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Phthanoperidinium
From Williams et al., 2017:
[Phthanoperidinium, Drugg and Loeblich Jr., 1967, p. 182; Emendations: Edwards and Bebout, 1981, p. 36-38; Islam, 1982, p. 306.
Tax. jr. syn.: Vectidinium, according to Islam (1982, p.313) — however, Lentin and Williams (1989, p.381) retained Vectidinium.
Type species: Phthanoperidium amoenum, Drugg and Loeblich, 1967 (pl.1, fig.4)]
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Original description: [Drugg and Loeblich, 1967]:
Diagnosis:
Proximate fossil cysts, more or less ovoidal in shape, with a short apical projection. Tabulation 4`, 3a, 7``, 5```, 2````. Additional furrow platelets may be present. The archeopyle is formed by the removal of intercalary plate 2a. Sutures delimited by low ridges, crests, or lines of spines.
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Modified description:
Stover and Evitt, 1978, p. 118:
Synopsis:
Cysts proximate, subspherical to ellipsoidal, generally with a short apical projection and less commonly an antapical projection as well; paratabulation peridiniacean, indicated principally by parasutural features and additionally by penitabular and intratabular features; archeopyle intercalary, Type I; archeopyle index < 0.5.
Description:
Shape: Subspherical to ellipsoidal, generally with a short apical and, occasionally, with a short antapical projection.
Wall relationships: Endophragm and periphragm appressed; both layers thin, or endophragm thicker and denser than periphragm.
Wall features: Parasutural ridges generally low, smooth to granulate; may be surmounted with long slender gonal and intergonal spines. Areas between parasutural ridges may be smooth or have (1) fine, uniform ornamentation, (2) penitabular rows of granules or small cones, or (3) a fine, intratabular reticulation. Narrow areas between parasutural and penitabular or intratabular features normally smooth.
Paratabulation: Expressed principally by parasutural features and in some cases, additionally, by penitabular and intratabular features; peridiniacean, formula: 4`, 3a, 7``, 6c, 5```, 2````, 0-5s; paraplates 2` and 4` not always clearly discernible.
Archeopyle: Intercalary, Type I (2a only); archeopyle index < 0.5; operculum free.
Paracingulum: Indicated by parallel transverse parasutural ridges; may be subdivided.
Parasulcus: Expressed as midventral depression mainly on the hypocyst; sulcal paraplates may be differentiated.
Size: Small to intermediate.
Affinities:
Phthanoperidium differs Ginginodinium in having a Type I rather than a Type 3I archeopyle; and in either lacking antapical horns or having a single, medial, antapical projection rather than two antapical horns, as in Ginginodinium.
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Emended descriptions:
Edwards and Bebout, 1981:
Description:
Shape: Subspherical, ovoidal, ellipsoidal, to polygonal; length to width ratio from 1:1 to 1.7:1; 1 apical horn; 0, 1, or 2 antapical horns (in many places merely suggested).
Wall relationships: 2 layers may be apparent in light microscopy, and some show a `cancellous` filling between layers that it is revealed only by electron microscope studies; separation of wall layers only below parasutural crests and apical and antapical horns (if present).
Wall features: Periphragms variously ornamented, many with parasutural ridges as much as 10 µm in height; parasutural ridges smooth or granulate, and some bear denticles, spines, or hairlike projections (simple or branched); penitabular features commonly present as rows of granules, pustules, short spines, or slender rods with bulbous tips; intratabular areas smooth, granulate, verrucate, vermiculate, reticulate, or dotted with pustules.
Paratabulation: Peridiniacean, expressed by parasutural crest or penitabular features; 4`, 3a, 7``, Xc, 5```, 2````, Xs.
Archeopyle: Simple or combination, 1 to 3 intercalaries, 0 to 3 (3``-5``) precingulars; 2a detached, other paraplates may be detached or displaced. On those forms with simple Type I archeopyles, the transverse archeopyle index is about 0.5. It need not be less than 0.5 as stated by Stover and Evitt (1978, p. 118).
Paracingulum: Usually delineated by parasutural crests; evidence of individual paraplates in a few specimens.
Parasulcus: Commonly prominent as a broad depression, especially on the hypocyst; individual paraplates rarely discernable.
Size: Maximum length (excluding sculpture) 26 to 62 µm
Affinities:
Phthanoperidinium differs from other small ellipsoidal peridiniacean genera with intercalary archeopyles in having principally parasutural ornamentation. Its size, shape, ornamentation, and lack of clearly separated wall layers serve to distinguish this genus from similar genera. Ginginodinium Cookson and Eisenack 1960, and Spinidinium Cookson and Eisenack 1962, and Palaeoperidinium Deflandre 1935 all show similarities to Phthanoperidinium but all lack parasutural features. In addition, Palaeoperidinium has a combination archeopyle that includes an apical paraplate as well as intercalaries and precingulars. In Phthanoperidinium only intercalaries, and in some species, precingulars, are involved.
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Islam, 1982:
Description:
The cyst possesses a subspherical to ellipsoidal shape with a short apical horn and one or two antapical lobes or without; composed of psilate to mildly ornamented periphragm and endophragm which are sometimes adpressed sufficiently to look like an autophragm only; endophragm may be relatively thicker; proximate; acavate to slightly cornucavate; periphragmal thickening, or parasutural and/or penitabular processes define a paratabulation of 4`, 3a, 7``, xc, 5```, 2````, xs; three different archeopyle types are recognized: (i) simple intercalary type I, (plate 2a), (ii) compound type (IP), (plates 2a and 4``) or IP, (plates 2a and 4``) and (iii) compound type (3I3P), (precingular plates 3``-5``) or 3I3P, (precingular plates 3``-5``); paracingulum is helicoidal, may possess raised margins, be slightly depressed and very narrow; parasulcus may also be slightly depressed and broader posteriorly.
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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.
Phthanoperidinium Drugg and Loeblich, Jr., 1967, emend. Edwards and Bebout, 1981, emend. Islam, 1982. According to Stover and Evitt (1978, p.118), Phthanoperidinium is a proximate cyst. Subspherical to ellipsoidal, generally with a short apical projection and less commonly also an antapical projection. Paratabulation peridiniacean indicated principally by parasutural features and additionally by penitabular and intratabular features; archeopyle intercalary type I, archeopyle index >0.5. Edwards and Bebout (1981, p.36) emended the genus to include forms with simple or combination archeopyles formed from the loss of 1-3 intercalaries, and 0-3 (3"-5") precingulars; 2a is detached, other paraplates may be detached or displaced. And the transverse archeopyle index does not have to be >0.5. Although the ornamentation is principally parasutural it can also be penitabular and there can be intratabular granules, verrucae, vermiculae or reticulum. Islam (1982, p.306) also emended the diagnosis to include three different archeopyle types; 1. Simple intercalary type I(2a), 2. Compound type [I(2a)P(4")] or I(2a)P(4"), and 3. Compound type 3I#P(3"-5") or 3I3P(3"-5").
[Phthanoperidinium, Drugg and Loeblich Jr., 1967, p. 182; Emendations: Edwards and Bebout, 1981, p. 36-38; Islam, 1982, p. 306.
Tax. jr. syn.: Vectidinium, according to Islam (1982, p.313) — however, Lentin and Williams (1989, p.381) retained Vectidinium.
Type species: Phthanoperidium amoenum, Drugg and Loeblich, 1967 (pl.1, fig.4)]
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Original description: [Drugg and Loeblich, 1967]:
Diagnosis:
Proximate fossil cysts, more or less ovoidal in shape, with a short apical projection. Tabulation 4`, 3a, 7``, 5```, 2````. Additional furrow platelets may be present. The archeopyle is formed by the removal of intercalary plate 2a. Sutures delimited by low ridges, crests, or lines of spines.
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Modified description:
Stover and Evitt, 1978, p. 118:
Synopsis:
Cysts proximate, subspherical to ellipsoidal, generally with a short apical projection and less commonly an antapical projection as well; paratabulation peridiniacean, indicated principally by parasutural features and additionally by penitabular and intratabular features; archeopyle intercalary, Type I; archeopyle index < 0.5.
Description:
Shape: Subspherical to ellipsoidal, generally with a short apical and, occasionally, with a short antapical projection.
Wall relationships: Endophragm and periphragm appressed; both layers thin, or endophragm thicker and denser than periphragm.
Wall features: Parasutural ridges generally low, smooth to granulate; may be surmounted with long slender gonal and intergonal spines. Areas between parasutural ridges may be smooth or have (1) fine, uniform ornamentation, (2) penitabular rows of granules or small cones, or (3) a fine, intratabular reticulation. Narrow areas between parasutural and penitabular or intratabular features normally smooth.
Paratabulation: Expressed principally by parasutural features and in some cases, additionally, by penitabular and intratabular features; peridiniacean, formula: 4`, 3a, 7``, 6c, 5```, 2````, 0-5s; paraplates 2` and 4` not always clearly discernible.
Archeopyle: Intercalary, Type I (2a only); archeopyle index < 0.5; operculum free.
Paracingulum: Indicated by parallel transverse parasutural ridges; may be subdivided.
Parasulcus: Expressed as midventral depression mainly on the hypocyst; sulcal paraplates may be differentiated.
Size: Small to intermediate.
Affinities:
Phthanoperidium differs Ginginodinium in having a Type I rather than a Type 3I archeopyle; and in either lacking antapical horns or having a single, medial, antapical projection rather than two antapical horns, as in Ginginodinium.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended descriptions:
Edwards and Bebout, 1981:
Description:
Shape: Subspherical, ovoidal, ellipsoidal, to polygonal; length to width ratio from 1:1 to 1.7:1; 1 apical horn; 0, 1, or 2 antapical horns (in many places merely suggested).
Wall relationships: 2 layers may be apparent in light microscopy, and some show a `cancellous` filling between layers that it is revealed only by electron microscope studies; separation of wall layers only below parasutural crests and apical and antapical horns (if present).
Wall features: Periphragms variously ornamented, many with parasutural ridges as much as 10 µm in height; parasutural ridges smooth or granulate, and some bear denticles, spines, or hairlike projections (simple or branched); penitabular features commonly present as rows of granules, pustules, short spines, or slender rods with bulbous tips; intratabular areas smooth, granulate, verrucate, vermiculate, reticulate, or dotted with pustules.
Paratabulation: Peridiniacean, expressed by parasutural crest or penitabular features; 4`, 3a, 7``, Xc, 5```, 2````, Xs.
Archeopyle: Simple or combination, 1 to 3 intercalaries, 0 to 3 (3``-5``) precingulars; 2a detached, other paraplates may be detached or displaced. On those forms with simple Type I archeopyles, the transverse archeopyle index is about 0.5. It need not be less than 0.5 as stated by Stover and Evitt (1978, p. 118).
Paracingulum: Usually delineated by parasutural crests; evidence of individual paraplates in a few specimens.
Parasulcus: Commonly prominent as a broad depression, especially on the hypocyst; individual paraplates rarely discernable.
Size: Maximum length (excluding sculpture) 26 to 62 µm
Affinities:
Phthanoperidinium differs from other small ellipsoidal peridiniacean genera with intercalary archeopyles in having principally parasutural ornamentation. Its size, shape, ornamentation, and lack of clearly separated wall layers serve to distinguish this genus from similar genera. Ginginodinium Cookson and Eisenack 1960, and Spinidinium Cookson and Eisenack 1962, and Palaeoperidinium Deflandre 1935 all show similarities to Phthanoperidinium but all lack parasutural features. In addition, Palaeoperidinium has a combination archeopyle that includes an apical paraplate as well as intercalaries and precingulars. In Phthanoperidinium only intercalaries, and in some species, precingulars, are involved.
----------------------------------------
Islam, 1982:
Description:
The cyst possesses a subspherical to ellipsoidal shape with a short apical horn and one or two antapical lobes or without; composed of psilate to mildly ornamented periphragm and endophragm which are sometimes adpressed sufficiently to look like an autophragm only; endophragm may be relatively thicker; proximate; acavate to slightly cornucavate; periphragmal thickening, or parasutural and/or penitabular processes define a paratabulation of 4`, 3a, 7``, xc, 5```, 2````, xs; three different archeopyle types are recognized: (i) simple intercalary type I, (plate 2a), (ii) compound type (IP), (plates 2a and 4``) or IP, (plates 2a and 4``) and (iii) compound type (3I3P), (precingular plates 3``-5``) or 3I3P, (precingular plates 3``-5``); paracingulum is helicoidal, may possess raised margins, be slightly depressed and very narrow; parasulcus may also be slightly depressed and broader posteriorly.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Phthanoperidinium Drugg and Loeblich, Jr., 1967, emend. Edwards and Bebout, 1981, emend. Islam, 1982. According to Stover and Evitt (1978, p.118), Phthanoperidinium is a proximate cyst. Subspherical to ellipsoidal, generally with a short apical projection and less commonly also an antapical projection. Paratabulation peridiniacean indicated principally by parasutural features and additionally by penitabular and intratabular features; archeopyle intercalary type I, archeopyle index >0.5. Edwards and Bebout (1981, p.36) emended the genus to include forms with simple or combination archeopyles formed from the loss of 1-3 intercalaries, and 0-3 (3"-5") precingulars; 2a is detached, other paraplates may be detached or displaced. And the transverse archeopyle index does not have to be >0.5. Although the ornamentation is principally parasutural it can also be penitabular and there can be intratabular granules, verrucae, vermiculae or reticulum. Islam (1982, p.306) also emended the diagnosis to include three different archeopyle types; 1. Simple intercalary type I(2a), 2. Compound type [I(2a)P(4")] or I(2a)P(4"), and 3. Compound type 3I#P(3"-5") or 3I3P(3"-5").