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Fibradinium annetorpense
From Fensome et al., 2019:
Fibradinium annetorpense Morgenroth, 1968, p.538, pl.42, figs.4–7; text-figs.1–2. Holotype: Morgenroth, 1968, pl.42, fig.4. Originally (and now) Fibradinium, subsequently Phanerodinium. Lentin and Williams (1989, p.135) retained this species in Fibradinium. Age: Danian
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Original description (complementary to the diagnosis of genus): Morgenroth 1968, p. 4
The double-layer theca wall consists of an inner thin membrane and a thick outer layer of fibrous structure on which the outlines of the plates are more or less clearly defined by slightly raised ridges. The apex is characterized by ?7 apical plates of which 1' lies on the extension of the longitudinal groove. A pentagonal "apical area" to which 6 pre-equatorial plates are adjacent, appears to be subdivided into 6 small plates; five of these surround one centrally located plate (see Fig . 2 ). However, the outlines of the plates on the apical are indistinct and cannot be determined in all specimens. In the formation of the archaeopyle, these ?6 apical plates are cast off so that a pentagonal opening is created. The transverse groove is circular in most specimens; in some, however, it spirals slightly in a counterclockwise direction. Six post-equatorial plates, one intercalary plate and one antapical plate are located on the hypotheca. The narrow longitudinal groove widens in the shape of a drop on the hypotheca.
Dimensions:
Length of theca: 32µ (28µ/3µ)
Width of theca: 28µ (22µ/31µ)
Thickness of theca wall: 3230 (2µ/5m) (25 measurements)
Number of specimens examined: 27
Supplemental description: Hultberg, 1985, p.122
Proximate cyst, composed of endophragm and periphragm, closely appressed. The surface of the periphragm is strongly granulate. The shape of the cyst is ellipsoidal.
Paratabulation is expressed by fibrous parasutural ridges, formed by the periphragm. Paraplates 1'' to 6'', 1''' to 6''', 1p, and 1'''', are clearly distinguishable. The apical paratabulation is not clearly discernible, but presumably follows the standard microdinioid paratabulation, which contains seven apical paraplates. Paracingulum and parasulcus are clearly indicated by parasutural ridges.
Size 27-32 µm (length), 20-32 µm (breadth).
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Emended description Vieira et al., 2025
Emended description: Cysts are cavate, ovoidal to ellipsoidal where the epicyst is smaller than the hypocyst. The cyst wall is composed of
endophragm and smooth periphragm. The cyst size has a width between 23 and 31 μm and a length of 28–36 μm. When observed with SEM, it
becomes clear that the fibrous outer layer described by Morgenroth (1968) is the result of continuous ridges and indentations across the
crests formed at the edge of each paraplate. The cysts also evidence the presence of nanno “indentations” forming a ring around the precingular, cingular, postcingular, posterior, and posterior sulcal paraplates. The number can vary from paraplate to paraplate and be more or less clear depending on the stage of preservation. The apical and anterior intercalary paraplates exhibit at least 1 nanno “indentation” depending on the size of the paraplate. It was possible to determine the tabulation using SEM as indicated by sutural features which are expressed by crests: 5′, 5a, 7″, 6c, 7″’, 1p, 1″“ (see Figs. 4, 5, 6, Supplementary material).
The archeopyle is apical-intercalary of the type (tAtI)a with an adnate operculum ventrally usually attached to the anterior sulcal paraplate; the operculum is composed of eleven paraplates of which there are 1 preapical, 5 apicals, and 5 anterior intercalaries. The 1′ and 5′ paraplates are elongated and larger than the other apical paraplates. The epicist has 7 precingular paraplates, a typical microdinioid feature that contrasts with other gonyaulacaceans. In the ventral area the presence of 1 anterior right sulcal paraplate (ras) and 1 anterior sulcal paraplate (as), close to the sulcus. The posterior sulcal paraplate is large and omegaform as observed in other microdinioids. There are 6 postcingular paraplates and two relatively large plates (1p and 1″“) form the antapex. Paraplate 1″“is significantly larger than 1p (Fig. 6E).
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Fibradinium annetorpense Morgenroth, 1968. The archeopyle is apical. Size: length 28-34 µm, width 22-31 µm, wall thickness 2-5 µm.
Fibradinium annetorpense Morgenroth, 1968, p.538, pl.42, figs.4–7; text-figs.1–2. Holotype: Morgenroth, 1968, pl.42, fig.4. Originally (and now) Fibradinium, subsequently Phanerodinium. Lentin and Williams (1989, p.135) retained this species in Fibradinium. Age: Danian
---------------------------------------------------------------------------------------------------
Original description (complementary to the diagnosis of genus): Morgenroth 1968, p. 4
The double-layer theca wall consists of an inner thin membrane and a thick outer layer of fibrous structure on which the outlines of the plates are more or less clearly defined by slightly raised ridges. The apex is characterized by ?7 apical plates of which 1' lies on the extension of the longitudinal groove. A pentagonal "apical area" to which 6 pre-equatorial plates are adjacent, appears to be subdivided into 6 small plates; five of these surround one centrally located plate (see Fig . 2 ). However, the outlines of the plates on the apical are indistinct and cannot be determined in all specimens. In the formation of the archaeopyle, these ?6 apical plates are cast off so that a pentagonal opening is created. The transverse groove is circular in most specimens; in some, however, it spirals slightly in a counterclockwise direction. Six post-equatorial plates, one intercalary plate and one antapical plate are located on the hypotheca. The narrow longitudinal groove widens in the shape of a drop on the hypotheca.
Dimensions:
Length of theca: 32µ (28µ/3µ)
Width of theca: 28µ (22µ/31µ)
Thickness of theca wall: 3230 (2µ/5m) (25 measurements)
Number of specimens examined: 27
Supplemental description: Hultberg, 1985, p.122
Proximate cyst, composed of endophragm and periphragm, closely appressed. The surface of the periphragm is strongly granulate. The shape of the cyst is ellipsoidal.
Paratabulation is expressed by fibrous parasutural ridges, formed by the periphragm. Paraplates 1'' to 6'', 1''' to 6''', 1p, and 1'''', are clearly distinguishable. The apical paratabulation is not clearly discernible, but presumably follows the standard microdinioid paratabulation, which contains seven apical paraplates. Paracingulum and parasulcus are clearly indicated by parasutural ridges.
Size 27-32 µm (length), 20-32 µm (breadth).
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Emended description Vieira et al., 2025
Emended description: Cysts are cavate, ovoidal to ellipsoidal where the epicyst is smaller than the hypocyst. The cyst wall is composed of
endophragm and smooth periphragm. The cyst size has a width between 23 and 31 μm and a length of 28–36 μm. When observed with SEM, it
becomes clear that the fibrous outer layer described by Morgenroth (1968) is the result of continuous ridges and indentations across the
crests formed at the edge of each paraplate. The cysts also evidence the presence of nanno “indentations” forming a ring around the precingular, cingular, postcingular, posterior, and posterior sulcal paraplates. The number can vary from paraplate to paraplate and be more or less clear depending on the stage of preservation. The apical and anterior intercalary paraplates exhibit at least 1 nanno “indentation” depending on the size of the paraplate. It was possible to determine the tabulation using SEM as indicated by sutural features which are expressed by crests: 5′, 5a, 7″, 6c, 7″’, 1p, 1″“ (see Figs. 4, 5, 6, Supplementary material).
The archeopyle is apical-intercalary of the type (tAtI)a with an adnate operculum ventrally usually attached to the anterior sulcal paraplate; the operculum is composed of eleven paraplates of which there are 1 preapical, 5 apicals, and 5 anterior intercalaries. The 1′ and 5′ paraplates are elongated and larger than the other apical paraplates. The epicist has 7 precingular paraplates, a typical microdinioid feature that contrasts with other gonyaulacaceans. In the ventral area the presence of 1 anterior right sulcal paraplate (ras) and 1 anterior sulcal paraplate (as), close to the sulcus. The posterior sulcal paraplate is large and omegaform as observed in other microdinioids. There are 6 postcingular paraplates and two relatively large plates (1p and 1″“) form the antapex. Paraplate 1″“is significantly larger than 1p (Fig. 6E).
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Fibradinium annetorpense Morgenroth, 1968. The archeopyle is apical. Size: length 28-34 µm, width 22-31 µm, wall thickness 2-5 µm.