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Spiniferites jarvisii
Spiniferites jarvisii Pearce, 2010, p.53,55, pl.6, figs.2–5.
Holotype: Pearce, 2010, pl.6, figs.2–5.
Type locality and horizon. Trunch borehole, Norfolk, UK; 307.9–308.0 m, Burnham–Flamborough Chalk (undifferentiated), high Marsupites testudinarius Zone (high upper Santonian).
Age: early Campanian.
Diagnosis (Pearce, 2010). A species of Spiniferites that possesses a thick endophragm that becomes thinner towards the paraplate margins.
Description (Pearce, 2010). Small to medium-sized spiniferate chorate dinoflagellate. The central body episome is prolate ellipsoid and the hyposome is roughly spherical to minorly oblate ellipsoid. The wall is two-layered, with a thick and smooth endophragm (w1.5 μm) that is thinned towards the margin of the paraplates and a smooth and thin periphragm (w0.5 μm) that forms the processes. The processes are gonal, approximately half the diameter of the central body in length, and trifurcate distally (with furcations up to 5 μm in length) before terminating in a minute bifurcation (1–2 μm long). Parasutural crests are highest against the processes and up to 2 μm high in between and clearly delineating the standard gonyaulacacean paratabulation. The paracingulum is distinctly laevorotatory by twice the width of the paracingulum; the parasulcus is straight and lacks clearly developed parasutural crests. The lateral margins of the sixth precingular paraplate taper apically and the paraplate appears to have a rectilinear contact with the apical series. The archaeopyle is precingular (Type 1P, operculum detached) and formed by the loss of the third precingular paraplate (3").
Comparison. Differs from other species of Spiniferites by possessing a thick endophragm that thins towards the margin of the paraplates. The mostly closely related species is Pterodinium crassimuratus (Davey & Williams, 1966a: 39, pl. 1, fig. 11) Thurow et al., 1988 that also possesses the characteristic thinning of the endophragm, but differs in lacking processes that project beyond the parasutural crests.
Holotype: Pearce, 2010, pl.6, figs.2–5.
Type locality and horizon. Trunch borehole, Norfolk, UK; 307.9–308.0 m, Burnham–Flamborough Chalk (undifferentiated), high Marsupites testudinarius Zone (high upper Santonian).
Age: early Campanian.
Diagnosis (Pearce, 2010). A species of Spiniferites that possesses a thick endophragm that becomes thinner towards the paraplate margins.
Description (Pearce, 2010). Small to medium-sized spiniferate chorate dinoflagellate. The central body episome is prolate ellipsoid and the hyposome is roughly spherical to minorly oblate ellipsoid. The wall is two-layered, with a thick and smooth endophragm (w1.5 μm) that is thinned towards the margin of the paraplates and a smooth and thin periphragm (w0.5 μm) that forms the processes. The processes are gonal, approximately half the diameter of the central body in length, and trifurcate distally (with furcations up to 5 μm in length) before terminating in a minute bifurcation (1–2 μm long). Parasutural crests are highest against the processes and up to 2 μm high in between and clearly delineating the standard gonyaulacacean paratabulation. The paracingulum is distinctly laevorotatory by twice the width of the paracingulum; the parasulcus is straight and lacks clearly developed parasutural crests. The lateral margins of the sixth precingular paraplate taper apically and the paraplate appears to have a rectilinear contact with the apical series. The archaeopyle is precingular (Type 1P, operculum detached) and formed by the loss of the third precingular paraplate (3").
Comparison. Differs from other species of Spiniferites by possessing a thick endophragm that thins towards the margin of the paraplates. The mostly closely related species is Pterodinium crassimuratus (Davey & Williams, 1966a: 39, pl. 1, fig. 11) Thurow et al., 1988 that also possesses the characteristic thinning of the endophragm, but differs in lacking processes that project beyond the parasutural crests.