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Hystrichosphaeridium arborispinum ssp. prolatum
Plate 9, Figures 18-20
Hystrichosphaeridium arborispinum Davey and Williams 1966b in DUXBURY 2019, pl. 18, figs. 18, 19 only
Holotype: Plate 9, Figures 18, 19
Type Locality: Speeton Clay Formation, early Barremian, Bed LB1, fissicostatum ammonite Zone. Holotype: Slide LB1(1), E.F. N35.1.
Derivation of Name: From the Latin prolatus, extended, elongated- in reference to the cyst outline.
Diagnosis: A subspecies of Hystrichosphaeridium arborispinum where the cyst is significantly longer than broad but which otherwise conforms to other morphological characteristics of this species, including a finely granular cyst wall, although in some cases some of the ornament consists of tiny spines or coni. Ragged-ended tubular processes can be proximally striate and the archeopyle is tetratabular apical. Some specimens possess a few deeply furcate processes, presumed to be cingular.
Dimensions: Holotype (complete): Central body - 58 × 40 μm.
Overall: 84 × 71 μm.
Operculum lost: Central body: 58 (52) 48 μm × 43 (40) 35 μm.
Overall: 89 (73) 58 μm × 78 (72) 68 μm.
Specimens Measured: 6.
Remarks: As suggested by the dimensions quoted above, it is the main body of this form that is clearly elongate; including the processes, this is less apparent. The specimen of this larger, elongate form illustrated by Duxbury (2019, Plate 18, Figs. 18, 19) was from the late Barremian.
The presence of this subspecies only in Bed LB1 here, combined with evidence from Duxbury (2019), proves a range to date for Hystrichosphaeridium arborispinum subsp. prolatum of latest early to late Barremian.
Hystrichosphaeridium arborispinum Davey and Williams 1966b in DUXBURY 2019, pl. 18, figs. 18, 19 only
Holotype: Plate 9, Figures 18, 19
Type Locality: Speeton Clay Formation, early Barremian, Bed LB1, fissicostatum ammonite Zone. Holotype: Slide LB1(1), E.F. N35.1.
Derivation of Name: From the Latin prolatus, extended, elongated- in reference to the cyst outline.
Diagnosis: A subspecies of Hystrichosphaeridium arborispinum where the cyst is significantly longer than broad but which otherwise conforms to other morphological characteristics of this species, including a finely granular cyst wall, although in some cases some of the ornament consists of tiny spines or coni. Ragged-ended tubular processes can be proximally striate and the archeopyle is tetratabular apical. Some specimens possess a few deeply furcate processes, presumed to be cingular.
Dimensions: Holotype (complete): Central body - 58 × 40 μm.
Overall: 84 × 71 μm.
Operculum lost: Central body: 58 (52) 48 μm × 43 (40) 35 μm.
Overall: 89 (73) 58 μm × 78 (72) 68 μm.
Specimens Measured: 6.
Remarks: As suggested by the dimensions quoted above, it is the main body of this form that is clearly elongate; including the processes, this is less apparent. The specimen of this larger, elongate form illustrated by Duxbury (2019, Plate 18, Figs. 18, 19) was from the late Barremian.
The presence of this subspecies only in Bed LB1 here, combined with evidence from Duxbury (2019), proves a range to date for Hystrichosphaeridium arborispinum subsp. prolatum of latest early to late Barremian.