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Cyclonephelium brevispinatum
From Fensome et al., 2019:
Cyclonephelium brevispinatum (Millioud, 1969, p.427–428, pl.1, figs.8–9) Below, 1981a, p.11 [February]. Holotype: Millioud, 1969, pl.1, figs.8–9. Originally Cyclonephelium distinctum var. brevispinatum, subsequently Cyclonephelium distinctum subsp. brevispinatum, thirdly Cyclonephelium brevispinatum, fourthly Circulodinium brevispinatum. Yun Hyesu (1981, p.51; May) also proposed this combination. Taxonomic senior synonym: Tenua hystrix, according to Fensome et al. (2019a, p.48). Age: late Hauterivian–early Aptian.
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Original description: Millioud, 1969, p. 427: Cyclonephelium distinctum var. brevispinatum
A variety of C. distinctum Deflandre and Cookson, 1955 bearing especially short processes (less than 2 µm), and having a very thin wall.
Occurence: Berriasian and Valanginian at Berrias, well represented in the upper Hautherivian and in the Lower Barremian at Angeles, but becomes scarce in the upper Hauterivian-lower Aptian
Yun, 1981, p. 55: Cyclonephelium brevispinatum (Millioud, 1969) stat. nov.
Description: The original diagnosis is supplemented as follows: The cyst is single layered. Next to the in outline elongate quadrangular spines, there are also thornlike ones. These may dominate in number or even entirely replace the quadrangular spines. As a rule, the spines are 3-4 µm long, but may partially be a little longer (c. 5 µm) at the apex.
Dimensions: size of central body: 54(62)76 µm, maximum length of spines: 2.4(4)5 µm.
Affinities:
Davey, 1978, p. 894: Cyclonephelium distinctum subsp. brevispinatum
To this species were attributed specimens possessing very short spines and a rounded to only slightly indented antapex. Similar specimens possessing a markedly indented antapex are placed in Canningia colliveri Cookson and Eisenack, 1960.
Yun, 1981, p. 55
Cookson and Eisenack, 1974, remarked that their specimens were quite constant in size and length. Nevertheless, they pointed out the transitional forms between C. distinctum and C. distinctum brevispinatum. The uniformity of shape of the processes can be affirmed by my material, however, the mentioned transitional forms have not been found. In my opinion, the uniformity of shape of the processes and the presence of the thornlike processes are sufficient for the differentiation of an individual species. C. brevispinatum occupies a place near C. paucispinum Davey, 1969 and C. densebarbatum Cookson and Eisenack, 1960, which have been erected mainly on the basis of the size and number of the processes.
C. brevispinatum differs from C.distinctum in the essentially shorter spines, which are partially or entirely thorn-shaped. C. paucispinum has a smaller number of spines (c. 90), whereas C. brevispinatum has over 160. In my material, however, transitions between the two species are present.
Below, 1981, p. 12
Forms were determined as Cyclonephelium brevispinatum (Millioud, 1969) Yun, of which the short processes stand mainly isolated and interconnected only scarcely at the bases. The species is numerous in the Hauterivian and Barremian. representatives of the species from the Aptian show an increasing proximal connection between neighbouring processes. This tendency intensifies during the Albian, and compels these forms to be determined as Cyclonephelium paucimarginatum Cookson and Eisenack, 1962.
Cyclonephelium brevispinatum (Millioud, 1969, p.427–428, pl.1, figs.8–9) Below, 1981a, p.11 [February]. Holotype: Millioud, 1969, pl.1, figs.8–9. Originally Cyclonephelium distinctum var. brevispinatum, subsequently Cyclonephelium distinctum subsp. brevispinatum, thirdly Cyclonephelium brevispinatum, fourthly Circulodinium brevispinatum. Yun Hyesu (1981, p.51; May) also proposed this combination. Taxonomic senior synonym: Tenua hystrix, according to Fensome et al. (2019a, p.48). Age: late Hauterivian–early Aptian.
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Original description: Millioud, 1969, p. 427: Cyclonephelium distinctum var. brevispinatum
A variety of C. distinctum Deflandre and Cookson, 1955 bearing especially short processes (less than 2 µm), and having a very thin wall.
Occurence: Berriasian and Valanginian at Berrias, well represented in the upper Hautherivian and in the Lower Barremian at Angeles, but becomes scarce in the upper Hauterivian-lower Aptian
Yun, 1981, p. 55: Cyclonephelium brevispinatum (Millioud, 1969) stat. nov.
Description: The original diagnosis is supplemented as follows: The cyst is single layered. Next to the in outline elongate quadrangular spines, there are also thornlike ones. These may dominate in number or even entirely replace the quadrangular spines. As a rule, the spines are 3-4 µm long, but may partially be a little longer (c. 5 µm) at the apex.
Dimensions: size of central body: 54(62)76 µm, maximum length of spines: 2.4(4)5 µm.
Affinities:
Davey, 1978, p. 894: Cyclonephelium distinctum subsp. brevispinatum
To this species were attributed specimens possessing very short spines and a rounded to only slightly indented antapex. Similar specimens possessing a markedly indented antapex are placed in Canningia colliveri Cookson and Eisenack, 1960.
Yun, 1981, p. 55
Cookson and Eisenack, 1974, remarked that their specimens were quite constant in size and length. Nevertheless, they pointed out the transitional forms between C. distinctum and C. distinctum brevispinatum. The uniformity of shape of the processes can be affirmed by my material, however, the mentioned transitional forms have not been found. In my opinion, the uniformity of shape of the processes and the presence of the thornlike processes are sufficient for the differentiation of an individual species. C. brevispinatum occupies a place near C. paucispinum Davey, 1969 and C. densebarbatum Cookson and Eisenack, 1960, which have been erected mainly on the basis of the size and number of the processes.
C. brevispinatum differs from C.distinctum in the essentially shorter spines, which are partially or entirely thorn-shaped. C. paucispinum has a smaller number of spines (c. 90), whereas C. brevispinatum has over 160. In my material, however, transitions between the two species are present.
Below, 1981, p. 12
Forms were determined as Cyclonephelium brevispinatum (Millioud, 1969) Yun, of which the short processes stand mainly isolated and interconnected only scarcely at the bases. The species is numerous in the Hauterivian and Barremian. representatives of the species from the Aptian show an increasing proximal connection between neighbouring processes. This tendency intensifies during the Albian, and compels these forms to be determined as Cyclonephelium paucimarginatum Cookson and Eisenack, 1962.