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Membranilarnacia wilsonii
Membranilarnacia wilsonii Pearce, 2010, p.66, pl.5, figs.1–3.
Holotype: Pearce, 2010, pl.5. figs.1–3.
Type locality and horizon. Trunch borehole, Norfolk, UK; 419.9–420.0 m, Burnham–Flamborough Chalk (undifferentiated), mid-Micraster cortestudinarium Zone (mid-lower Coniacian).
Age: early Coniacian–early Campanian.
Diagnosis. A species of Membranilarnacia with a thin ectophragm supported by a large number of fine supporting processes.
Original description (Pearce, 2010): Small to medium-sized cavate dinoflagellate with a sub-spherical central body. The central body is comprised of a thin autophragm (w0.5 μm) that forms numerous thin, solid, non-tabular processes that support a thin, smooth to finely reticulate ectophragm. The processes are linked proximally forming an irregular polygonal reticulum of variable size and shape. Processes not obviously concentrated on the hypocyst but where they appear to be thicker. The archaeopyle is apical (Type tA, the operculum may be attached, but more usually detached), formed by the loss of all apical paraplates.but where they appear to be thicker. The archaeopyle is apical (Type tA, the operculum may be attached, but more usually detached), formed by the loss of all apical paraplates.
Comparison. Many species of Membranilarnacia possess a particularly thin ectophragm but differ from M. wilsonii sp. nov. by possessing stronger, better developed processes. Membranilarnacia? picena Biffi & Manum, 1988 (190, 192, pl. 7, figs 1–3, 5–7, 9, 12) also possesses a thin veil-like ectophragm but differs in possessing a thicker spongy to externally pitted autophragm. Membranilarnacia polycladiata Cookson & Eisenack in Eisenack (1963b) (Cookson & Eisenack, 1958: 51, pl. 10, fig. 8) differs by possessing a thicker granular wall and processes that divide in such a way as to give a funnel-like appearance, which are more obviously concentrated on the hypocyst. Membranilarnacia? tenella Morgenroth, 1968 (554–555, pl. 48, figs 2–4) has 30–40 slender, stronger solid processes which may have tiny perforations. Membranilarnacia sp. of Kirsch (1991, pl. 26, figs 4–5) also possesses a thin ectophragm but it is supported by much shorter processes.
Holotype: Pearce, 2010, pl.5. figs.1–3.
Type locality and horizon. Trunch borehole, Norfolk, UK; 419.9–420.0 m, Burnham–Flamborough Chalk (undifferentiated), mid-Micraster cortestudinarium Zone (mid-lower Coniacian).
Age: early Coniacian–early Campanian.
Diagnosis. A species of Membranilarnacia with a thin ectophragm supported by a large number of fine supporting processes.
Original description (Pearce, 2010): Small to medium-sized cavate dinoflagellate with a sub-spherical central body. The central body is comprised of a thin autophragm (w0.5 μm) that forms numerous thin, solid, non-tabular processes that support a thin, smooth to finely reticulate ectophragm. The processes are linked proximally forming an irregular polygonal reticulum of variable size and shape. Processes not obviously concentrated on the hypocyst but where they appear to be thicker. The archaeopyle is apical (Type tA, the operculum may be attached, but more usually detached), formed by the loss of all apical paraplates.but where they appear to be thicker. The archaeopyle is apical (Type tA, the operculum may be attached, but more usually detached), formed by the loss of all apical paraplates.
Comparison. Many species of Membranilarnacia possess a particularly thin ectophragm but differ from M. wilsonii sp. nov. by possessing stronger, better developed processes. Membranilarnacia? picena Biffi & Manum, 1988 (190, 192, pl. 7, figs 1–3, 5–7, 9, 12) also possesses a thin veil-like ectophragm but differs in possessing a thicker spongy to externally pitted autophragm. Membranilarnacia polycladiata Cookson & Eisenack in Eisenack (1963b) (Cookson & Eisenack, 1958: 51, pl. 10, fig. 8) differs by possessing a thicker granular wall and processes that divide in such a way as to give a funnel-like appearance, which are more obviously concentrated on the hypocyst. Membranilarnacia? tenella Morgenroth, 1968 (554–555, pl. 48, figs 2–4) has 30–40 slender, stronger solid processes which may have tiny perforations. Membranilarnacia sp. of Kirsch (1991, pl. 26, figs 4–5) also possesses a thin ectophragm but it is supported by much shorter processes.