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Downiesphaeridium obtusum
Plate 13, Figures 6, 9
Holotype: Plate 13, Figure 6
Type Locality: Vergol outcrop, early Valanginian, Bed V88, inostranzewi ammonite Zone, inostranzewi Sub-zone. Holotype: Slide V88(Schulze), E.F. F41.0.
Derivation of Name: From the Latin obtusus, blunt - in reference to the distally closed and rounded processes.
Diagnosis: Chorate dinoflagellate cysts with a subspherical central body and microgranular to microspinose ornament. Sixty or more long, thin, smooth-walled processes extend outward perpendicularly. These are hollow, cylindrical to slightly tapering, distally closed and bluntly rounded. The archeopyle is apical with a simple type tA operculum which often remains attached. Other than the archeopyle margin there is no indication of tabulation.
Dimensions: Holotype Central body 35 × 38 μm.
Overall 61 × 61 μm.
Size range: Central body 46 (36) 33 × 46 (36) 29 μm.
Overall 68 (57) 51 × 66 (59) 48 μm.
Specimens measured - 7.
Remarks: Downiesphaeridium obtusum n. sp. is essentially similar to Dapsilidinium warrenii and Downiesphaeridium flexuosum but with closed, bluntly rounded process terminations as opposed to the distally open processes of D. warrenii and the acuminate, closed processes of D. flexuosum.
Occurrences of this species were largely restricted to the interval between Vergol Beds B110M and B118M (late Berriasian, alpillensis Zone, alpillensis to otopeta Sub-zones) but with sporadic occurrences in the early Valanginian, Vergol Beds V59M, V72M and V88, and in the late Valanginian of La Charce, Bed LCH118M.
Holotype: Plate 13, Figure 6
Type Locality: Vergol outcrop, early Valanginian, Bed V88, inostranzewi ammonite Zone, inostranzewi Sub-zone. Holotype: Slide V88(Schulze), E.F. F41.0.
Derivation of Name: From the Latin obtusus, blunt - in reference to the distally closed and rounded processes.
Diagnosis: Chorate dinoflagellate cysts with a subspherical central body and microgranular to microspinose ornament. Sixty or more long, thin, smooth-walled processes extend outward perpendicularly. These are hollow, cylindrical to slightly tapering, distally closed and bluntly rounded. The archeopyle is apical with a simple type tA operculum which often remains attached. Other than the archeopyle margin there is no indication of tabulation.
Dimensions: Holotype Central body 35 × 38 μm.
Overall 61 × 61 μm.
Size range: Central body 46 (36) 33 × 46 (36) 29 μm.
Overall 68 (57) 51 × 66 (59) 48 μm.
Specimens measured - 7.
Remarks: Downiesphaeridium obtusum n. sp. is essentially similar to Dapsilidinium warrenii and Downiesphaeridium flexuosum but with closed, bluntly rounded process terminations as opposed to the distally open processes of D. warrenii and the acuminate, closed processes of D. flexuosum.
Occurrences of this species were largely restricted to the interval between Vergol Beds B110M and B118M (late Berriasian, alpillensis Zone, alpillensis to otopeta Sub-zones) but with sporadic occurrences in the early Valanginian, Vergol Beds V59M, V72M and V88, and in the late Valanginian of La Charce, Bed LCH118M.