Canadaspis laevigata Arthropod from Chengjiang

Canadaspis laevigata

Phylum Arthropoda

Geological Time: Early Cambrian (~525 million years ago)

Size (25.4mm=1 inch): 9 mm long by 5 mm across on a 37 mm by 32 mm matrix

Fossil Site: Chengjiang Biota - Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation, Mafang Village , Anning, Kunming, Yunnan Province, China

Canadaspis laevigataDescription: This unusual arthropod is known as CanadaspisCandaspis lavigata, an animal whose systematic position has undergone several revisions. It has affinities with the younger Canadaspis perfecta, the type species. While it has been thought by some to be a crustacean, most think that is not the case, and that its primitive level of organization places it close to Fuxianhuia and its kin.

The genus Canadaspis is additionally found in the House Range formations in Utah, alnong with other Burgess Shale type fauna, and in the Lower Cambrian Pioche Shale of Nevada (see . Of these, Canadaspis laevigata from from the Chengjiang Maotianshan Shales is about 10 million years older than Canadapsis perfecta.

Discovered in 1984, the Chengjiang Biota now ranks as the most diverse faunal fossil assemblage of all the Burgess Shale like deposits. It is also some 10 million years older than the Burgess Shale. Like the Burgess Shale, non-mineralized soft tissue parts are often extraordinarily well preserved with high resolution as aluminosilicate films, sometimes with oxidized iron content. Various taphonomic processes leading extensive preservation of soft tissue have been proposed, including rapid death by asphyxia followed by rapid burial in anoxic sediment undisturbed by turbidity. The Chengjiang biota is dominated by phyla Arthropoda and Porifera. There are seven lobopodians, more than any other Lagerstätte that some scientists elevate to phylum rank, and seven members of the extinct phylum Vetulicolia. Members or potential members of phyla Priapulida, Nematomorpha, Hyolitha, Hemichordata, Echinodermata, Ctenophora, Chordata, Cnidaria, Chaetognatha, and Brachiopoda are found. A large number of enigmatic animals of uncertain affinity are found as well, some of which may represent failed evolutionary experiments, or even new phyla that did not persist for long in the early Cambrian, or were rapidly replaced by more derived forms. Among the diverse Maotianshan Shales fauna, of utmost important are the putative early chordates, particularly Haikouella, potentially an ancestor to or the earliest craniate chordate. Myllokunmingia and Haikouichthys are interpreted as early Craniata, and possibly very primitive agnathids, the progenitor of the fishes and all other vertebrates.

Also see: Chengjiang Biota, Chengjiang Fossils, Cambrian Explosion Canadaspis Phyllocarid Fossil from Utah Pioche Canadaspis

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