Landing, E., Geyer, G., Brasier, M.D. and Bowring, S.A. 2013. Cambrian Evolutionary Radiation： Context, correlation, and chronostratigraphyovercoming deficiencies of the first appearance datum (FAD) concept. EarthScience Reviews, 123, 133172.
Landing, E., Myrow, P., Benus, A.P. and Narbonne, G.M. 1989. The Placentian Series： Appearance of the Oldest Skeletalized Faunas in Southeastern Newfoundland. Journal of Paleontology, 63(6), 739769.
Li Guoxiang, Zhao Xin, Gubanov, A. et al. 2011. Early Cambrian mollusc Watsonella crosbyi： a potential GSSP index fossil for the Base of the Cambrian Stage 2. Acta Geologica Sinica, 85(2), 309319.
Parkhaev, P.Yu. and Demidenko, Yu.E. 2010. Zooproblematica and Mollusca from the Lower Cambrian Meishucun Section (Yunnan, China), and Taxonomy and Systematics of the Cambrian Small Shelly Fossils of China. Paleontological Journal, 44(8), 8831161.
Rozanov, V.V. and Missarzhevsky, V.V. 1966. Biostratigraphy and fauna of the basal Cambrian horizons. Moscow, Nauka. 81111 (in Russian).
Rozanov, A.Yu., Missarzhevsky, V.V., Volkova, N.A. et al. 1969. Tommotian Stage and Cambrian lower boundary problem. Moscow, Nauka. 380 pp.
Rozanov A.Yu., Parkhaev, P.Yu, Shabanov Yu.Ya. et al. 2008. The 13th International Conference of the Cambrian Stage Subdivision Working Group. Episodes, 31(4), 440441.
Rozanov, Yu., Parkhaev, P.Yu., Demidenko, Yu.E. et al. 2010. Fossils from the Lower Cambrian stage stratotypes. Moscow, PIN RAN. 228 pp (in Russian).
Rozanov, A.Yu. and Sokolov, B.S. (eds). 1984. Stage division of the Lower Cambrian： Stratigraphy. Moscow, Nauka. 184 pp (in Russian).
Steiner, M., Li Guoxiang, Qian Yi et al. Neoproterozoic to Early Cambrian Small Shelly Fossil Assemblages and a Revised Biostratigraphic Correlation of the Yangtze Platform (China). Palaeogeography, Palaeoclimatology, Palaeoecology, 254, 6799.
Varlamov, A.I., Rozanov, A.Yu., Khomentovsky, V.V., Shabanov, Yu.Ya., Abaimova, G.P., Demidenko, Yu.E., Karlova, G.A., Korovnikov, I.V., Luchinina, V.A., Malakhovskaya, Ya.E., Parkhaev, P.Yu., Pegel, T.V., Skorlotova, N.A., Sundukov, V.M., Sukhov, S.S., Fedorov, A.B. and Kipriyanova, L.D. 2008. The Cambrian System of the Siberian Platform. Part 1： The AldanLena Region. Moscow, PIN. 300 pp.
Middle and Upper Cambrian strata, depositional environments and trilobite faunas of the FenghuangChenxi area, western Hunan, China
DUAN Ye
College of Paleontology of Shenyang Normal University, 253 Huanghe North St. Shenyang, China 110034
There are a number of trilobite faunas in the DamaHaichongkouElitang area in western Hunan, which is known as one of the richest fossiliferous areas in South China during the Middle and Late Cambrian (Fig. 1). It has one of the most complete Cambrian successions in China. Particularly in the border region of eastern Guizhou and western Hunan, Cambrian rocks are relatively well exposed, undisturbed by tectonic activities, and easily accessible. The polymerid trilobites at the Haichongkou section have recently been published (Duan et al., 1999). A large collection of Middle and Late Cambrian trilobites has been obtained, in which some previously unreported taxa have been recognized.
Fig. 1. Locations of measured stratigraphic sections in western Hunan, China.
Research history
Previous studies on the Upper Cambrian of the Jiangnan Slope (Peng, 1990) were mostly in the area from eastern Guizhou to western Hunan. Tian (1940) was the first to recognize the Cambrian in this district. He divided the Cambrian rocks in the region into 6 Middle to Late Cambrian lithological units (Fig. 2), amongst which the dolomite that cropped out widely in that area was named as the “Loushankuan Limestone”. Since then, northern Guizhou has eventually become a classical area for Cambrian research, and many detailed investigations have been carried out there. Liu (1945) subdivided Tians 6 units into 2; Lu (1956) reassigned Lius 2 units to Later Cambrian. During the 1960s and 1970s, massive regional geological survey and mapping were conducted in Guizhou and Hunan. Detailed studies on trilobites and lithobiostratigraphy were previously conducted by Jegorova et al., (1963), the Regional Survey Team of Hunan (1964), Lin et al. (1966), Yang (1978) and Liu (1982). And investigations on Cambrian strata and fossils of western Hunan and Guizhou include Peng (1984, 1987, 1990, 1992), and Peng and Robison (2000). Regional Cambrian lithofacies and sedimentary patterns were discussed by Gao and Duan (1985), Ye and Pu (1991) and Pu et al. (1993). Song (1989) and Dong (1990, 1991) documented some Cambrian trilobites and conodonts in northwestern Hunan. Further investigations on the Middle and Upper Cambrian trilobite faunas and lithofacies of the DamaHaichongkouShishanguan (Chenxi) region have been carried out by present author between 1995 and 2003.
Fig. 2. Historical review of the Cambrian in western Hunan (platform slope areas).
Regional geology
Cambrian rocks in western Hunan represent part of the Lower Paleozoic succession of South China. Middle and Upper Cambrian stratigraphic sections in western Hunan contain rocks representing three major belts: the Yangtze Platform, the Jiangnan Slope Belt and the Jiangnan Basin (Fig. 3). These rocks formed across a broad paleogeographic area, representing a setting from shelf to basin. The Yangtze Platform occupies approximately the northwestern half of South China; the Jiangnan Basin (Peng, 1990) is located in the southeastern part of South China; while the Jiangnan Slope Belt (Peng, 1990) occupies a narrow strip between the Yangtze Platform and the Jiangnan Basin.
During the Middle and Upper Cambrian, the study area was across the Jiangnan Slope Belt (Dama, Haichongkou and Elitang) and the Jiangnan Basin (Chenxi) that covered the western part of Hunan and received dominantly shallow water sediments from Sinian (late Precambrian) to Ordovician (Fig. 3). Major sedimentary belts and faunal regions include the Jiangnan Slope Belt and Jiangnan Basin (Peng, 1990, 1992). Darkgray laminated limestone, and argillaceous limestone are dominanted with some pyrite crystals. The characters of faunas and deposits indicate a relative deeper water environment in that area. The regional pattern of lithofacies indicates sedimentary environment change from shallow water (upper slope at Dama to lower slope at Haichongkou) to deeper water (basin, at Chenxi) during the Middle and Late Cambrian.
Fig. 3. Map of eastern Guizhou and western Hunan, China, showing the outcrops of Cambrian rocks (modified from Peng and Babcock, 2001).
Conclusions
Middle and Late Cambrian trilobite faunas are described from the Dama, Haichongkou Elitang and Shishanguan (Chenxi) sections in western Hunan. There, trilobites are the most common macrofossils and include a mixture of cosmopolitan agnostoids and polymeroids. Most of the fossils are well preserved in dark gray or gray granular, laminated, argillaceous carbonates. The trilobite faunascontain 63 genera and subgenera, 84 species, and two indeterminates. Three new species are described: Hardyoides damaensis sp. nov., Meringaspis damaensis sp. nov., and Rhyssometopus (Rodtrifinis) nitidus sp. nov. Besides, Erixanium is recognised for the first time in the study area. Its discovery is significant for biostratigraphical correlation of the Late Cambrian in the AustaloAsia region.
During Middle and Late Cambrian, the study area had welldeveloped carbonate gravity deposits, particularly in the Fenghuang and adjacent areas. This paper described in details slope fan deposit characters of the Lejopyge laevigata to Corynexochus plumulaSinonproceratopyge cf. kiangshanensis Zones. According to their distribution and thickness, three main slope fan deposits have been recognised in the study area, namely, the Dama (dsf), the Machong (msf) and the Huangheyun (hsf) slope fans. The recognition of these slope fan deposits confirms the existence of a tectonically active setting for the study area during the Lejopyge laevigata to Corynexochus plumulaSinoproceratopyge cf. kiangshanensis zones.
According tothe vertical distribution regularity, Middle and Late Cambrian trilobites can be divided into 9 communities at Dama and 4 at Haichongkou sections. Both sections yield rich trilobites. Their ecological features reflect the evolution of the palaeoenvironments in the area.
Based on trilobite community analysis, it is concluded that from the east Mt. Lailong to Dama through Fenghuang, further east to Chenxi (close to central Hunan), the palaeoenvironments changed from shallowwater, oxygenrich (platform margin slope) to deepwater, oxygenpoor settings (basin).
References
Anhui Regional Geological Surveying Team. 1988. 1:200 000 Chuxian Sheet of Regional Geology. Anhui (in Chinese).
Anonymous. 1974. Regional Stratigraphic Chart of SouthCentral China. Beijing, Geological Publishing House. 534 pp (in Chinese).
Chu Chaoling. 1959. Trilobites from the Kushan Formation of north and northeastern China. Memoirs of Nanjing Institute of Geology and Palaeontology, Academia Sinica, 2, 4480 (in Chinese), 81128 (in English).
Duan Ye, Yang Jialu and Shi Guangrong. 1999. Middle and Upper Cambrian Polymerid Trilobites and Biostratigraphy, Fenghuang Area, western Hunan Province, China. Proceedings of the Royal Society of Victoria, 111(2), 141172.
Duan Ye, Li Jie and Lin Qixiang. 2003. Carbonate platform margin slope characteristics of Cambrian Chefu Age in BaojingFenghuang and adjacent areas, western Hunan, China. Journal of China University of Geosciences, 14(1), 1624.
Duan Ye. 2004. New polymerid trilobites and the first record of Erixanium from Upper Cambrian in western Hunan, China. Acta Palaeontologica Sinica, 43(1), 6371.
Endo, R. 1944. Restudies on the Cambrian formations and fossils of southern Manchoukuo. Central National Museum of Manchukuo, Bulletin, 7, 1100.
Ergaliev, G.Kh. 1980. Middle and Upper Cambrian Trilobites of the Malyi Karatau Range. Academy of Science, Kazakhstan SSR, K. I. Satpaev Institute of Geology Science, “Nauka” Publishing House, AlmaAta, 1221 (in Russian).
Jago, J.B. and Brown, A.V. 1992. Early Idamean (Late Cambrian) agnostoid trilobites from the Huskisson River, Tasmania. Paper and Proceedings of the Royal Society of Tasmania, 126, 5965.
Kobayashi, T. 1931. Studies on the stratigraphy and palaeontology of the CambroOrdovician formation of Hualienchai and Niuhsintai, south Manchuria. Journal of Japanese Geology and Geography, 8, 131189.
Kobayashi, T. 1938b. An occurrence of Lopnorites in Hunan. Journal of Geology Society Japan, 45, 323325.
Lin Tianrui. 1991. Middle Cambrian stratigraphy and trilobite fauna of Taoyuan. NW Hunan. Acta Palaeontologica Sinica, 30, 360376 (in Chinese with English summary).
Liu Yiren. 1977. A study of two genera of Late Cambrian Olenidae (Trilobita) from Taoyuan, Hunan. Acta Palaeontologica Sinica, 16(1), 120126 (in Chinese with English summary).
Lu Yanhao, Chu Chaolin, Chien Yiyuan, Lin Huanlin, Zhou Zhiyi and Yuan Kexing. 1974. Bioenvironmental control hypothesis and its application to the Cambrian biostratigraphy and palaeozoogeography. Memoir of the Nanjing Institute of Geology and Palaeontology, Academia Sinica, 5, 27110 (in Chinese).
Peng Shanchi. 1999. Cambrian biostratigraphical Frame in the Jiangnan Slope Belt, South China. Geosciences, 13(2), 242243 (in Chinese).
Peng Shanchi. 2000. Cambrian of the slope facies. 2338. In: Nanjing Institute of Geology and Palaeontology, the Chinese Academy of Sciences (ed.), Stratigraphical Studies in China (19791999). Hefei, China University of Technology and Sciences, Hefei. 397 pp (in Chinese).
Peng Shanchi and Robison, R.A. 2000. Agnostoid Biostratigraphy across the MiddleUpper Cambrian boundary in Hunan, China. The Paleontological Society Memoir 53, supplement to Journal of Paleontology, 74(4), 1104.
Peng Shanchi and Babcock, L.E. 2001. Cambrian of the HunanGuizhou Region, South China. 351. In: Peng Shanchi, Babcock, L.E. and Zhu Maoyan (eds), Cambrian System of South China. Palaeoworld, 13. Hefei, Press of University of Science and Technology of China.
Yang Jialu. 1978. Middle and Upper Cambrian stratigraphy and trilobites from western Hunan and eastern Guizhou. Professional Paper Stratigraphy and Palaeontology, 4, 182 (in Chinese with English summary).
Yang Jialu. 1981. The Cambrian system of Jiangnan. In: Xiang Liwen (ed.), The Cambrian of China. Stratigraphy of China, 4, 115135 (in Chinese).
Zhou Tianmei, Liu Yiren, Meng Xiansong and Sun Zhenhua. 1977. Class Trilobita. In: Palaeontological atlas of Central and South China. Early Paleozoic. Beijing, Geological Publishing House. 104266 (in Chinese).
Zhou Zhiqiang, Li Jinseng and Qu Xinguo. 1982. Trilobita. In: Palaeontological Atlas of northwest China, ShanxiGansuNingxia. Vol. 1. Beijing, Geological Publishing House. 215294 (in Chinese).
Zhou Zhiyi, Yuan Jinliang, Zhang Zhenghua, Wu Xiaoru and Yin Gongzheng. 1979. Cambrian biogeographical province of Guizhou and neighboring area. Journal of Stratigraphy, 3(4), 258271 (in Chinese).
Morphological variation in paradoxid trilobites from Cambrian Series 3 of Spain
Jorge ESTEVE
Center of Biology, Geosciences and Environment, University of West Bohemia, Klatovska, 51. 306 14. Pilsen, Czech Republic
Trilobites have been intensely studied and described from the second half of the nineteenth century with a special interest on those Cambrian trilobites. Taxonomic studies of these Cambrian trilobites sometimes lack of morphological variability analysis, especially of those characters used in the diagnosis of different genera and\/or species. This is largely due to the fossil record of the Cambrian trilobites, which is often scarce and fragmentary. One of the most common Cambrian trilobites in Europe (also in Avalonia) is “paradoxid”. There are more than 140 species and subspecies of paradoxidid trilobites however some species are only known for a few sclerites or were defined with limited material (see Esteve, 2014 for details).
Eccaparadoxides? pradoanus (Veneuil and Barrande in Prado et al., 1860) and Eccaparadoxides mediterraneus (Pompeckj, 1901) are two of the most common trilobites in Cambrian strata in the Mediterranean area (see Sdzuy, 1961, 1968; Courtessole, 1973; Lin and Gozalo, 1986; GilCid, 1982; Pillola et al., 2002; Dieslvarez et al., 2010). Thus I decided to carried out a biometric and morphological analysis of those diagnostic characters for these species because these paradoxid species are so wellknown, and have a strict stratigraphic control in Cambrian Series 3, Drumian Stage (see Dieslvarez et al., 2010; Esteve 2014) and they are very common in one level in the top of the Murero Formation (Drumian Stage, Languedocian Stage in the regional scale) in the locality of Purujosa, north of the Iberian Chains (Esteve et al., 2011 ), where I could collect more than 500 specimens, many of them articulated (ca. 80%). Unfortunately there is no other collection of these taxa of a single level from other localities, although there are large collections at the University of Zaragoza or Paris, the specimens were collected from different levels. Besides the lack of deformation in the trilobites from Purujosa, or at least not as much as those of other Spanish and French classic localities, make this paradoxid trilobites in Purujosa the suitable candidates to study their variability. Esteve (2014) showed a detailed analysis of all morphological analysis and biometrics. But in this summary I present only a description and evaluation of the significant diagnostic characters of these two taxa, leaving aside the biometric analysis which can be found in Esteve (2014).
Morphological differences betweenEccaparadoxides? pradoanus and Eccaparadoxides
mediterraneus
The main features used for differentiating these taxa by different authors (see Sdzuy, 1961; Dieslvarez et al., 2010) were: (i) the presence of 2 furrows in the glabella in E.? pradoanus (this character is typical of the genus Acadoparadoxides but not in Eccaparadoxides, hence the dubious assignment to this genus by Lián and Gózalo, 1986) and 4 glabellar furrows in E. mediterraneus; (ii) lack of posterolateral spines in the pygidium of E.? pradoanus and two posterolateral spines on E. mediterraneus; (iii) homonomous trunk in E. pradoanus but homonomous or heteronomous in E. mediterraneus.
Morphological analysis and discussion
The characters described above for differentiating both taxa were analyzed in a sample of about 500 individuals:
(1) Number of glabellar furrows: The analysis shows that the glabellar furrows in the Purujosa population has a high variability. The specimens show between 1 or 2 glabellar furrows (S1S2) and 4 glabellar furrows (S1S4). The problem of assignation of the species pradoanus to the genus Eccaparadoxides (see Sdzuy, 1961; Lin and Gozalo, 1986) seems to be caused by a sampling bias, besides the type species of both materials show the same variability in the population of Purujosa. This difference in the number of furrows in the glabella is mainly due to biological causes, but also taphonomic since furrows could be more or less accentuated depending how much the fossils are squashing.
(2) Posterolateral spines: The posterolateral spines have an allometric growth and show a high variability in the smaller sizes, among the small specimens there are specimens with relatively long spines but others with shorter spines or without spines. Nevertheless among the larger specimens there is a tendency to increase the length of these spines, and no large specimens lack posterolateral spines.
(3) Type of trunk: The heteronomous trunk bears different types of pleural spines (macro and micro). The paradoxidid trilobites have two macrospines (1st and 2nd) in the later stages of protaspids and in the early stages of meraspids. These macrospines disappear to be transformed into a regular pleural spine, in the next moult so that the trilobite is reduced in the relative length of the two macrospinous segment and increases in the relative length of the microspinous segments; a procedure that may have been repeated until the last trace of the microspinous condition has disappeared. Therefore, after several moults a specimen with the heteronomous condition, Eccaparadoxides mediterraneus may have transformed into a form with a homonomous trunk, E. pradoanus. Lin and Gózalo (1986) and Gózalo et al. (2003) interpreted these two morphotypes as sexual dimorphism, however the study of paradoxid from Purujosa as well as in other paradoxidid trilobites (see najdr, 1957) show that there is a delay in the development of adult pleural spines.
Conclusions
Nixon and Wheeler (1990, p. 218) suggested a species concept as “the smallest aggregation of populations [...] diagnosable by a unique combination of character states in comparable individuals”. Continuous variation within an assemblage hinders the subdivision of phylogenetic species. Therefore, the continuity in these morphological characters provides evidence for the integration of the species. The species of Eccaparadoxides of Purujosa show a continuous spectrum in all nominal, ordinal characters but also biometric (see Esteve, 2014 for details). This continuity suggests that there is only one species is present in Purujosa. Because the rates of both species are within the range of variation observed in Purujosa, its status as a separate species is challenged.
References
Courtessole, R. 1973.Le Cambrien Moyen de la Montagne Noire. Biostratigraphie. 248 pp. Imprimérie dOc, Toulouse.
Dies lvarez, M.E., Rushton, A.W.A., Gozalo, R., Pillola, G.L., Lin, E. and Ahlberg, P. 2010. Paradoxides brachyrhachis Linnarsson, 1883 versus Paradoxides mediterraneus Pompeckj, 1901: a problematic determination. GFF, 132, 95104.
Esteve, J. 2014. Intraspecific variability in paradoxidid trilobites from the Purujosa trilobite assemblage (middle Cambrian, northeast Spain). Acta Palaeontologica Polonica, 59(2), 215250
Esteve, J., Hughes, N.C. and Zamora, S. 2011. The Purujosa trilobite assemblage and the evolution of trilobite enrollment. Geology, 39, 575578.
GilCid, M.D. 1982. Hallazgo de Paradoxides (Eccaparadoxides) brachyrhachis Linnarsson 1883, en el Cmbrico Medio de Zafra (Badajoz). Boletín Geológico y Minero, 93, 1014.
Gozalo, R., Lin, E. and Dies lvarez, M.E. 2003.Intraspecific dimorphism in an evolutionary series of paradoxidids from the Middle Cambrian of Murero, Spain. Special Papers in Palaeontology, 70, 141156.
Lin, E. and Gozalo, R. 1986. Trilobites del Cmbrico inferior y medio de Murero (Cordillera Ibérica). Memorias del Museo Paleontologico de la Universidad de Zaragoza, 2, 7104.
Nixon, K.C. and Wheeler, Q.D. 1990. An amplification of the phylogenetic species concept.Cladistics, 6, 211223.
Pillola, G.L., Leone, F. and Loi, A. 2002. The typesection of the Iglesias Group (SW Sardinia, Italy). Rendiconti della Società Paleontologica Italiana, 1, 217221.
Sdzuy, K. 1961.Neue Funde aus den LeimitzSchiefern (Tremadoc). Sencken Bergiana Lethaea, 42, 227243.
Sdzuy, K. 1968. Trilobites del Cmbrico Medio de Asturias.Trabajos de Geologia, Facultad de Ciencias, Universidad de Oviedo (ao 1967), 1, 77133.
najdr, M. 1957. O novch trilobitech z cˇeského kambria.Vestnik U＇str＇edního ústavu geologického, 32, 235244.
Enrolment of Guzhangian trilobites from Shandong Province,
North China
Jorge ESTEVE1 and YUAN Jinliang2
1 Center of Biology, Geosciences and Environment, University of West Bohemia, Klatovska, 51. 306 14. Pilsen, Czech Republic
2 Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China.
Enrolled Cambrian trilobites are poorly known (e.g. Stitt, 1983), however in the past years new findings have been reported (Esteve et al., 2011; OrtegaHernndez et al., 2013; Esteve, 2013). These enrolled specimens are associated with catastrophic events (i.e. obruption) which entombed the trilobites very fast allowing preservation of enrolled specimens due to trilobites enrolled for protection (Esteve et al., 2011; Brett et al., 2012). These enrolled Cambrian trilobites, although rare, provide many data to understand the early evolution of trilobites (Esteve et al., 2013; OrtegaHernndez et al., 2013).
Recently we have discovered one level from the Kushan Formation (Guzhangian, Cambrian Series 3) of Shandong Province (North China) belonging to the Damesella paronai Zone with enrolled specimens of Monkaspis daulis (Walcott, 1905) and Damesella paronai (Airaghi, 1902). This summary reports this new discovery and introduces the evolutionary implications for the early stage of trilobites.