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Acanthogonyaulax venusta
Acanthogonyaulax venusta, (Klement, 1960, p. 44–45), Sarjeant, 1966b, p.132.
Originally Gonyaulax, subsequently Acanthogonyaulax (combination not validly published), thirdly Acanthaulax, fourthly Gonyaulacysta, fifthly Cribroperidinium.
Tax. sr. syn.: Gonyaulax (as Cribroperidinium) granulata, according to Schrank (2005, p.56).
Holotype: Klement, 1960, pl. 5, figs. 10–11.
Age: middle Oxfordian–Kimmeridgian.
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Original description as Gonyaulax venusta: [Klement 1960, p. 44-45]
Diagnosis:
A species of the genus Gonyaulax, possessing the following tabulation scheme: 4', 6'', 6''', 1p, 1''''. Spheroidal to thick-set-ovaloidal theca, apically displaying a thin proturberance, which is either solid or consists of three filamentous processes which stand close to one another. Plates are covered with closely spaced, short spines. Sutures are thickened in a striation-like manner, they are granulated and are likewise covered with short spines. The helicoidal girdle furrow is shallow and, distally, displaced one to two times its on width. Longitudinal furrow extends from the 1st. apical plate to the antapex.
Description:
This species, which - likewise - does not occur very frequently, has a sharp ranging from being spheroidal to thick-set-ovaloidal. The plates are definitely convex; they are covered with closely spaced, short spines which, distally, terminate in a knobular manner. It is for this reason that, when viewed from the top, one gains the impression of viewing a surface which is considerably punctated. On the sutures (which are thickened in striation-like manner), we also find short spines displaying the aforementioned knobular terminations.
The epitheca is made up of 4 apical plates and 6 precingular plates which, in form and arrangement, correspond to the plates of the precedingly described species (note: Gonyaulax aculeata). As apex proturberance, we find three isolated, closely spaced , filamentous processes or a single process which is somewhat thicker.
The heliocoidal girdle furrow has a width of about 4-5 microns and is displaces distally 1.5 to 2 times its own width; furthermore, it is not very much indented. What is noteworthy here is the fact that the girdle furrow is likewise covered with spines and, thus, has a punctuated appearance. However, the longitudinal furrow (which extends from the 1st. apical plate to the antapex), is mostly not covered by spines.
The hypotheca consists of 6 postcingular plates, of one accessory plate (1p) and of one polygonal, convex antapical plate. Here again, plate 1''' is greatly reduced, and plate 2''' likewise has not as yet reached the normal size of the remaining postequatorial plates.
The range of variations of this species is of a small order of magnitude and is limited to slight deviations from the spherical shape of the envelope and to different lengths of the spines located on plates and sutures; however, even in the extreme case, these spines can not attain lengths of more than 4 microns.
The membrane appears to be have a light yellow coloration, however, due to the spine coverage, gives an overall appearance of being somewhat darker.
Relationships:
This species differs from the G. aculeata in that the plates display here a dense and isolated spine-coverage (whereas in the case of G. aculeata the plates are ornamented with vermicular, low tubercle seams); a further criterion is the fact that the granulated sutures, which are developed in a striation-like manner, are not very prominent here.
Originally Gonyaulax, subsequently Acanthogonyaulax (combination not validly published), thirdly Acanthaulax, fourthly Gonyaulacysta, fifthly Cribroperidinium.
Tax. sr. syn.: Gonyaulax (as Cribroperidinium) granulata, according to Schrank (2005, p.56).
Holotype: Klement, 1960, pl. 5, figs. 10–11.
Age: middle Oxfordian–Kimmeridgian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Gonyaulax venusta: [Klement 1960, p. 44-45]
Diagnosis:
A species of the genus Gonyaulax, possessing the following tabulation scheme: 4', 6'', 6''', 1p, 1''''. Spheroidal to thick-set-ovaloidal theca, apically displaying a thin proturberance, which is either solid or consists of three filamentous processes which stand close to one another. Plates are covered with closely spaced, short spines. Sutures are thickened in a striation-like manner, they are granulated and are likewise covered with short spines. The helicoidal girdle furrow is shallow and, distally, displaced one to two times its on width. Longitudinal furrow extends from the 1st. apical plate to the antapex.
Description:
This species, which - likewise - does not occur very frequently, has a sharp ranging from being spheroidal to thick-set-ovaloidal. The plates are definitely convex; they are covered with closely spaced, short spines which, distally, terminate in a knobular manner. It is for this reason that, when viewed from the top, one gains the impression of viewing a surface which is considerably punctated. On the sutures (which are thickened in striation-like manner), we also find short spines displaying the aforementioned knobular terminations.
The epitheca is made up of 4 apical plates and 6 precingular plates which, in form and arrangement, correspond to the plates of the precedingly described species (note: Gonyaulax aculeata). As apex proturberance, we find three isolated, closely spaced , filamentous processes or a single process which is somewhat thicker.
The heliocoidal girdle furrow has a width of about 4-5 microns and is displaces distally 1.5 to 2 times its own width; furthermore, it is not very much indented. What is noteworthy here is the fact that the girdle furrow is likewise covered with spines and, thus, has a punctuated appearance. However, the longitudinal furrow (which extends from the 1st. apical plate to the antapex), is mostly not covered by spines.
The hypotheca consists of 6 postcingular plates, of one accessory plate (1p) and of one polygonal, convex antapical plate. Here again, plate 1''' is greatly reduced, and plate 2''' likewise has not as yet reached the normal size of the remaining postequatorial plates.
The range of variations of this species is of a small order of magnitude and is limited to slight deviations from the spherical shape of the envelope and to different lengths of the spines located on plates and sutures; however, even in the extreme case, these spines can not attain lengths of more than 4 microns.
The membrane appears to be have a light yellow coloration, however, due to the spine coverage, gives an overall appearance of being somewhat darker.
Relationships:
This species differs from the G. aculeata in that the plates display here a dense and isolated spine-coverage (whereas in the case of G. aculeata the plates are ornamented with vermicular, low tubercle seams); a further criterion is the fact that the granulated sutures, which are developed in a striation-like manner, are not very prominent here.