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Dingodinium globosum
Dingodinium? globosum Duxbury n. sp.
Plate 5, Figures 1-4, 6, 7
Nelchinopsis kostromiensis (Vozzhennikova 1967) Wiggins 1972. – CHAROLLAIS et al. 2023, pl. 11, fig. 6, pl. 12, fig. 6
Holotype: Plate 5, Figures 1, 6
Paratype: Plate 5, Figure 7
Type Locality: Vergol outcrop, early Valanginian, Bed V91M, inostranzewi ammonite Zone, inostranzewi Sub-zone. Holotype: Slide V91M (Schulze), E.F. T.48.4. Paratype: Slide V91M (Schulze), E.F. V54.0.
Derivation of Name: From the Latin globosus, round as a ball - in reference to the shape.
Diagnosis: Camocavate cysts with a spheroidal endocyst with no apical projection and a more delicate pericyst produced into a broad-based, distally perforate, rounded apical horn. The endophragm is largely free of ornament but may bear isolated coni or low verrucate ornament. The apical archeopyle involves splitting between apical and precingular plates; the operculum remains attached. Tabulation, apparently gonyaulacoid, is fully developed on the pericyst as indicated by denticulate septa which are higher on the hypocyst. The cingulum is laevorotatory and offset by 1-2 cingular widths; an irregular claustrum in the pericyst represents the sulcus. Gonal areas are raised, creating an angularity to the pericyst.
Dimensions: Holotype 51 × 48 μm. Paratype 53 × 53 μm. Overall: 53 (50) 48 μm × 53 (47) 43 μm. Specimens measured – 10.
Remarks: This species is difficult to place taxonomically. Its camocavate nature and archeopyle type suggest Dingodinium, and its overall structure, including denticulate crests, is reminiscent of Dingodinium spinosum (Duxbury 1977) Davey 1979b. It differs from the last species in its much more rounded outline, in the more complete sutural crest development and in its characteristic, distally perforate "pepper pot" apical horn. Like D. spinosum, it is atypical of Dingodinium where the large majority of species show significantly greater separation of the cyst walls and where the tabulation, when indicated at all, tends to be restricted to periphragm folds. Also, although Dingodinium? globosum can have verrucose endocystal ornament, this is usually reduced and tends to be very irregular, leaving areas of the endocyst smooth.
There is also marked similarity between Dingodinium? globosum and Nelchinopsis kostromiensis (Vozzhennikova 1967) Wiggins 1972 emend. Harding 1996, a species it resembles in its spheroidal endocyst, its raised gonal areas, its broad-based, low apical horn and its regularly denticulate crests (compare pl. 5, figs. 1-4, 6, 7 and pl. 5, fig. 5). However, in Harding's (1996) re-appraisal of the genus Nelchinopsis Wiggins 1972, he described an, "autophragm supporting a thin ectophragm on densely-packed, solid, slender processes". This is not the case in Dingodinium? globosum.
Specimens referred to Nelchinopsis kostromiensis in Charollais et al. 2023 (pl. 11, fig. 6, pl. 12, fig. 6) display the typical "pepper pot" apical horn termination of Dingodinium? globosum and are included here. Charollais et al. (2023, p. 39) stated (translation), "Nelchinopsis kostromiensis, present in sample AP 644, appears at the base of the campylotoxus Zone (Monteil, 1992b)", which is a very similar level to the FO of D.? globosum here.
The observed range of this species in the current study was between Beds V45M and V132M, early Valanginian, neocomiensiformis Zone, neocomiensiformis Sub-zone to late Valanginian, peregrinus Zone, peregrinus Sub-zone, although it was consistently recorded only as high as Bed V111. A single specimen was also recorded from La Charce sample LCH113, top verrucosum Zone. The absence of this species from higher samples at La Charce may be due to its rarity towards the top of its range.
Plate 5, Figures 1-4, 6, 7
Nelchinopsis kostromiensis (Vozzhennikova 1967) Wiggins 1972. – CHAROLLAIS et al. 2023, pl. 11, fig. 6, pl. 12, fig. 6
Holotype: Plate 5, Figures 1, 6
Paratype: Plate 5, Figure 7
Type Locality: Vergol outcrop, early Valanginian, Bed V91M, inostranzewi ammonite Zone, inostranzewi Sub-zone. Holotype: Slide V91M (Schulze), E.F. T.48.4. Paratype: Slide V91M (Schulze), E.F. V54.0.
Derivation of Name: From the Latin globosus, round as a ball - in reference to the shape.
Diagnosis: Camocavate cysts with a spheroidal endocyst with no apical projection and a more delicate pericyst produced into a broad-based, distally perforate, rounded apical horn. The endophragm is largely free of ornament but may bear isolated coni or low verrucate ornament. The apical archeopyle involves splitting between apical and precingular plates; the operculum remains attached. Tabulation, apparently gonyaulacoid, is fully developed on the pericyst as indicated by denticulate septa which are higher on the hypocyst. The cingulum is laevorotatory and offset by 1-2 cingular widths; an irregular claustrum in the pericyst represents the sulcus. Gonal areas are raised, creating an angularity to the pericyst.
Dimensions: Holotype 51 × 48 μm. Paratype 53 × 53 μm. Overall: 53 (50) 48 μm × 53 (47) 43 μm. Specimens measured – 10.
Remarks: This species is difficult to place taxonomically. Its camocavate nature and archeopyle type suggest Dingodinium, and its overall structure, including denticulate crests, is reminiscent of Dingodinium spinosum (Duxbury 1977) Davey 1979b. It differs from the last species in its much more rounded outline, in the more complete sutural crest development and in its characteristic, distally perforate "pepper pot" apical horn. Like D. spinosum, it is atypical of Dingodinium where the large majority of species show significantly greater separation of the cyst walls and where the tabulation, when indicated at all, tends to be restricted to periphragm folds. Also, although Dingodinium? globosum can have verrucose endocystal ornament, this is usually reduced and tends to be very irregular, leaving areas of the endocyst smooth.
There is also marked similarity between Dingodinium? globosum and Nelchinopsis kostromiensis (Vozzhennikova 1967) Wiggins 1972 emend. Harding 1996, a species it resembles in its spheroidal endocyst, its raised gonal areas, its broad-based, low apical horn and its regularly denticulate crests (compare pl. 5, figs. 1-4, 6, 7 and pl. 5, fig. 5). However, in Harding's (1996) re-appraisal of the genus Nelchinopsis Wiggins 1972, he described an, "autophragm supporting a thin ectophragm on densely-packed, solid, slender processes". This is not the case in Dingodinium? globosum.
Specimens referred to Nelchinopsis kostromiensis in Charollais et al. 2023 (pl. 11, fig. 6, pl. 12, fig. 6) display the typical "pepper pot" apical horn termination of Dingodinium? globosum and are included here. Charollais et al. (2023, p. 39) stated (translation), "Nelchinopsis kostromiensis, present in sample AP 644, appears at the base of the campylotoxus Zone (Monteil, 1992b)", which is a very similar level to the FO of D.? globosum here.
The observed range of this species in the current study was between Beds V45M and V132M, early Valanginian, neocomiensiformis Zone, neocomiensiformis Sub-zone to late Valanginian, peregrinus Zone, peregrinus Sub-zone, although it was consistently recorded only as high as Bed V111. A single specimen was also recorded from La Charce sample LCH113, top verrucosum Zone. The absence of this species from higher samples at La Charce may be due to its rarity towards the top of its range.