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Raphidodinium minor
From Fensome et al., 2019:
Raphidodinium minor
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Original description Duxbury, 2019:
Plate 1, Figures 15–17
Holotype: Plate 1, Figure 15.
Paratype: Plate 1, Figure 17.
Type Locality: Heslerton No. 2 at 21.00 m (core chip), late Barremian age. Holotype: E.F. S41.0. Paratype: G40.2.
Derivation of Name: From the Latin minor, less - in reference to the small size of this species.
Diagnosis: A small, thin-walled dinocyst, elongate ovoidal to ellipsoidal with rounded polar areas. The cyst surface is finely granular and faint tabulation is outlined by very low ridges. A prominent, fairly wide and indented cingulum with little sulcal offset is clearly marked, dividing the cyst unevenly, the epicyst being invariably shorter than the hypocyst. Long, flexuous, distally acuminate, solid gonal processes are present towards the apices but absent from much of the cyst. Equal numbers of processes can occur at the apex and antapex, but there are normally fewer at the apex; the maximum total number of spines observed is twelve.
Dimensions: Holotype: Central body - 25 × 18 μm; Overall - 48 × 38 μm.
Paratype: Central body - 33 × 18 μm; Overall - 58 × 43 μm.
All measured specimens: Central body - 33 (26) 20 μm × 18 (16) 15 μm.
Overall - 58 (51) 43 μm × 43 (36) 30 μm.
Specimens Measured: 8.
Remarks: Although the archeopyle type of Raphidodinium minor is unknown, there is a marked similarity between this small, thin-walled species and R. fucatum, particularly in the possession of a small number of long gonal processes, an elongate central body, a clear “feebly laevorotatory” cingulum and low ridges marking faint tabulation. It differs, however, in possessing a more elongate central body and in having its spines polarised, with no cingular processes observed. The number of spines possessed by Raphidodinium minor appears to be greater than those demonstrated for R. fucatum. Sarjeant and Downie (1982) described “typically or constantly nine” (3 apical, 4 cingular and 2 antapical) processes for R. fucatum, whereas R. minor possesses up to twelve with no cingulars. The specimen of R. fucatum illustrated by Setoyama et al. (2013, Figure 5.23) has even fewer processes (?6), although some processes loss may have occurred due to breakage. Sarjeant and Downie (op. cit.) quoted an age range for R. fucatum of late Turonian to early Maastrichtian in France, Belgium and the North Sea Basin. Therefore there is a significant time interval between that species and R. minor, which was restricted to a very short interval within the late Barremian of Heslerton No. 2 (21.00 m to 19.00 m) and to a single sample, at 11,187.00 ft in well 22/26a-2.
Raphidodinium minor
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Original description Duxbury, 2019:
Plate 1, Figures 15–17
Holotype: Plate 1, Figure 15.
Paratype: Plate 1, Figure 17.
Type Locality: Heslerton No. 2 at 21.00 m (core chip), late Barremian age. Holotype: E.F. S41.0. Paratype: G40.2.
Derivation of Name: From the Latin minor, less - in reference to the small size of this species.
Diagnosis: A small, thin-walled dinocyst, elongate ovoidal to ellipsoidal with rounded polar areas. The cyst surface is finely granular and faint tabulation is outlined by very low ridges. A prominent, fairly wide and indented cingulum with little sulcal offset is clearly marked, dividing the cyst unevenly, the epicyst being invariably shorter than the hypocyst. Long, flexuous, distally acuminate, solid gonal processes are present towards the apices but absent from much of the cyst. Equal numbers of processes can occur at the apex and antapex, but there are normally fewer at the apex; the maximum total number of spines observed is twelve.
Dimensions: Holotype: Central body - 25 × 18 μm; Overall - 48 × 38 μm.
Paratype: Central body - 33 × 18 μm; Overall - 58 × 43 μm.
All measured specimens: Central body - 33 (26) 20 μm × 18 (16) 15 μm.
Overall - 58 (51) 43 μm × 43 (36) 30 μm.
Specimens Measured: 8.
Remarks: Although the archeopyle type of Raphidodinium minor is unknown, there is a marked similarity between this small, thin-walled species and R. fucatum, particularly in the possession of a small number of long gonal processes, an elongate central body, a clear “feebly laevorotatory” cingulum and low ridges marking faint tabulation. It differs, however, in possessing a more elongate central body and in having its spines polarised, with no cingular processes observed. The number of spines possessed by Raphidodinium minor appears to be greater than those demonstrated for R. fucatum. Sarjeant and Downie (1982) described “typically or constantly nine” (3 apical, 4 cingular and 2 antapical) processes for R. fucatum, whereas R. minor possesses up to twelve with no cingulars. The specimen of R. fucatum illustrated by Setoyama et al. (2013, Figure 5.23) has even fewer processes (?6), although some processes loss may have occurred due to breakage. Sarjeant and Downie (op. cit.) quoted an age range for R. fucatum of late Turonian to early Maastrichtian in France, Belgium and the North Sea Basin. Therefore there is a significant time interval between that species and R. minor, which was restricted to a very short interval within the late Barremian of Heslerton No. 2 (21.00 m to 19.00 m) and to a single sample, at 11,187.00 ft in well 22/26a-2.