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TitleThe dinoflagellate cysts Thalassiphora subreticulata n.sp. and Thalassiphora balcanica: their taxonomy, ontogenetic variation and evolution
AuthorMudie, P J; Fensome, R A; Rochon, A; Bakrac, K
SourcePalynology vol. 43, 2019 p. 1-33,
Alt SeriesNatural Resources Canada, Contribution Series 20180742
PublisherInforma UK Limited
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®)
ProvinceNova Scotia; Eastern offshore region
AreaEurope; Black Sea; Caspian Sea; Scotian Slope; Atlantic Ocean; Canada
Lat/Long WENS -61.4786 -61.4783 42.8247 42.8244
Lat/Long WENS 10.0000 56.0000 49.0000 38.0000
Subjectspaleontology; stratigraphy; Nature and Environment; Neogene; Pliocene; Miocene; Paleogene; Oligocene; Eocene; Paleocene; systematic paleontology; taxonomy; fossil morphology; fossil descriptions; evolution; micropaleontology; microfossils; paleoenvironment; paleoecology; paleogeography; sea water geochemistry; salinity; oxygen; scanning electron microscopy; models; basins; ontogeny; fossil distribution, strata; Dinoflagellates; Dinocysts; Thalassiphora; Thalassiphora subreticulata n.sp.; Thalassiphora balcanica; Thalassiphora pelagica; Galeacysta; Galeacysta etrusca; Nematosphaeropsis; Spiniferites; Spiniferites balcanicus; Paratethys Sea; Pannonian Basin; Lake Pannon; Dacian Basin; Black Sea Basin; Caspian Basin; Shubenacadie H-100 Well; Phanerozoic; Cenozoic; Tertiary
Illustrationspaleontological drawings; flow diagrams; location maps; geoscientific sketch maps; photomicrographs; models; geochronological charts; tables
ProgramGEM2: Geo-mapping for Energy and Minerals Baffin Petroleum Systems
Released2019 03 22
AbstractThalassiphora and other large 'winged' dinoflagellate cysts common in Oligocene-Pliocene stratified epicontinental seas display morphological variation greater than the plasticity of extant taxa, thereby raising questions about causes. This variation has been attributed either to directed ontogeny in response to salinity or oxygen gradients or to evolutionary development in response to special environmental conditions. Some authors have grouped certain taxa that mark the closing phases of European Paratethyan basins into an intergradational plexus including species of Thalassiphora, Galeacysta, Nematosphaeropsis and cruciform Spiniferites. Spiniferites (previously Thalassiphora) balcanicus and Galeacysta etrusca were considered end members of this plexus, despite large differences in morphology. We re-evaluate interpretations of the plexus through comparison primarily with a new north-western Atlantic Eocene species Thalassiphora subreticulata and new Croatian material of Thalassiphora balcanica, and we comment on differences from other Thalassiphora species. The large Eocene species Thalassiphora subreticulata (up to 148 micrometres maximum dimension) is camocavate, and has a coarsely reticulo-fibrous, irregularly perforate periphragm forming a shallow, bowl-shaped structure, as in Thalassiphora pelagica. Electron microscopy shows the perforations are crossed by fibrils in accord with a proposed 'stretched net' model of periphragm development. The smaller Late Miocene Paratethyan species Thalassiphora balcanica (maximum dimension to 115 micrometres) is also camocavate, with a similar fibrous periphragm which encloses about half the ventral surface and has smooth-edged and open perforations. Scanning electron microscope images show this species lacks the branched spinous processes used to justify its transfer from Thalassiphora to Spiniferites by Suto-Szentai. In both Thalassiphora species, morphological variations do not support either the benthic-planktonic stage ontogenetic model or the oxidation-state model previously proposed for Thalassiphora pelagica. Among 30 species currently assigned to Thalassiphora, no correlation was found between cyst size and age. However, the range of morphology in this genus points to the need for taxonomic re-assessment, which might help reveal evolutionary trends.
Summary(Plain Language Summary, not published)
Within-species morphological variation in some fossil dinoflagellate-cyst species has been explained as either the fossilization of different development stages in the life cycle of the organism (i.e. ontogenetic) , or as a response to environmental conditions. The presence of well-preserved material of a new Paleogene species, Thalassiphora subreticulata, from offshore eastern Canada and new specimens of the Miocene eastern European species, Thalassiphora balcanica, allow us to explore possible explanations, and thus how a new understanding might be applied to paleoenvironmental analysis. We conclude that the variation is just natural variation in cyst morphology not related to ontogeny. At least the variation shown by our material is difficult to relate to environmental factors.

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