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Pontiadinium szentaiae
Holotype. Plate 4, figures 1–8, sample B1, slide no. 4 (catalogue number: HGI-VB-1P-NAC-V-B1/4), England Finder coordinate J48, embedded in silicone oil. Housed at Department of Geology, Croatian Geological Survey. Catalogue numbers: HGI-VB-1M-NAC-V-B1 (organic residue), HGI-VB-R-NAC-V-B1 (rock residue).
Paratype. Plate 3, figures 9–11, sample B1, slide no. 4 (catalogue number: HGI-VB-1P-NAC-V-B1/4), England Finder coordinate H51, embedded in silicone oil. Housed at Department of Geology, Croatian Geological Survey. Catalogue numbers: HGI-VB-1M-NAC-V-B1 (organic residue), HGI-VB-R-NAC-V-B1 (rock residue).
Holotype and paratype locality. Našice Quarry, Vranović section, 45°27′10.69′′N, 18°2′4.12′′E, Našice, northern Croatia, upper Pannonian (Tortonian), Galeacysta etrusca Zone, Spiniferites cruciformis assemblage, younger than c. 8 Ma (Sütő-Szentai 2000; Bakrač et al. 2012; Sebe et al. 2020).
Diagnosis. A species of Pontiadinium with biconical, rhomboidal to subspherical outline, prominent apical horn and small antapical protuberance. A gonyaulacacean tabulation is indicated by trabeculate sutural septa formed by columellae supporting a beaded (micro-nodal) tegillum or possibly by rod-like luxuriae distally joined. Outer surface is scabrate-granulate.
Description. Proximate acavate organic-walled dinoflagellate cyst with biconical, rhomboidal (holotype) to subspherical (paratype) central body outline and with a hollow apical horn (18–10 µm in length) and small antapical (3–6 µm in length) protuberance. Epicyst and hypocyst are of similar size, the equatorial region appearing expanded in anterior polar view (Plate 4, figure 9). Raised trabeculate sutural septa (∼3.5–5 µm in height) are formed by columellae supporting a beaded (micro-nodal) tegillum or possibly by rod-like luxuriae distally joined (e.g. Plate 2, figure 12; Plate 4, figure 12). The sutural septa delineate a standard S-type gonyaulacacean tabulation formula (Plate 4, figures 8–9). The 6″ plate is narrow, triangular in shape and has no contact with the apical plate 4′ (Plate 3, figures 6–8; Plate 4, figures 1, 6). Plate 4′ is longer than 1′ (Plate 3, figures 6–8; Plate 4, figures 1, 6). The precingular archeopyle is pentagonal (type P) with a free operculum formed by the loss of plate 3″ (Plate 3, figure 15; Plate 4, figures 2, 9). The first postcingular plate is a homologue plate (, figure 8) that is located in the broad sulcus. The apical and antapical plate boundaries are sometimes obscured due to elongation of the protuberances. The cyst wall is ∼1.3–1.8 µm thick, with a scabrate-granulate outer surface and smooth inner surface (Plate 3, figures 1–12).
Dimensions. The total length of the cyst body including the apical and antapical protuberances is 69 (77) 118 µm; the equatorial width range is 48 (56) 86 µm. The length of the apical protuberance is 18 (11) 10 µm; the antapical protuberance is ∼3.5 (4.2) 6.0 µm in length. Fifteen specimens were measured including the holotype and paratype from the type stratum at Našice and from the PAET 34P materials. The holotype measurements are: length 77 µm, equatorial width 57 µm, apical protuberance length 11 µm, and antapical protuberance length 3 µm.
Comments and comparisons. Pontiadinium szentaiae sp. nov. differs from all other Pontiadinium taxa by its characteristic well-developed trabeculate septa. The apical and antapical horns of Pontiadinium inequicornutum are usually more elongated than in Pontiadinium szentaiae sp. nov. Pontiadinium obesum has a more rounded outline with much larger equatorial width and shorter height. Pontiadinium szentaiae sp. nov. differs from Impagidinium caspienense in its biconical shape, two distinct polar protuberances, strongly expressed tabulation with distinctive trabeculate septa, and relatively small triangular 6″ plate that is not in contact with apical plate 4′. Plate 4′ is also longer than 1′ in contrast to the equal lengths found in Impagidinium caspienense (Marret et al. 2004). The Middle Miocene gonyaulacoid cyst Unipontidinium may have a comparable wall structure but the septa lack trabeculae or a beaded appearance, the cyst lacks polar protuberances and the cyst body outline is not biconical (Wrenn 1988).
The evolution of the trabeculate sutural septum type within Lake Pannon dinoflagellate cyst assemblages is unclear but low septa with small areas bearing traces of the columellae or rod-like luxuria can be seen in some specimens of Pontiadinium pecsvaradensis (Plate 2, figures 1–2, 9–10). Possibly the raised trabeculate sutural morphological feature in Pontiadinium szentaiae sp. nov. represents its fullest (terminal) development, but we have not found a clear intergradation in septal development from the scattered traces to the end-point continuous septal expression. It is noteworthy, however, that these distinctive sutural septa with columellae or rods appear to be confined to proximate cysts with bipolar protuberances in Lake Pannon.
Derivation of name. In honour of Hungarian palynologist Mária Sütő-Szentai, to acknowledge her pioneering work on Lake Pannon dinoflagellate cysts.
Paratype. Plate 3, figures 9–11, sample B1, slide no. 4 (catalogue number: HGI-VB-1P-NAC-V-B1/4), England Finder coordinate H51, embedded in silicone oil. Housed at Department of Geology, Croatian Geological Survey. Catalogue numbers: HGI-VB-1M-NAC-V-B1 (organic residue), HGI-VB-R-NAC-V-B1 (rock residue).
Holotype and paratype locality. Našice Quarry, Vranović section, 45°27′10.69′′N, 18°2′4.12′′E, Našice, northern Croatia, upper Pannonian (Tortonian), Galeacysta etrusca Zone, Spiniferites cruciformis assemblage, younger than c. 8 Ma (Sütő-Szentai 2000; Bakrač et al. 2012; Sebe et al. 2020).
Diagnosis. A species of Pontiadinium with biconical, rhomboidal to subspherical outline, prominent apical horn and small antapical protuberance. A gonyaulacacean tabulation is indicated by trabeculate sutural septa formed by columellae supporting a beaded (micro-nodal) tegillum or possibly by rod-like luxuriae distally joined. Outer surface is scabrate-granulate.
Description. Proximate acavate organic-walled dinoflagellate cyst with biconical, rhomboidal (holotype) to subspherical (paratype) central body outline and with a hollow apical horn (18–10 µm in length) and small antapical (3–6 µm in length) protuberance. Epicyst and hypocyst are of similar size, the equatorial region appearing expanded in anterior polar view (Plate 4, figure 9). Raised trabeculate sutural septa (∼3.5–5 µm in height) are formed by columellae supporting a beaded (micro-nodal) tegillum or possibly by rod-like luxuriae distally joined (e.g. Plate 2, figure 12; Plate 4, figure 12). The sutural septa delineate a standard S-type gonyaulacacean tabulation formula (Plate 4, figures 8–9). The 6″ plate is narrow, triangular in shape and has no contact with the apical plate 4′ (Plate 3, figures 6–8; Plate 4, figures 1, 6). Plate 4′ is longer than 1′ (Plate 3, figures 6–8; Plate 4, figures 1, 6). The precingular archeopyle is pentagonal (type P) with a free operculum formed by the loss of plate 3″ (Plate 3, figure 15; Plate 4, figures 2, 9). The first postcingular plate is a homologue plate (, figure 8) that is located in the broad sulcus. The apical and antapical plate boundaries are sometimes obscured due to elongation of the protuberances. The cyst wall is ∼1.3–1.8 µm thick, with a scabrate-granulate outer surface and smooth inner surface (Plate 3, figures 1–12).
Dimensions. The total length of the cyst body including the apical and antapical protuberances is 69 (77) 118 µm; the equatorial width range is 48 (56) 86 µm. The length of the apical protuberance is 18 (11) 10 µm; the antapical protuberance is ∼3.5 (4.2) 6.0 µm in length. Fifteen specimens were measured including the holotype and paratype from the type stratum at Našice and from the PAET 34P materials. The holotype measurements are: length 77 µm, equatorial width 57 µm, apical protuberance length 11 µm, and antapical protuberance length 3 µm.
Comments and comparisons. Pontiadinium szentaiae sp. nov. differs from all other Pontiadinium taxa by its characteristic well-developed trabeculate septa. The apical and antapical horns of Pontiadinium inequicornutum are usually more elongated than in Pontiadinium szentaiae sp. nov. Pontiadinium obesum has a more rounded outline with much larger equatorial width and shorter height. Pontiadinium szentaiae sp. nov. differs from Impagidinium caspienense in its biconical shape, two distinct polar protuberances, strongly expressed tabulation with distinctive trabeculate septa, and relatively small triangular 6″ plate that is not in contact with apical plate 4′. Plate 4′ is also longer than 1′ in contrast to the equal lengths found in Impagidinium caspienense (Marret et al. 2004). The Middle Miocene gonyaulacoid cyst Unipontidinium may have a comparable wall structure but the septa lack trabeculae or a beaded appearance, the cyst lacks polar protuberances and the cyst body outline is not biconical (Wrenn 1988).
The evolution of the trabeculate sutural septum type within Lake Pannon dinoflagellate cyst assemblages is unclear but low septa with small areas bearing traces of the columellae or rod-like luxuria can be seen in some specimens of Pontiadinium pecsvaradensis (Plate 2, figures 1–2, 9–10). Possibly the raised trabeculate sutural morphological feature in Pontiadinium szentaiae sp. nov. represents its fullest (terminal) development, but we have not found a clear intergradation in septal development from the scattered traces to the end-point continuous septal expression. It is noteworthy, however, that these distinctive sutural septa with columellae or rods appear to be confined to proximate cysts with bipolar protuberances in Lake Pannon.
Derivation of name. In honour of Hungarian palynologist Mária Sütő-Szentai, to acknowledge her pioneering work on Lake Pannon dinoflagellate cysts.