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Fibrocysta brevispinosa
Fibrocysta brevispinosa Slimani et al., 2012, p.346–347, fig.6A–F.
Holotype: Slimani et al., 2012, figs.6A–C.
Age: early Danian.
Original description (Slimani et al., 2012):
Fibrocysta brevispinosa sp. nov. (Fig. 6A–F)
1996 Fibrocysta sp. A; Brinkhuis & Schiøler, pp. 195, 211, pl. 1, fig. 8.
2010 Fibrocysta sp. A of Brinkhuis & Schiøler (1996); Slimani et al., p. 103, pl. 4, figs 1, 2.
Holotype. Sample OH 14, slide 2, England Finder G36/3 (Fig. 6A–C).
Type locality and bed. Ouled Haddou section, north of Taza, northern Morocco; marl 50 cm above the K/ T boundary, lower Danian.
Etymology. From ‘brevis’ (Latin): short, and ‘spina’ (Latin): thorn; with reference to the short processes.
Diagnosis. Thick-walled Fibrocysta species with a microreticulate surface and characteristic short processes. The archeopyle is the only indication of tabulation.
Description. The proximate dinoflagellate cyst has an ovoid body and two short apical and antapical horns. The wall consists of a smooth and thick endophragm (maximum thickness 4 µm), which is closely appressed to a thin, microreticulate periphragm with a maximum thickness of 0.5 µm (Fig. 6A, B). The number of processes is usually between 50 and 60, and they are more or less regularly distributed over the surface of the cyst. The processes are 3 µm in maximum width. The processes are simple and solid with truncated to slightly expanded distal ends. The distinct apical and antapical horns are solid and microreticulate, and sporadically bear a few short processes (Fig. 6B). The precingular (type P) archeopyle has a pentagonal outline and is formed by release of plate 3’’ (Fig. 6E). The operculum is free.
Dimensions. Holotype: central body length, 70 µm; central body width, 66 µm; apical horn length, 17 µm; antapical horn length, 5 µm; maximum process length, 5 µm. Range: central body length, 55(69)80 µm; central body width, 55(65)70 µm; average length of apical horn, 8–17 µm; average length of antapical horn, 5–7 µm; average length of processes, 1(5)8 µm (10 specimens measured).
Remarks. Fibrocysta brevispinosa sp. nov. is conspecific with Fibrocysta sp. A of Brinkhuis & Schiøler (1996, pp. 195, 211, pl. 1, fig. 8). The new species differs from all other Fibrocysta species mainly by its short processes. It differs from Fibrocysta axialis (Eisenack, 1965) Stover & Evitt, 1978, in having much shorter processes, and apical and antapical horns locally ornamented with a few short processes, rather than branched distinct processes. Fibrocysta lappacea (Drugg, 1970) Stover & Evitt, 1978 differs by its larger size and densely distributed fibrous and thin processes. The Paleocene specimen assigned to Fibrocysta lappacea by Soncini & Rauscher (1988, p. 443, pl. 2, fig. 10) may be similar to the new species based on its short, densely spaced processes. Exochosphaeridium brevitruncatum Slimani, 1994 also possesses short processes, but differs by its smaller size and the absence of a distinct antapical horn. Carpatella truncata Willumsen, 2004 resembles Fibrocysta brevispinosa sp. nov. in having apical and antapical horns and short processes, but differs by its spongy wall, fewer and tabular processes (one per plate), and the presence of a cingulum marked by a thick fibrous ridge.
Stratigraphic occurrence. Samples OH 0–19, planktic foraminiferal Abathomphalus mayaroensis Zone (upper Maastrichtian), Guembelitria cretacea and Parvularugoglobigerina eugubina zones (lower Danian), Ouled Haddou section; lower Danian of the Geulhemmerberg caves, Limbourg, SE Netherlands (Brinkhuis & Schiøler 1996); uppermost Maastrichtian of the Turnhout borehole (personal observation, H. Slimani) and Danian of the Meer borehole (Slimani et al. 2011), northwestern Belgium.
Holotype: Slimani et al., 2012, figs.6A–C.
Age: early Danian.
Original description (Slimani et al., 2012):
Fibrocysta brevispinosa sp. nov. (Fig. 6A–F)
1996 Fibrocysta sp. A; Brinkhuis & Schiøler, pp. 195, 211, pl. 1, fig. 8.
2010 Fibrocysta sp. A of Brinkhuis & Schiøler (1996); Slimani et al., p. 103, pl. 4, figs 1, 2.
Holotype. Sample OH 14, slide 2, England Finder G36/3 (Fig. 6A–C).
Type locality and bed. Ouled Haddou section, north of Taza, northern Morocco; marl 50 cm above the K/ T boundary, lower Danian.
Etymology. From ‘brevis’ (Latin): short, and ‘spina’ (Latin): thorn; with reference to the short processes.
Diagnosis. Thick-walled Fibrocysta species with a microreticulate surface and characteristic short processes. The archeopyle is the only indication of tabulation.
Description. The proximate dinoflagellate cyst has an ovoid body and two short apical and antapical horns. The wall consists of a smooth and thick endophragm (maximum thickness 4 µm), which is closely appressed to a thin, microreticulate periphragm with a maximum thickness of 0.5 µm (Fig. 6A, B). The number of processes is usually between 50 and 60, and they are more or less regularly distributed over the surface of the cyst. The processes are 3 µm in maximum width. The processes are simple and solid with truncated to slightly expanded distal ends. The distinct apical and antapical horns are solid and microreticulate, and sporadically bear a few short processes (Fig. 6B). The precingular (type P) archeopyle has a pentagonal outline and is formed by release of plate 3’’ (Fig. 6E). The operculum is free.
Dimensions. Holotype: central body length, 70 µm; central body width, 66 µm; apical horn length, 17 µm; antapical horn length, 5 µm; maximum process length, 5 µm. Range: central body length, 55(69)80 µm; central body width, 55(65)70 µm; average length of apical horn, 8–17 µm; average length of antapical horn, 5–7 µm; average length of processes, 1(5)8 µm (10 specimens measured).
Remarks. Fibrocysta brevispinosa sp. nov. is conspecific with Fibrocysta sp. A of Brinkhuis & Schiøler (1996, pp. 195, 211, pl. 1, fig. 8). The new species differs from all other Fibrocysta species mainly by its short processes. It differs from Fibrocysta axialis (Eisenack, 1965) Stover & Evitt, 1978, in having much shorter processes, and apical and antapical horns locally ornamented with a few short processes, rather than branched distinct processes. Fibrocysta lappacea (Drugg, 1970) Stover & Evitt, 1978 differs by its larger size and densely distributed fibrous and thin processes. The Paleocene specimen assigned to Fibrocysta lappacea by Soncini & Rauscher (1988, p. 443, pl. 2, fig. 10) may be similar to the new species based on its short, densely spaced processes. Exochosphaeridium brevitruncatum Slimani, 1994 also possesses short processes, but differs by its smaller size and the absence of a distinct antapical horn. Carpatella truncata Willumsen, 2004 resembles Fibrocysta brevispinosa sp. nov. in having apical and antapical horns and short processes, but differs by its spongy wall, fewer and tabular processes (one per plate), and the presence of a cingulum marked by a thick fibrous ridge.
Stratigraphic occurrence. Samples OH 0–19, planktic foraminiferal Abathomphalus mayaroensis Zone (upper Maastrichtian), Guembelitria cretacea and Parvularugoglobigerina eugubina zones (lower Danian), Ouled Haddou section; lower Danian of the Geulhemmerberg caves, Limbourg, SE Netherlands (Brinkhuis & Schiøler 1996); uppermost Maastrichtian of the Turnhout borehole (personal observation, H. Slimani) and Danian of the Meer borehole (Slimani et al. 2011), northwestern Belgium.