Back
Aprobolocysta reticulata
From Fensome et al., 2019:
Aprobolocysta reticulata, (Stover and Helby, 1987a, p.101–103, figs.1A–N) Duxbury, 2018, p.174.
Emendation: Duxbury, 2018, p.174–175, as Aprobolocysta reticulata.
Holotype: Stover and Helby, 1987a, figs.1E–G; Helby et al., 1987, fig.25I; Fensome et al., 1996, figs.1–3 — p.2325.
Originally Batioladinium, subsequently Necrobroomea, thirdly (and now) Aprobolocysta.
Age: Berriasian.
---------------------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------------------
Emended diagnosis (Duxbury, 2018):
Emended diagnosis: Cyst proximate to proximochorate, ovoidal to ellipsoidal with a short apical and 2 short, rounded, poorly-developed antapical horns. The cyst is formed of a smooth to finely granulate endophragm and a folded periphragm which forms usually low, poorly-defined crests. These can be restricted to the broad cingulum, which is offset ventrally by about one cingular width, but can also outline the tabulation to some extent. Distally, crests are entire and cingular crests can have a wavy appearance. A secondary, fine reticulum, again formed by periphragm folds, covers much of the cyst surface, although this can be reduced to an irregular granulation towards the apex. Archeopyle apical, with a deep sulcal notch typical of the genus.
Dimensions: Overall (operculum detached): 68 (57) 46 × 51 (44) 41 µm.
Specimens Measured: 12.
Complete specimens: 81(70)63 × 48(45)41 µm.
Specimens Measured: 3.
Remarks: This species has been transferred to Aprobolocysta Duxbury 1977, based on its pareodinioid shape, two wall layers and an apical archeopyle. Emendation of the specific diagnosis combines current observations with those of Stover and Helby (1987) and Pourtoy (1988).
In their original description of this species, Stover and Helby (1987, p. 101) considered the periphragm of this species (termed ectophragm) to be, “supported by irregularly distributed, curved rows of small capitate processes”. Such processes were not observed here, although junctions within the surface reticulum might give this impression in side-view.
The morphological range of this species is fairly wide, but never approaches the very high crests of Aprobolocysta neista Duxbury 1980, ranging from specimens with relatively low surface features and indistinct tabulation (similar to the type material of Stover and Helby 1987) to those with better-developed sutural crests and more overt tabulation. This morphological range appears to be related to stratigraphic position, with specimens from older material having less-developed ornamentation and lower crests; a similar difference was illustrated by Davey (1982) between his specimens (attributed to Aprobolocysta neista Duxbury 1980) from Speeton Bed D3 (Plate 7, Figure 7) and the Hauterivian of the Haldager No. 1 borehole (Plate 7, Figures 5, 6). The specimen illustrated here in Plate 5, Figures 6, 11 has well-developed sutural crests and although a complete tabulation could not be discerned, the presence on the dorsal surface of at least two plates above the precingular series is
reminiscent of the scheme proposed for this genus by Fensome et al. (1993, Figure 79D).
Aprobolocysta reticulata is a rare species, recorded consistently here from the lower Valanginian (Speeton Bed D4A) to the lower Hauterivian, Palyzone LKP10.3, a much longer range and apparently entirely younger than its Berriasian-restricted occurrence in Australasia (Stover and Helby 1987, Helby et al. 1987).
Aprobolocysta reticulata, (Stover and Helby, 1987a, p.101–103, figs.1A–N) Duxbury, 2018, p.174.
Emendation: Duxbury, 2018, p.174–175, as Aprobolocysta reticulata.
Holotype: Stover and Helby, 1987a, figs.1E–G; Helby et al., 1987, fig.25I; Fensome et al., 1996, figs.1–3 — p.2325.
Originally Batioladinium, subsequently Necrobroomea, thirdly (and now) Aprobolocysta.
Age: Berriasian.
---------------------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------------------
Emended diagnosis (Duxbury, 2018):
Emended diagnosis: Cyst proximate to proximochorate, ovoidal to ellipsoidal with a short apical and 2 short, rounded, poorly-developed antapical horns. The cyst is formed of a smooth to finely granulate endophragm and a folded periphragm which forms usually low, poorly-defined crests. These can be restricted to the broad cingulum, which is offset ventrally by about one cingular width, but can also outline the tabulation to some extent. Distally, crests are entire and cingular crests can have a wavy appearance. A secondary, fine reticulum, again formed by periphragm folds, covers much of the cyst surface, although this can be reduced to an irregular granulation towards the apex. Archeopyle apical, with a deep sulcal notch typical of the genus.
Dimensions: Overall (operculum detached): 68 (57) 46 × 51 (44) 41 µm.
Specimens Measured: 12.
Complete specimens: 81(70)63 × 48(45)41 µm.
Specimens Measured: 3.
Remarks: This species has been transferred to Aprobolocysta Duxbury 1977, based on its pareodinioid shape, two wall layers and an apical archeopyle. Emendation of the specific diagnosis combines current observations with those of Stover and Helby (1987) and Pourtoy (1988).
In their original description of this species, Stover and Helby (1987, p. 101) considered the periphragm of this species (termed ectophragm) to be, “supported by irregularly distributed, curved rows of small capitate processes”. Such processes were not observed here, although junctions within the surface reticulum might give this impression in side-view.
The morphological range of this species is fairly wide, but never approaches the very high crests of Aprobolocysta neista Duxbury 1980, ranging from specimens with relatively low surface features and indistinct tabulation (similar to the type material of Stover and Helby 1987) to those with better-developed sutural crests and more overt tabulation. This morphological range appears to be related to stratigraphic position, with specimens from older material having less-developed ornamentation and lower crests; a similar difference was illustrated by Davey (1982) between his specimens (attributed to Aprobolocysta neista Duxbury 1980) from Speeton Bed D3 (Plate 7, Figure 7) and the Hauterivian of the Haldager No. 1 borehole (Plate 7, Figures 5, 6). The specimen illustrated here in Plate 5, Figures 6, 11 has well-developed sutural crests and although a complete tabulation could not be discerned, the presence on the dorsal surface of at least two plates above the precingular series is
reminiscent of the scheme proposed for this genus by Fensome et al. (1993, Figure 79D).
Aprobolocysta reticulata is a rare species, recorded consistently here from the lower Valanginian (Speeton Bed D4A) to the lower Hauterivian, Palyzone LKP10.3, a much longer range and apparently entirely younger than its Berriasian-restricted occurrence in Australasia (Stover and Helby 1987, Helby et al. 1987).