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Systematophora geminus
Systematophora geminus Riding and Helby, 2001e, p.123–126, figs.7A,8A–I,9A–I.
Holotype: Riding and Helby, 2001e, figs.8D–F. N.I.A.
Age: Callovian–Oxfordian.
Original description (Riding &Helby, 2001e):
Systematophora geminus sp. nov. (Figs 7A, 8A-I, 9A-I)
Previous Australian usage
Systematophora? Sp. A – Helby.
Systematophora areolata (pars) – Morgan
Description: A species of Systematophora with a subspherical cyst body, the autophragm of which is microreticulate to scabrate. Slender, solid processes, which may branch both proximally and distally, emerge from subcircular to subquadrangular annulate penitabular process groups in the major transverse paraplate series. The processes are joined proximally by low, smooth penitabular ridges; the distal terminations may be joined by trabeculae. Typically, the distal processes endings are bifid, however they also may be branched or multifurcate and frequently form continuous distal trabecular rings, which may be joined by trabecular filaments. Two pairs of solid slender, distally bifid, processes are present within each paracingular paraplate. Low reflief elements, which range to short processes, are present within and close to the boundary of the parasulcus. Short, solid, simple processes or low relief elements may be present within areas defined by the major process complexes.
Dimensions (µm, n=34, loistocysts only): Min.(Mean)Max.
Length of cyst incl. processes: 55 (77) 97
Length of cyst body (excl. processes): 35 (54) 67
Width of cyst incl. processes: 56 (79) 97
Width of cyst body (excl. processes): 39 (57) 74
Length of proceses: 7 (14) 23
A single cyst with operculum attached was measured at 97 µm overall length with a cyst body 63 µm long. The measured specimens are from sidewall core samples from Arunta-1 well at 2135.00m and Bogong-1 well at 3530.00m
Comments: The thin, solid processes in Systematophora geminus vary in morphology and length; they are generally shorter than in other species. The apical, precingular, postcingular, posterior intercalary and antapical processes arise from subcircular to rounded subrectangular, annulate, penitabular ridges. Short, simple processes or denticles may arise within the process complexes, causing darkening of these areas. Typically, the main processes are branched, this occurring distally more consistently than proximally. The distal tips of the processes/branches are typically bifurcate, although multifurcate extremities may be present. The distal parts of the processes may also be trabeculate. The length of the processes on each cyst is relatively constant accessory archeopyle sutures within the precingular paraplate series are common.
Comparisons: the presence of a relatively thick, microreticulate autophragm, occasional short processes within the annulate processes complexes and paired processes within the paracingulum distinguish S. geminus from other species of the genus. Typically, single processes arise from each of end of low, intratabular, rectilinear paracingular crests (Klement, 1960, figs. 32-33; Riding & Thomas, 1988, fig. 10). There are no known occurrences of paired sets as in S. geminus. This new species differs from the genotype, S. complicate and many other species of the genus in having branched processes, which are sometimes distally trabeculate. The species S. complicata Neale & Sarjeant 1962 and S. orbifera Klement 1960 are, by contrast, consistently distally trabeculate. Systematophora daveyi Riding & Thomas 1988 and S. septate Wilson 1988 have arcuate penitabular process complexes and septate penitabular ornamentation respectively. In some suites, the distal trabecular filaments. Polystephanephorus Sarjeant 1961 emend. Stancliffe & Sarjeant 1990 includes forms which have distally connected trabeculate filamnets (Standcliffe & Sarjeant 1990, figs. 1, 2). These are distinguished from S. geminus in lacking the double paired paracingular process of the latter.
Derivation of name: from the Latin geminus meaning twin, in reference to the pairing of the paracingular processes.
Holotype and type locality: Figures 8D-F, CPC 35565, Bogong-1 well, sidewall core at 3530.00m.
Stratigraphical distribution. Systematophora geminus ranges from the Callovian lower Rigaudella aemula Zone (7aiib) to the Oxfordian basal part of the Wanaea spectabilis Zone (6ciiib) in the Timor Sea region (Foster, this volume; Helby & Partridge, in prep.)
Holotype: Riding and Helby, 2001e, figs.8D–F. N.I.A.
Age: Callovian–Oxfordian.
Original description (Riding &Helby, 2001e):
Systematophora geminus sp. nov. (Figs 7A, 8A-I, 9A-I)
Previous Australian usage
Systematophora? Sp. A – Helby.
Systematophora areolata (pars) – Morgan
Description: A species of Systematophora with a subspherical cyst body, the autophragm of which is microreticulate to scabrate. Slender, solid processes, which may branch both proximally and distally, emerge from subcircular to subquadrangular annulate penitabular process groups in the major transverse paraplate series. The processes are joined proximally by low, smooth penitabular ridges; the distal terminations may be joined by trabeculae. Typically, the distal processes endings are bifid, however they also may be branched or multifurcate and frequently form continuous distal trabecular rings, which may be joined by trabecular filaments. Two pairs of solid slender, distally bifid, processes are present within each paracingular paraplate. Low reflief elements, which range to short processes, are present within and close to the boundary of the parasulcus. Short, solid, simple processes or low relief elements may be present within areas defined by the major process complexes.
Dimensions (µm, n=34, loistocysts only): Min.(Mean)Max.
Length of cyst incl. processes: 55 (77) 97
Length of cyst body (excl. processes): 35 (54) 67
Width of cyst incl. processes: 56 (79) 97
Width of cyst body (excl. processes): 39 (57) 74
Length of proceses: 7 (14) 23
A single cyst with operculum attached was measured at 97 µm overall length with a cyst body 63 µm long. The measured specimens are from sidewall core samples from Arunta-1 well at 2135.00m and Bogong-1 well at 3530.00m
Comments: The thin, solid processes in Systematophora geminus vary in morphology and length; they are generally shorter than in other species. The apical, precingular, postcingular, posterior intercalary and antapical processes arise from subcircular to rounded subrectangular, annulate, penitabular ridges. Short, simple processes or denticles may arise within the process complexes, causing darkening of these areas. Typically, the main processes are branched, this occurring distally more consistently than proximally. The distal tips of the processes/branches are typically bifurcate, although multifurcate extremities may be present. The distal parts of the processes may also be trabeculate. The length of the processes on each cyst is relatively constant accessory archeopyle sutures within the precingular paraplate series are common.
Comparisons: the presence of a relatively thick, microreticulate autophragm, occasional short processes within the annulate processes complexes and paired processes within the paracingulum distinguish S. geminus from other species of the genus. Typically, single processes arise from each of end of low, intratabular, rectilinear paracingular crests (Klement, 1960, figs. 32-33; Riding & Thomas, 1988, fig. 10). There are no known occurrences of paired sets as in S. geminus. This new species differs from the genotype, S. complicate and many other species of the genus in having branched processes, which are sometimes distally trabeculate. The species S. complicata Neale & Sarjeant 1962 and S. orbifera Klement 1960 are, by contrast, consistently distally trabeculate. Systematophora daveyi Riding & Thomas 1988 and S. septate Wilson 1988 have arcuate penitabular process complexes and septate penitabular ornamentation respectively. In some suites, the distal trabecular filaments. Polystephanephorus Sarjeant 1961 emend. Stancliffe & Sarjeant 1990 includes forms which have distally connected trabeculate filamnets (Standcliffe & Sarjeant 1990, figs. 1, 2). These are distinguished from S. geminus in lacking the double paired paracingular process of the latter.
Derivation of name: from the Latin geminus meaning twin, in reference to the pairing of the paracingular processes.
Holotype and type locality: Figures 8D-F, CPC 35565, Bogong-1 well, sidewall core at 3530.00m.
Stratigraphical distribution. Systematophora geminus ranges from the Callovian lower Rigaudella aemula Zone (7aiib) to the Oxfordian basal part of the Wanaea spectabilis Zone (6ciiib) in the Timor Sea region (Foster, this volume; Helby & Partridge, in prep.)