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TitleDinoflagellate evolution: a fossil perspective with modern overtones
AuthorFensome, R A; Riding, J B; Williams, G L; Carbonell-Moore, C; Janouskevec, J; Saldarriaga, J
Alt SeriesNatural Resources Canada, Contribution Series 20170218
Meeting11th International Conference on Modern and Fossil Dinoflagellates; Bordeaux; FR; July 17-21, 2017
Subjectsfossils; fossil assemblages; gonyaulacoid; peridinioid; dynophysioids; Wetselielloideae; Cladopyxiaceae; dinoflagellates species; dinocysts; Mesozoic; Triassic; Jurassic
ProgramBaffin Petroleum Systems, GEM2: Geo-mapping for Energy and Minerals
ProgramBaffin Petroleum Systems, GEM2: Geo-mapping for Energy and Minerals
LinksOnline - En ligne (1.77 MB)
AbstractSome extant dinoflagellate species produce cysts (dinocysts) that can be preserved as fossils, the record of which strongly attests to a real radiation in the early Mesozoic. Recent molecular phylogenetic evidence also supports such a radiation, especially with regard to a common origin for thecate dinoflagellates. The earliest fossils are from the later Triassic, and early forms show a diversity of morphologies not closely reflected in later taxa. Most modern thecate dinoflagellates can be classified as gonyaulacoid or peridinioid, reflecting a divergence that occurred during the Jurassic. Although incomplete, the dinoflagellate fossil record reveals critical evidence, such as the occurrence of now-extinct groups, including the nannoceratopsialeans (a ¿missing link¿ between dinophysioids and gonyaulacoid-peridinioids) and the peridiniacean subfamily Wetzelielloideae. Also, some groups were more common once than they are today, for example the Cladopyxiaceae. Modern cladopyxiaceans have not yet been sequenced, but details of their tabulation suggest that they may be close to the common ancestry of gonyaulacaleans and peridinialeans. Molecular evidence shows that gonyaulacoids are a unified branching clade, but the coherence of modern peridinioids has been more equivocal. Tabulation is variable among modern peridiniaceans, in contrast to the strikingly stable tabulation of fossil peridinioids. Perhaps most non-calcareous fossil organic-walled peridiniaceans (in contrast to protoperidiniaceans) belong to a clade that ended with the extinction of Palaeocystodinium in the Miocene. All such examples show that the fossil record is integral to understanding dinoflagellate evolution when integrated with molecular and anatomical evidence from modern forms.
Summary(Plain Language Summary, not published)
Dinoflagellates are part of the modern plankton, and some species produce cysts that have left a significant fossil record. Historically, study of the morphology of fossil and living dinoflagellates provided our only insights into dinoflagellate evolution, but recently the advent of molecular studies (e.g. RNA) have substantially added to our understanding of the groups history. Fossils, however, remain our only way of ground-truthing evolutionary scenarios, providing the only evidence for extinct groups and past evolutionary patterns of extant groups. Collaboration between experts from different disciplines leads to the best-supported evolutionary scenarios using multiple lines of evidence. And a better understanding of the groups past enables us to more effectively use fossil dinoflagellates as biostratigraphic and pelaeoenvironmental tools.