Exceptionally preserved brachiopods from the Chengjiang Lagerstatte (Yunnan, China): Perspectives on the Cambriane explosion of metazoans
2013 (English)In: Science Foundation in China, ISSN 1005-0841, Vol. 21, no 2, 66-80 p.Article in journal (Refereed) Published
The Cambrian explosion was coined to describe the geologically sudden appearance of numerous bilaterian body plans (Phyla) around the Ediacaran-Cambrian transition, around 565-520 million years ago. Many explanations and conjectures have been postulated in order to explain the pattern and duration of this explosive radiation of many different phyla of early metazoans. Here, we focus on the evolution of a phylum of marine suspension-feeding animals – the brachiopods, as exemplified by the exceptionally preserved taxa from the celebrated Chengjiang Konservat Lagerstätte (Yunnan, China). The abundant soft-bodied preservation at these fossil quarries gives us the only firm insights into what brachiopods looked like and how they functioned and lived when they first appeared on the Earth. Studies of Chengjiang brachiopods demonstrate that the early animals developed a remarkable varied organization of tissues and organs shortly after the onset of Cambrian explosion. In the marine suspension-feeding brachiopods, most importantly the tentaculate feeding structure of early brachiopods is already differentiated into two shapes of lophophore, anteriorly coiled (spiralled) and posteriorly arching tentacle crowns and the unique latter type was previously not documented from fossil and living brachiopods. Also unlike any known Recent brachiopod, all the known Cambrian brachiopods from Chengjiang have an open digestive tract that was disposed either as a U-shaped gut in linguliform and stem group brachiopods, or straight gut with a posterior anus in some calcareous-shelled stocks. Moreover, in contrast to living lingulids, all the Cambrian brachiopods have an epibenthic lifestyle either cemented by a ventral valve or attached by variable pedicles to establish complex ecological community encompassing primary tierers and variable secondary tierers. It is therefore assumed that brachiopods were the first benthic metazoan that achieved their success in ecological stratification and tiering complexity by late Atdabanian. The setae are also important for the brachiopod suspension-feeding life style, and in the Chengjiang brachiopods they include two types - cilia-like and spine-like setae. The mantle canals of different brachiopod species are also distinctly variable in arrangement, mainly disposed in pinnate, baculate and peripheral conditions. Of these, the peripheral disposition of mantle canals is for the first time proposed here so as to differentiate from the bifurcate condition in recent lingulids in that the former is devoid of posteriorly extending main trunks of sinus, but possesses a diverging dorsal vascular media in dichotomy.
Place, publisher, year, edition, pages
2013. Vol. 21, no 2, 66-80 p.
Research subject Historical Geology and Paleontology
IdentifiersURN: urn:nbn:se:uu:diva-216848OAI: oai:DiVA.org:uu-216848DiVA: diva2:691078
FunderSwedish Research Council, 2009-4395, 2012-1658