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TitleA review of the Jurassic dinoflagellate cyst genus Gonyaulacysta Deflandre 1964 emend. nov.
AuthorRiding, J B; Mariani, E; Fensome, R A
SourceReview of Palaeobotany and Palynology vol. 299, 104605, 2022 p. 1-37,
Alt SeriesNatural Resources Canada, Contribution Series 20210363
Mediapaper; on-line; digital
File formatpdf
SubjectsNature and Environment; paleontology; biostratigraphy; Middle Jurassic; Upper Jurassic; taxonomy; Jurassic
Illustrationsfigures; schematic representations; tables; stratigraphic columns; photographs
ProgramGEM2: Geo-mapping for Energy and Minerals Western Arctic-Beaufort-Northern Yukon
Released2022 01 19
AbstractThe Middle-Late Jurassic gonyaulacacean dinoflagellate cyst genus Gonyaulacysta is characterised by an epicyst which is around twice the length of the hypocyst. The sulcus is L-type and may be slightly sigmoidal in shape, but is never S-type sensu stricto. The formswith slightly sigmoidal L-type sulcuses may have developed into species with S-type sulcuses. Gonyaulacysta jurassica, the holotype of which is the nomenclatural type of the genus, had a global distribution. A total of 151 species have been assigned to Gonyaulacysta although 126 of these have been transferred to other genera. Prior to this contribution, 25 species were accepted in the current Lentin and Williams Index. This is herein reduced to eight and 18 species are transferred to other genera. The accepted species are: Gonyaulacysta adecta stat. nov., emend. nov.; Gonyaulacysta australica comb. nov.,emend. nov.; Gonyaulacysta ceratophora; Gonyaulacysta desmos stat. nov., emend. nov.; Gonyaulacysta dualis emend. nov.; Gonyaulacysta fenestrata emend. nov.; Gonyaulacysta jurassica emend. nov.; and Gonyaulacysta longicornis stat. nov., emend. nov. These species form a closely related plexus, and are distinguished on differences in cavation style, form of sutural crests/ridges and size of the apical horn. All except Gonyaulacysta australica are reliable marker taxa. Our main taxonomic proposals involve the elevation of all subspecies and varieties of species here retained in Gonyaulacysta to species rank, or their synonymisation. This avoids cumbersome infraspecific names. Gonyaulacysta exhibits substantial provincialism; for example Gonyaulacysta dualis is confined to the Oxfordian-Kimmeridgian of the Boreal Realm. Gonyaulacysta adecta, Gonyaulacysta desmos and Gonyaulacysta longicornis are present in the Bathonian to Oxfordian of Laurasia and surrounding areas. Three species, Gonyaulacysta australica, Gonyaulacysta ceratophora and Gonyaulacysta fenestrata, are restricted to the Oxfordian to Tithonian of Australasia. Gonyaulacysta adecta and the cosmopolitan Gonyaulacysta jurassica both exhibit overall size increases throughout the Bathonian to Kimmeridgian of Europe.
Summary(Plain Language Summary, not published)
Microfossils remain the principal tool to determine the ages of rocks in sedimentary basins formed over the past 550 million years, and thus this field of biostratigraphy is critical to understanding sedimentary basin evolution and the hydrocarbon and mineral systems that they may contain. For scientists applying these fossils it is essential to have an effective classification for them and a clear mutual understanding of species concepts (taxonomy). Gonyaulacysta jurassica and its allies form a group of distinctive Jurassic fossil dinoflagellate species that have been recognized since the 1930s; but their biostratigraphic utility has been compromised by inconsistent and confusing taxonomy at both generic and specific levels. In this paper we revise the taxonomy of the group to refine its biostratigraphic usefulness, and also re-assess aspects of its paleoenvironmental interpretation and evolutionary position among dinoflagellates as a whole.

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