Resolving the position of problematic lower to middle Cambrian Lophotrochozoa: a critical appraisal of tommotiid and stem-brachiopod character homologies.
2012 (English)In: 23.1 Martin Glaessner Symposium: The Ediacaran and the Cambrian Explosion, 2012Conference paper, Presentation (Refereed)
The origin and early evolution of Brachiopoda can be traced back to the plethora of scleritomes and brachiopod-like taxa in the lower Cambrian. Most conspicuous are members of Lagerstätten such as the Burgess Shale and Chengjiang faunas. By combining records of exceptionally-preserved faunas with more widespread records of lower Cambrian stem-brachiopods and small shelly faunas, we aim to determine the characters suites associated with the evolution of these organisms. This determination is crucial to reconstructing the brachiopod stem-group and to polarising character changes associated with a transition from scleritome organisms to crown-group brachiopods. Critical comparison of the shell structure and setae of extant lophotrochozoans with those from fossil specimens from Sweden, Estonia and Nevada reveals the extent of taphonomic alteration, further informing previous taxonomic efforts.
Characters previously proposed as systematically important are re-evaluated, based on critical examination of two distinct character suites: firstly examination of the homology of striated tubes which are associated with the secretion of setae, which are exceptionally preserved in many cases; and secondly, the occurrence of phosphatised columnar shell structures previously referred to as 'punctae'. Overall we provide further support for homologous character suites shared between tommotiids such as Micrina, Sunnaginia and Eccentrotheca, and stem-brachiopods including Mickwitzia and Setatella. These suggested homologies are of phylogenetic significance, and shed further light on the early evolution of the lophotrochozoan body plan in the early Cambrian.
Place, publisher, year, edition, pages
Other Earth and Related Environmental Sciences
Research subject Earth Science with specialization in Historical Geology and Palaeontology
IdentifiersURN: urn:nbn:se:uu:diva-190270OAI: oai:DiVA.org:uu-190270DiVA: diva2:583259
34th International Geological Congress
FunderSwedish Research Council