form of three dimensionally preserved ribbons and discoidal units.
Fig.9. The Ediacaran fossils of Shaxnxilithes ningqiangensis
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Day 3 (28 May) — Kunming to Meishucun Section, Jinning County Stop 1
（20 minutes）
Start point of the Meishucun Section The Meishucun Section in Jinning County, Yunnan Province had been well investigated when it served as a stratotype section for both the Early Cambrian Meishucunian Stage and the Chinese candidate for global stratotype section and point proposed for the Precambrian-Cambrian boundary. This particular area is located on the southwestern margin of Yangtze Platform, at 102°34′E and 24°44′N. The Meishucun Section is located on the southern limb of the approximately EW-trending Xiangtiaochong anticline which dips to 140°-244° at an angle of 15°-17°and extends latitudinally for about 12 km. In ascending order, the strata comprise the Baiyanshao, Xiaowaitoushan, Zhongyicun and Dahai Members in Yuhucun Formation, the Shiyantou and Yu’anshan Members in Heilinpu Formation.
Stop 2
（30 minutes）
Point A proposed as the E-C boundary
Fig.10. Showing the point A, proposed as E-C boundary in the Meishucun Section.
Stop 3
（30 minutes）
Point B proposed as the E-C boundary
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Fig.11. Showing the point B, proposed as E-C boundary in the Meishucun Section.
Stop 4
（With lunch in 60 minutes）
Point C proposed as the E-C boundary At the stop 4, you will see the earliest trilobites and brachiopods in the uppermost thin-bedded siltstone of the Shiyantou Member in Heilinpu Formation.
Fig.12. Fossils from the Meishucun Section. A and B. Fossils from ∈1y4; A. Trace fossil; B. SSFs; C and D. newly discovered fossils of Diandongia from the top of Shiyantou Member (Bed 12) 13
Description of the Meishucun Section (from Luo et al., 1984): The section has been surveyed along Tuanshanding, Xiaowaitoushan and Badaowan by layers and layers. The Overlying Strata: Middle Devonian Haikou Formation (D2h), Grey-purple and grey-green, moderately thick-bedded, fine-grained quartz-sandstone, intercalated with yellow shales. At the bottom, there is a layer of yellow-brown conglomerate with a thickness of 0.3-0.6m, containing fish: Yangaspis jinningensis Liu et Wang. -------Disconformity-------Lower Cambrian (∈1) Heilinpu (formerly Qiongzhusi) Formation (∈1h) Yu’anshan Member (∈1h2)
126.4m 72.4m
18. Yellow-green, thin-bedded shale, containing trilobites: Eoredlichia intermedia (Lu), E. carinata(Mansuy), E. walcotti (Mansuy) and Yunnanocephalus planifrons Luo; brachiopod: Diandongia pista Rong; some archaeostracods and verms. 17. Yellow-green shale, intercalated with moderaterly thick-bedded, powedery to fine-grained, detrital quartz-sandstone with ripple marks, oblique bedding and flute cast, containing, at the bottom, trilobites: Yunnanocephalus planifrons Luo, Y. subparallelus Luo; brachiopod: Diandongia pista Rong; some bradoriids, verms and acritarchs. 16. Dark-grey, thin-bedded, argillaceous shale, intercalated with yellow, thin-bedded, mica-quartz-siltstone, containing a 20cm-thick layer of calcareous siltstone in the middle part, yielding bradoriids and acritarchs. 15. Dark-grey, thin-bedded, argillaceous shale, containing fragments of trilobites and acritarchs. 14. Black, thin-bedded, carbonaceous and argillaceous shale, intercalated with a 10cm-thick layer of yellow silty and argillaceous fine-crystaline dolomite at the bottom, and calcareous concretions in the middle part, containing (in the lower part) trilobites represented by Wutingaspos tingi Kobayashi; bradoriids, by Auriculatella sp.; and acritarchs, by Baltisphaeridium aff. dasyacanthum (Tim.). 13. Black, thin-bedded, carbonaceous and argillaceous quartz-siltstone, intercalated with silty shale, showing characteristic of spheroidal weathering, with a thin layer (0.2m thick) of grey-black sandy brecciated bioclastic phosphorite at the bottom. It contains descendingly three trilobite-bearing horizons with the top one yielding Mianxiandiscus badaowanensis Luo and M. jinningensis Luo, the middle one (at 10.6m from bottom) yielding Wutingaspis kunyangensis Luo, and the lower one (at 2.4m from bottom) yielding Parabadiella conica Luo, P. yunnanensis Luo; brachiopods: Botsfordia cealata (Hell); some bradoriids, hyolithids, chancelloriids and acritarchs; with the basal 20cm-thick phosphorite layer yielding hyolithids, hyolithelmithes, tubelichitids, monoplacophorans, camenitids, chancelloriids and Porifera. Shiyantou Member(∈1h1)
54m
12. Grey, thin and moderately thick-bedded, argillaceous siltstone, intercalated with laminated or microscopic current bedding, containing a layer (0.2m thick) of 14
glauconite-bearing quartz-sandstone at the bottom, yielding trace fossils. 11. Dark-grey, thin-bedded, argillaceous siltstone, intercalated with grey, moderately thick-bedded, dolomitic siltstone and silty dolomite, containing hyolithids at the bottom, hyolithelmithes, monoplacophorans, chancelloriids, and acritarchs. 10. Grey-black, thin-bedded, phosphorus-bearing dolomitic argillaceous quartz-siltstone, interbedded with grey, moderately thick-bedded, quartzose and arenaceous dolomite, containing acritarchs. 9. Black, thin and moderately thick-bedded, phosphorus-bearing argillaceous quartz-siltstone, intercalated with a layer (0.4m thick) of nodular glauconitic siliceous phosphorite and argillaceous shale at the bottom, containing acritarchs. Yuhucun Formation(∈1y) Dahai Member(∈1y5)
206.1m 1.1m
8. Grey, thin-and moderately thick-bedded, quartzose silty phosphorus and manganese-bearing dolomite, intercalated with striped cherts, yielding hyolithids, hyolithelmithes, tubelichitids, conodontomorphs, monoplacophorans and gastropods. Zhongyicun Member (∈1y4)
11.6m
7. Grey, thin-bedded, oolitic or pseudo-oolitic dolomitic phosphorite, containing a large number of hyolithids, hyolithelmithes, tubelichitids, conodontomorphs, globomorphs, monoplacophorans, gastropods, and trace fossils. 6. Blue-grey, moderately thick-bedded pseudo-oolitic or oolitic, siliceous and dolomitic phosphorite, intercalated with a thin layer (0.2m thick) of phosphatic, intrapsammatic argillaceous shale; yielding hyolithids, hyolithelmithes, monoplacophorans, trace fossils and acritarchs. 5. Light-grey, (white-grey when weathered) thin-bedded phosphorous and glauconite-bearing, arenaceous and argillaceous shale, yielding hyolithids and hyolithelmithes. 4. Blue-grey, thin-bedded, striped, oolitic, dolomitic and siliceous phosphorites, containing hyolithids, conodontomorphs, globomorphs, trace fossils and microfossils. 3. Blue-grey, moderately thick-bedded, intraclastic, pseudo-oolitic and siliceous phosphorites with crumble structure, dolomitic phosphorite, intercalated with phosphorous-bearing dolomite bands at the bottom, showing a gradual transition to the Xiaowaitoushan Member, containing hyolithids, hyolithelmithes, tubelichitids, globomorphs, with the basal part yielding trace fossils and stromatolites. Xiaowaitoushan Member (∈1y3)
8.2m
2. Light-grey, thick-bedded, phosphorous-bearing quartzose and arenaceous dolomite with cherts strips and oblique bedding, containing hyolithids and globomorphs. 1. Grey, moderately thick-bedded dolomite with chert stripes and lenses, and with a thin layer (0.1m thick) of white-grey, laminated, argillaceous dolomite at the bottom, yielding hyolithids and monoplacophorans. Baiyanshao Member (Z2y2)
165.2m 15
0-1. Light-grey (light-purple-grey when weathered), thin and moderately thick-bedded, phosphorous-bearing arenaceous and argillaceous, intraclastic, powdery and fine crystalline dolomite with lenticular stratifications. 0-2. Grey coloured, thick-bedded to massive quartzose intraclastic dolomite, yielding acritarchs. 0-3. Purple-grey, thin and moderately thick-bedded, argillaceous, siliceous, quartzose, arenaceous and phosphatic intrapsammatic dolomite. 0-4. Dark-grey, thin-bedded, phosphorus-bearing, argillaceous powdery–crystalline dolomite, containing microfossils. --------Covered --------
Lithostratigraphy and biostratigraphy of the Meishucun section are shown in Fig.16. The Baiyanshao, Xiaowaitoushan, and Dahai Members of the Yuhucun Formation dominantly comprise dolomite, and the Zhongyicun Member is dominantly composed of phosphorite and tuff layer. A distinctive tuff layer, Bed 5, is inter-bedded within the phosphorite, approximately 536.5±2.5 Ma by a recent radiometric dating (Fig.16). This bed subdivides the phosphorite bed of the Zhongyicun Member into the “lower phosphorite layer” and “upper phosphorite layer” as called by Chinese geologists. The Meishucun section is divided into three Stages, the Ediacaran Dengyingxian stage, the Cambrian Meishucunian and Qiongzhusian (Chiungchussuan) stages in ascending order. Four biostratigraphic marker levels are of great importance and can be well correlated in southern China: Marker A, 0.8 m above the bottom of Bed 1, marks the first appearance datum (FAD) of SSFs. Marker B indicates a marked increase of Small Shelly Fossils (SSFs) diversity. Markers A and B were suggested as two alternatives of the Precambrian-Cambrian boundary. Marker C, the uppermost thin-bedded siltstone of the Bed 12 in Shiyantou Formation (recent geological investigation suggests), marks the FAD of trilobites in southern China.
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Fig.13. Showing the stratigraphic level containing the Chengjiang fauna, and proposed international stratigraphic correlation of lower Cambrian. 17
Stop 5
( minutes)
Erjie section The Erjie section is located in the south of the Erjie Town, Jinning. Since 2004, the working group of the Early Life Institute (Prex: ELI) in Northwest University, Xi’an have made a continuing fossil campaign around this section. So far, more than 20, 000 specimens have been collected and moved to ELI, Xi’an of China. Of them, the lower Cambrian vendobiont Stromatoveris psygmoglena Shu, Conway Morris and Han, 2006 was published in the international journal of SCIENCE (Shu et al., 731-734 Science). Recently, five specimens with exceptionally preserved scleritome of Wiwaxia were collected therefrom. In addition, abundant specimens of brachiopods are collected there, such as Heliomedusa, Kutorgina, Eoglossa and Lingulellotreta, as well as the most recently described brachiopod-stem Yuganotheca elegans Zhang et al., 2014. The section is, therefore, one of the most important fossil localities that yields abundant Chengjiang-type fossils. At the stop, you will see the fossil campaign by tens of local peoples organized by ELI working group. In addition, you can collect the Chengjiang fossils by yourself in this quarry opened by ELI.
Fig.14. Outcrop of the Erjie fossil quarry in Jinning County.
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Day 4 (29 May) —Kunming to Shilin The Stone Forest (Shilin), a 5A-class tourist site and a National Geopark
Fig.15. The Stone Forest scenic images. - 19 -
The Stone Forest or Shilin is a notable set of limestone formations located in Shilin Yi Autonomous County, Yunn an Province, People's Republic of China, approximately 90 km (56 mi) from the provincial capital Kunming. The tall rocks seem to fall to the ground in the manner of stalagmites, with many looking like petrified trees thereby creating the illusion of a forest made of stone. Since 2007, two parts of the site, the Naigu Stone Forest and Suogeyi Village, have been UNESCO World Heritage Sites as part of the South China Karst. The site is classified as a 5A-class tourist site. Shilin National Scenic Area covers an area of 350 km2 and is divided into seven scenic areas as follows: Greater & Lesser Stone Forests, also known as the Lizijing Stone Forest, Naigu Stone Forest, Zhiyun Cave, Lake Chang (literally Long Lake), Lake Yue (literally Moon Lake), Dadie Waterfall, Qifeng Cave. These formations, caused by the dissolution of limestone, are believed to be over 270 million years old and are a tourist attraction for both overseas and domestic tourists, with bus tours bringing tourists from Kunming. There are also a number of hotels in the area. According to legend, the forest is the birthplace of A’shima, a beautiful girl of the Yi people. After falling in love, she was forbidden to marry her chosen suitor and instead turned into a stone in the forest that still bears her name. Each year on the 24th day of the sixth lunar month, many Yi people celebrate the Torch Festival (火把节 Huǒbă Jié), which features folk dances and wrestling competitions.
The field trip will be finished with a dinner on the evening of Friday, 29 May.
Day 5 (30 May)
Dismiss after breakfast.
Cost: 790$/person (standard room occupied by one person) or 650$/person (hotel room shared by two persons) The cost covers one way flight from Nanjing to Kunming, room and meals (4 days and 4 nights), geopark tickets and travelling expenses during the field trip.
- 20 -
Fig.16. Stratigraphic column across the Ediacaran-Cambrian boundary of Meishucun Section, Jinning county, Yuanan (Modified from Luo et al., 1984). 21
The Early Cambrian Chengjiang Lagerstätte The Chengjiang Fossil-Lagerstätte is an exceptional conservation deposit that contains a variety of abundant soft-bodied and biomineralized metazoans representing one of the earliest records of Cambrian explosion. The fossils are recovered from the mudstone of the Yu’anshan Member(Eoredlichia-Wudingaspis Trilobite Zone), i.e. the upper part of the Early Cambrian Heilinpu (formerly Qiongzhusi) Formation, widely exposed in a wide area around the Dianchi Lake of Kunming. The strata are ordinarily correlated with the late Atdabanian or Botoman Stagein Siberia, belonging to the newly unnamed Cambrian Stage 3. So far, more than 10 fossil quarries were found and made of heavy excavation by the working group of the Early Life Institute in Northwest University, Xi’an of China. Studies of Chengjiang Lagerstätte revealed more than 200 species of animals among 18 phyla, of which arthropods including Anomalocardids predominate in species abundance, markedly exceeding 100 species (Zhao et al. 2010). The Chengjiang Lagerstätte is very important because it not only expands the temporal and geographic distribution of Burgess Shale-type faunas,but also contains a series of exquisitely preserved taxa that have radically changing our understanding of deep history of some important animal groups,such as Chordata including the agnathan like Myllokunmingia and Haikouichthus (Shu et al., 1999; Shu et al., 2003). It is in the Chengjiang deposits that nearly all the Cambrian representatives of deuterostome were recovered (Shu et al., 2010), by contrast in the classic Burgess Shale only two genera of deuterostomes have been described in detail (Morris and Caron, 2012; Caron et al., 2013). In addition, the preservation of soft-tissues, such as the lophophore and digestive canal of brachiopods, is largely only known from the Chengjiang.
- 22 -
The occurrence of various metazoans in Chengjiang fauna and their species diversity marked by numbers (Modified from Edgecombe et al., 2011) - 23 -
- 24 -
The first “fish” Myllokunmingia fengjiaoa
Xidazoon stephanus (Phylum Vetulicolia)
- 25 -
Eoredlichia intermadia
- 26 -
Waptia ovate
Xandarella spectaculum
- 27 -
Retifacies abnormalis
Naraoia compacta
- 28 -
Microdictyon sinicum
Miraluolishania - 29 -
Circocosmia jinningensis
Chioia xiaolantianensis - 30 -
Dinomischus venustus
Wiwaxia sp.
- 31 -
Cotyledion tylodes - 32 -
The brachiopods from Cambrian Series 2 of eastern Yunnan, China In the last decades, fossil discoveries from around the world, particularly from the Chengjiang and Guanshan Konservat-Lagerstättens in South China, have greatly added to our understanding of the magnitude, tempo and ecological complexity of the explosive radiation of metazoans during the Cambrian.
Fig. A. The occurrence and horizon of Early Cambrian (Series 2) brachiopods from Eastern Yunnan (Our unpublished material).
The Brachiopoda is one of the most important lophotrochozoan phyla that dominated the benthic communities throughout all the Palaeozoic era, and it has an extensive fossil record, exhibiting morphological diversity and geological continuity. In South China, the earliest crown brachiopods can be traced back to the base of the - 33 -
Chiungchussuan (Qiongzhusian) (Fig. A), where they are found mostly as small fragmentary pieces of phosphatic shells in the black bioclastic siltstone of the uppermost Shiyantou Formation. Even small pieces of phosphatic shells can be readily identified as lingulate brachiopods thanks to their characteristic with regularly pustulose or pitted ornamentation. In a few cases, the lingulate brachiopods can be found as partial or incomplete internal mold of shell valves. In the early publications, these lingulate brachiopods were referred to Botsfordia sp. Re-investigation and re-examination of tens of specimens, derived from the black siltstone of the uppermost Shiyantou Formation at the Meishucun section in Jinning, permits us to reassign them to Diandongia pista Rong 1974 of the Family Botsfordiidae. Diandongia is one of the most abundant and mineralized brachiopods from the overlying muddy and siltstone deposits of Yu’anshan Member in Heilinpu Formation, typified by its ornamentation of regularly distributed pustules or pits on the external surface of immature shell valves. The onset of a more highly diversified brachiopod fauna took place in muddy deposits of the Maotianshan Shale Member (Chengjiang muddy deposits) belonging to Eoredlichia-Wudingaspis Zone. Aside from Diandongia pista, Eoglossa chengjiangensis, Lingulellotreta ergalievi, Xianshanella haikouensis, Longtancunella chengjiangensis, Kutorgina chengjiangensis, Heliomedusa orienta, Yuganotheca elegans and an unidentified species of Alisina make their first appearance in the Middle Chiungchussuan Maotianshan Shale. Of these, Lingulellotreta ergalievi and Heliomedusa orienta are two of the most numerically abundant and characteristic forms, and thus thought as representatives of the Chengjiang Maotianshan shale brachiopod assemblages. The Late Chiungchussuan brachiopods are found in the upper siltstone of the Yu'anshan Menber at Kuangshan section in Malong County of eastern Yunnan. With the exception of Diandongia pista, Late Chiungchussuan brachiopods are typified by the occurrence of the acrotretid Kuangshanotreta malungensis Zhang, Holmer and Hu, in a slab of fossil which is accompanied by the trilobite Malungia laevigata whose occurrences suggest the uppermost part of Eoredlichia Zone (Chiungchussuan Stage) or the lowermost Botomian. Recently, a new fossil assemblage of late Chiungchussuan Stage has been found in the muddy siltstone intercalated within thick-bedded quartz sandstone of lower Hongjingshao Formation exposed around the Guanshan reservoir in Xiazhuang Village of Chenggong county of Kunming, eastern Yunnan. It is in the lower Hongjingshao siltstone that yields a high-density concentration of monotaxic shell of brachiopods, prominently allied with Kutorgina. In some cases, the strongly crushed and closely stacked specimens of shell valves have soft bodied preservation of stout pedicles. However, the detailed systematic description of the brachiopod species has not yet been completed. The monotaxic aggregation of shell valves with high density - 34 -
suggests the first expansion, in species abundance and ecological dominance, of calcareous-shelled brachiopods from the brachiopod Subphylum Rhynchonelliformea. Higher up, the components of Chiungchussuan brachiopod fauna are sharply diminished and then disappear in East Yunnan. Most likely this can be linked to a regressive event and the shallow-water environment is evident by the thick-bedded quartz sandstone of lower Hongjingshao Formation in Kunming-Wuding area, and by the coarse-grained siltstone interbedded with sandstone in Malong-Yiliang area. However, the siltstone that are intercalated within the thick sandstone in the middle-upper Hongjingshao Formation around Hongjingshao village in Malong county contains high-density accumulation of Palaeobolus shells, which are found in clusters on bedding planes. The rich stacked well-sorted shells of Palaeobolus have usually been referred to Lingulepis yunnanensis Rong, 1974 in earlier publications, dealing with Cambrian fauna in eastern Yunnan. The Early Tsanglangpuan brachiopod assemblage is characterized by a large number of Palaeobolus that are strikingly different from assemblages in the Chiungchussuan fauna, and Diandongia pista is replaced by a new genus and species of botsfordiid brachiopod, Hongjingshaothele rectangulatus gen et sp. Nov. in the restricted shallow water environment. H. rectangulatus is characterized by a rectangular shell with strongly developed muscles on the raised muscular platform. Late Tsanglangpuan brachiopods are well preserved in the silty mudstone of Wulongqing Formation, containing the soft-bodied Guanshan fauna (Hu et al., 2013). The brachiopods of Guanshan fauna were largely collected from the Gaoloufang section in the Chenggong county of Kunming. Until now, the fauna includes ten brachiopod species, assigned to eight genera, including Acanthotretella decaius Hu et al., 2010, Eoobolus malongensis (Rong) 1974, Heliomedusa minuta Luo et Hu 2008, Palaeobolus liantuoensis Zeng 1987, Kutorgina sinensis Rong 1979, two indeterminate brachiopod Diandongia sp. and Nisusia sp. All the brachiopods await to be described in detail. It is interesting to note that Nisusia sp. represents the FAD of the Superfamily Nisusioidea, and Diandongia sp. and Eoobolus malongensis are one of the numerically predominant brachiopod taxa in the Guanshan fauna. Of these, A. decaius, E. malongensis, P. liantuoensis and Diandongia sp. have thin and elongate pedicles preserved; H. minuta and Diandongia sp have exceptionally preserved setae fringing around the marginal edge of shells. Moreover, the exceptionally preserved specimens of A. decaius show a spiral lophophore. In addition, the high concentration of acrotretid brachiopods, herein referred for the first time to cf. Eohadrotreta zhenbaensis, was recovered from the mudstone of Wulongqing Formation at Shijiangjun and Sapushan sections in Wuding county ca. 60 km northwest of Kunming (Fig. B). In summary, the brachiopods from the Chengjiang fauna show a rather high diversity with ten families, first occurring in the Chiungchussuan (Stage 3) of China. - 35 -
By contrast, each family is represented uniquely by a monotaxic species. The low-diversity and high-disparity of Chiungchussuan brachiopods coincides well with the explosive radiation of metazoans in general among phyla. Studies of Chengjiang brachiopods demonstrate that the Cambrian Stage 3 brachiopods developed a remarkable varied organization of tissues and organs shortly after the onset of Cambrian explosion. All the Cambrian brachiopods have an epibenthic lifestyle either cemented by a ventral valve or attached by variable pedicles to establish complex ecological community encompassing primary tierers and variable secondary tierers. Upwards, the Chiungchussuan assemblage was succeeded by 11 species and eight families of brachiopods, dominated by components from Eoobolidae, Obolidae and Acrotretidae, showing an accelerated radiation at the species level, in contrast, slower addition at the family level.
Fig. B. The brachiopod occurrences in the lower Cambrian of South China, and the potential brachiopod-based correlation of the “traditional” Lower Cambrian in the Yangtze Platform of China (After Zhang et al., 2015, in press).
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