https://orcid.org/0000-0002-1194-9903
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Abstract
The biota of the brackish-water Lake Pannon in the Pannonian Basin is characterised by remarkable endemism due to the isolated evolution of the lake for 8 myr after the last Miocene marine connection ceased (∼11.6 Ma). A conspicuous feature of this endemism is the large, probably ecophenotypic variation in the morphology of brackish-water dinoflagellate cysts that challenges taxonomy and complicates biostratigraphical and ecological interpretations. We conclude that a widely debated Lake Pannon genus, Pontiadinium, includes several proximate dinoflagellate cyst species with prominent apical and antapical protuberances, and we show how the genus differs from the morphologically similar gonyaulacacean cyst genera Impagidinium, Leptodinium, Cribroperidinium and Komewuia. The generic description of Pontiadinium is emended together with the species descriptions of Pontiadinium inequicornutum, Pontiadinium obesum and Pontiadinium pecsvaradanesis. A new species is described as Pontiadinium szentaiae sp. nov. from Našice (northern Croatia) that is characterised by unique trabeculate sutural septa formed from a beaded tegillum supported by columellae or rod-like luxuriae. The dinoflagellate cyst assemblages of the long-lived brackish-water Lake Pannon clearly demonstrate that dinoflagellate cysts in low-salinity, isolated epicontinental seas display greater morphological plasticity than their normal-marine relatives. The development of an antapical horn appears to be a previously undocumented example of phenotypic morphological features that developed in response to subnormal salinities within at least two dinoflagellate cyst genera endemic to Lake Pannon and the Post-Paratethyan seas of the Ponto-Caspian realm. This ecophenotypic variation resulted in a higher level of morphological adaptation, leading to the evolutionary development of new dinoflagellate cyst species and genera.
Acknowledgements
Reviewer Dr Martin J. Head, two anonymous reviewers and Editor Dr James B. Riding are thanked for their thorough review and constructive comments that helped to improve the manuscript. The Paks II Nuclear Power Plant Private Limited Company is acknowledged for providing access to the Paks cores and for permitting their study and publication of the results. We thank Rob Fensome (Geological Survey of Canada Atlantic) for his extremely helpful reviews of earlier manuscript drafts and help with the systematics section of this paper. Dragica Kovačić (Croatian Geological Survey) prepared the palynological samples. Krisztina Buczkó (Hungarian Natural History Museum) and Marija Horvat (Croatian Geological Survey) are thanked for enabling the SEM analysis of selected samples. Vivien Csoma is thanked for the information on the ostracods from the PAET cores and Našice. Sarolta Lőrincz (Geological Institute of Romania) is thanked for the information on the holotype material of Nicolae Balteş. Ágnes Görög (Eötvös Loránd University, Hungary) is thanked for access to the PAET 27 and PAET 30 palynological samples.
Disclosure statement
No potential conflict of interest was reported by the authors.
Plate 6. Pyxidinopsis? sp. 1 from the Vranović section, Našice, and its comparision to the Lake Pannon Tectatodinium pellitum specimens. All scale bars represent 10 µm except 15 where it is 20 µm. 1–4. Scanning electron microscope (SEM) micrographs of Pyxidinopsis? sp. 1 from Našice. All material is from SEM stub B2 housed at the Department of Botany, Hungarian Natural History Museum, Budapest, Hungary. Working distance 6.6 mm, acceleration voltage 15 kV. Note the large archeopyle in precingular position in figures 3–4. 5–6. Pyxidinopsis? sp. 1 specimen with sub-cruciform outline, apical and antapial notches in dorso-lateral view. Našice, sample B4, slide number 2, embedded in silicone oil. Specimen was rotated in silicone oil. 7. Pyxidinopsis? sp. 1 specimen in lateral view, Našice, sample B4, slide number 1, embedded in glycerine jelly. 8. Pyxidinopsis? sp. 1 specimen in dorso-apical view, Našice, sample B4, slide number 2, embedded in silicone oil. 9–10. Pyxidinopsis? sp. 1 specimen in dorsal (9) and dorso-apical (10) view, Našice, sample B4, slide number 2, embedded in silicone oil. Specimen was rotated in silicone oil. 11–12, 16. Pyxidinopsis? sp. 1 specimen in dorsal view, Našice, sample B4, slide number 2, embedded in silicone oil. Specimen was rotated in silicone oil. 13–14. Pyxidinopsis? sp. 1 specimen in dorso-lateral view, Našice, sample B5, slide number 2, embedded in silicone oil. 15. Pyxidinopsis? sp. 1 specimen in fluorescent light, lateral view, Našice, sample B5, slide number 2, embedded in silicone oil. 17–20. Lake Pannon Tectatodinium pellitum specimens from the Paks area (central Hungary). Note the differences in wall features between Pyxidinospis? sp. 1 and Tectatodinium pellitum. 17. Tectatodinium pellitum PAET 27, depth 189.1 m, slide number 1, embedded in glycerine jelly. 18. Tectatodinium pellitum specimen in lateral view, PAET 30, depth 492 m, slide number 1, embedded in glycerine jelly. 19. Tectatodinium pellitum specimen in dorso-lateral view, PAET 30, depth 477 m, slide number 1, embedded in glycerine jelly. 20. Tectatodinium pellitum, PAET 27, depth 375 m, slide number 1, embedded in glycerine jelly.
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Notes on contributors
Viktória Baranyi
VIKTÓRIA BARANYI is a postdoctoral researcher with the Croatian Geological Survey. Her work currently focuses on Neogene Lake Pannon and Paratethyan brackish-water dinoflagellate cysts, their morphology and endemic evolution. She has also expertise in Triassic–Jurassic terrestrial and marine palynomorphs, vegetation changes and organic geochemistry and has studied the biotic response to the Carnian Pluvial Episode (Late Triassic) and the Jenkyns Event (Early Jurassic). She received her PhD from the University of Oslo, Norway, in 2018. She is also involved in projects on palaeoenvironmental reconstruction, vegetation dynamics and stratigraphy of terrestrial Middle Triassic–Early Jurassic successions from the Ordos and Sichuan basins in China.
Peta J. Mudie
PETA J. MUDIE has studied the Pliocene–Recent palynology of Mediterranean seas, including the Arctic Ocean, first as a postdoctoral student at Dalhousie University, then as a research scientist with the Geological Survey of Canada, combined with joint adjunct appointments at Memorial University of Newfoundland and Dalhousie University, for 35 years. Her field work includes four seasons on an ice island in the Canadian Arctic, work on Arctic icebreakers and ocean drilling ships, and International Geological Correlation Program excursions to Neogene–Pleistocene type sections around the Black Sea.
Imre Magyar
IMRE MAGYAR is a geologist with MOL Hungarian Oil and Gas Company, and a member of the MTA-MTM-ELTE Research Group for Palaeontology Budapest (Hungarian Academy of Sciences). He received his PhD from the Eötvös University, Budapest, in 1995, and worked as a postdoctoral researcher at the Geological and Geophysics Department of the University of Wisconsin, Madison between 1996 and 1998. His major interest is in the endemic evolution and adaptive radiation of molluscs in long-lived lakes and stratigraphy (including biostratigraphy and seismic stratigraphy) and depositional history of lacustrine basins in the Paratethyan region. He has carried out research on the endemic mollusc fauna and deposits of Lake Pannon, a Late Miocene–Pliocene long-lived lake in the Pannonian Basin. Various aspects of this fossil fauna, including its origin, palaeoecology, tempo and mode of evolution, phylogenetic relationships, etc. have been addressed in his studies. His stratigraphical and palaeogeographical research has provided a firm basis for palaeobiological and palaeobiogeographical interpretations.
Ádám Kovács
ÁDÁM KOVÁCS is a PhD student at the Eötvös Loránd University, Budapest, Hungary. In his master’s thesis he focused on the Upper Miocene strata of the Drava Basin, including the ones in the Našice Quarry. Currently, he is building numerical stratigraphical models to study the Late Miocene evolution of the Pannonian Basin, with special attention to the formation of unconformities and the clinoform architecture in lacustrine settings.
Mária Sütő-Szentai
MÁRIA SÜTŐ-SZENTAI is a retired palynologist from Komló, Hungary. She started as a geological technician at the Laboratory of the former Deep Well Drilling Company Komló, Hungary, where she specialised in the palynological analysis of Neogene sediments. She pioneered in the analysis of Lake Pannon dinoflagellate cysts and described one new genus, 22 species and eight subspecies of dinoflagellate cysts, as well as two new prasinophyte species. Her work resulted in a Lake Pannon dinoflagellate cyst zonation scheme that is still frequently used in hydrocarbon exploration and cross-correlation of the deep lacustrine sediments of Lake Pannon. Recently she has been working on a compendium of Silurian to Holocene organic-walled microplankton taxa recorded in Hungarian geological profiles.
Koraljka Bakrač
KORALJKA BAKRAČ is a research scientist with the Geological Survey of Croatia in their Geological Department. She has focused mainly on the Cenozoic dinoflagellate cysts from the Central Paratethys Sea – their stratigraphy and ecology. Most recently she has worked on projects involving Holocene palynomorph assemblages from the eastern Adriatic Sea and coastal lakes. This work includes spores and pollen as well as nonpollen palynomorphs.
