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Systematophora silvosa
Systematophora silvosa Davey in Kennedy et al., 2000, p.636,638–639, figs.30a–d.
In the protologue the epithet is given as "silvosus"; since the epithet is an adjective, the spelling is here made to agree with the gender of the generic name.
Holotype: Kennedy et al., 2000, fig.30a.
Age: latest Aptian.
Original dscription (Kennedy et al., 2000):
Systematophora silvosus Davey sp. nov. Figure 30a–d
Derivation of name. Latin, silvosus, well wooded, with reference to the relatively dense covering of upright solid processes.
Holotype. FD586, Slide To9, deposited in the collections of The Natural History Museum, London. Tartonne, Le Pillart, Alpes-de-Haute-Provence, France. Uppermost Aptian, Marnes Bleues Formation, approximately 8 m below the Niveau Paquier.
Diagnosis. Shape: cyst chorate, subspherical in outline with minor dorso-ventral flattening. Wall: cyst wall apparently two-layered, walls being closely appressed except where the periphragm alone forms the processes. The pericyst is hyaline and the surface is smooth. Processes: solid and smooth-walled, arising abruptly from the cyst body. Some of the processes branch medially and the majority terminate distally with a brief bifurcation. Rarely neighbouring processes may be linked medially by a short ‘bridge’. Processes are of approximately equal length and width; typically they are one-third to one-half the cyst body in length. The processes are aligned along the cingulum with each cingular plate bearing two processes. In the apical, pre- and postcingular and antapical regions each plate bears processes which may be arranged in poorly developed annular complexes. These processes, however, do not arise from basal, plate-centred ridges. Archaeopyle: normally developed by the detachment of the apical plates as a unit (type A). The margin is strongly zizag with a sulcal notch. Tabulation: the processes reflect a gonyaulacean tabulation of the probable con figuration 4’, 6’’, 6c, 5’’’, 1p, 1’’’’, 1 ps.
Dimensions:
Holotype: Cyst body length (archeopyle developed), 35 µm; cyst body width, 43 µm, length of processes 17-20 µm
Range: Cyst body length (archeopyle developed), 35 (38) 41 µm; cyst body width, 37 (40) 43 µm, length of processes 11 (c. 17) 24 µm
Number of specimens measured 10.
Description. The overall appearance is of a basically subspherical cyst with an apical archaeopyle, having a wall of moderate thickness which bears many, rather than numerous, solid processes. There are more than one process per plate. They may be unbranched or branch medially or distally, and are relatively upright or stiff. Distinct ring complexes are absent.
Discussion. The occurrence of more than one process per plate places the present species in Systematophora Klement, 1960, rather than Surculosphaeridium Davey et al., 1966, which has only one process per plate (see also Davey, 1982b). For this reason, the processes of the latter genus are invariably stouter (thicker) than those of Systematophora. However, it is acknowledged that the two genera are closely related. Systematophora silybum Davey, 1979, described from the Lower Barremian, is most similar and differs in having a densely granulate wall and typically finer, more flexuous processes. Systematophora vestitum (Deflandre, 1938 ) Davey, 1982b, from the Upper Jurassic, is similar in that the wall is smooth. However, this species has fewer processes, which are more irregularly branched. The questionable placing of vestitum in Surculosphaeridium by Stancliffe & Sarjeant (1990) is here rejected. The occurrence of one or more than one process per plate in the precingular, postcingular and antapical regions appears to be the most satisfactory way of differentiating the genera Surculosphaeridium and Systematophora. Annular complexes, although clear in many species, are sometimes difficult to observe [e.g., in Systematophora complicata Neale & Sarjeant (1962) and S. silybum], and this is particularly so when the number of processes is reduced.
In the protologue the epithet is given as "silvosus"; since the epithet is an adjective, the spelling is here made to agree with the gender of the generic name.
Holotype: Kennedy et al., 2000, fig.30a.
Age: latest Aptian.
Original dscription (Kennedy et al., 2000):
Systematophora silvosus Davey sp. nov. Figure 30a–d
Derivation of name. Latin, silvosus, well wooded, with reference to the relatively dense covering of upright solid processes.
Holotype. FD586, Slide To9, deposited in the collections of The Natural History Museum, London. Tartonne, Le Pillart, Alpes-de-Haute-Provence, France. Uppermost Aptian, Marnes Bleues Formation, approximately 8 m below the Niveau Paquier.
Diagnosis. Shape: cyst chorate, subspherical in outline with minor dorso-ventral flattening. Wall: cyst wall apparently two-layered, walls being closely appressed except where the periphragm alone forms the processes. The pericyst is hyaline and the surface is smooth. Processes: solid and smooth-walled, arising abruptly from the cyst body. Some of the processes branch medially and the majority terminate distally with a brief bifurcation. Rarely neighbouring processes may be linked medially by a short ‘bridge’. Processes are of approximately equal length and width; typically they are one-third to one-half the cyst body in length. The processes are aligned along the cingulum with each cingular plate bearing two processes. In the apical, pre- and postcingular and antapical regions each plate bears processes which may be arranged in poorly developed annular complexes. These processes, however, do not arise from basal, plate-centred ridges. Archaeopyle: normally developed by the detachment of the apical plates as a unit (type A). The margin is strongly zizag with a sulcal notch. Tabulation: the processes reflect a gonyaulacean tabulation of the probable con figuration 4’, 6’’, 6c, 5’’’, 1p, 1’’’’, 1 ps.
Dimensions:
Holotype: Cyst body length (archeopyle developed), 35 µm; cyst body width, 43 µm, length of processes 17-20 µm
Range: Cyst body length (archeopyle developed), 35 (38) 41 µm; cyst body width, 37 (40) 43 µm, length of processes 11 (c. 17) 24 µm
Number of specimens measured 10.
Description. The overall appearance is of a basically subspherical cyst with an apical archaeopyle, having a wall of moderate thickness which bears many, rather than numerous, solid processes. There are more than one process per plate. They may be unbranched or branch medially or distally, and are relatively upright or stiff. Distinct ring complexes are absent.
Discussion. The occurrence of more than one process per plate places the present species in Systematophora Klement, 1960, rather than Surculosphaeridium Davey et al., 1966, which has only one process per plate (see also Davey, 1982b). For this reason, the processes of the latter genus are invariably stouter (thicker) than those of Systematophora. However, it is acknowledged that the two genera are closely related. Systematophora silybum Davey, 1979, described from the Lower Barremian, is most similar and differs in having a densely granulate wall and typically finer, more flexuous processes. Systematophora vestitum (Deflandre, 1938 ) Davey, 1982b, from the Upper Jurassic, is similar in that the wall is smooth. However, this species has fewer processes, which are more irregularly branched. The questionable placing of vestitum in Surculosphaeridium by Stancliffe & Sarjeant (1990) is here rejected. The occurrence of one or more than one process per plate in the precingular, postcingular and antapical regions appears to be the most satisfactory way of differentiating the genera Surculosphaeridium and Systematophora. Annular complexes, although clear in many species, are sometimes difficult to observe [e.g., in Systematophora complicata Neale & Sarjeant (1962) and S. silybum], and this is particularly so when the number of processes is reduced.