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Guersteinia
Guersteinia, Sluijs and Brinkhuis, 2024, p. 454-455.
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Original description: [Sluijs and Brinkhuis, 2024, p. 454-455]:
Guersteinia gen. nov.
Type species.
Guersteinia delicata comb. nov. Williams and Downie (1966), p. 235, Pl. 26, Fig. 8
Basionyms.
Thalassiphora delicata (Williams and Downie, 1966)
Disphaeria delicata (Norvick, 1973)
Thalassiphora delicata (Eaton, 1976)
Thalassiphora delicata (Lentin and Williams, 1977)
Thalassiphora delicata (Bujak in Bujak et al., 1980)
Derivation of name. Named for G. Raquel Guerstein in recognition of her achievements in marine palynology, at the Instituto Geológico del Sur (INGEOSUR), Departamento de Geología, Bahia Blanca, Argentina.
Diagnosis. Guersteinia accommodates intermediate to large, thin-walled, camocavate, non-cribroperidinioid sexiform gonyaulacoid cysts. The small endocyst is subspherical to ellipsoidal, and the dorso-ventrally compressed, often partially tabulated periphragm is connected to the endocyst dorsally but strongly separated ventrally. It forms an umbrellalike structure. Archeopyle is precingular, formed by the detachment of paraplate 3”. Operculum free.
Description.
Shape: central body (endophragm) and periphragm appear subspherical from a dorsal and ventral view, which is how it is typically oriented in slides for light microscopy.
Wall relationships: cysts camocavate. Endophragm and periphragm are appressed in the mid-dorsal area but strongly separated ventrally so that the dorso-ventrally compressed periphragm forms an umbrella-like structure.
Wall features: endophragm typically thin and smooth, occasionally scabrate. Parasutural features (e.g., traces or
low ridges) are often present on the periphragm. Major paraplate boundaries appear to be at least partially reflected, indicating a standard symmetric gonyaulacoid pattern, i.e., not cribroperidinioid displaying dextral torsion.
Processes: absent.
Paratabulation: often at least partially indicated by parasutural septa and/or low ridges on the periphragm, delineating a standard symmetric sexiform gonyaulacoid tabulation.
Archeopyle: type P (3” only), detached.
Paracingulum: often indicated by parasutural features on the periphragm.
Parasulcus: typically indicated by parasutural ridges on the periphragm.
Size: intermediate to very large.
Re-attributed species.
Guersteinia delicata gen et comb. nov. Plate S17, S41
Guersteinia lacunata (Vieira et al., 2018) comb. nov.
Guersteinia succincta (Morgenroth, 1966) comb. nov.
Remarks. In a recent paper, Mudie et al. (2020) discussed wall relationships within species of Thalassiphora at length while describing T. subreticulata and T. balcaniensis. They provide a detailed overview of all “accepted” species included in the index of Fensome et al. (2019), noting differences in wall structure, size range, type location, and age (see their Table 2, p. 260). Importantly, in that study, the authors follow Fensome et al. (1993), who regard Thalassiphora as a part of the subfamily Cribroperidinioideae of the family Gonyaulacaceae. This subfamily is mainly characterized by having an “offset” hypocyst, reflecting “dextral torsion” relative to the “symmetric” sexiform gonyaulacoids. However,
Mudie et al. (2020, p. 257) also note that, on some specimens, where visible, T. balcaniensis may be in fact be characterized as reflecting standard gonyaulacean organization rather than being cribroperidinioid. Moreover, they note that, within typical Thalassiphora, i.e., as in the type species T. pelagica and allies, the wall structures are typically thick, fibrous, and without clear reflection of paratabulation. In addition, these taxa often also show an antapical protrusion of some kind.
In the ACEX material, specimens assignable to T. delicata are numerous. While we can mention large variability in overall size, all these specimens may be characterized by having a distinctly thin endophragm and periphragm, with the latter showing clear paratabulation (Plate S17 and SEM image Plate S41, g). The reflected pattern is somewhat difficult to interpret because of the massive “inflation” of the periphragm. However, the typical sexiform organization of the sulcal plates and 1”” may often be discerned, and, from there, it follows that epicystal major plate sutures are reflected as well. Importantly, this taxon does not display the dextral torsion of the hypocyst relative to the epicyst that is characteristic of the cribroperidinioid lineage but rather a standard gonyaulacoid. Furthermore, its (thin) wall, the absence of an antapical protrusion, and the well-reflected paratabulation setit apart from Thalassiphora and its type species T. pelagica (Eisenack and Gocht, 1960) and from the many morphologically related genera such as Muratodinium, Cordosphaeridium, Ifecysta, and Damassadinium. Hence, based on the standard sexiform gonyaulacoid paratabulation reflected on the periphragm of the many recorded specimens of T. delicata and on the holotype (Williams and Downie, 1966, p. 235, Pl. 26, Fig. 8, refigured in Bujak et al., 1980, Pl. 8, Fig. 10) and its typical transparent, thin walls, we conclude that these aspects do not match the definition of the genus Thalassiphora. We therefore erect Guersteinia to accommodate this
widely recorded taxon.
Recently, Vieira et al. (2018) described Thalassiphora lacunata from the Paleocene of NW Europe, a taxon they already considered to be morphologically closely related to delicata. Indeed, we concur, and we attribute that species here to Guersteinia.
Differential diagnosis. Guersteinia differs from Thalassiphora in its standard sexiform plate organization rather than the dextral torsion as recorded in all taxa within the cribroperidinioid lineage. The periphragm of Guersteinia is typically larger than its endocyst and is dorso-ventrally compressed, which sets it apart from Lophocysta (Manum, 1979). It differs from Invertocysta (Edwards, 1984) by the dorsally appressed endophragm and periphragm, rather than vice versa.
There are more thin-walled cavate gonyaulacoid taxa currently assigned to Thalassiphora, like T. rota (Schiøler,
2005), that clearly lack the typical overall features manifest for the former genus. Other superficially similar cavate gonyaulacoid taxa have been placed in other genera (either formally or in “open nomenclature”), e.g., Invertocysta, Gelatia, Saturnodinium, Dalella, and Lophocysta and perhaps even Aiora and likely others. For these, further studiesshould confirm a more precise allocation.
------------------------------------------------------------------------------------------------------
Original description: [Sluijs and Brinkhuis, 2024, p. 454-455]:
Guersteinia gen. nov.
Type species.
Guersteinia delicata comb. nov. Williams and Downie (1966), p. 235, Pl. 26, Fig. 8
Basionyms.
Thalassiphora delicata (Williams and Downie, 1966)
Disphaeria delicata (Norvick, 1973)
Thalassiphora delicata (Eaton, 1976)
Thalassiphora delicata (Lentin and Williams, 1977)
Thalassiphora delicata (Bujak in Bujak et al., 1980)
Derivation of name. Named for G. Raquel Guerstein in recognition of her achievements in marine palynology, at the Instituto Geológico del Sur (INGEOSUR), Departamento de Geología, Bahia Blanca, Argentina.
Diagnosis. Guersteinia accommodates intermediate to large, thin-walled, camocavate, non-cribroperidinioid sexiform gonyaulacoid cysts. The small endocyst is subspherical to ellipsoidal, and the dorso-ventrally compressed, often partially tabulated periphragm is connected to the endocyst dorsally but strongly separated ventrally. It forms an umbrellalike structure. Archeopyle is precingular, formed by the detachment of paraplate 3”. Operculum free.
Description.
Shape: central body (endophragm) and periphragm appear subspherical from a dorsal and ventral view, which is how it is typically oriented in slides for light microscopy.
Wall relationships: cysts camocavate. Endophragm and periphragm are appressed in the mid-dorsal area but strongly separated ventrally so that the dorso-ventrally compressed periphragm forms an umbrella-like structure.
Wall features: endophragm typically thin and smooth, occasionally scabrate. Parasutural features (e.g., traces or
low ridges) are often present on the periphragm. Major paraplate boundaries appear to be at least partially reflected, indicating a standard symmetric gonyaulacoid pattern, i.e., not cribroperidinioid displaying dextral torsion.
Processes: absent.
Paratabulation: often at least partially indicated by parasutural septa and/or low ridges on the periphragm, delineating a standard symmetric sexiform gonyaulacoid tabulation.
Archeopyle: type P (3” only), detached.
Paracingulum: often indicated by parasutural features on the periphragm.
Parasulcus: typically indicated by parasutural ridges on the periphragm.
Size: intermediate to very large.
Re-attributed species.
Guersteinia delicata gen et comb. nov. Plate S17, S41
Guersteinia lacunata (Vieira et al., 2018) comb. nov.
Guersteinia succincta (Morgenroth, 1966) comb. nov.
Remarks. In a recent paper, Mudie et al. (2020) discussed wall relationships within species of Thalassiphora at length while describing T. subreticulata and T. balcaniensis. They provide a detailed overview of all “accepted” species included in the index of Fensome et al. (2019), noting differences in wall structure, size range, type location, and age (see their Table 2, p. 260). Importantly, in that study, the authors follow Fensome et al. (1993), who regard Thalassiphora as a part of the subfamily Cribroperidinioideae of the family Gonyaulacaceae. This subfamily is mainly characterized by having an “offset” hypocyst, reflecting “dextral torsion” relative to the “symmetric” sexiform gonyaulacoids. However,
Mudie et al. (2020, p. 257) also note that, on some specimens, where visible, T. balcaniensis may be in fact be characterized as reflecting standard gonyaulacean organization rather than being cribroperidinioid. Moreover, they note that, within typical Thalassiphora, i.e., as in the type species T. pelagica and allies, the wall structures are typically thick, fibrous, and without clear reflection of paratabulation. In addition, these taxa often also show an antapical protrusion of some kind.
In the ACEX material, specimens assignable to T. delicata are numerous. While we can mention large variability in overall size, all these specimens may be characterized by having a distinctly thin endophragm and periphragm, with the latter showing clear paratabulation (Plate S17 and SEM image Plate S41, g). The reflected pattern is somewhat difficult to interpret because of the massive “inflation” of the periphragm. However, the typical sexiform organization of the sulcal plates and 1”” may often be discerned, and, from there, it follows that epicystal major plate sutures are reflected as well. Importantly, this taxon does not display the dextral torsion of the hypocyst relative to the epicyst that is characteristic of the cribroperidinioid lineage but rather a standard gonyaulacoid. Furthermore, its (thin) wall, the absence of an antapical protrusion, and the well-reflected paratabulation setit apart from Thalassiphora and its type species T. pelagica (Eisenack and Gocht, 1960) and from the many morphologically related genera such as Muratodinium, Cordosphaeridium, Ifecysta, and Damassadinium. Hence, based on the standard sexiform gonyaulacoid paratabulation reflected on the periphragm of the many recorded specimens of T. delicata and on the holotype (Williams and Downie, 1966, p. 235, Pl. 26, Fig. 8, refigured in Bujak et al., 1980, Pl. 8, Fig. 10) and its typical transparent, thin walls, we conclude that these aspects do not match the definition of the genus Thalassiphora. We therefore erect Guersteinia to accommodate this
widely recorded taxon.
Recently, Vieira et al. (2018) described Thalassiphora lacunata from the Paleocene of NW Europe, a taxon they already considered to be morphologically closely related to delicata. Indeed, we concur, and we attribute that species here to Guersteinia.
Differential diagnosis. Guersteinia differs from Thalassiphora in its standard sexiform plate organization rather than the dextral torsion as recorded in all taxa within the cribroperidinioid lineage. The periphragm of Guersteinia is typically larger than its endocyst and is dorso-ventrally compressed, which sets it apart from Lophocysta (Manum, 1979). It differs from Invertocysta (Edwards, 1984) by the dorsally appressed endophragm and periphragm, rather than vice versa.
There are more thin-walled cavate gonyaulacoid taxa currently assigned to Thalassiphora, like T. rota (Schiøler,
2005), that clearly lack the typical overall features manifest for the former genus. Other superficially similar cavate gonyaulacoid taxa have been placed in other genera (either formally or in “open nomenclature”), e.g., Invertocysta, Gelatia, Saturnodinium, Dalella, and Lophocysta and perhaps even Aiora and likely others. For these, further studiesshould confirm a more precise allocation.