Back
Amphorosphaeridium fenestratum
Amphorosphaeridium fenestratum, Davey, 1969
Holotype: Davey, 1969, pl.3, figs.1-2; Fensome et al., 1993, p.1183, figs.1-2
Locus typicus: Northern Natal, South Africa
Stratum typicum: Campanian-Maastrichtian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Davey, 1969, p. 30-31]:
Diagnosis:
Central body subspherical, wall moderately thick, fibrous and pitted.
Processes one or two, rarely three, per plate-area, of variable width but constant length (approximately one-third central body diameter); they are typically hollow, tubiform and spinous distally. Apical process broad, branching; antapical process tubiform, distinctively large.
Archaeopyle usually present.
Description:
The wall of the central body is 1 to 1.5 µm thick and is fibrous with subpolygonal to elongate pits or perforations between the fibres.
The cingulum, which is rarely present, may be delimited by parallel rows of aligned pits.
The processes are also fibrous, the fibres of each process splaying out proximally over the surface of the central body. The majority of the processes are tubiform and are angular in cross-section, usually quadrilateral, due to three or four longitudinal ribs ([Davey, 1969] fig. 1, no. 2a, b, d). Solid processes sometimes also occur but are always in a minority and are usually restricted to the sulcal region. The processes vary considerably in width on an individual and on different specimens depending mainly on the number of processes per plate-area present. The processes on specimens possessing one process per plate-area are typically broader than those with two or three per plate-area. Normally, however, there are one or two processes per plate-area and any additional ones are finer, perhaps solid, although being of equal length to the normal processes. The processes have broad bases and taper distally before expanding to produce a small number of spines. The latter of the tubiform processes are usually formed by extensions of the more strongly developed fibres (longitudinal ribs) of the processes and are often recurved to some extent. The broader processes are very rarely fenestrate. The sulcal region, as mentioned earlier, may either bear relatively fine solid processes or may be devoid of any processes. In the latter case this region is surrounded by normal processes which tend to be joined proximally and so clearly delimit it ([Davey, 1969c] Pl. 1, fig. 6). Some process alignment may be noticeable along the cingulum. The apical process is a broad fibrous structure which gives rise medially to two to four subsidiary processes; the antapical process is similar to the normal processes in structure but is larger.
The archaeopyle is of a rounded triangular shape and is formed by the loss of the reflected precingular plate 3" - Type P of Evitt (1967).
Dimensions:
Holotype: central body diameter 57x64 µm, process length 25-27 µm.
Range of 12 specimens: central body diameter 52(60)77 µm, process length 19(21)27 µm.
Holotype: Davey, 1969, pl.3, figs.1-2; Fensome et al., 1993, p.1183, figs.1-2
Locus typicus: Northern Natal, South Africa
Stratum typicum: Campanian-Maastrichtian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Davey, 1969, p. 30-31]:
Diagnosis:
Central body subspherical, wall moderately thick, fibrous and pitted.
Processes one or two, rarely three, per plate-area, of variable width but constant length (approximately one-third central body diameter); they are typically hollow, tubiform and spinous distally. Apical process broad, branching; antapical process tubiform, distinctively large.
Archaeopyle usually present.
Description:
The wall of the central body is 1 to 1.5 µm thick and is fibrous with subpolygonal to elongate pits or perforations between the fibres.
The cingulum, which is rarely present, may be delimited by parallel rows of aligned pits.
The processes are also fibrous, the fibres of each process splaying out proximally over the surface of the central body. The majority of the processes are tubiform and are angular in cross-section, usually quadrilateral, due to three or four longitudinal ribs ([Davey, 1969] fig. 1, no. 2a, b, d). Solid processes sometimes also occur but are always in a minority and are usually restricted to the sulcal region. The processes vary considerably in width on an individual and on different specimens depending mainly on the number of processes per plate-area present. The processes on specimens possessing one process per plate-area are typically broader than those with two or three per plate-area. Normally, however, there are one or two processes per plate-area and any additional ones are finer, perhaps solid, although being of equal length to the normal processes. The processes have broad bases and taper distally before expanding to produce a small number of spines. The latter of the tubiform processes are usually formed by extensions of the more strongly developed fibres (longitudinal ribs) of the processes and are often recurved to some extent. The broader processes are very rarely fenestrate. The sulcal region, as mentioned earlier, may either bear relatively fine solid processes or may be devoid of any processes. In the latter case this region is surrounded by normal processes which tend to be joined proximally and so clearly delimit it ([Davey, 1969c] Pl. 1, fig. 6). Some process alignment may be noticeable along the cingulum. The apical process is a broad fibrous structure which gives rise medially to two to four subsidiary processes; the antapical process is similar to the normal processes in structure but is larger.
The archaeopyle is of a rounded triangular shape and is formed by the loss of the reflected precingular plate 3" - Type P of Evitt (1967).
Dimensions:
Holotype: central body diameter 57x64 µm, process length 25-27 µm.
Range of 12 specimens: central body diameter 52(60)77 µm, process length 19(21)27 µm.