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Tenua diversa
Plate 28, Figures 8, 11, 12, 17
Holotype: Plate 28, Figure 11, 17
Type Locality: Speeton Clay Formation, Bed C11B, early Hauterivian, regale ammonite Zone. Holotype: Slide top C11B(2), E.F. O51.0
Derivation of Name: From the Latin diversus, different, diverse– in reference to the variable surface ornament.
Diagnosis: Cyst composed of autophragm only, sub-circular with one or two antapical protuberances, the left better-developed so that there is some “stretching” of the cyst obliquely. Surface ornament covers the cyst and is in the form of short, flat spines of very variable width, which are distally capitate to broadly furcate, occasionally linking distally. Adepression runs from a shallow sulcal notch to the ventral antapex and some reduction or loss of ornament is associated with it. There is no alignment of ornament and an increase in spine height is seen over each antapical protrusion. The archeopyle is type tA, with a zigzag principal archeopyle suture and a sulcal notch offset to the left.
Dimensions: Holotype (operculum detached): 89 × 99 μm.
Overall (operculum detached) - 89 (81) 76 μm × 99 (94) 86 μm
Specimens Measured: 7
Remarks: This is a relatively large, robust species whose main characteristic features are a distinct asymmetry to the cyst outline and its usually broad spines which can vary significantly in width on individual specimens.
This species was observed only in the early Hauterivian of Speeton, being recorded between Beds C11B and C7F, regale to lower inversum ammonite Zones, although it was only consistently present between Beds C8B and C7F (across the regale/inversum boundary).
Holotype: Plate 28, Figure 11, 17
Type Locality: Speeton Clay Formation, Bed C11B, early Hauterivian, regale ammonite Zone. Holotype: Slide top C11B(2), E.F. O51.0
Derivation of Name: From the Latin diversus, different, diverse– in reference to the variable surface ornament.
Diagnosis: Cyst composed of autophragm only, sub-circular with one or two antapical protuberances, the left better-developed so that there is some “stretching” of the cyst obliquely. Surface ornament covers the cyst and is in the form of short, flat spines of very variable width, which are distally capitate to broadly furcate, occasionally linking distally. Adepression runs from a shallow sulcal notch to the ventral antapex and some reduction or loss of ornament is associated with it. There is no alignment of ornament and an increase in spine height is seen over each antapical protrusion. The archeopyle is type tA, with a zigzag principal archeopyle suture and a sulcal notch offset to the left.
Dimensions: Holotype (operculum detached): 89 × 99 μm.
Overall (operculum detached) - 89 (81) 76 μm × 99 (94) 86 μm
Specimens Measured: 7
Remarks: This is a relatively large, robust species whose main characteristic features are a distinct asymmetry to the cyst outline and its usually broad spines which can vary significantly in width on individual specimens.
This species was observed only in the early Hauterivian of Speeton, being recorded between Beds C11B and C7F, regale to lower inversum ammonite Zones, although it was only consistently present between Beds C8B and C7F (across the regale/inversum boundary).