Back
Rhynchodiniopsis ingens
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 is
restricted 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.
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 is
restricted 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.