PROGRESS IN NATURAL SCIENCE Vol .15 , No .8 , August 2005

Discovery of body fossils from the late Meishucunian (Cambrian)at Jinsha , , south ＊

YANG Xinglian1, 2＊＊ , ZHAO Yuanlong2 , WANG Yue2 and WANG Pingli2

(1 .Nanjing Institute of Geology and Palaeontology , Chinese Academy of S ciences, Nanjing 210008 , C hina;2 .Institute of Resource and Environm ent , Guizhou University , 550003 , China)

Received December 28 , 2004 ;revised March 3 , 2005

Abstract Here w e report discovery of a sponge body fossil Triticispongia sp .from the base of low er Camb rian Niu titang Forma- tion at Jinsha , Guizhou .Stratigraphically , the fossil horizon is located below Ni-Mo ore layer with the Niutitang Biota above , and is equiv- alent to the late Meishucunian .The species is global in shape with skeletons composed of stau ractins and monaxons.Triticispongia sp .re- ported here may be the earliest sponge body fossils of Cambrian , w hich provides new information for understanding early evolution and ra- diation of sponge .

Keywords: , Cambrian, Niutitang Formation, Guizhou, China .

Since abundant sponges and large bivalved first radiation of sponges should happen in the Niuti- arthropods from the low er Cambrian Niutitang For- tang time interval[ 8] . mation at Sancha , Dayong , Hunan Province were discovered[ 1, 2] , much attention has been paid to why Here we report the earliest sponge body fossils there are so many fossils preserved in the early Cam- located below Ni-M o ore layer from the late Meishu- brian black shale in this oxy gen-deficient environ- cunian pelitic silicalite , siliceous mudstone at the base ment .During recent years , m any w ell preserved mul- of the Niutitang Formation in Jinsha , Guizhou ti-phyla fossils were reported from the early Cambrian (Fig .1).Energy-dispersive X-ray (EDX) analysis [ 3—5] black shale no t only in Guizhou Province , but al- revealed that the sponge spicules are com posed of SiO 2 so in western Zhejiang and southern Anhui[ 6, 7] , south (Fig .2). China . 1 Geologic setting Previous studies of systematic description and classificatio n of these fossils from the Niutitang For- Jinsha is located in the southwest of the Yang tze mation[ 1—3 , 8 —10] , and from the Hetang Form a- platfo rm and belongs to -Zhijin stratig raphic [ 12] tion[ 6 , 7] demonstrated that fossil assemblages in these sub-district .The fossils described here are from black shales are characterized by abundant sponge fos- the lower Cambrian Niutitang Form ation at sils .The well-documented Niutitang Biota from Zun- Zhangy angou Village , w hich is 13km northwest from yi area , Guizhou consists of 26 genera , including Yankong Tow n , Jinsha County , Guizhou Province sponges , coelenterates , mollusks , arthropods , and (Fig .1).In the ascending order , the sectio n consists algae .Sponges in the Niutitang Formation are abun- of the Dengying , Niutitang and Ming xinsi forma- dant not only in numbers but also in diversity , num- tions .There is a parallel unconformity betw een the bers of 13 sponge genera make up 70 % of the w hole Niutitang and Dengy ing fo rmations , but the Niuti- bio ta .According to previous comparisons , many tang Formation and Ming xinsi Formation is con- scholars considered that the age of lower limit of Niu- formably contacted .The section is w ell exposed and titang Biota is earlier than that of the Chengjiang Bio- has been regarded as the type section of the Niutitang [ 12, 13] ta[ 3, 5, 8, 11] .Therefore , Zhao once proposed that the Formation by Zhang et al .since 1970 .

＊ Supported by National Natural Science Foundation of China (Grant Nos.40162002 and 40232020), the Ministry of Technology and S cience of China (Grant No .2002 .CCC 02600), Chinese Academy of S ciences (KZCX3-SW-141), and the Basic Research Funds of Guizhou Province (Grant No .2002-309) ＊＊ To w hom correspondence should be addressed .Email:yangxinglian2002 @163 .com Prog ress in Natural Science Vol.15 No .8 2005 w ww .tandf.co .uk/journals 709

Fig.1 . Generalized stratigraphic log and fossil distribution of the Yankong section in com parison to the well investigated shallow w ater section of Yunnan .(1)Meishucun section , Jinning County , Yunnan (after Zhu et al.[ 14]);(2) Yankong section , Jinsha County , Guizhou .

M ass original sponge body fossils have been zon of these trilobites should be the early Qiong zhu- found for the first time in the pelitic silicalite at 2 .2 m sian[ 11] .According to correlation of strata , Zhao et above the boundary between the Dengying and Niuti- al.[ 3, 8] , Yuan et al .[ 11] , Steiner et al .[ 5] and Peng et tang formatio ns (Fig .1).The fossil horizon is 3 m al.[ 16] considered the age of the lower limit of Niuti- below the Ni-Mo o re layer and 3 .3 m below the low- tang Biota as early Qiong zhusian (Parabadiella est horizon of Niutitang Bio ta .The Niutitang Biota in zone).Therefore the base of the Niutitang Formation this section contains abundant Tsuny idiscus (Fig .3) is lower than that of the Qiongzhusi Formation in bradoriids, large bivalved arthropods , sponges , and Yunnan[ 15, 18] . trace fossils .

2 Age

The Niutitang Fo rmation is characterized by a diachronous, transg ressive black shale succession . Tsuny idiscus first appeared in the lower part of the Niutitang Formation and becomes abundant in the middle and upper parts of the Niutitang Form a- tion[ 13, 15 , 16] .The Cheng jiang Bio ta is know n from middle and upper parts of Eored lichia Zone at the middle and upper parts of Qiongzhusian Stage . Fig .2 . EDX spectrum of the sponge spicules. Parabadiella Chang , 1966 and Mian xiandiscus (Tsunyidiscus)Zhang and Zhu , 1980 were wo rld- The multi-metal layer rich in Ni and Mo is a sta- w ide considered as the oldest o ne by Zhang[ 17] and ble datum horizon from the lower Cambrian Niutitang collected in the subjacent sediments .Thus the ho ri- Formation in Guizhou Province and neig hbo ring re- 710 w ww .tandf.co .uk/journals Prog ress in Natural Science Vol .15 No .8 2005 gion .The multi-metal layer (Ni-M o o re layer)is an w hich w ere ever reg arded as the earliest sponge body event bed and considered as an equivalent time ho ri- rem ains[ 1 , 23] from the low er Cambrian Niutitang For- zon widespread in Yang tze Platform .So it is used as a mation at Sancha , Day ong , Hunan Province w ere stratigraphic marker fo r defining the base of the discovered by Steiner et al.in 1993 .But these Qiong zhusian[ 14] , and the marker of the lower limit sponges from Hunan collected above Ni-Mo ore bed of the Niutitang Bio ta , too . directly overlies the dark cherts , and the horizon of them coincides w ith the ho rizon of the Niutitang Bio- According to the correlations above , phosphates , ta from Songlin , Zunyi and Yankong , Jinsha of dark silicalite , siliceous shale with the sponges w hich Guizhou Province , indicating that previously reported are less than 2 m in thickness below Ni-M o ore bed at sponge body fossils are not older than Qiongzhusian . the base of the Niutitang Formation represent the So the late Meishucunian sponge body fossils reported sediments of late Meishucunian age . here from the base of Niutitang Formation at Only isolate spicules had been repo rted at the Yankong , Jinsha m ay be the earliest sponge body fos- lowermost Cambrian[ 19—22] until abundant sponges sils of Cambrian found so far .

3 Systematic paleontology

Class Hexactinellida Schmidt , 1870 Subclass Amphidiscophora Schulze , 1887 Order Reticulosa Reid, 1958 Superfamily Protospongidea Finks, 1960 Family Protospongiidae Hinde , 1887 Genus Triticispongia Mehl et Reitner , in Steiner et al ., 1993 Triticispongia sp. (Fig .3 , 1 , 2 , 3 , 4 , 6 ;Fig .4)

Material :50 compressed specimens available fo r Comparison :Triticispongia sp .is similar to the the present study .All are kept at the M useum of Pa- type species Triticispongia diagonata[ 1] of Hunan leontology , Guizhou University . and specimens of Yunnan[ 24] , because their shape is global and their bodies and spicules are very sm all. Locality and horizon:Zhangy angou Village , However , the former can be distinguished from the Yanko ng Town , Jinsha , Guizhou ;the base of the both latter by denser stauractins and presence of scale lower Cambrian Niutitang Fo rmation . monaxons. Diagnosis :Global sponges with stauractins and 4 Conclusions monaxons in various sizes , generally 5 to 10 mm in diameter .The spicules are very fine and range in (1)The original sponge body fossils from the oblique . base of Niutitang Fo rmation , Yankong , Jinsha may be the earliest sponge body fossils of Cambrian so far . Description:The global sponge with skeleton composed of stauractins and scale monaxons in differ- (2) Through analy sis of EDX to reveal their ent sizes .Tw o moderately well-org anized spicule se- composition , and the sponge body fossils are com- ries present w ith rectangular patterns .One series posed generally of SiO 2 . w ith prominent spicule axes arranged parallel and normal to principal sponge axis, and the second some- (3)M ost people believed that spo nges appeared w hat obliquely .Stauractins present tw o types with in late Neopro terozoic[ 1 , 25—30] and more diverse different intersected deg ree .One is 90°, the other is sponges have been repo rted in Atdabanian age[ 31 —33] diaxon w ith 70°(Fig .4).The larger spicules are or in early Qiongzhusian age[ 8] .The sponge body fos- 0 .02 —0 .05 mm in w idth and up to 2 mm in length , sils from the base of Niutitang Form ation , Yankong , mainly distributed o n the surface of sponges .The Jinsha may be a forerunner before the first radiation sm all spicules are 0 .003 —0 .005 mm in diameter and of sponge , and their discovery provides lots of impor- 0 .2 —0 .5 mm in length .Ex cept for stauractins, we tant information and materials for understanding the can find scale monaxons nearly 2 —3 mm long . early evolution of sponge animals . Prog ress in Natural Science Vol.15 No .8 2005 w ww .tandf.co .uk/journals 711

Fig.3 . 1 , Triticispongia sp ., JS-5-67 , scale bar =2 mm ;2 , Triticispongia sp ., JS-2 .5-3a , scale bar =2 mm ;3 , Triticispongia sp ., JS-5-118-1, scale bar =2 mm ;4 , Triticispongia sp ., JS-2 .5-4 , scale bar =2 mm ;5 , Tsu nyidiscus n iutitangensis, JS-5 .5-15a, scale bar =1 mm ;6 , Triticispongia sp ., JS-5-100 , scale bar =1 mm .

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