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Pyxidinopsis rigida
Plate 6, Figures 1-10
Holotype: Plate 6, Figure 3, 4, 8, 9
Paratype: Plate 6, Figure 1, 2
Type Locality: Speeton Bed C7C, early Hauterivian, inversum ammonite Zone. Holotype: Slide Lr.C7C(1). E.F. T40.2.
Paratype: Slide C7B(5). E.F. R48.3.
Derivation of Name: From the Latin rigidus, stiff, hard, inflexible- in reference to the robust nature of this species.
Diagnosis: A very small, thick-walled, ovoidal dinocyst, which is smooth and covered in a reticulum of varying mesh size; reduction or absence of the reticulum is often observed equatorially, marking the cingulum. Some disorganisation of the reticulum can occur, and some longitudinal elongation of the reticulum may be seen immediately adjacent to the cingulum. The archeopyle is single-plate precingular.
Dimensions: Holotype: Length - 35 μm. Width - 33 μm.
Paratype: Length - 33 μm. Width - 33 μm.
Overall: 38 (34) 25 μm × 38 (34) 33 μm.
Specimens Measured: 7.
Remarks: This rare species is thick-walled and tends to be preserved in “3D”. In size, it is similar to Pyxidinopsis minuta Duxbury 2018, but the latter is a very delicate cyst which is easily folded, in contrast to the rigid nature of P. rigida. In addition, P. minuta has slightly raised peaks which mark each junction point within the reticulum, a feature not seen in P. rigida. Pyxidinopsis rigida n. sp. is significantly smaller than Pyxidinopsis challengerensis Habib 1976 and P. fragilis n. sp., and has a surface reticulum of a relatively larger mesh size. Also, P. challengerensis was described by Habib (1976, p. 382) as having “a periphragm texture composed of sharply defined short ridges which tend to be straight, and which partially interconnect at well-defined angles to form an incomplete polygonal reticulum”. The reticulum of P. rigida is mainly composed of curved muri and can be discontinuous.
This species was recorded consistently between Speeton Beds C7C and C6 (across the early/late Hauterivian boundary, inversum to speetonensis ammonite Zones), with a single, isolated occurrence in Bed C8B (early Hauterivian, upper regale Zone).
Holotype: Plate 6, Figure 3, 4, 8, 9
Paratype: Plate 6, Figure 1, 2
Type Locality: Speeton Bed C7C, early Hauterivian, inversum ammonite Zone. Holotype: Slide Lr.C7C(1). E.F. T40.2.
Paratype: Slide C7B(5). E.F. R48.3.
Derivation of Name: From the Latin rigidus, stiff, hard, inflexible- in reference to the robust nature of this species.
Diagnosis: A very small, thick-walled, ovoidal dinocyst, which is smooth and covered in a reticulum of varying mesh size; reduction or absence of the reticulum is often observed equatorially, marking the cingulum. Some disorganisation of the reticulum can occur, and some longitudinal elongation of the reticulum may be seen immediately adjacent to the cingulum. The archeopyle is single-plate precingular.
Dimensions: Holotype: Length - 35 μm. Width - 33 μm.
Paratype: Length - 33 μm. Width - 33 μm.
Overall: 38 (34) 25 μm × 38 (34) 33 μm.
Specimens Measured: 7.
Remarks: This rare species is thick-walled and tends to be preserved in “3D”. In size, it is similar to Pyxidinopsis minuta Duxbury 2018, but the latter is a very delicate cyst which is easily folded, in contrast to the rigid nature of P. rigida. In addition, P. minuta has slightly raised peaks which mark each junction point within the reticulum, a feature not seen in P. rigida. Pyxidinopsis rigida n. sp. is significantly smaller than Pyxidinopsis challengerensis Habib 1976 and P. fragilis n. sp., and has a surface reticulum of a relatively larger mesh size. Also, P. challengerensis was described by Habib (1976, p. 382) as having “a periphragm texture composed of sharply defined short ridges which tend to be straight, and which partially interconnect at well-defined angles to form an incomplete polygonal reticulum”. The reticulum of P. rigida is mainly composed of curved muri and can be discontinuous.
This species was recorded consistently between Speeton Beds C7C and C6 (across the early/late Hauterivian boundary, inversum to speetonensis ammonite Zones), with a single, isolated occurrence in Bed C8B (early Hauterivian, upper regale Zone).