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Rhynchodiniopsis ingens
From Fensome et al., 2019:
Rhynchodiniopsis ingens Duxbury, 2018, p.191, pl.12, figs.6–7. Holotype: Duxbury, 2018, pl.12, fig.6. Age: early Hauterivian.
[note: this species was erroneously put at Rhombodinium in Fensome et al., 2019].
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Plate 12, figures 6, 7
Holotype: Plate 12, Figure 6.
Paratype: Plate 12, Figure 7.
Type Locality: Well 20/01-10Y at 6967.5 ft (sidewall core), lower Hauterivian. Holotype: E.F. U42.2. Paratype: E.F. H50.1.
Derivation of Name: From the Latin ingens, huge, great, immoderately large, in reference to the unusual size of this species.
Diagnosis: A very large, ovoidal gonyaulacacean dinocyst species, with a low, rounded apical protrusion. The cyst surface ranges from densely but finely granular to scabrate or finely and irregularly reticulate. Tabulation of the formula 4', 6", ?c, 6"', 1p, 1p.v., 1"" is outlined by denticulate to spinose crests which are particularly high bordering the narrow cingulum. Gonal areas areas may have simple spinose crestal extensions notably exceeding the normal crestal height. Distally, crestal spines may be capitate or furcate, and crestal coalescence forms a feathered structure beyond the apical protrusion, terminating in a small coronate structure. The archeopyle is single plate precingular, formed by detachment of plate 3".
Dimensions:Holotype: 159 × 175 μm. Apical horn: 25 μm.
Cingular crests: 25 μm.
Paratype: 177 × 152 μm. Apical horn: 18 μm. Cingular crests: 25 μm.
Overall: 197 (162) 139 μm × 192 (163) 147 μm. Apical horn: 35 (25) 15 μm. Cingular crests: 25 (22) 18 μm.
Specimens Measured: 23.
Remarks: This species is reminiscent of several others, notably Rhynchodiniopsis anglese (Zahiri 1981) Duxbury n comb., with which it shares many features, including the overall body shape and, particularly, the high cingular crests. Rhynchodiniopsis ingens n. sp. differs, however, in its much larger size, and in the absence of the characteristic, furcate antapical spines and coarsely granular body ornament described for R. anglese (Zahiri 1981, p. 15). In addition, R. anglese was described from the lower Barremian of southeast France, whereas R. ingens isrestricted to the lower Hauterivian.
In possessing gonal spines higher than the general crest height, R. ingens n. sp. is similar to Rhynchodiniopsis martonensis Bailey et al. 1997, although the latter species is much smaller and has more prominent gonal spines; the LAD of R. martonensis is Middle Volgian (Duxbury et al. 1999 – as R. “machaera”). The stratigraphic range of Rhynchodiniopsis ingens n. sp. is very restricted, occurring only within the early Hauterivian. Although its total range is unclear, it is particularly abundant at a mid-Palyzone LKP13 level (text-fig. 10), where it can constitute 20–30% of the total assemblage. This influx is a valuable correlative feature in the UKCS Central North Sea but because of the very high abundance within Palyzone LKP13, deeper ditch cuttings samples invariably yield this species also.
Rhynchodiniopsis ingens Duxbury, 2018, p.191, pl.12, figs.6–7. Holotype: Duxbury, 2018, pl.12, fig.6. Age: early Hauterivian.
[note: this species was erroneously put at Rhombodinium in Fensome et al., 2019].
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Plate 12, figures 6, 7
Holotype: Plate 12, Figure 6.
Paratype: Plate 12, Figure 7.
Type Locality: Well 20/01-10Y at 6967.5 ft (sidewall core), lower Hauterivian. Holotype: E.F. U42.2. Paratype: E.F. H50.1.
Derivation of Name: From the Latin ingens, huge, great, immoderately large, in reference to the unusual size of this species.
Diagnosis: A very large, ovoidal gonyaulacacean dinocyst species, with a low, rounded apical protrusion. The cyst surface ranges from densely but finely granular to scabrate or finely and irregularly reticulate. Tabulation of the formula 4', 6", ?c, 6"', 1p, 1p.v., 1"" is outlined by denticulate to spinose crests which are particularly high bordering the narrow cingulum. Gonal areas areas may have simple spinose crestal extensions notably exceeding the normal crestal height. Distally, crestal spines may be capitate or furcate, and crestal coalescence forms a feathered structure beyond the apical protrusion, terminating in a small coronate structure. The archeopyle is single plate precingular, formed by detachment of plate 3".
Dimensions:Holotype: 159 × 175 μm. Apical horn: 25 μm.
Cingular crests: 25 μm.
Paratype: 177 × 152 μm. Apical horn: 18 μm. Cingular crests: 25 μm.
Overall: 197 (162) 139 μm × 192 (163) 147 μm. Apical horn: 35 (25) 15 μm. Cingular crests: 25 (22) 18 μm.
Specimens Measured: 23.
Remarks: This species is reminiscent of several others, notably Rhynchodiniopsis anglese (Zahiri 1981) Duxbury n comb., with which it shares many features, including the overall body shape and, particularly, the high cingular crests. Rhynchodiniopsis ingens n. sp. differs, however, in its much larger size, and in the absence of the characteristic, furcate antapical spines and coarsely granular body ornament described for R. anglese (Zahiri 1981, p. 15). In addition, R. anglese was described from the lower Barremian of southeast France, whereas R. ingens isrestricted to the lower Hauterivian.
In possessing gonal spines higher than the general crest height, R. ingens n. sp. is similar to Rhynchodiniopsis martonensis Bailey et al. 1997, although the latter species is much smaller and has more prominent gonal spines; the LAD of R. martonensis is Middle Volgian (Duxbury et al. 1999 – as R. “machaera”). The stratigraphic range of Rhynchodiniopsis ingens n. sp. is very restricted, occurring only within the early Hauterivian. Although its total range is unclear, it is particularly abundant at a mid-Palyzone LKP13 level (text-fig. 10), where it can constitute 20–30% of the total assemblage. This influx is a valuable correlative feature in the UKCS Central North Sea but because of the very high abundance within Palyzone LKP13, deeper ditch cuttings samples invariably yield this species also.