Chengjiang Faunal Community

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Maotianshania cylindrica from the Chengjiang Fauna Community

The Chengjiang Faunal Community ( 澄江 动物 群 , Chéngjiāng dòngwùqún ) is a Lower Cambrian fossil fauna that occurs in a conservation deposit in the Maotianshan Shale of the Yunnan Province of the People's Republic of China . Their age is between 525 and 520 million years.

The Chengjiang fossil site was added to the UNESCO World Heritage List in 2012.

History and scientific significance

Even if fossils in Chengjiang are known from the early 20th century, the site only became famous in 1984 with the discovery of Misszhouia - a trilobite-like arthropod belonging to the Naraoiidae . The find was characterized by exquisite soft tissue preservation. Since then, Chengjiang has been extensively studied by international research teams; this led to constant new discoveries and an abundance of scientific publications on the often problematic interpretation of the finds. During this period, various taxa were revised or assigned to different groups. The reinterpretations have resulted in refinements in the phylogenetic development of several groups, with the primitive Deuterostomia even the reorganization of the tribe of Vetulicolia took place . The Chengjiang Faunal Community already has all of the animal groups found in the younger Burgess Slate. However, since it is around 10 million years older, it underscores the conclusion that the Metazoa had already undergone a rather rapid diversification process in the Lower Cambrian much more clearly than the Burgess slate . The fossil preservation of an extremely species-rich faunal community made Chengjiang a unique site in the world for understanding the evolution of early multicellular organisms - members of the Chordata tribe , which also includes all vertebrates , should be mentioned in particular . The fossils of the Chengjiang faunal community represent the oldest known (and already very species-rich) metazoan collection after the Proterozoic - Phanerozoic turn, they also serve as a unique database for understanding the then very rapid diversification process of life, which is also known as Cambrian radiation .

Conservation and Taphonomy

The fossils occur in the Yuanshan Member of the Heilinpu Formation (formerly known as the Qiongzhusi Formation or "Chiungchussu"), a 50-meter-thick claystone layer. The Yuanshan Member is a very extensive stratification that covers tens of thousands of square kilometers in eastern Yunnan. There are numerous, quite scattered fossil-bearing outcrops. An examination of the rock sequence suggests tropical environmental conditions, and sea level fluctuations and tectonic unrest can also be identified. The deposit area was a shallow sea with a clay-silty seabed. Most of the preserved fauna is benthic and is likely to have been periodically buried by turbid currents , since most fossils show no signs of relocation after death. The fossils occur in layers that are centimeter thick. Similar to the more recent fossils of the Burgess slate, the environmental conditions prevailing at the time enabled soft body conservation. The soft parts are preserved as thin film-like aluminum silicate layers - often in connection with a high content of oxidized iron (Fe 3+ ). Most of them show the finest details in excellent condition.

fauna

The Chengjiang Fauna Community is extremely species-rich, 185 species had been scientifically described by June 2006. Almost half of them are arthropods, only about 3% are hard-shelled, mainly trilobites (5 species), which are in an amazing and extremely rare state of preservation (with remains of legs, antennae and other soft tissues). The phyla Porifera with 15 species and Priapulida with a total of 16 species are also fairly well represented . The strains Brachiopoda , Chaetognatha , Cnidaria , Ctenophora , Echinodermata , Hyolithida , Nematomorpha , Phoronida , Protista and Chordata are also present. About an eighth of the animal species are problematic with an uncertain position - possible evolutionary forms of experimentation that only survived for a short time, as the benthic habitats changed rapidly in the Cambrian. Chengjiang is the richest source of Lobopodia , which are often considered to be a separate tribe; There are six genera at present: Luolishania , Paucipodia , Cardiodictyon , Hallucigenia (also known from the Burgess schist), Microdictyon and Onychodictyon .

Artist's impression of Hallucigenia fortis

Important fossil finds from Chengjiang are eight possible members of the Chordata tribe , which contains all vertebrates , including the fossil Myllokunmingia - possibly an agnathic fish. Haikouichthys ercaicunensis , another primitive fish-like species, is reminiscent of Myllokunmingia in its appearance .

The fossil Yunnanozoon lividum is considered the earliest hemichordate , it has many of the typical features of the chordata and represents an anatomical link between the invertebrata and the chordata. Haikouella lanceolata is described as the earliest representative of craniota-like chordata. This fish-like animal has a lot in common with Yunnanozoon lividum , but differs from it in several ways: it has a recognizable heart, has a dorsal and a ventral aorta, has gill nets and already has a notochord .

At the moment there is still no agreement with regard to the systematic position of the Vetulicolia , which are represented in the Chengjiang fauna with seven species (status 2008). Originally they were classified as cancerous arthropods, but later elevated to their own strain of primitive deuterostomia by DG Shu et al. (Shu, 2001) . Another researcher puts them on the basis of an affinity with the chordata to the urochordata. It is generally assumed that they were free swimming and feeding on suspended matter by filtering.

About two dozen animals of the Chengjiang fauna are very problematic in their phylogenetic classification, including Anomalocaris saron , allegedly a predator of the Lower Cambrian. Stromatoveris psygmoglena was recently described by Shu (2006) as a possible bilateral link between the Ediacara forms and the Cambrian Ctenophora .

List of the Chengjiang Faunal Community by tribe

Empire Animalia

Phylum Arthropoda - 78 species

Phylum Arthropoda - Nectaspida - 2 species

Phylum Arthropoda - Class Trilobita - 5 species

Tribe Brachiopoda - 5 species

Tribe Chaetognatha - 1 kind

Tribe Cnidaria - 2 species

Tribe Chordata - 8 species

Tribe Ctenophora - 3 species

Echinodermata strain - 1 species

Tribe Hyolithida - 8 species

Tribe Lobopodia - 6 species

Originating Nematomorpha - 3 types

Phoronida strain - 1 species

Phylum Porifera - 15 species

Priapulida strain - 16 species

Tribe Vetulicolia - 7 species

Trunk of uncertain assignment - 4 species

Puzzling - 24 types

Reich Protista (seaweed)

swell

  • Simon Conway Morris : The Cambrian "explosion" of metazoans and molecular biology: would Darwin be satisfied? International Journal of Development Biology, Vol. 47, No. 7-8, pp. 505-515, 2003.
  • Fossils of the Chengjiang Maotianshan Shale - URL found on September 20 , 2006
  • Xian-Guang Hou, Richard Aldridge , Jan Bengstrom, David J. Siveter, Xiang-Hong Feng: The Cambrian Fossils of Chengjang, China. Blackwell Science Ltd., 233 S., 2004 ( online excerpt )
  • Preservation, Taphonomy and Palaeoecology of the Chengjiang Biota - URL retrieved September 20, 2006
  • DG Shu, HL Luo, S. Conway Morris, XL Zhang, SX Hu, L. Chen, J. Han, M. Zhu, Y. Li, LZ Chen: Lower Cambrian Vertebrates from South China. Nature, Vol. 402, pp. 42-46, 1999
  • DG Shu, S. Conway Morris, J. Han, L. Chen, XL Zhang, ZF Zhang et al .: Primitive deuterostomes from the Chengjiang deposit (Lower Cambrian, China). Nature, Vol. 414 (6862), pp. 419-424, 2001
  • DG Shu, S. Conway Morris, ZF Zhang, JN Liu, J. Han, L. Chen et al .: A new species of yunnanozoan with implications for deuterostome evolution. Science, Vol. 299 (5611), pp. 1380-1384, 2003
  • DG Shu, S. Conway Morris, J. Han, ZF Zhang, JN Liu: Ancestral echinoderms from the Chengjiang deposits of China. Nature, Vol. 430 (6998), pp. 422-428, 2004
  • DG Shu, S. Conway Morris, J. Han, Y. Li, XL Zhang, H. Hua et al .: Lower Cambrian vendobionts from China and early diploblast evolution. Science, Vol. 312 (5774), pp. 731-734, 2006
  • D. Waloszek, A. Maas: The evolutionary history of crustacean segmentation: a fossil-based perspective. Evolution & Development, Vol. 7, No. 6, pp. 515-527, 2005
  • H. Xian-guang, RJ Aldridge, DJ Siveter, F. Xiang-hong: New evidence on the anatomy and phylogeny of the earliest vertebrates. Proceedings of the Royal Society B: Biological Sciences, Vol. 269 (1503), pp. 1865-1869, 2002
  • ZX. hang, J. Han, Z. Zhang, H. Liu, D. Shu: Reconsideration of the supposed naraoiid larva from the Early Cambrian Chengjiang deposit, South China. Palaeontology, Vol. 46, No. 3, pp. 447-66, 2003
  • XG Zhang, XG Hou: Evidence for a single median fin-fold and tail in the Lower Cambrian vertebrate, Haikouichthys ercaicunensis. Journal of Evolutionary Biology, Vol. 17, No. 5, pp. 1162-1166, 2004

See also

Stephen Jay Gould

Individual evidence

  1. ↑ UNESCO World Heritage Center: Chengjiang Fossil Site

Web links