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Plethysyrinx lata
Plethysyrinx lata (Klumpp, 1953) emend. Sarjeant, 1981
Now Cordosphaeridium latum. Originally Hystrichosphaeridium diktyoplokus ssp. Iatum, subsequently Cordosphaeridium diktyoplokus ssp. Iatum, thirdly Areosphaeridium diktyoplokus ssp. Iatum, fourthly Plethysyrinx lata, fifthly (and now) Cordosphaeridium latum.
Holotype: Klumpp, 1953, pl.18, figs.89
Age: Eocene
Translation Klummp, 1953: Sarjeant, 1981, p. 106
Original Diagnosis: Klummp, 1953, p. 392: Hystrichosphaeridium diktyoplokus ssp. latum
A subspecies of the species Hystrichosphaeridium diktyoplokus with the following distinguishing characteristics: most processes are, from their bases, very wide and only the minority are narrow at the bases. These widen towards their outer ends in funnel-like fashion.
Emended diagnosis: Sarjeant, 1981, p. 107-108
Cyst spheroidal to broadly ovoidal, broadly skoloc phragmochorate. Surface of phragma punctate to shagreenate. Processes broadly intratabular to penitabular in situation, cylindrical to buccinate, with fibrous, fenestrate walls. The fibers connect with rootlike extensions surrounding the process bases; the fenestrae are of variable size but never very large and typically have a subquadrate to quadrate outline. Distally the processes widen abruptly and give rise to many irregular prolongations of variable length, having the appearance of an unraveled and stretched woollen sock. They may be linked to adjacent processes by a complete or incomplete investing mesh of trabeculae. Paratabulation: 1-?4", 6"", 0c, 5-?6""", ?0p, 1"""". Archaeopyle apparently single plate precingular (Type P); operculum free.
Dimensions: Holotype: diameter of cyst (in oblique polar view) c. 70 µm, length of processes 22-36 µm.
Description. The holotype is folded and proved particularly difficult to interpret; the paratabulation and archaeopyle position, quoted above, are emphatically provisional. The hollow processes might equally be considered as closely interlinked process clusters; their situation appears broadly intratabular rather than penitabular. Despite these difficulties, the form of the processes is so characteristic that this species is readily identifiable. The investing trabecula was not mentioned by Klummp and probably taken by her to be an adherent plant fiber.
Affinities: Sarjeant, 1981, p. 107
The distinctive nature of the processes of this species clearly characterises it and distinguishes it, not only at specific but also at generic level, from the very different Areosphaeridium diktyoplokus, of which latum was hitherto a subspecies. Cingular processes are certainly lacking; the processes are conspicuously fibrous and fenestrate, with rootlike proximal extensions and a partial development of trabecular linkage with adjacent processes. For these reasons this species has been provisionally attributed to Plethysyrinx. However, since the precingular location of the archaeopyle was not confirmed with complete certainty, this generic assignation is very much subject to future review when further specimens become available.
Some similarity may be noted with Cordosphaeridium fibrospinosum, which has broad penitabular processes with perforate walls. However, the processes in that species are more exactly cylindrical in shape, perforate rather than fenestrate, and without the "unravelled" extremities characteristic of Plethysyrinx; moreover, the archaeopyle is considered by Davey and Williams to be "apical haplotabular". It may be that these two species will prove to be congeneric, but I consider it highly unlikely that they will prove conspecific.
Now Cordosphaeridium latum. Originally Hystrichosphaeridium diktyoplokus ssp. Iatum, subsequently Cordosphaeridium diktyoplokus ssp. Iatum, thirdly Areosphaeridium diktyoplokus ssp. Iatum, fourthly Plethysyrinx lata, fifthly (and now) Cordosphaeridium latum.
Holotype: Klumpp, 1953, pl.18, figs.89
Age: Eocene
Translation Klummp, 1953: Sarjeant, 1981, p. 106
Original Diagnosis: Klummp, 1953, p. 392: Hystrichosphaeridium diktyoplokus ssp. latum
A subspecies of the species Hystrichosphaeridium diktyoplokus with the following distinguishing characteristics: most processes are, from their bases, very wide and only the minority are narrow at the bases. These widen towards their outer ends in funnel-like fashion.
Emended diagnosis: Sarjeant, 1981, p. 107-108
Cyst spheroidal to broadly ovoidal, broadly skoloc phragmochorate. Surface of phragma punctate to shagreenate. Processes broadly intratabular to penitabular in situation, cylindrical to buccinate, with fibrous, fenestrate walls. The fibers connect with rootlike extensions surrounding the process bases; the fenestrae are of variable size but never very large and typically have a subquadrate to quadrate outline. Distally the processes widen abruptly and give rise to many irregular prolongations of variable length, having the appearance of an unraveled and stretched woollen sock. They may be linked to adjacent processes by a complete or incomplete investing mesh of trabeculae. Paratabulation: 1-?4", 6"", 0c, 5-?6""", ?0p, 1"""". Archaeopyle apparently single plate precingular (Type P); operculum free.
Dimensions: Holotype: diameter of cyst (in oblique polar view) c. 70 µm, length of processes 22-36 µm.
Description. The holotype is folded and proved particularly difficult to interpret; the paratabulation and archaeopyle position, quoted above, are emphatically provisional. The hollow processes might equally be considered as closely interlinked process clusters; their situation appears broadly intratabular rather than penitabular. Despite these difficulties, the form of the processes is so characteristic that this species is readily identifiable. The investing trabecula was not mentioned by Klummp and probably taken by her to be an adherent plant fiber.
Affinities: Sarjeant, 1981, p. 107
The distinctive nature of the processes of this species clearly characterises it and distinguishes it, not only at specific but also at generic level, from the very different Areosphaeridium diktyoplokus, of which latum was hitherto a subspecies. Cingular processes are certainly lacking; the processes are conspicuously fibrous and fenestrate, with rootlike proximal extensions and a partial development of trabecular linkage with adjacent processes. For these reasons this species has been provisionally attributed to Plethysyrinx. However, since the precingular location of the archaeopyle was not confirmed with complete certainty, this generic assignation is very much subject to future review when further specimens become available.
Some similarity may be noted with Cordosphaeridium fibrospinosum, which has broad penitabular processes with perforate walls. However, the processes in that species are more exactly cylindrical in shape, perforate rather than fenestrate, and without the "unravelled" extremities characteristic of Plethysyrinx; moreover, the archaeopyle is considered by Davey and Williams to be "apical haplotabular". It may be that these two species will prove to be congeneric, but I consider it highly unlikely that they will prove conspecific.