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Impagidinium
From Fensome et al., 2019:
Impagidinium, Stover and Evitt, 1978, p.165–166.
Type: Cookson and Eisenack, 1965a, pl.12, figs.5–6, as Leptodinium dispertitum.
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Original description: [Stover and Evitt, 1978]:
Synopsis:
Cyst proximochorate, acavate, subspherical to ellipsoidal, and typically without an apical projection or horn; paratabulation gonyaulacacean, indicated by parasutural septa only; paraplate 4` characteristically about as long as 1` and contact with subtriangular paraplate 6`` very short; archaeopyle precingular, type P.
Description:
Shape: Subspherical to ellipsoidal, typically without apical projection or horn.
Wall relationships: Generally autophragm only; some forms with appressed endophragm and periphragm.
Wall features: Parasutural septa generally smooth and imperforate, occasionally striate or perforate, and of more or less uniform height; crests normally smooth; areas between septa smooth or with features of low relief. Paratabulation: Indicated by parasutural features; gonyaulacacean, formula 3-4`, 5-6``, 4-6c, 5-6```, 0-1p, 1````, 0-3s. Paraplates 1` and 4` tend to be narrow, subparallel, and about equal in length; paraplate 6`` usually subtriangular, and contact with paraplate(s) very short. Certain septa, commonly between paraplates 1` and 4`, and in some species also along paracingulum and parasulcus, consistently reduced or absent.
Archaeopyle: Precingular, Type P(3`` only), reduced on some species; operculum free.
Paracingulum: Indicated by four to six rectangular to elongate-hexagonal paraplates (central part longer than ends); ventral offset moderate to strong, and terminal paraplates (1c and 6c) may be incompletely defined.
Parasulcus: Generally clearly delimited by parasutural features except where bordering septa are absent; posterior sulcal paraplate usually delimited.
Size: Small to large.
Affinities:
Impagidinium differs from Leptodinium in having the first and fourth apical paraplates of similar shape, of about equal length, and often imperfectly separated. The sixth precingular paraplate is usually subtriangular, and its contact with the apical paraplate(s) is very short. In Leptodinium, the first apical paraplate is typically longer than the fourth, the sixth precingular is quadrangular or pentangular rather than subtriangular, and the contact between paraplate 6`` and the contiguous apical paraplate is substantial. In general, species of Impagidinium tend to be subspherical to ellipsoidal, to lack an apical projection, and to have reduced paratabulation in some instances. Species of Leptodinium, in contrast, tend to be more elongate, even subpolygonal, to possess an apical horn, and rarely, if ever, to have reduced paratabulation. Additionally, epicystal intercalary paraplates occur on some species of Leptodinium, whereas such paraplates have not been observed on species of Impagidinium.
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Fensome et al., 1991, p. 280:
Discussion: (editors` remarks)
Stover and Evitt (1978, p.165, 273-275) compared Impagidinium with Leptodinium Klement, 1960. They noted that "We view Impagidinium as a distinctive cyst type whose biological affinity lies close to Spiniferites, i.e., to the group of species represented today by Gonyaulax spinifera (Claparede & Lachmann 1858) Diesing 1866." They included lmpagidinium in Category 5 of their Gonyaulacysta complex, together with Heslertonia Sarjeant, 1966, Leptodinium and Prionodinium Leffingwell and Morgan 1977. Taxa in Category 5 are characterized by "prominent, essentially even-topped septa." They also provided a summation of selected characteristics of Gonyaulacysta complex genera, including Impagidinium.
Helenes (1984) included the type species of Impagidinium as an acavate gonyaulacoid genus with parasutural features, a type P archeopyle and an S-type ventral organization. However, he also indicated that other species of Impagidinium have an L-type ventral organization.
Evitt (1985, p.100) considered Impagidinium to have an "S- type ventral organization". He listed as characteristic for this type of organization the following: a strongly offset paracingulum; a parasulcus narrowest between the ends of the paracingulum and often sigmoid- a quasi triangular or three-sided 6`` (1i); an enlarged 3` (C); an elongate 4` (A) almost equal in size and shape to 1` (1u) and commonly fusing with that plate or reduced and having minimal or no contact with 6`` (1i) ; weakly developed parasutures within and adjacent to the parasulcus- and a geniculate anterior margin to the anterior sulcal paraplate (ai). Evitt (1985, p.222) included Impagidinium in his Gs-Cysts, Leptodinium Complex. Genera of the Leptodinium Complex have a gonyaulacoid paratabulation delineated by parasutural features and a sexiform hypocyst. Jan du Chêne et al. (1986, p.167) reiterated the original diagnosis for Impagidinium using slightly different phraseology. They also included Impagidinium in their key to genera of the "Complex Gonyaulacysta".
Helenes (1986, p.90) considered the type species of Impagidinium, Impagidinium dispertitum, to have the "Californiense Pattern" of paratabulation. Taxa with the Californiense Pattern have paraplates P (first preapical) and C (3`) in contact, an anteriorly planate 1i (6``) and an anteriorly camerate ai (anterior sulcal), termed the A/ai (4`/as) arrangement, and an asymmetrically quadrate sexiform Y (1`````) paraplate. Helenes (1986, p.90) noted that Impagidinium dispertitum "... shows an A/ai arrangement; however neither the apical nor the antapical arrangements have been illustrated with enough detail." In the same paper (p.107), Helenes included Impagidinium dispertitum in his "Californiense Complex". Helenes (1986, p.104) assigned other species of Impagidinium, such as Impagidinium sphaericum (Wall, 1967) Lentin and Williams, 1981, to his "Sphaericum Pattern" of paratabulation.
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Zorzi, C. et al., 264, 24–37, 2019:
Discussion/Remarks:
Impagidinium species can be distinguished by (a) the degree to which tabulation is expressed: Impagidinium sphaericum (Wall,1967) and Impagidinium? diaphanum sp. nov.: excellently expressed, including some delineation of plates in the sulcal area; Impagidinium aculeatum and Impagidinium detroitense sp. nov.: generally well expressed but weakly expressed in the sulcal area; Impagidinium patulum: incompletely expressed in the ventral region but well expressed elsewhere; Impagidinium strialatum (Wall, 1967): poorly expressed, frequently reduced on the dorsal and ventral surface (b) the degree of suturocavation variation: Impagidinium patulum and Impagidinium sphaericum: absent to slight; Impagidinium cantabrigiense, Impagidinium detroitense sp. nov., Impagidinium? diaphanum sp. nov.: moderate; Impagidinium multiplex: high
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Impagidinium Stover and Williams, 1978. Synopsis, from Stover and Evitt (1978, p.165), cysts proximochorate, acavate, subspherical to ellipsoidal, and typically without an apical projection or horn; paratabulation gonyaulacacean, indicated by parasutural septa only; paraplate 4` characteristically about as long as 1` and contact with subtriangular paraplate 6" very short; archeopyle precingular, type P.
Impagidinium, Stover and Evitt, 1978, p.165–166.
Type: Cookson and Eisenack, 1965a, pl.12, figs.5–6, as Leptodinium dispertitum.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Stover and Evitt, 1978]:
Synopsis:
Cyst proximochorate, acavate, subspherical to ellipsoidal, and typically without an apical projection or horn; paratabulation gonyaulacacean, indicated by parasutural septa only; paraplate 4` characteristically about as long as 1` and contact with subtriangular paraplate 6`` very short; archaeopyle precingular, type P.
Description:
Shape: Subspherical to ellipsoidal, typically without apical projection or horn.
Wall relationships: Generally autophragm only; some forms with appressed endophragm and periphragm.
Wall features: Parasutural septa generally smooth and imperforate, occasionally striate or perforate, and of more or less uniform height; crests normally smooth; areas between septa smooth or with features of low relief. Paratabulation: Indicated by parasutural features; gonyaulacacean, formula 3-4`, 5-6``, 4-6c, 5-6```, 0-1p, 1````, 0-3s. Paraplates 1` and 4` tend to be narrow, subparallel, and about equal in length; paraplate 6`` usually subtriangular, and contact with paraplate(s) very short. Certain septa, commonly between paraplates 1` and 4`, and in some species also along paracingulum and parasulcus, consistently reduced or absent.
Archaeopyle: Precingular, Type P(3`` only), reduced on some species; operculum free.
Paracingulum: Indicated by four to six rectangular to elongate-hexagonal paraplates (central part longer than ends); ventral offset moderate to strong, and terminal paraplates (1c and 6c) may be incompletely defined.
Parasulcus: Generally clearly delimited by parasutural features except where bordering septa are absent; posterior sulcal paraplate usually delimited.
Size: Small to large.
Affinities:
Impagidinium differs from Leptodinium in having the first and fourth apical paraplates of similar shape, of about equal length, and often imperfectly separated. The sixth precingular paraplate is usually subtriangular, and its contact with the apical paraplate(s) is very short. In Leptodinium, the first apical paraplate is typically longer than the fourth, the sixth precingular is quadrangular or pentangular rather than subtriangular, and the contact between paraplate 6`` and the contiguous apical paraplate is substantial. In general, species of Impagidinium tend to be subspherical to ellipsoidal, to lack an apical projection, and to have reduced paratabulation in some instances. Species of Leptodinium, in contrast, tend to be more elongate, even subpolygonal, to possess an apical horn, and rarely, if ever, to have reduced paratabulation. Additionally, epicystal intercalary paraplates occur on some species of Leptodinium, whereas such paraplates have not been observed on species of Impagidinium.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Fensome et al., 1991, p. 280:
Discussion: (editors` remarks)
Stover and Evitt (1978, p.165, 273-275) compared Impagidinium with Leptodinium Klement, 1960. They noted that "We view Impagidinium as a distinctive cyst type whose biological affinity lies close to Spiniferites, i.e., to the group of species represented today by Gonyaulax spinifera (Claparede & Lachmann 1858) Diesing 1866." They included lmpagidinium in Category 5 of their Gonyaulacysta complex, together with Heslertonia Sarjeant, 1966, Leptodinium and Prionodinium Leffingwell and Morgan 1977. Taxa in Category 5 are characterized by "prominent, essentially even-topped septa." They also provided a summation of selected characteristics of Gonyaulacysta complex genera, including Impagidinium.
Helenes (1984) included the type species of Impagidinium as an acavate gonyaulacoid genus with parasutural features, a type P archeopyle and an S-type ventral organization. However, he also indicated that other species of Impagidinium have an L-type ventral organization.
Evitt (1985, p.100) considered Impagidinium to have an "S- type ventral organization". He listed as characteristic for this type of organization the following: a strongly offset paracingulum; a parasulcus narrowest between the ends of the paracingulum and often sigmoid- a quasi triangular or three-sided 6`` (1i); an enlarged 3` (C); an elongate 4` (A) almost equal in size and shape to 1` (1u) and commonly fusing with that plate or reduced and having minimal or no contact with 6`` (1i) ; weakly developed parasutures within and adjacent to the parasulcus- and a geniculate anterior margin to the anterior sulcal paraplate (ai). Evitt (1985, p.222) included Impagidinium in his Gs-Cysts, Leptodinium Complex. Genera of the Leptodinium Complex have a gonyaulacoid paratabulation delineated by parasutural features and a sexiform hypocyst. Jan du Chêne et al. (1986, p.167) reiterated the original diagnosis for Impagidinium using slightly different phraseology. They also included Impagidinium in their key to genera of the "Complex Gonyaulacysta".
Helenes (1986, p.90) considered the type species of Impagidinium, Impagidinium dispertitum, to have the "Californiense Pattern" of paratabulation. Taxa with the Californiense Pattern have paraplates P (first preapical) and C (3`) in contact, an anteriorly planate 1i (6``) and an anteriorly camerate ai (anterior sulcal), termed the A/ai (4`/as) arrangement, and an asymmetrically quadrate sexiform Y (1`````) paraplate. Helenes (1986, p.90) noted that Impagidinium dispertitum "... shows an A/ai arrangement; however neither the apical nor the antapical arrangements have been illustrated with enough detail." In the same paper (p.107), Helenes included Impagidinium dispertitum in his "Californiense Complex". Helenes (1986, p.104) assigned other species of Impagidinium, such as Impagidinium sphaericum (Wall, 1967) Lentin and Williams, 1981, to his "Sphaericum Pattern" of paratabulation.
----------------------------------------------------------------------------
Zorzi, C. et al., 264, 24–37, 2019:
Discussion/Remarks:
Impagidinium species can be distinguished by (a) the degree to which tabulation is expressed: Impagidinium sphaericum (Wall,1967) and Impagidinium? diaphanum sp. nov.: excellently expressed, including some delineation of plates in the sulcal area; Impagidinium aculeatum and Impagidinium detroitense sp. nov.: generally well expressed but weakly expressed in the sulcal area; Impagidinium patulum: incompletely expressed in the ventral region but well expressed elsewhere; Impagidinium strialatum (Wall, 1967): poorly expressed, frequently reduced on the dorsal and ventral surface (b) the degree of suturocavation variation: Impagidinium patulum and Impagidinium sphaericum: absent to slight; Impagidinium cantabrigiense, Impagidinium detroitense sp. nov., Impagidinium? diaphanum sp. nov.: moderate; Impagidinium multiplex: high
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Impagidinium Stover and Williams, 1978. Synopsis, from Stover and Evitt (1978, p.165), cysts proximochorate, acavate, subspherical to ellipsoidal, and typically without an apical projection or horn; paratabulation gonyaulacacean, indicated by parasutural septa only; paraplate 4` characteristically about as long as 1` and contact with subtriangular paraplate 6" very short; archeopyle precingular, type P.