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Vesperopsis longicornis
From Fensome et al., 2019:
Vesperopsis longicornis (Batten and Lister, 1988, p.340–341, figs.1b–e,g) Harding, 1990b, p.21.
Emendation: Harding, 1990b, p.21–22, as Vesperopsis longicornis.
Holotype: Batten and Lister, 1988, figs.1b–c.
Originally Australisphaera, subsequently (and now) Vesperopsis.
Locus typicus: Shepherd"s Chine Member of the Vectis Formation, Isle of Wight
Stratum typicum: Barremian
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Original diagnosis: Batten and Lister, 1988, p.340: Australisphaera longicornis
Proximate ceratioid cyst, dorsoventrally flattened; maximum diameter 66(76)85x48(63)78 µm (10 specimens). Apical horn prominent, somewhat elongate and distally rounded. Lateral horns developed as paracingular extensions bearing postparacingular, sharply tapering digitations c.12-25 µm (rarely > 40 µm) long. Usually two antapical horns present; left is strong, narrow, tapering and distally rounded; right is very reduced, sometimes a small triangular cone or low prominence, or absent altogether. Cyst wall thin (1µm or less), scabrate to microgranulate and without any indication of paratabulation. Margin of archeopyle angular; six precingular paraplates and a deep parasulcal notch offset to left are indicated by splitting along accessory sutures. Archeopyle type (tA), operculum free but sometimes remaining attached after dehiscence.
Emended Diagnosis: Harding, 1990, p. 21
Shape: Ambitus typically ceratioid/muderongioid. Main body basically pentagonal in outline modified by apical, two lateral (post-cingular) and two antapical horns. Epicyst and hypocyst of equal length. Greatest width across post-cingular horn extremities. Strong dorso-ventral compression.
Phragma: Autophragm thin (ca. 1 µm), laevigate to microgranulate. Developed into long tapering horns in apical and left antapical positions. Right antapical position may be occupied by a well developed horn or, more usually by only a bulge. Paracingular bulges in the periphragm are sub-rectangular in shape and bear downward curving horns on their distal antapical extremities.
Paratabulation: As far as can be determined, typically corniform gonyaulacoid. Paratabulation of the epicyst is 4", 6" + ai indicated by the archaeopyle suture.
Archaeopyle: Type (tA), involving the apical series as an attached, simple, polyplacoid operculum. The operculum is often found to have been mechanically removed. Parasulcal notch offset to the left.
Paracingulum: Developed between bar-like autophragmal outgrowths of the precingular and postcingular paraplate series, as a parallel sided indentation.
Parasulcus: ai offset to left, rest of the tabulation of this area is unknown.
Dimensions: Length, plus operculum (136)119.5 (100) µm. Width (90) 70.7 (68) µm. Length, less operculum (90) 79.8 (70) µm. Specimens = 23 (15).
Affinities:
Harding, 1990, p. 21: Following a re-examination of the type material of Australisphaera fragilis Harding 1986, the emendation of the genus Australisphaera (Harding, 1986) is questioned. The two closely adpressed wall layers described for the type material of A. fragilis have been found to be an artifact of preservation. By far the majority of specimens of A. fragilis are found with an adnate operculum. It is clear that most of the specimens of this species which are found without operculae lost this part of the cyst by mechanical disruption - either postmortem or during processing (Harding, 1986a, Pl. 17, Fig. 9, clearly shows a torn ventral archaeoplye margin). Thus it is felt unwise to maintain the generic assignment of A. fragilis. Following Stover and Williams (1987), all early Cretaceous identifications of the genus Australisphaera are treated as suspect.
The species described by Batten & Lister (1988) cannot be allocated to Muderongia Cookson & Eisenack or Nyktericysta Bint, as both of these genera possess two wall layers. Although A. Iongicornis, as illustrated by Batten & Lister (1988, Figs. lb-e, g), appears to possess a free operculum, the paratabulation along the principal archaeopyle suture is very difficult to determine. This may also be the result of mechanical damage, as the vast majority of specimens observed during the present study possess adnate operculae (Pl. 2). With these facts in mind, and those already given above, it appears unwise to allocate this species to the genus Australisphaera Davey. The adnate nature of the operculum of the majority of specimens of this species in the present study would argue for placement into the genus Vesperopsis Bint 1986. The species of this genus all possess adnate operculae, however, these are attached ventrally via the parasulcal region, whereas the site of attachment in the present species would appear to be dorsal.
This species is usually found crumpled and in a relatively poor state of preservation due to the diaphanous nature of the autophragm. However, the mounting of individual well-preserved specimens in this study has allowed a clarification of the morphology. This species is distinguished from other members of the genus Vesperopsis by the more complicated morphology of the lateral/post-cingular horns. Lister and Batten found this species to be rare in the samples from the Hurlands Farm Borehole (Lister and Batten, 1988), but no abundance information was given in the specific diagnosis of (Batten and Lister, 1988) from the Weald Clay of the Isle of Wight. In the present study this species has been found in often flood abundance in the highest parts of the Weald Clay in the Warlingham borehole, associated with "A." fragilis (as found by Batten and Lister, 1988).
Vesperopsis longicornis (Batten and Lister, 1988, p.340–341, figs.1b–e,g) Harding, 1990b, p.21.
Emendation: Harding, 1990b, p.21–22, as Vesperopsis longicornis.
Holotype: Batten and Lister, 1988, figs.1b–c.
Originally Australisphaera, subsequently (and now) Vesperopsis.
Locus typicus: Shepherd"s Chine Member of the Vectis Formation, Isle of Wight
Stratum typicum: Barremian
---------------------------------------------------------------------------------------------------
Original diagnosis: Batten and Lister, 1988, p.340: Australisphaera longicornis
Proximate ceratioid cyst, dorsoventrally flattened; maximum diameter 66(76)85x48(63)78 µm (10 specimens). Apical horn prominent, somewhat elongate and distally rounded. Lateral horns developed as paracingular extensions bearing postparacingular, sharply tapering digitations c.12-25 µm (rarely > 40 µm) long. Usually two antapical horns present; left is strong, narrow, tapering and distally rounded; right is very reduced, sometimes a small triangular cone or low prominence, or absent altogether. Cyst wall thin (1µm or less), scabrate to microgranulate and without any indication of paratabulation. Margin of archeopyle angular; six precingular paraplates and a deep parasulcal notch offset to left are indicated by splitting along accessory sutures. Archeopyle type (tA), operculum free but sometimes remaining attached after dehiscence.
Emended Diagnosis: Harding, 1990, p. 21
Shape: Ambitus typically ceratioid/muderongioid. Main body basically pentagonal in outline modified by apical, two lateral (post-cingular) and two antapical horns. Epicyst and hypocyst of equal length. Greatest width across post-cingular horn extremities. Strong dorso-ventral compression.
Phragma: Autophragm thin (ca. 1 µm), laevigate to microgranulate. Developed into long tapering horns in apical and left antapical positions. Right antapical position may be occupied by a well developed horn or, more usually by only a bulge. Paracingular bulges in the periphragm are sub-rectangular in shape and bear downward curving horns on their distal antapical extremities.
Paratabulation: As far as can be determined, typically corniform gonyaulacoid. Paratabulation of the epicyst is 4", 6" + ai indicated by the archaeopyle suture.
Archaeopyle: Type (tA), involving the apical series as an attached, simple, polyplacoid operculum. The operculum is often found to have been mechanically removed. Parasulcal notch offset to the left.
Paracingulum: Developed between bar-like autophragmal outgrowths of the precingular and postcingular paraplate series, as a parallel sided indentation.
Parasulcus: ai offset to left, rest of the tabulation of this area is unknown.
Dimensions: Length, plus operculum (136)119.5 (100) µm. Width (90) 70.7 (68) µm. Length, less operculum (90) 79.8 (70) µm. Specimens = 23 (15).
Affinities:
Harding, 1990, p. 21: Following a re-examination of the type material of Australisphaera fragilis Harding 1986, the emendation of the genus Australisphaera (Harding, 1986) is questioned. The two closely adpressed wall layers described for the type material of A. fragilis have been found to be an artifact of preservation. By far the majority of specimens of A. fragilis are found with an adnate operculum. It is clear that most of the specimens of this species which are found without operculae lost this part of the cyst by mechanical disruption - either postmortem or during processing (Harding, 1986a, Pl. 17, Fig. 9, clearly shows a torn ventral archaeoplye margin). Thus it is felt unwise to maintain the generic assignment of A. fragilis. Following Stover and Williams (1987), all early Cretaceous identifications of the genus Australisphaera are treated as suspect.
The species described by Batten & Lister (1988) cannot be allocated to Muderongia Cookson & Eisenack or Nyktericysta Bint, as both of these genera possess two wall layers. Although A. Iongicornis, as illustrated by Batten & Lister (1988, Figs. lb-e, g), appears to possess a free operculum, the paratabulation along the principal archaeopyle suture is very difficult to determine. This may also be the result of mechanical damage, as the vast majority of specimens observed during the present study possess adnate operculae (Pl. 2). With these facts in mind, and those already given above, it appears unwise to allocate this species to the genus Australisphaera Davey. The adnate nature of the operculum of the majority of specimens of this species in the present study would argue for placement into the genus Vesperopsis Bint 1986. The species of this genus all possess adnate operculae, however, these are attached ventrally via the parasulcal region, whereas the site of attachment in the present species would appear to be dorsal.
This species is usually found crumpled and in a relatively poor state of preservation due to the diaphanous nature of the autophragm. However, the mounting of individual well-preserved specimens in this study has allowed a clarification of the morphology. This species is distinguished from other members of the genus Vesperopsis by the more complicated morphology of the lateral/post-cingular horns. Lister and Batten found this species to be rare in the samples from the Hurlands Farm Borehole (Lister and Batten, 1988), but no abundance information was given in the specific diagnosis of (Batten and Lister, 1988) from the Weald Clay of the Isle of Wight. In the present study this species has been found in often flood abundance in the highest parts of the Weald Clay in the Warlingham borehole, associated with "A." fragilis (as found by Batten and Lister, 1988).