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Explodinium priabonensis
Type locality: Priabona section, northeast Italy
Original diagnosis: Brinkhuis 1994, p. 158-159
A species of Glaphyrocysta that is characterized by its irregularly perforate periphragm, causing a reticulate appearance, with typically aculeate spiny outgrowths. The lenticular to sphaerical shaped endophragm is smooth to faintly granulate. The periphragm is of variable shape and size, and is in contact with the endophragm ventrally. Most specimens display wide separation of the periphragm and endophragm dorsally. Indications of paratabulation are lacking, except for the archaeopyle, parasulcus and paracingulum. The latter is formed by a ventrally located, irregularly shaped rim of the periphragm which is in contact with the endophragm in the parasulcal area (see Fig. 16). Ventrally, the periphragm is supported by solid, slender, irregularly branched processes. The apical archeopyle, which is invariably evident with a detached operculum, reflects the loss of all the apical paraplates.
Dimensions: Central body length: 45-61µm (holotype, 53 µm); width: 39-59 µm (holotype, 44 µm).
Overall length/width: 69-102 µm (holotype, 81-85 µm). Twenty-five specimens were measured.
Occurrence: common to rare.
Observed stratigraphic range: Upper Eocene. Someisolated specimens occur slightly above the LO of
the hantkeninids (=P17/P18 boundary).
Remarks: Glaphyrocysta priabonensis sp. nov. differs from all other species of the genus by its irregularly perforated periphragm with typical aculeate spiny outgrowths. Similar forms have not been reported on in the literature.
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Explodinium priabonensis gen. et comb. nov., emend. nov. Plates I–VIII
1993 Glaphyrocysta sp. Brinkhuis and Biffi (pl. VI, figs. 5–6).
1994 Glaphyrocysta priabonensis Brinkhuis (pl. I, fig. 8, pl. II, figs. 1–8).
2015 Glaphyrocysta priabonensis Bati (pl. IX, fig. 6).
2025 Glaphyrocysta priabonensis Kaya et al. (SI: pl. 4, fig. g).
Remarks: This case may be taken as a good example of the proverbial ‘Murphy’s Law’. As it turns out now, and indicated already above, anno 2025, based on much better-preserved material from the Karaburun section, NW Turkey, relative to the material from central and NE Italy, including the Type Priabonian, the original diagnosis of this species by Brinkhuis and Biffi (1993) and, more significantly, Brinkhuis (1994) is flawed. Moreover, on top of that, and unfortunately, the holotype must be regarded as lost. We therefore establish a neotype (and paratypes) herein and provide a more detailed (emended) description of the species, including its quite extensive morphological variability. In hindsight, apparently impressed by the rather large archaeopyle, combined with the occasionally widely separated wall layers, Brinkhuis (1994) surmised an apical archaeopyle, and from there, interpreted the irregular, but in the case of the holotype, widely separated wall layers as indicative for a morphological relationship to Glaphyrocysta species (e.g., Brinkhuis, 1994, fig. 16). The unusual situation of having compressed walls (and thus absence of cavation) in the area what is here reinterpreted as the dorsal side, added back then to the notion that it concerned a new species of Glaphyrocysta. Indeed, the better-preserved specimens from Karaburun (see pls. I–VII) now allow for a much clearer picture of the peculiar morphology and large morphological variability of this species, both in terms of size as well as in degree of cavation. (Neo)Type locality and horizon: Sample A5969, level 59,69 m, Karaburun section, Turkey (cf. Kaya et al., 2025).
(Neo)Type and paratypes: As noted above, the holotype as figured in Brinkhuis (1994) is lost, and hence a neotype is established here, viz., neotype: Plate I, figs. a–f., sample KR22-S1Y8, slide 2, EF: K42; lodged at Utrecht University, The Netherlands. Further, Brinkhuis (1994) did not assign any paratypes, but we do so herein, viz.: Paratype 1: Plate II, figs. a. f., sample KR22-S1-Y10, slide 1, EF: O9. Paratype 2: Plate III, figs. c–d., and Plate IV, figs. a–d., sample KR22-S3-Y17, slide 1, EF: G19/3, all lodged at Utrecht University, The Netherlands. Studied material: Karaburun section, Turkey (cf. Kaya et al., 2025), and the Priabona and Bressana sections from Italy (cf. Brinkhuis, 1994). Neotype and paratypes are from the ˙Ihsaniye Formation, Karaburun section, subsections KR22-S1 and KR22-S3 of Kaya et al., 2025 (samples KR22-S1-Y8 through KR22-S3-Y17).
Emended diagnosis: An intermediate to large sized species of Explodinium, bearing numerous, often basally to mid-length interconnected, solid-fibroid, distally closed, processes with acuminate to (more typical) bifurcate tips. Typically, no, to little separation occurs between the two walls on the postcingular area likely reflecting 4″’ (i.e. mid-dorsally, symmetrical to 3″), nor are there many processes formed in that sector (i.e., giving a ‘camo-cavate’ impression). This while the cingular-portion adjacent to the archaeopyle margin seems to be reflected by a set of small spines ‘per cingular plate area’ (see e.g., Plate I, figs. e–f., Plate II, figs. e. f.). The wall-separation is highly irregular, as is the degree of cavation, ranging from a few μm to tens of μm.
Emended description:
Shape: Endophragm: Ovoidal. Periphragm: spiny, highly irregular in outline, processes basally to mid-process irregularly connected, with mostly bifurcate terminations.
Wall relationships: The endophragm is except for the middorsal area irregularly overlain by an often perforated, sometimes alveolate periphragm, irregularly disconnecting and giving rise to numerous spiny processes, mostly distally bifurcated.
Wall features: Endophragm smooth, or scabrate to microgranulated, overlain by an irregularly disconnecting periphragm giving rise to numerous spiny processes, or complexes.
Processes: These are typically basally to mid-process irregularly connected, with mostly bifurcate terminations, typically occurring in sets of two (somewhat resembling giving a ‘V’ or ‘victory’ sign with your fingers). In extreme cases, the periphragm is widely separated from the endophragm and processes may be very short (aculeate to bifurcate) in those cases (compare e.g., the illustrations of Brinkhuis (1994), notably pl. II, figs. 1–5, and Plate VIIIherein, all from the type Priabonian sections).
Paratabulation: Indicated by the archaeopyle only, plus perhaps some (para) cingular features (sets of small processes) on the dorsal side, below the archaeopyle margin. Tabulation likely standard (neutral torsion) Gonyaulacean; likely formula 4′, 5–6″, 5c?, 5″, 1p, 1″”.
Archeopyle: Precingular, type P (paraplate 3″), operculum free.
Dimensions: Central body length: 40–77 μm (neotype, 62 μm); width: 35–75 μm (neotype, 63 μm). Overall length/width: 65–115 μm (neotype, 80-90 μm). Thirty-five specimens were measured.
Stratigraphic range: Upper Priabonian (consistent) to lowermost Rupelian (isolated specimens).
Comparison: The morphology of Explodinium priabonense gen. nov. and nov. comb. is quite unique. Some middle to late Eocene forms that e. g., Heilmann-Clausen and Van Simaeys (2005, pl. 2, fig. 12)assigned to ‘Cordosphaeridium aff. callosum’ from the Danish Basin, and/or those that are assigned to ‘Lanternosphaeridium lanosum’ by Iakovleva et al. (2024, pl. 11, fig. 9)from Armenia appear somewhat similar, but lack the detached periphragm, and are much more fibrous in nature. Specimens close to these morphotypes also occur in the present material, and are assigned to Operculodinium cf. hirsutum, (Plate XXIV, figs. c–d) but are quite rare and much longer ranging.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Glaphyrocysta priabonensis Brinkhuis, 1994, has an irregularly perforate periphragm, causing a reticulate appearance, with typically aculeate spiny outgrowths. The periphragm is of variable shape and size and in contact with the endophragm ventrally. In most specimens, the endophragm and periphragm are widely separated dorsally. The paracingulum is formed by a ventrally located, irregularly shaped rim of the periphragm, which is in contact with the endophragm in the parasulcal region. Ventrally the periphragm is supported by solid, slender, irregularly branched processes. Size: central body length 45-61 µm, width 39-59 µm, overall length/width 69-102 µm
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Original diagnosis: Brinkhuis 1994, p. 158-159
A species of Glaphyrocysta that is characterized by its irregularly perforate periphragm, causing a reticulate appearance, with typically aculeate spiny outgrowths. The lenticular to sphaerical shaped endophragm is smooth to faintly granulate. The periphragm is of variable shape and size, and is in contact with the endophragm ventrally. Most specimens display wide separation of the periphragm and endophragm dorsally. Indications of paratabulation are lacking, except for the archaeopyle, parasulcus and paracingulum. The latter is formed by a ventrally located, irregularly shaped rim of the periphragm which is in contact with the endophragm in the parasulcal area (see Fig. 16). Ventrally, the periphragm is supported by solid, slender, irregularly branched processes. The apical archeopyle, which is invariably evident with a detached operculum, reflects the loss of all the apical paraplates.
Dimensions: Central body length: 45-61µm (holotype, 53 µm); width: 39-59 µm (holotype, 44 µm).
Overall length/width: 69-102 µm (holotype, 81-85 µm). Twenty-five specimens were measured.
Occurrence: common to rare.
Observed stratigraphic range: Upper Eocene. Someisolated specimens occur slightly above the LO of
the hantkeninids (=P17/P18 boundary).
Remarks: Glaphyrocysta priabonensis sp. nov. differs from all other species of the genus by its irregularly perforated periphragm with typical aculeate spiny outgrowths. Similar forms have not been reported on in the literature.
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Explodinium priabonensis gen. et comb. nov., emend. nov. Plates I–VIII
1993 Glaphyrocysta sp. Brinkhuis and Biffi (pl. VI, figs. 5–6).
1994 Glaphyrocysta priabonensis Brinkhuis (pl. I, fig. 8, pl. II, figs. 1–8).
2015 Glaphyrocysta priabonensis Bati (pl. IX, fig. 6).
2025 Glaphyrocysta priabonensis Kaya et al. (SI: pl. 4, fig. g).
Remarks: This case may be taken as a good example of the proverbial ‘Murphy’s Law’. As it turns out now, and indicated already above, anno 2025, based on much better-preserved material from the Karaburun section, NW Turkey, relative to the material from central and NE Italy, including the Type Priabonian, the original diagnosis of this species by Brinkhuis and Biffi (1993) and, more significantly, Brinkhuis (1994) is flawed. Moreover, on top of that, and unfortunately, the holotype must be regarded as lost. We therefore establish a neotype (and paratypes) herein and provide a more detailed (emended) description of the species, including its quite extensive morphological variability. In hindsight, apparently impressed by the rather large archaeopyle, combined with the occasionally widely separated wall layers, Brinkhuis (1994) surmised an apical archaeopyle, and from there, interpreted the irregular, but in the case of the holotype, widely separated wall layers as indicative for a morphological relationship to Glaphyrocysta species (e.g., Brinkhuis, 1994, fig. 16). The unusual situation of having compressed walls (and thus absence of cavation) in the area what is here reinterpreted as the dorsal side, added back then to the notion that it concerned a new species of Glaphyrocysta. Indeed, the better-preserved specimens from Karaburun (see pls. I–VII) now allow for a much clearer picture of the peculiar morphology and large morphological variability of this species, both in terms of size as well as in degree of cavation. (Neo)Type locality and horizon: Sample A5969, level 59,69 m, Karaburun section, Turkey (cf. Kaya et al., 2025).
(Neo)Type and paratypes: As noted above, the holotype as figured in Brinkhuis (1994) is lost, and hence a neotype is established here, viz., neotype: Plate I, figs. a–f., sample KR22-S1Y8, slide 2, EF: K42; lodged at Utrecht University, The Netherlands. Further, Brinkhuis (1994) did not assign any paratypes, but we do so herein, viz.: Paratype 1: Plate II, figs. a. f., sample KR22-S1-Y10, slide 1, EF: O9. Paratype 2: Plate III, figs. c–d., and Plate IV, figs. a–d., sample KR22-S3-Y17, slide 1, EF: G19/3, all lodged at Utrecht University, The Netherlands. Studied material: Karaburun section, Turkey (cf. Kaya et al., 2025), and the Priabona and Bressana sections from Italy (cf. Brinkhuis, 1994). Neotype and paratypes are from the ˙Ihsaniye Formation, Karaburun section, subsections KR22-S1 and KR22-S3 of Kaya et al., 2025 (samples KR22-S1-Y8 through KR22-S3-Y17).
Emended diagnosis: An intermediate to large sized species of Explodinium, bearing numerous, often basally to mid-length interconnected, solid-fibroid, distally closed, processes with acuminate to (more typical) bifurcate tips. Typically, no, to little separation occurs between the two walls on the postcingular area likely reflecting 4″’ (i.e. mid-dorsally, symmetrical to 3″), nor are there many processes formed in that sector (i.e., giving a ‘camo-cavate’ impression). This while the cingular-portion adjacent to the archaeopyle margin seems to be reflected by a set of small spines ‘per cingular plate area’ (see e.g., Plate I, figs. e–f., Plate II, figs. e. f.). The wall-separation is highly irregular, as is the degree of cavation, ranging from a few μm to tens of μm.
Emended description:
Shape: Endophragm: Ovoidal. Periphragm: spiny, highly irregular in outline, processes basally to mid-process irregularly connected, with mostly bifurcate terminations.
Wall relationships: The endophragm is except for the middorsal area irregularly overlain by an often perforated, sometimes alveolate periphragm, irregularly disconnecting and giving rise to numerous spiny processes, mostly distally bifurcated.
Wall features: Endophragm smooth, or scabrate to microgranulated, overlain by an irregularly disconnecting periphragm giving rise to numerous spiny processes, or complexes.
Processes: These are typically basally to mid-process irregularly connected, with mostly bifurcate terminations, typically occurring in sets of two (somewhat resembling giving a ‘V’ or ‘victory’ sign with your fingers). In extreme cases, the periphragm is widely separated from the endophragm and processes may be very short (aculeate to bifurcate) in those cases (compare e.g., the illustrations of Brinkhuis (1994), notably pl. II, figs. 1–5, and Plate VIIIherein, all from the type Priabonian sections).
Paratabulation: Indicated by the archaeopyle only, plus perhaps some (para) cingular features (sets of small processes) on the dorsal side, below the archaeopyle margin. Tabulation likely standard (neutral torsion) Gonyaulacean; likely formula 4′, 5–6″, 5c?, 5″, 1p, 1″”.
Archeopyle: Precingular, type P (paraplate 3″), operculum free.
Dimensions: Central body length: 40–77 μm (neotype, 62 μm); width: 35–75 μm (neotype, 63 μm). Overall length/width: 65–115 μm (neotype, 80-90 μm). Thirty-five specimens were measured.
Stratigraphic range: Upper Priabonian (consistent) to lowermost Rupelian (isolated specimens).
Comparison: The morphology of Explodinium priabonense gen. nov. and nov. comb. is quite unique. Some middle to late Eocene forms that e. g., Heilmann-Clausen and Van Simaeys (2005, pl. 2, fig. 12)assigned to ‘Cordosphaeridium aff. callosum’ from the Danish Basin, and/or those that are assigned to ‘Lanternosphaeridium lanosum’ by Iakovleva et al. (2024, pl. 11, fig. 9)from Armenia appear somewhat similar, but lack the detached periphragm, and are much more fibrous in nature. Specimens close to these morphotypes also occur in the present material, and are assigned to Operculodinium cf. hirsutum, (Plate XXIV, figs. c–d) but are quite rare and much longer ranging.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Glaphyrocysta priabonensis Brinkhuis, 1994, has an irregularly perforate periphragm, causing a reticulate appearance, with typically aculeate spiny outgrowths. The periphragm is of variable shape and size and in contact with the endophragm ventrally. In most specimens, the endophragm and periphragm are widely separated dorsally. The paracingulum is formed by a ventrally located, irregularly shaped rim of the periphragm, which is in contact with the endophragm in the parasulcal region. Ventrally the periphragm is supported by solid, slender, irregularly branched processes. Size: central body length 45-61 µm, width 39-59 µm, overall length/width 69-102 µm
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