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Glaphyrocysta turgida
Derivation of name. From Latin turgidus, meaning turgid, distended - with reference to the inflated appearance of this species.
Holotype. Fig. 4 (1); from a core sample at 2884.70 m, well 6305/4-2 S; Central body length 61 μm and width 71 μm (including operculum). Cyst size including processes 99 μm long and 97 μm wide; slide co-ordinate EF. X29/2. Repository of type: NHMUK PM FD 1136.
Type locality. Ormen Lange field, Møre Basin (Norway).
Diagnosis. A species of Glaphyrocysta characterised by the development of numerous non-tabular, elaborate process complexes which are often distinctively expanded distally giving rise to a funnel-shaped structure. The process complexes are either arcuate or linear at their base and have more or less the same length across the entire cyst surface. The expanded portions of the processes interconnect distally creating a dense net of membranous trabeculae covering the entire surface of the cyst (ectophragm). Additionally, characteristic processes with a variety of distal endings (acuminate, capitate, bifid, and irregular bi- and trifurcate) arise either from the central body as individual processes or, more commonly, from the distal-most part of the membranous trabeculae system.
Stratigraphic position. Upper Maastrichtian, Springar Formation.
Dimensions. Central body length without operculum 42(54)61 μm, width 51(61)85 μm. Cyst size including processes 77(89)101 μm, width 68(90)105 μm (20 specimens measured).
Description. Dinoflagellate cysts with subspherical to ellipsoidal central body, dorsoventrally compressed, composed of two closely appressed layers. The endophragm is slightly thicker than the periphragm and has a scabrate to finely granulate surface. It also displays folds that run approximately parallel to the margin of the central body. The periphragm is thin and smooth. The archaeopyle is apical (Type tA), with operculum usually not present, slightly angular and bearing similar ornament to the rest of the cyst (see arrow Fig. 4. 1,2). The tabulation is not expressed. The funnel-shaped process complexes are hollow (see arrow Fig. 4. 4,5) and vary considerably in length and width with well-defined hollows unevenly distributed are present in the membranous trabecular ectophragm.
Comparison. Glaphyrocysta turgida sp. nov. displays a certain degree of similarity with various coeval species from different genera, notably Areoligera, Palynodinium and Riculacysta. However, G. turgida lacks the ring-like arrangement of processes characteristic of the Areoligera species. In Palynodinium, a significant number of the processes are arranged forming two lobes on each side of the ventral surface (Stover and Evitt, 1978). Besides, the tabulation is to some extent reflected in the position of the gonal and intergonal processes. None of the latter features occur in G. turgida. Furthermore, the genus Riculacysta, described by Stover (1977) from the ‘middle’ Oligocene of the North America Atlantic shelf, possesses dorso-ventral processes that are significantly longer than the lateral ones and are arranged into two well-defined lobes. In G. turgida, the processes have a more or less uniform length across the entire surface and do not form lobes. Among other similar Glaphyrocysta species, G. turgida differs from Glaphyrocysta perforata Hultberg and Malmgren, 1985 in having a membranous trabecular ectophragm rather than an entire perforate ectophragm. The informal taxon Glaphyrocysta sp. 1, described by Schiøler et al. (1997, pl. IV, figs. 5–8) from the Maastrichtian of the Netherlands, differs from the new species in having bilobate antapex and solate processes on the dorsal side. Riculacysta shauka, described by Slimani et al. (2012) from the Maastrichtian of northern Morocco, differs from the new species by having a perforate and spinose ectophragm, as well as two antapical lobes, with the left antapical lobe being more pronounced.
Remarks. Although the stratigraphic range of the genus Glaphyrocysta is not well established, according to the abundant published records, its first occurrence is in the Late Cretaceous, probably in the Coniacian or Santonian, reaching its maximum abundance and diversity in the Paleogene (Fensome et al., 2019). In the Møre Basin, some upper Maastrichtian samples are overwhelmingly dominated by this new species, which co-occurs with C. diebelii, Circulodinium distinctum, Palynodinium grallator and Trithyrodinium evittii. The peaks in abundance of Glaphyrocysta together with other areoligeracean genera are characteristic bioevents of the late Maastrichtian.
Holotype. Fig. 4 (1); from a core sample at 2884.70 m, well 6305/4-2 S; Central body length 61 μm and width 71 μm (including operculum). Cyst size including processes 99 μm long and 97 μm wide; slide co-ordinate EF. X29/2. Repository of type: NHMUK PM FD 1136.
Type locality. Ormen Lange field, Møre Basin (Norway).
Diagnosis. A species of Glaphyrocysta characterised by the development of numerous non-tabular, elaborate process complexes which are often distinctively expanded distally giving rise to a funnel-shaped structure. The process complexes are either arcuate or linear at their base and have more or less the same length across the entire cyst surface. The expanded portions of the processes interconnect distally creating a dense net of membranous trabeculae covering the entire surface of the cyst (ectophragm). Additionally, characteristic processes with a variety of distal endings (acuminate, capitate, bifid, and irregular bi- and trifurcate) arise either from the central body as individual processes or, more commonly, from the distal-most part of the membranous trabeculae system.
Stratigraphic position. Upper Maastrichtian, Springar Formation.
Dimensions. Central body length without operculum 42(54)61 μm, width 51(61)85 μm. Cyst size including processes 77(89)101 μm, width 68(90)105 μm (20 specimens measured).
Description. Dinoflagellate cysts with subspherical to ellipsoidal central body, dorsoventrally compressed, composed of two closely appressed layers. The endophragm is slightly thicker than the periphragm and has a scabrate to finely granulate surface. It also displays folds that run approximately parallel to the margin of the central body. The periphragm is thin and smooth. The archaeopyle is apical (Type tA), with operculum usually not present, slightly angular and bearing similar ornament to the rest of the cyst (see arrow Fig. 4. 1,2). The tabulation is not expressed. The funnel-shaped process complexes are hollow (see arrow Fig. 4. 4,5) and vary considerably in length and width with well-defined hollows unevenly distributed are present in the membranous trabecular ectophragm.
Comparison. Glaphyrocysta turgida sp. nov. displays a certain degree of similarity with various coeval species from different genera, notably Areoligera, Palynodinium and Riculacysta. However, G. turgida lacks the ring-like arrangement of processes characteristic of the Areoligera species. In Palynodinium, a significant number of the processes are arranged forming two lobes on each side of the ventral surface (Stover and Evitt, 1978). Besides, the tabulation is to some extent reflected in the position of the gonal and intergonal processes. None of the latter features occur in G. turgida. Furthermore, the genus Riculacysta, described by Stover (1977) from the ‘middle’ Oligocene of the North America Atlantic shelf, possesses dorso-ventral processes that are significantly longer than the lateral ones and are arranged into two well-defined lobes. In G. turgida, the processes have a more or less uniform length across the entire surface and do not form lobes. Among other similar Glaphyrocysta species, G. turgida differs from Glaphyrocysta perforata Hultberg and Malmgren, 1985 in having a membranous trabecular ectophragm rather than an entire perforate ectophragm. The informal taxon Glaphyrocysta sp. 1, described by Schiøler et al. (1997, pl. IV, figs. 5–8) from the Maastrichtian of the Netherlands, differs from the new species in having bilobate antapex and solate processes on the dorsal side. Riculacysta shauka, described by Slimani et al. (2012) from the Maastrichtian of northern Morocco, differs from the new species by having a perforate and spinose ectophragm, as well as two antapical lobes, with the left antapical lobe being more pronounced.
Remarks. Although the stratigraphic range of the genus Glaphyrocysta is not well established, according to the abundant published records, its first occurrence is in the Late Cretaceous, probably in the Coniacian or Santonian, reaching its maximum abundance and diversity in the Paleogene (Fensome et al., 2019). In the Møre Basin, some upper Maastrichtian samples are overwhelmingly dominated by this new species, which co-occurs with C. diebelii, Circulodinium distinctum, Palynodinium grallator and Trithyrodinium evittii. The peaks in abundance of Glaphyrocysta together with other areoligeracean genera are characteristic bioevents of the late Maastrichtian.