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Heslertonia inferior
Plate 11, Figures 1-3, 5, 7
Holotype: Plate 11, Figure 3, 7.
Paratype: Plate 11, Figure 2.
Type Locality: Vergol outcrop. Holotype: early Valanginian, Bed V19M, pertransiens ammonite Zone, salinarium Sub-zone, slide V19M/2, E.F. E59.1. Paratype: late Valanginian, Bed V124M, base peregrinus ammonite Zone, peregrinus Sub-zone, slide V124M(Schulze)/1, E.F. K46.1
Derivation of Name: From the Latin inferior, lower - in reference to the reduced sutural crests of this species.
Diagnosis: A spheroidal cyst of moderate size with smooth, thin wall layers and no apical projection. Tabulation is apparently typically gonyaulacacean and is outlined by low, smooth sutural crests. Crests contact the main body along narrow sutures and distally bear narrow linear thickenings which may be entire or variably denticulate; crests of equal height, similar to those elsewhere on the cyst, outline and sub-divide a narrow cingulum. The archeopyle is epicystal and the operculum usually remains attached ventrally.
Dimensions: Holotype: Length - 53 μm. Width - 56 μm.
Paratype 56 μm. Width - 58 μm.
Overall 63 (53) 46 × 61 (57) 48 μm.
Specimens measured - 6.
Remarks: This species is similar to Heslertonia heslertonensis (Neale and Sarjeant 1962) Sarjeant 1966b in being thin-walled and in having sutural crests which are of even height over the entire cyst. It differs in having particularly low crests and in lacking crestal striations. Low crests are features shared with Heslertonia reticulata Duxbury 2023 and Heslertonia striata (Eisenack and Cookson 1960) n. comb. In his diagnosis of Heslertonia senecta Harding 1990 ex Harding in Williams et al. 1998, Harding (1990, p. 27) stated that the sutural crests of that species, "are two-layered and usually distally entire (if open the edges are denticulate)". This variability was also observed in Heslertonia inferior, where the distal crestal thickenings may bear very small to more conspicuous denticles (see pl. 11 fig. 2).
The moderate size and lack of any apical prominence are highlighted here to contrast Heslertonia inferior and Cauca redacta n. sp. The latter species has a rounded-triangular epicyst, and an apical protuberance typical of Cauca and it is significantly smaller than H. inferior: Cauca redacta: 43 (41) 38 μm × 38 (35) 33 μm. Heslertonia inferior: 63 (53) 46 μm × 61 (57) 48 μm. Heslertonia inferior was a rare but long-ranging species in the current study, occurring between Beds B134M and V124M, top Berriasian, alpillensis Zone, otopeta Sub-zone to late Valanginian, base peregrinus Zone, peregrinus Sub-zone.
Holotype: Plate 11, Figure 3, 7.
Paratype: Plate 11, Figure 2.
Type Locality: Vergol outcrop. Holotype: early Valanginian, Bed V19M, pertransiens ammonite Zone, salinarium Sub-zone, slide V19M/2, E.F. E59.1. Paratype: late Valanginian, Bed V124M, base peregrinus ammonite Zone, peregrinus Sub-zone, slide V124M(Schulze)/1, E.F. K46.1
Derivation of Name: From the Latin inferior, lower - in reference to the reduced sutural crests of this species.
Diagnosis: A spheroidal cyst of moderate size with smooth, thin wall layers and no apical projection. Tabulation is apparently typically gonyaulacacean and is outlined by low, smooth sutural crests. Crests contact the main body along narrow sutures and distally bear narrow linear thickenings which may be entire or variably denticulate; crests of equal height, similar to those elsewhere on the cyst, outline and sub-divide a narrow cingulum. The archeopyle is epicystal and the operculum usually remains attached ventrally.
Dimensions: Holotype: Length - 53 μm. Width - 56 μm.
Paratype 56 μm. Width - 58 μm.
Overall 63 (53) 46 × 61 (57) 48 μm.
Specimens measured - 6.
Remarks: This species is similar to Heslertonia heslertonensis (Neale and Sarjeant 1962) Sarjeant 1966b in being thin-walled and in having sutural crests which are of even height over the entire cyst. It differs in having particularly low crests and in lacking crestal striations. Low crests are features shared with Heslertonia reticulata Duxbury 2023 and Heslertonia striata (Eisenack and Cookson 1960) n. comb. In his diagnosis of Heslertonia senecta Harding 1990 ex Harding in Williams et al. 1998, Harding (1990, p. 27) stated that the sutural crests of that species, "are two-layered and usually distally entire (if open the edges are denticulate)". This variability was also observed in Heslertonia inferior, where the distal crestal thickenings may bear very small to more conspicuous denticles (see pl. 11 fig. 2).
The moderate size and lack of any apical prominence are highlighted here to contrast Heslertonia inferior and Cauca redacta n. sp. The latter species has a rounded-triangular epicyst, and an apical protuberance typical of Cauca and it is significantly smaller than H. inferior: Cauca redacta: 43 (41) 38 μm × 38 (35) 33 μm. Heslertonia inferior: 63 (53) 46 μm × 61 (57) 48 μm. Heslertonia inferior was a rare but long-ranging species in the current study, occurring between Beds B134M and V124M, top Berriasian, alpillensis Zone, otopeta Sub-zone to late Valanginian, base peregrinus Zone, peregrinus Sub-zone.