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Pyxidinopsis iakovlevae
Pyxidinopsis iakovlevae, Sluijs and Brinkhuis, 2024, p. 452-453, pl. 5.
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Original description: [Sluijs and Brinkhuis, 2024, p. 452-453]:
Pyxidinopsis iakovlevae sp. nov.
Plates 5, 6, S25, 26, 27
Derivation of name. Named for Alina I. Iakovleva, in recognition of her achievements in marine palynology, at the Geological Institute, Russian Academy of Sciences, Moscow, Russian Federation
Diagnosis. A species of Pyxidinopsis, intermediate in size, with a relatively thick, punctate to most often microreticulate surface, characterized by frequent small, solid, irregularly shaped and distributed rod-like features. No other surface ornamentation present. Archeopyle relatively large, precingular, type P (300 only); operculum free. Paratabulation indicated by archeopyle only. No traces of paracingulum or parasulcus.
Holotype. Plate 6, A–C
Paratypes. Plate 5, A–C, D–E, F–H; Plate 6, D–E, F–G
Material. IODP 302 Hole M0004A, Lomonosov Ridge, Arctic Ocean
Type locality and horizon. IODP 302 Hole M0004A, Lomonosov Ridge, Arctic Ocean, upper Eocene, sample 302-4A-27X-3-20/22
Age. Late Paleocene–early Eocene
Description.
Shape: subspherical, almost circular to ovoid in outline.
Wall relationships: autophragm only.
Wall features: a relatively thick autophragm, with a punctate to microreticulate surface, with frequently occurring small, irregularly distributed solid, rod-like features and a maximum height of ∼ 3 µm. These features may be simple and straight to distally T-shaped.
Processes: absent.
Paratabulation: indicated by archeopyle only.
Archeopyle: relatively large, precingular, type P (300 only); operculum free.
Paracingulum: indeterminable.
Parasulcus: indeterminable.
Dimensions. Range: overall diameter 38(45)54 µm (n = 5).
Holotype. 42 µm.
Paratypes. 45 µm.
Stratigraphic range/occurrence. Upper Paleocene–lower Eocene.
Remarks. The original description of Pyxidinopsis does not include any kind of projections, spines, or other possible features on the periphragm (Habib, 1975). Stover and Evitt (1978) noted that the type species, and others in the genus, most often have (micro)reticulated surfaces. Furthermore, several taxa subsequently attributed to Pyxidinopsis, even the type species, P. fairhavenensis (cf. De Verteuil and Norris, 1996), have additional wall features like coni or small projections, but none of them are like those displayed by P. iakovlevae. These features would not support assignment to Operculodinium, since the rod-like extensions are too few and of very low relief compared to the typically longer spines
in taxa of the latter. Attribution to Xenicodinium (Klement, 1960) is refuted, since that genus is even less well defined than Pyxidinopsis (e.g., with an uncertain archeopyle).
----------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Sluijs and Brinkhuis, 2024, p. 452-453]:
Pyxidinopsis iakovlevae sp. nov.
Plates 5, 6, S25, 26, 27
Derivation of name. Named for Alina I. Iakovleva, in recognition of her achievements in marine palynology, at the Geological Institute, Russian Academy of Sciences, Moscow, Russian Federation
Diagnosis. A species of Pyxidinopsis, intermediate in size, with a relatively thick, punctate to most often microreticulate surface, characterized by frequent small, solid, irregularly shaped and distributed rod-like features. No other surface ornamentation present. Archeopyle relatively large, precingular, type P (300 only); operculum free. Paratabulation indicated by archeopyle only. No traces of paracingulum or parasulcus.
Holotype. Plate 6, A–C
Paratypes. Plate 5, A–C, D–E, F–H; Plate 6, D–E, F–G
Material. IODP 302 Hole M0004A, Lomonosov Ridge, Arctic Ocean
Type locality and horizon. IODP 302 Hole M0004A, Lomonosov Ridge, Arctic Ocean, upper Eocene, sample 302-4A-27X-3-20/22
Age. Late Paleocene–early Eocene
Description.
Shape: subspherical, almost circular to ovoid in outline.
Wall relationships: autophragm only.
Wall features: a relatively thick autophragm, with a punctate to microreticulate surface, with frequently occurring small, irregularly distributed solid, rod-like features and a maximum height of ∼ 3 µm. These features may be simple and straight to distally T-shaped.
Processes: absent.
Paratabulation: indicated by archeopyle only.
Archeopyle: relatively large, precingular, type P (300 only); operculum free.
Paracingulum: indeterminable.
Parasulcus: indeterminable.
Dimensions. Range: overall diameter 38(45)54 µm (n = 5).
Holotype. 42 µm.
Paratypes. 45 µm.
Stratigraphic range/occurrence. Upper Paleocene–lower Eocene.
Remarks. The original description of Pyxidinopsis does not include any kind of projections, spines, or other possible features on the periphragm (Habib, 1975). Stover and Evitt (1978) noted that the type species, and others in the genus, most often have (micro)reticulated surfaces. Furthermore, several taxa subsequently attributed to Pyxidinopsis, even the type species, P. fairhavenensis (cf. De Verteuil and Norris, 1996), have additional wall features like coni or small projections, but none of them are like those displayed by P. iakovlevae. These features would not support assignment to Operculodinium, since the rod-like extensions are too few and of very low relief compared to the typically longer spines
in taxa of the latter. Attribution to Xenicodinium (Klement, 1960) is refuted, since that genus is even less well defined than Pyxidinopsis (e.g., with an uncertain archeopyle).