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Riculacysta shauka
Riculacysta shauka Slimani et al., 2012, p.348–349, fig.7A–I. Holotype: Slimani et al., 2012, fig.7A–E. Age: late Maastrichtian–Thanetian.
Original description (Slimani et al., 2012)
Holotype. Sample OH 17, slide 2, England Finder F58/2 (Fig. 7A–E).
Type locality and bed. Ouled Haddou section, north of Taza, northern Morocco; marl 65 cm above the K/T boundary, lower Danian.
Etymology. From ‘shauki’ (Arabic): spiny, with reference to the small pointed spines on the ectophragm.
Diagnosis. A species of Riculacysta characterized by a pronounced left antapical lobe and an ectophragm with variable perforation, bearing aligned spines indicating tabulation on dorsal surface. Ectophragm closely appressed to central body dorsally, but separated from it and supported by processes at lateral margins. Apical archeopyle is of type (tA); operculum free.
Description. The skolochorate dinoflagellate cyst is slightly compressed dorsoventrally and has a lenticular to subcircular central body outline. The left antapical lobe is pronounced whereas the right antapical lobe is reduced or absent. The autophragm is granular and has a maximum thickness of 1 μm. The central body bears on its lateral margins solid, non-tabular processes of varying thickness. The processes are unevenly distributed, proximally isolated and distally confluent with the ectophragm. The perforations of the ectophragm are rare to abundant from specimen to specimen. On the other hand these perforations are more abundant towards the distal margins of the ectophragm on a single specimen. The ectophragm is closely appressed to the autophragm on the dorsal surface, and becomes separated from the autophragm at a circumferential zone where it is supported by processes, and extends outwards to form a veil. The margin of the veil is commonly curved distally towards the ventral surface (Fig. 7E, I). It terminates with an entire to undulate or echinate distal margin (Fig. 7E). Where the ectophram is strongly perforated, its distal margin is commonly jagged (Fig. 7H, I). The ectophram bears small spines, which are solid, conical and simple to bifurcate. The spines may be aligned and then reflect a tabulation (Fig. 7A, F). On well-preserved specimens, the ectophragm forms two unequal antapical lobes (Fig. 7C, D). The processes, spines and ectophragm are absent on the ventral surface of the cyst (Fig. 7D, H). The apical archeopyle is of type (tA) and has a zig-zag margin. The simple operculum is mostly free.
Dimensions. Holotype: length of central body (without operculum), 60 μm; width of central body, 60 μm; overall length (without operculum), 80 μm; overall width, 85 μm; Range: length of central body (without operculum), 42(55)62 μm; width of central body, 54(62)74 μm; overall length (without operculum), 55(69)85 μm; overall width, 64(79)93 μm; average length of spines, 2–8 μm (10 specimens measured).
Remarks. Riculacysta chaouka sp. nov. is characterized by its perforate and spiny ectophragm. The number of perforations on the ectophragm is typically variable. The new species is conspecific with Riculacysta sp. of Soncini & Rauscher, forme ‘Cyclonephelium expansum’ of Soncini and possibly with Riculacysta sp. of Kirsch 1991 in having an ectophragm with spines, which indicates a tabulation on the dorsal surface. Riculacysta perforata Stover, 1977 resembles some specimens of the new species in having a perforate ectophragm, but differs in lacking the two antapical lobes on its central body and spines on the ectophragm.
Stratigraphic occurrence. Samples OH 0–19, planktic foraminiferal Abathomphalus mayaroensis Zone (upper Maastrichtian), Guembelitria cretacea and Parvularugoglobigerina eugubina zones (lower Danian), Ouled Haddou section; Danian–Thanetian of the Moroccan Phosphate Plateau (Soncini & Rauscher 1988,Soncini 1990); and upper Maastrichtian of southern Germany (Kirsch 1991).
Original description (Slimani et al., 2012)
Holotype. Sample OH 17, slide 2, England Finder F58/2 (Fig. 7A–E).
Type locality and bed. Ouled Haddou section, north of Taza, northern Morocco; marl 65 cm above the K/T boundary, lower Danian.
Etymology. From ‘shauki’ (Arabic): spiny, with reference to the small pointed spines on the ectophragm.
Diagnosis. A species of Riculacysta characterized by a pronounced left antapical lobe and an ectophragm with variable perforation, bearing aligned spines indicating tabulation on dorsal surface. Ectophragm closely appressed to central body dorsally, but separated from it and supported by processes at lateral margins. Apical archeopyle is of type (tA); operculum free.
Description. The skolochorate dinoflagellate cyst is slightly compressed dorsoventrally and has a lenticular to subcircular central body outline. The left antapical lobe is pronounced whereas the right antapical lobe is reduced or absent. The autophragm is granular and has a maximum thickness of 1 μm. The central body bears on its lateral margins solid, non-tabular processes of varying thickness. The processes are unevenly distributed, proximally isolated and distally confluent with the ectophragm. The perforations of the ectophragm are rare to abundant from specimen to specimen. On the other hand these perforations are more abundant towards the distal margins of the ectophragm on a single specimen. The ectophragm is closely appressed to the autophragm on the dorsal surface, and becomes separated from the autophragm at a circumferential zone where it is supported by processes, and extends outwards to form a veil. The margin of the veil is commonly curved distally towards the ventral surface (Fig. 7E, I). It terminates with an entire to undulate or echinate distal margin (Fig. 7E). Where the ectophram is strongly perforated, its distal margin is commonly jagged (Fig. 7H, I). The ectophram bears small spines, which are solid, conical and simple to bifurcate. The spines may be aligned and then reflect a tabulation (Fig. 7A, F). On well-preserved specimens, the ectophragm forms two unequal antapical lobes (Fig. 7C, D). The processes, spines and ectophragm are absent on the ventral surface of the cyst (Fig. 7D, H). The apical archeopyle is of type (tA) and has a zig-zag margin. The simple operculum is mostly free.
Dimensions. Holotype: length of central body (without operculum), 60 μm; width of central body, 60 μm; overall length (without operculum), 80 μm; overall width, 85 μm; Range: length of central body (without operculum), 42(55)62 μm; width of central body, 54(62)74 μm; overall length (without operculum), 55(69)85 μm; overall width, 64(79)93 μm; average length of spines, 2–8 μm (10 specimens measured).
Remarks. Riculacysta chaouka sp. nov. is characterized by its perforate and spiny ectophragm. The number of perforations on the ectophragm is typically variable. The new species is conspecific with Riculacysta sp. of Soncini & Rauscher, forme ‘Cyclonephelium expansum’ of Soncini and possibly with Riculacysta sp. of Kirsch 1991 in having an ectophragm with spines, which indicates a tabulation on the dorsal surface. Riculacysta perforata Stover, 1977 resembles some specimens of the new species in having a perforate ectophragm, but differs in lacking the two antapical lobes on its central body and spines on the ectophragm.
Stratigraphic occurrence. Samples OH 0–19, planktic foraminiferal Abathomphalus mayaroensis Zone (upper Maastrichtian), Guembelitria cretacea and Parvularugoglobigerina eugubina zones (lower Danian), Ouled Haddou section; Danian–Thanetian of the Moroccan Phosphate Plateau (Soncini & Rauscher 1988,Soncini 1990); and upper Maastrichtian of southern Germany (Kirsch 1991).