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Cerbia tabulata
Cerbia tabulata, (Davey and Verdier, 1974), Below, 1981
Originally Cyclonephelium, subsequently Canninginopsis, thirdly (and now) Cerbia.
Taxonomic senior synonym: Tenua hystrix, according to Sarjeant (1985a, p.94; 1992b, p.681) - however, by retaining Cerbia, Duxbury (2002, p.76,78) retained Cerbia tabulata by implication.
Holotype: Davey and Verdier 1974, pl.92, fig.1,4; Sarjeant, 1992, figs.3-4
Locus typicus: La BÚdoule, SE-France
Stratum typicum: Aptian: Gargasian
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Original description as Cyclonephelium tabulatum: [Davey and Verdier, 1974, p. 630-631]:
Diagnosis:
The cyst is subcircular in outline and possesses a thin, smooth to lightly tuberculate wall.
The processes are predominantly peritabular in position and clearly define the precingular and postcingular plates and the cingulum. The central part of the plates and the sulcal region are practically devoid of processes. The processes are short, stout, and capitate; they rarely branch distally or are joined proximally.
The archaeopyle is apical and has a strongly zigzag margin and a sulcal notch; the operculum is typically detached.
Description:
Since all the identified specimens possessed an apical archaeopyle and only rarely detached opercula were identified, it is difficult to precisely define the shape of the apical region. It is surmised, however, that it is of similar shape to that found in related species. That is, the cyst is rounded apically or has a reduced apical boss.
The main part of the cyst is subcircular, or rarely slightly angular, in outline.
The processes are neatly aligned just within the plate margins and hence clearly define the tabulation in the precingular and postcingular regions. In each case five or six plates appear to be present. The parallel lines of processes, either side of a plate boundary, are 3 to 4 µm apart. Rare processes on the cingulum may indicate the position of plate boundaries; a distinct cingular tabulation, however, is not present. Two to three antapical and four apical plates appear to be present.
Affinities:
The shape of the cyst and its processes are identical to that of C. distinctum Deflandre and Cookson 1955. C. tabulatum differs significantly from C. distinctum, and other members of Cyclonephelium, by the possession of peritabular processes and an encircling cingulum; the processes of C. distinctum are concentrated towards the circumferential region. The two species are clearly closely related, and although C. tabulatum does not conform exactly with the generic diagnosis of Cyclonephelium it is considered best placed in this genus at present.
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Supplemental description:
Below, 1981, p. 9-10: (Translation: LPP):
Description:
The examples from Morocco show in opposite to the type material and those forms described by Duxburry 1977 stronger modifications of the outline. Cysts with rounded antapex coexist with specimens of this species which antapical pole is convex indented, resulting in two antapical bulges of unequal size. Numerous completely preserved individuals of the species allow a detailed description of the paratabulation scheme and the apical region.
The paratabulation scheme is 4", 6"", Xc, 6""", pc, 1"""". The squat triangular 1" and 2" as well as the quadrangular, elongated 3" and 4" form the apical paraplate series. Six trapezoidal to quadrangular precingular plates follow posterior. The triangular 2""", 6""" and the trapezoidal 3"""-5""" are always clearly visible. The very small first postcingular often lies within an undifferentiated ventral area without ornamentation. This area is rarely structured by penitabular rows of spines. 1"""" is moved dorsal and seldom bordered against the parasulcal zone, which reaches the antapex. The spiral paracingulum lies between the penitabular spine-rows of the praecingular and postcingular paraplates. Isolated spines hint on a differentiation of the girdle furrow. The single paracingular paraplates are never surrounded by penitabular spine-rows. The parasulcus is sigmoidal. The archaeopyle is apical with a zig-zag margin.
Along the archaeopyle margin small undifferentiated fragments can be detached or the operculum is enlarged and consists, in addition to the four apical plates, of the anteriour parts of the precingular paraplates. The simple operculum corresponds to the apical quarter of the cyst. The antapex is triangular in outline or rounded or, as already recognized by Davey and Verdier 1974, extended to a low, wide process.
Originally Cyclonephelium, subsequently Canninginopsis, thirdly (and now) Cerbia.
Taxonomic senior synonym: Tenua hystrix, according to Sarjeant (1985a, p.94; 1992b, p.681) - however, by retaining Cerbia, Duxbury (2002, p.76,78) retained Cerbia tabulata by implication.
Holotype: Davey and Verdier 1974, pl.92, fig.1,4; Sarjeant, 1992, figs.3-4
Locus typicus: La BÚdoule, SE-France
Stratum typicum: Aptian: Gargasian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Cyclonephelium tabulatum: [Davey and Verdier, 1974, p. 630-631]:
Diagnosis:
The cyst is subcircular in outline and possesses a thin, smooth to lightly tuberculate wall.
The processes are predominantly peritabular in position and clearly define the precingular and postcingular plates and the cingulum. The central part of the plates and the sulcal region are practically devoid of processes. The processes are short, stout, and capitate; they rarely branch distally or are joined proximally.
The archaeopyle is apical and has a strongly zigzag margin and a sulcal notch; the operculum is typically detached.
Description:
Since all the identified specimens possessed an apical archaeopyle and only rarely detached opercula were identified, it is difficult to precisely define the shape of the apical region. It is surmised, however, that it is of similar shape to that found in related species. That is, the cyst is rounded apically or has a reduced apical boss.
The main part of the cyst is subcircular, or rarely slightly angular, in outline.
The processes are neatly aligned just within the plate margins and hence clearly define the tabulation in the precingular and postcingular regions. In each case five or six plates appear to be present. The parallel lines of processes, either side of a plate boundary, are 3 to 4 µm apart. Rare processes on the cingulum may indicate the position of plate boundaries; a distinct cingular tabulation, however, is not present. Two to three antapical and four apical plates appear to be present.
Affinities:
The shape of the cyst and its processes are identical to that of C. distinctum Deflandre and Cookson 1955. C. tabulatum differs significantly from C. distinctum, and other members of Cyclonephelium, by the possession of peritabular processes and an encircling cingulum; the processes of C. distinctum are concentrated towards the circumferential region. The two species are clearly closely related, and although C. tabulatum does not conform exactly with the generic diagnosis of Cyclonephelium it is considered best placed in this genus at present.
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Supplemental description:
Below, 1981, p. 9-10: (Translation: LPP):
Description:
The examples from Morocco show in opposite to the type material and those forms described by Duxburry 1977 stronger modifications of the outline. Cysts with rounded antapex coexist with specimens of this species which antapical pole is convex indented, resulting in two antapical bulges of unequal size. Numerous completely preserved individuals of the species allow a detailed description of the paratabulation scheme and the apical region.
The paratabulation scheme is 4", 6"", Xc, 6""", pc, 1"""". The squat triangular 1" and 2" as well as the quadrangular, elongated 3" and 4" form the apical paraplate series. Six trapezoidal to quadrangular precingular plates follow posterior. The triangular 2""", 6""" and the trapezoidal 3"""-5""" are always clearly visible. The very small first postcingular often lies within an undifferentiated ventral area without ornamentation. This area is rarely structured by penitabular rows of spines. 1"""" is moved dorsal and seldom bordered against the parasulcal zone, which reaches the antapex. The spiral paracingulum lies between the penitabular spine-rows of the praecingular and postcingular paraplates. Isolated spines hint on a differentiation of the girdle furrow. The single paracingular paraplates are never surrounded by penitabular spine-rows. The parasulcus is sigmoidal. The archaeopyle is apical with a zig-zag margin.
Along the archaeopyle margin small undifferentiated fragments can be detached or the operculum is enlarged and consists, in addition to the four apical plates, of the anteriour parts of the precingular paraplates. The simple operculum corresponds to the apical quarter of the cyst. The antapex is triangular in outline or rounded or, as already recognized by Davey and Verdier 1974, extended to a low, wide process.