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TitleThe extant representation of the fossil dinoflagellate cyst Cladopyxidium McLean 1978
AuthorCarbonell-Moore, C; Fensome, R A; Williams, G L
Alt SeriesNatural Resources Canada, Contribution Series 20170222
Meeting11th International Conference on Modern and Fossil Dinoflagellates; Bordeaux; FA; July 17-21, 2017
Mediapaper; on-line; digital
File formatpdf
Subjectsfossil assemblages; biostratigraphy; fossils; Cladopyxis; Cladopyxidium; Cladopyxis brachiolata; gonyaulacaleans; peridinialeans
ProgramBaffin Petroleum Systems, GEM2: Geo-mapping for Energy and Minerals
LinksOnline - En ligne (1.77 MB)
AbstractExtant dinoflagellates with a similar tabulation to Cladopyxis hemibrachiata but lacking the process-like extensions unique to Cladopyxis have been observed in plankton samples from the Atlantic, Indian, and central equatorial Pacific oceans, mostly from surface waters. The tabulation is closely similar to that of the fossil dinoflagellate cyst Cladopyxidium, which has a partiform gonyaulacalean (cladopyxiacean) plate pattern consisting of six precingulars, six postcingulars, two antapicals (equivalent to the 1'''' and 1p of the standard gonyaulacalean pattern) and up to 7 climactal (apical + anterior intercalary) plates. Partiform dinoflagellates are diverse in the fossil record, especially in Middle Jurassic to Paleocene strata, but are uncommon in the later Cenozoic, and only a few genera, including Cladopyxis, live in modern oceans. Partiform dinoflagellates share features in common with gonyaulacaleans and peridinialeans, and so may have important evolutionary significance. The co-occurrence in some samples of Cladopyxis brachiolata and forms with similar tabulation to this species but lacking extensions suggests that the number of cladopyxiaceans in the modern plankton has been underestimated. The largest number of cladopyxiaceans was observed in the Indian Ocean, so the potential exists to collect enough material to sequence these dinoflagellates. This would lead to a better understanding of the evolutionary relationship between gonyaulacaleans and peridinialeans.
Summary(Plain Language Summary, not published)
The dinoflagellate fossil record consists of some forms that are more or less closely related to modern forms and some of which are extinct. Among the former group, but with a much more extensive fossil record than a modern one, are members of the family Cladopyxiacaeae. Cladopyxiaceans are especially interesting in that they appear to represent a "missing link" between two prominent modern groups, peridinioids and gonyaulacoids. This possible relationship has been revealed largely through well-preserved fossil cladopyxiaceans. We have thus predicted that molecular analysis of modern members of the group could provide interesting insights into dinoflagellate evolution as a whole. Modern forms are hard to "catch", but the first author has now recognized more widely in the Indian Ocean, which enhances the possibility of their analysis, and thus of leading to a better understanding of dinoflagellate evolution and consequently the use of these fossils in ancient rocks.