Back
Avellodinium variabilis
Plate 27, Figures 1, 2, 4, 6, 9-14
Holotype: Plate 27, Figure 12
Paratype: Plate 27, Figures 4, 6
Type Locality: Well 14/19-E9 at 11449.50ft (conventional core chip), early Hauterivian.
Holotype: Well 14/19-E9 at 11449.50ft (slide 1) E.F. R55.2.
Paratype:Well 14/19-E9 at 11408.40ft (slide 2) E.F. P35.1.
Derivation of Name: From the Latin variabilis, changeable - in reference to the wide morphological range of this species.
Diagnosis: A spheroidal, chorate cyst with a thick, fibro-perforate wall. Long, distally-furcate gonal processes may be present, joined by microperforate crests of varying height. Increase in regularity and height of sutural crests can be extreme, resulting in the loss of processes, only high crests remaining. The archeopyle is epicystal and the operculum often remains attached.
Dimensions: Holotype: 86 × 76μm
Paratype: 63 × 51μm
Overall (complete specimens): 86 (67) 61 μm × 76 61) 51 μm
Specimens Measured: 18
Remarks: Avellodinium variabilis is an unusual species in ranging from specimens which bear long, flexuous, distally-furcate gonal processes (i.e. “typical” Avellodinium) to others which display only high sutural crests and which are reminiscent of Heslertonia Sarjeant 1966b emend. Duxbury 1980. There is a complete gradation between these types.
Specimens with distally-furcate gonal spines bear some resemblance to Avellodinium falsificum Duxbury 1977, although the fibro-perforate texture and relatively high microperforate crests are atypical (compare Plate 11, Figs. 2, 4, 10 with Plate 27, Figs. 12-14 here). The texture of the cyst wall and crests is also atypical of Heslertonia. The observed stratigraphic range of this species is entirely within the early Hauterivian.
Holotype: Plate 27, Figure 12
Paratype: Plate 27, Figures 4, 6
Type Locality: Well 14/19-E9 at 11449.50ft (conventional core chip), early Hauterivian.
Holotype: Well 14/19-E9 at 11449.50ft (slide 1) E.F. R55.2.
Paratype:Well 14/19-E9 at 11408.40ft (slide 2) E.F. P35.1.
Derivation of Name: From the Latin variabilis, changeable - in reference to the wide morphological range of this species.
Diagnosis: A spheroidal, chorate cyst with a thick, fibro-perforate wall. Long, distally-furcate gonal processes may be present, joined by microperforate crests of varying height. Increase in regularity and height of sutural crests can be extreme, resulting in the loss of processes, only high crests remaining. The archeopyle is epicystal and the operculum often remains attached.
Dimensions: Holotype: 86 × 76μm
Paratype: 63 × 51μm
Overall (complete specimens): 86 (67) 61 μm × 76 61) 51 μm
Specimens Measured: 18
Remarks: Avellodinium variabilis is an unusual species in ranging from specimens which bear long, flexuous, distally-furcate gonal processes (i.e. “typical” Avellodinium) to others which display only high sutural crests and which are reminiscent of Heslertonia Sarjeant 1966b emend. Duxbury 1980. There is a complete gradation between these types.
Specimens with distally-furcate gonal spines bear some resemblance to Avellodinium falsificum Duxbury 1977, although the fibro-perforate texture and relatively high microperforate crests are atypical (compare Plate 11, Figs. 2, 4, 10 with Plate 27, Figs. 12-14 here). The texture of the cyst wall and crests is also atypical of Heslertonia. The observed stratigraphic range of this species is entirely within the early Hauterivian.