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Hystrichosphaeridium diversum
From Fensome et al., 2019:
Hystrichosphaeridium diversum Duxbury, 2018, p.182–183, pl.2, figs.12,15–17. Holotype: Duxbury, 2018, pl.2, fig.12. Age: early
Valanginian.
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Original description Duxbury, 2018:
Holotype: Plate 2, Figure 12.
Paratypes: Plate 2, Figures 15, 16.
Type Locality: Division D3C, lower Valanginian, Speeton Clay, Speeton, England. Holotype: Speeton Division D3C. E.F. H50.1. Paratypes: Speeton Division LrD2E, E.F.S43.0 and E.F. O30.0.
Derivation of Name: From the Latin diversus, different, diverse.
Diagnosis: A small, spheroidal dinoflagellate cyst with a finely granular surface and mesotabular tubular processes indicating a reflected tabulation pattern of 4', 6", 6c, 5-6"', 1p, 1"". Processes vary considerably, ranging in length from one-third to two-thirds of the main body diameter and from gradually-flaring, striate tubes to narrower, fibrous types which narrow to about one-third of their length before flaring distally. Cingular processes are significantly narrower than others, but of equal length. Larger processes may bear longitudinal holes and, occasional, very fine trabeculae may be present. The archeopyle is tetratabular apical and the operculum is invariably detached.
Dimensions: Holotype (operculum detached): Central body – 38 × 41 μm.
Overall: 63 × 68 μm.
All measured specimens (operculum detached): Central body – 43 (37) 30 μm × 43 (38) 33 μm.
Overall: 66(57)46 μm × 71(62)53 μm.
Specimens Measured: 22.
Remarks: Hystrichosphaeridium diversum n. sp. differs from other species of this genus in possessing distinct, very variable processes. These range from entire, broadly-striate tubes with relatively simple distal margins more or less at right angles to the process axis (Plate 2, Figure 15) to flamboyant, fibrous examples with longitudinal holes which occasionally penetrate the distal margin and distinctly angular distal terminations (Plate 2, Figures 16, 17). There appears to be a complete gradation between these process types, although they are consistent on individual specimens.
This species is similar in size and in some characteristics to Hystrichosphaeridium arborispinum Davey and Williams 1966; the irregular and fibrous process terminations in H. arborispinum are similar to some processes in some specimens of H. diversum n. sp., although they are much broader in the latter.
Hystrichosphaeridium arborispinum has much narrower and much more “stable” processes that H. diversum (Plate 6, Figure 18). The observed range of H. diversum n. sp. is entirely within the lower Valanginian and at Speeton its inception is within Bed D4B. The oldest occurrence of H. arborispinum is within Bed D3B, associated with common H. diversum n. sp. (text-fig. 2).
Hystrichosphaeridium diversum Duxbury, 2018, p.182–183, pl.2, figs.12,15–17. Holotype: Duxbury, 2018, pl.2, fig.12. Age: early
Valanginian.
---------------------------------------------------------------------------------------------------
Original description Duxbury, 2018:
Holotype: Plate 2, Figure 12.
Paratypes: Plate 2, Figures 15, 16.
Type Locality: Division D3C, lower Valanginian, Speeton Clay, Speeton, England. Holotype: Speeton Division D3C. E.F. H50.1. Paratypes: Speeton Division LrD2E, E.F.S43.0 and E.F. O30.0.
Derivation of Name: From the Latin diversus, different, diverse.
Diagnosis: A small, spheroidal dinoflagellate cyst with a finely granular surface and mesotabular tubular processes indicating a reflected tabulation pattern of 4', 6", 6c, 5-6"', 1p, 1"". Processes vary considerably, ranging in length from one-third to two-thirds of the main body diameter and from gradually-flaring, striate tubes to narrower, fibrous types which narrow to about one-third of their length before flaring distally. Cingular processes are significantly narrower than others, but of equal length. Larger processes may bear longitudinal holes and, occasional, very fine trabeculae may be present. The archeopyle is tetratabular apical and the operculum is invariably detached.
Dimensions: Holotype (operculum detached): Central body – 38 × 41 μm.
Overall: 63 × 68 μm.
All measured specimens (operculum detached): Central body – 43 (37) 30 μm × 43 (38) 33 μm.
Overall: 66(57)46 μm × 71(62)53 μm.
Specimens Measured: 22.
Remarks: Hystrichosphaeridium diversum n. sp. differs from other species of this genus in possessing distinct, very variable processes. These range from entire, broadly-striate tubes with relatively simple distal margins more or less at right angles to the process axis (Plate 2, Figure 15) to flamboyant, fibrous examples with longitudinal holes which occasionally penetrate the distal margin and distinctly angular distal terminations (Plate 2, Figures 16, 17). There appears to be a complete gradation between these process types, although they are consistent on individual specimens.
This species is similar in size and in some characteristics to Hystrichosphaeridium arborispinum Davey and Williams 1966; the irregular and fibrous process terminations in H. arborispinum are similar to some processes in some specimens of H. diversum n. sp., although they are much broader in the latter.
Hystrichosphaeridium arborispinum has much narrower and much more “stable” processes that H. diversum (Plate 6, Figure 18). The observed range of H. diversum n. sp. is entirely within the lower Valanginian and at Speeton its inception is within Bed D4B. The oldest occurrence of H. arborispinum is within Bed D3B, associated with common H. diversum n. sp. (text-fig. 2).