Maotianshan shales
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The Maotianshan shale is a lower Cambrian Konservat Lagerstätte named for Maotianshan Hill in Chengjiang County, Yunnan Province, China. More commonly, the multiple, scattered fossil sites are referred to as the Chengjiang biota after its extremely diverse assemblage of organisms, and more simply still, just Chengjiang. The Chengjiang fauna occurs in outcrops of the Qiongzhusi Formation that date to between 525 and 520 mya, or to about the middle of the early Cambrian epoch, at least some 10 million years earlier than the Burgess Shale. It is one of some 40 Cambrian, fossil locations worldwide exhibiting Burgess Shale-like, exquisite preservation of rarely preserved, non-mineralized soft-tissue.
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[edit] History and Scientific Significance
Although fossils from the region have been known from the early part of the twentieth century, Chengjiang was first recognized for its exquisite preservation with the 1984 discovery of the naraoiid Misszhouia, a soft-bodied relative of trilobites. Since then, the locality has been intensively studied by scientists from throughout the world, yielding an extensive literature, a constant flow of new discoveries, as well as scientific debate surrounding the interpretation of discoveries. Over this time, various taxa have been revised or re-assigned to different groups. Interpretations have led to many refinements of the phylogeny of various groups and even the erection of the new phylum Vetulicolia of primitive deuterostomes. The Chengjiang biota has all the animal groups found in the Burgess Shale. However, since it is 10 million years younger, it supports the deduction of earlier or faster diversification of metazoans in the early Cambrian than does the Burgess Shale fauna. The preservation of an extremely diverse faunal assemblage renders the Maotianshan shale as the world’s most important locality for understanding the evolution of early multi-cellular life, and particularly the members of phylum Chordata that includes all vertebrates. The Chengjiang fossils comprise the oldest, diverse metazoan assemblage above the Proterozoic-Phanerozoic transition, and thus the fossil record’s best data source for understanding the apparently rapid diversification of life known as the Cambrian Explosion.
[edit] Preservation and Taphonomy
Fossils occur in a 50 meter thick section of mudstone in the Yuanshan Member of the Qiongzhusi Formation. The Yuanshan Member is extensive, covering tens of thousands of square kilometers of eastern Yunnan Province, where there are numerous, scattered outcrops yielding fossils. Studies of the strata are consistent with a tropical environment with sea level changes and tectonic activity. The region is believed to have been a shallow sea with a muddy bottom. The preserved fauna is primarily benthic and was likely buried by periodic turbidity currents, since most fossils do not show evidence of post mortem transport. Like the younger Burgess Shale fossils, the paleo-environment enabled preservation of non-mineralized, soft body parts. Fossils are found in thin layers less than an inch thick. The soft parts are preserved as aluminosilicate films, often with high and oxidized iron content, often exhibiting exquisite details.
[edit] Fauna
The Chengjiang biota comprises an extremely diverse faunal assembly, with some 185 species described in the literature as of June, 2006. Of these, nearly half are arthropods, few of which had hard, mineral-reinforced exoskeletons. Only about 3% of the organisms known from Chengjiang have hard shells, and most of those are the trilobites of which there are five species. All species of Chengjiang trilobites have been found with traces of legs, antennae, and other soft body parts, an exceedingly rare occurrence in the fossil record. Phylum Porifera (15 species) and Priapulida (16 species) are also well represented. Other phyla represented are Brachiopoda, Chaetognatha, Cnidaria, Ctenophora, Echinodermata, Hyolitha, Nematomorpha, Phoronida, Protista, and Chordata. About one in eight animals are problematic forms of uncertain affinity, some of which may have been evolutionary experiments that survived for only a brief period as benthic environments rapidly changed in the Cambrian. Chengjiang is the richest source of the lobopodia, often considered a distinct phylum, with six species represented: Luolishania, Paucipodia, Cardiodictyon, Hallucigenia (also known from the Burgess Shale), Microdictyon, and Onychodictyon.
Perhaps the most important fossils from Chengjiang are eight putative members of phylum Chordata, the phylum to which all vertebrates belong. The most famous is Myllokunmingia, possibly a very primitive agnathid (i.e., jawless fish). The enigmatic Yannanozoon lividum is considered to be the earliest hemichordate, possessing many of the characteristic chordate features and providing an anatomical link between invertebrates and chordates. Haikouella lanceolata is described to be the earliest craniate-like chordate. This fish-like animal has many similarities to the Yunnanozoon lividum, but also differs in several aspects: it has a discernible heart, dorsal and ventral aorta, gill filaments, and a notochord (neural chord). Similar to Myllokunmingia, Haikouichthys ercaicunensis is another fish-like primitive, fish-like animal.
Originally described as crustacean arthropods, Shu (2001) later erected the Vetulicola as a new phylum of primitive deuterostomes that is represented by seven species from Chengjiang. Another researcher places them with the Urochordates based on putative affinity with the Phylum Chordata. At present, there is no agreement as to their systematic placement. They are thought to have been swimmers that either were filter feeders or detritivores.
Some two dozen animals from the Chengjiang biota are problematic regarding phylogenetic assignment. Among these, Anomalocaris saron, the alleged predatory terror of the early Cambrian is the most famous. Shu (2006) recently described Stromatoveris psygmoglena as a possible bilateran missing link between Ediacaran fronds and Cambrian ctenophores.
[edit] List of Chengjiang Biota Species by Phylum
[edit] Kingdom Animalia
Phylum Arthropoda - 77 species
- Acanthomeridion serratum
- Alalcomenaeus
- Almenia spinosa
- Apiocephalus elegans
- Branchiocaris yunnanensis
- Canadaspis laevigata
- Chengjiangocaris longiformis
- Chuandianella ovata
- Cindarella eucalla
- Clypecaris pteroidea
- Combinivalvula chengjiangensis
- Comptaluta inflata
- Comptulata leshanensis
- Cyathocepalus bispinosus
- Dianchia mirabilis
- Diplopyge forcipatus
- Diplopyge minutus
- Dongshanocaris foliiformis
- Ercaia minuscula
- Ercaicunia multinodosa
- Forfexicaris valida
- Forticeps foliosa
- Fuxianhuia protensa
- Glossocaris occulatus
- Haikoucaris ercaiensis
- Isoxys auritus
- Isoxys curvirostratus
- Isoxys paradoxus
- Jianfengia multisegmentalis
- Jianshania furcatus
- Jiucunella paulula
- Kuamaia lata
- Kuamaia muricata
- Kuanyangia pustulosa
- Kunmingella angustacostata
- Kunmingella douvillei
- Kunmingella guanshanensis
- Kunmingocaris bispinosus
- Kunyangella cheni
- Leanchoilia asiatica
- Leanchoilia illecebrosa
- Liangshanella liangshenensis
- Mafangia subscalaria
- Mafangocaris multinodus
- Malongella bituerculata
- Occacaris oviformis
- Odaraia eurypetala
- Ovalicephalis mirabilis
- Parakunmingella malongensis
- Parapaleomerus sinensis
- Pectocaris spatiosa
- Petalilium latus
- Pisinnocaris subconigera
- Primicaris larvaformis
- Pseudoiulia cambriensis
- Pterotum triacanthus
- Pygmaclypeatus daiensis
- Rectifacies abnormalis
- Rhombicalvaria acanthi
- Saperion glumaceum
- Sidneyia sinica
- Sinoburius lunaris
- Skioldia aldna
- Spinokunmingella typical
- Sunella grandis
- Squamacula clypeata
- Syrrhaptis intestinalis
- Urokodia aequalis
- Tanglangia caudata
- Trigoides aclis
- Tsunydiscus aclis
- Tsunyiella daindongensis
- Tuzoia sinensis - a Phyllocarid
- Waptia ovata
- Wutingella binodosa
- Xandarella spectaculum
- Yiliangocaris ellipticus
- Yunnanocaris megista
Phylum Arthropoda - Arachnomorpha - 2 species
- Naraoia Misszhouia longicaudata
- Naraoia spinosa
Phylum Arthropoda - Class Trilobita - 5 species
- Eoredlichia intermedia; Family Redlichiidae
- Kuanyangia pustulosa; Family Redlichiidae
- Wutingaspis tingi; Family Redlichiidae
- Yunnanocephalus yunnanensis; Family Yunnanocephalidae
- Palaeolenus lantenoisi; Family Palaeolenidae
Phylum Brachiopoda - 5 species
- Diandongia pista
- Heliomedusa orienta
- Lingulella chengjiangensis
- Lingulellotreta malongensis
- Longtancunella chengjiangensis
Phylum Chaetognatha - 1 species
- Eognathacantha ercainella
Phylum Cnidaria - 2 species
- Priscapennamarina angusta
- Xianguangia sinica
Phylum Chordata - 8 species
- Cathaymyrus diadexus
- Cathaymyrus haikouensis
- Haikouella jianshanensis
- Haikouella lanceolata
- Haikouichthys ercaicunensis
- Myllokunmingia fengjiaoa
- Shancouclava anningense - a Tunicate
- Zhongxiniscus intermedius
Phylum Ctenophora - 3 species
- Maotianoascus octonarius
- Sinoascus paillatus
- Stromatoveris psygmoglena
Phylum Echinodermata - 1 species
- Cotyledion tylodes
Phylum Hyolitha - 8 species
- Ambrolinevitus maximus
- Ambrolinevitus platypluteus
- Ambrolinevitus ventricosus
- Burithes yunnanensis
- Glossolithes magnus
- Linevitus billingsi
- Linevitus flabellaris
- Linevitus opimus
Phylum Lobopodia - 6 species
- Cardiodictyon catenulum
- Hallucigenia fortis
- Luolishania longicruris
- Microdictyon sinicum
- Onychodictyon ferox
- Paucipodia inermis
Phylum Nematomorpha - 3 species
- Cricocosmia jinningensis
- Maotianshania cylindrica
- Palaeoscolex sinensis
Phylum Phoronida - 1 species
- Iotuba chengjiangensis
Phylum Porifera - 15 species
- Allantospongia mica
- Choia xiaolantianensis
- Choiaella radiata
- Hazelia sp.
- Leptomitella confusa
- Leptomitella conica
- Leptomitella metta
- Leptomitus teretiusculus
- Paraleptomitella dictyodroma
- Paraleptomitella globula
- Quadrolaminiella crassa
- Quadrolaminiella diagonalis
- Saetaspongia densa
- Sinfoflabrum antiquum
- Triticispongia diagonata
Phylum Priapulida - 16 species
- Acosmia maotiania
- Archotuba conoidalis
- Corynetis brevis
- Gantoucunia aspera
- Lagenula triolata
- Oligonodus specialis
- Paraselkirkia jinningensis
- Palaeopriapulites parvus
- Protopriapulites haikouensis
- Sandaokania latinodosa
- Selkirkia elongata
- Selkirkia sinica
- Sicyophorus rarus
- Xiaoheiqingella peculiaris
- Xishania longgiusula
- Yunnanopriapulus halteroformis
Phylum Vetulicolia - 7 species
- Banffia confusa
- Didazoon hoae
- Vetulicola cuneata
- Vetulicola gantoucunensis
- Vetulicola rectangulata
- Xidazoon stephanus
- Yuyuanozoon magnificissimi
Phylum Uncertain - 4 species
- Amplectobelua symbrachiata
- Anomalocaris saron
- Cucumericrus decoratus
- Parapeytoia yunnanensis
Enigmatic - 24 species
- Allonnia phrixothrix
- Amiskwia sinica
- Anthrotum robustus
- Batofasciculus ramificans
- Cambrotentacus sanwuia
- Conicula straita
- Dinomischus venustus
- Discoides abnormalis
- Eldonia eumorpha
- Facivermis yunnanicus
- Hippotrum spinatus
- Jiucunia petalina
- Maanshania crusticeps
- Macrocephalus elongates
- Parvulonoda dubia
- Phacatrum tubifer
- Phasangula striata
- Phlogites brevis
- Phlogites longus
- Priscapennamarina angusta
- Pristitoites bifarius
- Rhipitrus calvifer
- Rotadiscus grandis
- Yunnanozoon lividum - earliest known hemichordate
[edit] Kingdom Protista (algae)
- Fuxianospira gyrata
- Megaspirellus houi
- Sinocylindra yunnanensis
- Yuknessia sp.
[edit] Reference
[edit] References
- Conway-Morris, S. (2003). The Cambrian "explosion" of metazoans and molecular biology: would Darwin be satisfied? Int J Dev Biol, 47(7-8), 505-515.
- Fossils of the Chengjiang Maotianshan Shale - URL retrieved Septermber 20 2006
- Hou, Xian-Guang; Aldridge, Richard J., Bengstrom, Jan; Siveter, David J. ;Feng, Xiang-Hong 2004; The Cambrian Fossils of Chengjang, China, Blackwell Science Ltd, 233 pp.
- Preservation, Taphonomy and Palaeoecology of the Chengjiang Biota - URL retrieved Septermber 20 2006
- Shu, D-G; Luo, H-L; Conway Morris, S.; Zhang X-L; Hu, S-X; Chen, L. ;Han, J.; Zhu, M.;Li, Y; Chen, L-Z 1999, Lower Cambrian Vertebrates from South China, Nature 402 pp 42-46.
- Shu, D. G., Morris, S. C., Han, J., Chen, L., Zhang, X. L., Zhang, Z. F., et al. (2001). Primitive deuterostomes from the Chengjiang Lagerstatte (Lower Cambrian, China). Nature, 414(6862), 419-424.
- Shu, D., Morris, S. C., Zhang, Z. F., Liu, J. N., Han, J., Chen, L., et al. (2003). A new species of yunnanozoan with implications for deuterostome evolution. Science, 299(5611), 1380-1384.
- Shu, D. G., Morris, S. C., Han, J., Zhang, Z. F., & Liu, J. N. (2004). Ancestral echinoderms from the Chengjiang deposits of China. Nature, 430(6998), 422-428.
- Shu, D. G., Morris, S. C., Han, J., Li, Y., Zhang, X. L., Hua, H., et al. (2006). Lower Cambrian vendobionts from China and early diploblast evolution. Science, 312(5774), 731-734.
- Waloszek, D., & Maas, A. (2005). The evolutionary history of crustacean segmentation: a fossil-based perspective. Evol Dev, 7(6), 515-527.
- Xian-guang, H., Aldridge, R. J., Siveter, D. J., & Xiang-hong, F. (2002). New evidence on the anatomy and phylogeny of the earliest vertebrates. Proc Biol Sci, 269(1503), 1865-1869.
- Zhang, X.; Han J.; Zhang Z.; Liu H.; and Shu D. (2003) Reconsideration of the supposed naraoiid larva from the Early Cambrian Chngjiang Lagerstätte, South China. Palaeontology 46(3):447-66.
- Zhang, X. G., & Hou, X. G. (2004). Evidence for a single median fin-fold and tail in the Lower Cambrian vertebrate, Haikouichthys ercaicunensis. J Evol Biol, 17(5), 1162-1166.
[edit] See also
[edit] External links
- Chengjiang (Web page). Retrieved on November 22, 2005.
