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Heslertonia reticulata
Plate 27, Figures 3, 5, 7, 8
Holotype: Plate 27, Figure 3, 8.
Type Locality: Well 14/19-E9 at 11408.40ft (conventional core chip), early Hauterivian.
Holotype: Well 14/19-E9, slide 11408.40ft /2. E.F. D56.1.
Derivation of Name: From the Latin reticulatus, netlike, netted - in reference to the characteristic surface reticulum of this species.
Diagnosis: Aspheroidal chorate cyst of intermediate size with a relatively thick-walled endophragm bearing a low surface reticulum. The tabulation 4', 6'', 6c, 6''', 1p, 1'''' is outlined by smooth sutural crests of moderate height. Crests contact the main body along narrow sutures and distally bear narrow linear thickenings; cingular crests are lower than elsewhere on the cyst and outline distinctly zig-zag plate margins. The archeopyle is epicystal and the operculum remains attached ventrally.
Dimensions: Holotype: Length - 101 μm. Width - 86 μm.
Overall: 101 (86) 76 μm × 89 (78) 58 μm.
Specimens Measured: 14.
Remarks: This species was restricted to the early Hauterivian in the present study; it differs from other members of the genus by its reticulate sculpture. A similarly ornate species, Heslertonia senecta Harding 1990 ex Harding in Williams et al. 1998 is restricted to the late Barremian and has a distinctly rugulate sculpture and crests covered in parallel, radiating striae or corrugations (Harding 1990, p. 27), features not seen in Heslertonia reticulata. Also, the cingular plates of H. senecta appear to be narrow and bounded by essentially parallel epi- and hypocystal crests, whereas those crests are distinctly zig-zag in H. reticulata.
Heslertonia heslertonensis, the only other species of this genus recorded here, does not have any distinctive surface ornament. Also, the proximal “vacuolar structures” noted in the crests of H. heslertonensis and H. senecta by Duxbury (1980, p. 124) and Harding (1990, p. 27) respectively were not observed in Heslertonia reticulata.
Holotype: Plate 27, Figure 3, 8.
Type Locality: Well 14/19-E9 at 11408.40ft (conventional core chip), early Hauterivian.
Holotype: Well 14/19-E9, slide 11408.40ft /2. E.F. D56.1.
Derivation of Name: From the Latin reticulatus, netlike, netted - in reference to the characteristic surface reticulum of this species.
Diagnosis: Aspheroidal chorate cyst of intermediate size with a relatively thick-walled endophragm bearing a low surface reticulum. The tabulation 4', 6'', 6c, 6''', 1p, 1'''' is outlined by smooth sutural crests of moderate height. Crests contact the main body along narrow sutures and distally bear narrow linear thickenings; cingular crests are lower than elsewhere on the cyst and outline distinctly zig-zag plate margins. The archeopyle is epicystal and the operculum remains attached ventrally.
Dimensions: Holotype: Length - 101 μm. Width - 86 μm.
Overall: 101 (86) 76 μm × 89 (78) 58 μm.
Specimens Measured: 14.
Remarks: This species was restricted to the early Hauterivian in the present study; it differs from other members of the genus by its reticulate sculpture. A similarly ornate species, Heslertonia senecta Harding 1990 ex Harding in Williams et al. 1998 is restricted to the late Barremian and has a distinctly rugulate sculpture and crests covered in parallel, radiating striae or corrugations (Harding 1990, p. 27), features not seen in Heslertonia reticulata. Also, the cingular plates of H. senecta appear to be narrow and bounded by essentially parallel epi- and hypocystal crests, whereas those crests are distinctly zig-zag in H. reticulata.
Heslertonia heslertonensis, the only other species of this genus recorded here, does not have any distinctive surface ornament. Also, the proximal “vacuolar structures” noted in the crests of H. heslertonensis and H. senecta by Duxbury (1980, p. 124) and Harding (1990, p. 27) respectively were not observed in Heslertonia reticulata.