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Wilsonidium aechmophorum
Wilsonidium? aechmophorum (Benedek, 1972, p.41, pl.5, figs.7,11; text-fig.17) Lentin and Williams, 1976, p.139. Emendation: Benedek and Sarjeant, 1981, p.340–341, as Gerlachidium aechmophorum
NOW Gerlachidium. Originally Lejeunia (generic name illegitimate), subsequently Wilsonidium?, thirdly Lejeunecysta, fourthly (and now) Gerlachidium. Questionable assignment: Lentin and Williams (1976, p.139).
Holotype: Benedek, 1972, pl.5, fig.7; text-fig.17; Benedek and Sarjeant, 1981, figs.7,9, nos.1–2; Fensome et al., 1993a, figs.1–2 — p.887.
Age: Middle-Late Oligocene
Original description: Benedek, 1972, p. 41: Lejeunia aechmophora
Diagnosis: A Lejeunia species with a smooth shell, which is locally set with smaller or larger spines, as well as bundles of spines. The broad, circular girdle furrow and the especially broad longitudinal field are delimited by edges of small teeth.
Description: The clearly bilaterally symmetrical, pentagonal shell has a thin, smooth membrane, which may be locally set with spines and small spinous processes. The circular, relatively broad girdle-furrow is indented, and is delimited on both sides by an edge of small teeth. The triangular epitheca runs into a small, pointed, apical horn, which is sometimes also set with spinous processes. The trapezoidal hypotheca ends in two broad, but distally streched, pointed antapical horns.
Dimensions: Shell length 66 (57-73) µm, width 60 (52-66) µm, processes appr. 8-12 µm, apical horn appr. 5-6 µm.
Emended description: Benedek and Sarjeant, 1981, p. 340-341
Diagnosis: Cyst proximate; ambitus rounded-pentagonal, the antapical face concave. Epitract conical, with a rounded apical prominence; hypotract a truncated cone, prolonged into two asymmetrical horns, that at left larger than at right, both pointed. Paracingulum broad, faintly indented and irregularly bordered by discontinuous crests of moderate height and with serrate, denticulate or spinose edges. Similar discontinuous crests, lines of processes or isolated processes, sutural or penitabular in situation, are irregularly distributed elsewhere on the cyst. Surface of phragma laevigate or only minutely ornamented. A broad region, bare of processes or crests, on the ventral surface may correspond to the paracingulum. Archaeopyle horseshoe-shaped, formed by the opening of an anterior intercalary paraplate (Type I); operculum normally attached posteriorly; archaeopyle index 0.40 to 0.45.
Description: The phragma, though thin, appears to be two-layered, the periphragm giving rise to the crests and processes. Apart from those bordering the paracingulum, these are so discontinuous in distribution that it was not possible to decide whether their situation is sutural or penitabular. These crests give a ragged appearance to the cyst, especially to the margins and to the horns. In part they are fairly continuous structures with serrate edges, the serrations varying into denticles or finger-like outgrowths, simple or (more often) bifurcate or trifurcate; some crests actually coalesce, e.g. at the tips of the antapical horns. Elsewhere, however, they are so broken as to instead effectively consist of lines of processes. In places (e.g. on the middorsal surface of the hypotract of the holotype), single processes are present.
The archaeopyle is not conspicuous and, if the operculum has fully closed up, may indeed be virtually invisible (as in the related genus, Lejeunecysta). Its posterior margin is sufficiently separated from the paracingulum to make it evident that this is an anterior intercalary archaeopyle and is shape, roughly the "standard hexa" outline of Lentin and Williams (1976), makes evident the fact that only one paraplate is involved.
Dimensions: Holotype -- Overall length 73 µm, overall breadth 62 µm, height of crests up to 12 µm. Range of Dimensions: Overall length 57-73 µm (mean 60 µm), overall breadth 52-66 µm (mean 60 µm), height of crests ca. 8-12 µm. 19 specimens.
Affinities.
Benedek, 1972, p. 41: Lejeunia aechmophora
As yet, no Lejeunia species has been described bearing similar processes. Against L. tenella, the shell of L. aechmophorum is not overall set with spines, but possesses smooth fields. Only the transverse and longitudinal furrow, as well as the marginal zones have small pointed appendices.
Benedek and Sarjeant, 1981, p. 342: Gerlachidium aechmophorum
In its overall morphology and inconspicuous style of archaeopyle formation, this species resembles Lejeunecysta, but it differs in retaining a direct, if incomplete, reflection of paratabulation by crests and processes.
NOW Gerlachidium. Originally Lejeunia (generic name illegitimate), subsequently Wilsonidium?, thirdly Lejeunecysta, fourthly (and now) Gerlachidium. Questionable assignment: Lentin and Williams (1976, p.139).
Holotype: Benedek, 1972, pl.5, fig.7; text-fig.17; Benedek and Sarjeant, 1981, figs.7,9, nos.1–2; Fensome et al., 1993a, figs.1–2 — p.887.
Age: Middle-Late Oligocene
Original description: Benedek, 1972, p. 41: Lejeunia aechmophora
Diagnosis: A Lejeunia species with a smooth shell, which is locally set with smaller or larger spines, as well as bundles of spines. The broad, circular girdle furrow and the especially broad longitudinal field are delimited by edges of small teeth.
Description: The clearly bilaterally symmetrical, pentagonal shell has a thin, smooth membrane, which may be locally set with spines and small spinous processes. The circular, relatively broad girdle-furrow is indented, and is delimited on both sides by an edge of small teeth. The triangular epitheca runs into a small, pointed, apical horn, which is sometimes also set with spinous processes. The trapezoidal hypotheca ends in two broad, but distally streched, pointed antapical horns.
Dimensions: Shell length 66 (57-73) µm, width 60 (52-66) µm, processes appr. 8-12 µm, apical horn appr. 5-6 µm.
Emended description: Benedek and Sarjeant, 1981, p. 340-341
Diagnosis: Cyst proximate; ambitus rounded-pentagonal, the antapical face concave. Epitract conical, with a rounded apical prominence; hypotract a truncated cone, prolonged into two asymmetrical horns, that at left larger than at right, both pointed. Paracingulum broad, faintly indented and irregularly bordered by discontinuous crests of moderate height and with serrate, denticulate or spinose edges. Similar discontinuous crests, lines of processes or isolated processes, sutural or penitabular in situation, are irregularly distributed elsewhere on the cyst. Surface of phragma laevigate or only minutely ornamented. A broad region, bare of processes or crests, on the ventral surface may correspond to the paracingulum. Archaeopyle horseshoe-shaped, formed by the opening of an anterior intercalary paraplate (Type I); operculum normally attached posteriorly; archaeopyle index 0.40 to 0.45.
Description: The phragma, though thin, appears to be two-layered, the periphragm giving rise to the crests and processes. Apart from those bordering the paracingulum, these are so discontinuous in distribution that it was not possible to decide whether their situation is sutural or penitabular. These crests give a ragged appearance to the cyst, especially to the margins and to the horns. In part they are fairly continuous structures with serrate edges, the serrations varying into denticles or finger-like outgrowths, simple or (more often) bifurcate or trifurcate; some crests actually coalesce, e.g. at the tips of the antapical horns. Elsewhere, however, they are so broken as to instead effectively consist of lines of processes. In places (e.g. on the middorsal surface of the hypotract of the holotype), single processes are present.
The archaeopyle is not conspicuous and, if the operculum has fully closed up, may indeed be virtually invisible (as in the related genus, Lejeunecysta). Its posterior margin is sufficiently separated from the paracingulum to make it evident that this is an anterior intercalary archaeopyle and is shape, roughly the "standard hexa" outline of Lentin and Williams (1976), makes evident the fact that only one paraplate is involved.
Dimensions: Holotype -- Overall length 73 µm, overall breadth 62 µm, height of crests up to 12 µm. Range of Dimensions: Overall length 57-73 µm (mean 60 µm), overall breadth 52-66 µm (mean 60 µm), height of crests ca. 8-12 µm. 19 specimens.
Affinities.
Benedek, 1972, p. 41: Lejeunia aechmophora
As yet, no Lejeunia species has been described bearing similar processes. Against L. tenella, the shell of L. aechmophorum is not overall set with spines, but possesses smooth fields. Only the transverse and longitudinal furrow, as well as the marginal zones have small pointed appendices.
Benedek and Sarjeant, 1981, p. 342: Gerlachidium aechmophorum
In its overall morphology and inconspicuous style of archaeopyle formation, this species resembles Lejeunecysta, but it differs in retaining a direct, if incomplete, reflection of paratabulation by crests and processes.