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Sumatradinium
From Williams et al., 2017:
[Sumatradinium, Lentin and Williams, 1976, p. 77–78; Emendation: Lentin et al., 1994, p. 570.
Matsuoka (1992, p.451) considered Xandarodinium to be a possible taxonomic junior synonym of this genus.
Type species: as Xenicodinium hispidum, Drugg, 1970a (fig.12)]
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Original description: [Lentin and Williams, 1976]:
Description:
Pericyst: Ambitus rounded to ovoidal to pentagonal, widest in the pericingular region. Apex rounded, apical horn absent. Antapex rounded, flattened or with very weakly developed symmetrically located antapical lobes. Epipericyst and hypopericyst of approximately equal size.
Length: breadth ratio ca. 1. Compression dorso-ventral, usually extreme.
Endocyst: Not always observable. In some specimens appears to be appressed to pericyst throughout.
Pericoels: Absent.
Periphragm: Surface rarely laevigate, generally scabrate to granulate, reticulate or rugulate, the rugulae often developed into a hieroglyphic ornamentation. Generally nontabular, occasionally penetabular, processes of varying length are always present. They may be uniformly distributed or concentrated along the ambitus. The processes are hollow, slender, distally acuminate, oblate or bifid. Occasionally they are separated along their length by septa.
Endophragm: Where observed, very thin and laevigate.
Pericyst: Some processes appear to be penetabular but the paratabulation is obscure, although it must be peridinioid from the nature of the archeopyle. The 2a paraplate is very large, extending almost to the pericingulum, from which it is separated by a very narrow 4" paraplate. Pericingulum: May be partially delineated by penitabular processes. Planar or slightly helicoidal.
Perisulcus: Rarely determinable; when visible appears to be largely restricted to hypopericyst.
Endocyst: Paratabulation unknown, other than presumably in the vicinity of the endoarcheopyle. Large, broad hexa intercalary [archeopyle] resulting from the partial or complete detachment of the second anterior intercalary paraplate 2a. Operculum free or remaining attached along parasuture H4. Since the endophragm and periphragm are appressed in the vicinity of the archeopyle, there is no separation of the endoperculum and perioperculum so that effectively there is one archeopyle and one operculum. Transverse archeopyle index is 0.45. Transverse archeopyle ratio is 1:8. Archeopyle Formula: I/l (2a/2a?).
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Modified description:
Stover and Evitt 1978, p. 125-126:
Synopsis:
Cysts proximochorate, lenticular; outline subcircular, with or without shallow antapical concavity; autophragm variously ornamented with features of low relief and relatively short, generally nontabular processes; paratabulation indicated by archeopyle only, or by paracingulum and archeopyle; latter intercalary, Type l; archeopyle index about 0.45.
Description:
Shape: Compressed, outline subcircular; may have shallow midantapical concavity.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Surface has various features of low relief (granulate, finely reticulate, rugulate) and numerous relatively short, generally nontabular processes; occasionally processes may be concentrated near lateral margins of cyst or in poorly defined penitabular groups.
Paratabulation: Generally indicated by archeopyle only; additionally, although less frequently, indicated by paracingulum and the vague penitabular arrangement of processes.
Archeopyle: Intercalary, Type I (2a only); operculum free. Because of its large size, archeopyle may appear to be precingular, but it has the hexagonal shape characteristic of most intercalary archeopyles.
Paracingulum: Generally not indicated, or delimited partly by transverse alignment of processes.
Parasulcus: Normally not discernible.
Size: Intermediate.
Affinities:
Sumatradinium differs from other relatively simple cysts with short nontabular processes (e.g., Operculodinium, Trichodinium, Xenicodinium) in having an intercalary rather than a precingular archeopyle, and in being dorso-ventrally flattened.
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Emended description:
Lentin et al., 1994, p.570-571:
Diagnosis:
Acavate to rarely narrowly circumcavate, dorsoventrally compressed peridinialean cysts with the single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 µm in diameter. Processes or spines generally hollow, nontabulate to penitabulate or sutural, and may show a tendency to be more concentrated marginally; they may have annular thickenings or septa. The middorsal intercalary paraplate is large hexa isodeltaform, posteriorly extending almost to the equator of the cyst; this paraplate usually forms the archeopyle alone.
Description:
Shape: Cyst weakly to strongly dorsoventrally compressed, ambitus subcircular, suboval, rounded pentagonal to peridinioid. Apex rounded; antapex rounded to weakly bilobate and symmetrical or asymmetrical. Epicyst and hypocyst appear to be more or less equal in size.
Wall relationships: Usually acavate with autophragm only or with endophragm and periphragm appressed; rarely circumcavate, with periphragm and endophragm narrowly separated.
Wall features: Periphragm or autophragm bearing a complete or incomplete reticulum, with lumina generally less than 2 µm in diameter. Processes or spines generally hollow and tapering, commonly with annular thickenings (or septa) along their length; they are distally closed, acuminate to evexate to bulbous, bifid or branched. Endophragm, where observed, thin and laevigate. Processes occurring on middorsal and midventral surfaces, but commonly concentrated marginally, nontabulate to penitabulate or sutural.
Mode of excystment: Archeopyle usually involves the loss of a large hexa isodeltaform middorsal intercalary paraplate, presumably 2a, posteriorly extending almost to the equator of the cyst. The operculum is usually free but may be adnate anteriorly. Rarely, accessory archeopyle sutures develop between paraplates adjacent to 2a and a second intercalary paraplate may be dislodged. When two wall layers are observed, they appear fused on the operculum.
Paratabulation: Generally indicated by archeopyle only and assumed to be peridinialean; occasionally the alignment of processes suggests a paracingulum and possibly other parasutures. Parasulcus not identified.
Affinities:
Sumatradinium is unique among peridinialean genera with a hexa intercalary archeopyle in having processes and a complete or incomplete surface reticulation. The diagnosis and description of Sumatradinium are herein modified to restrict the genus to forms with this distinct type of ornamentation and the possession of processes or spines (the latter term is used as defined in Fensome et al. 1993, p. 261). The description is also modified to include the possibility of circumcavation and compound excystment openings and to more fully describe process variation. These modifications have resulted from study of the new species described in this paper plus reexamination of the type material of S. hispidum, the type species. Erymnodinium has the same surface ornamentation as Sumatradinium, but possesses parasutural septa and lacks processes. Barssidinium is similar to Sumatradinium in possessing processes but does not have a reticulate surface. In Barssidinium the processes tend to be concentrated marginally, whereas in Sumatradinium they tend to be more uniformly distributed. Although primary pigmentation (as observed in many protoperidinioid cysts) was not a common feature in our specimens of Sumatradinium, it is apparently an important feature of specimens from other areas (M.J. Head, pers. comm., 1992). Its absence in most offshore eastern Canadian specimens may be due to preservational or processing factors. The relationship of the two wall layers in S. soucouyantiae was described in detail by de Verteuil and Norris (1992). Matsuoka (1992) made a detailed comparison of the genera Sumatradinium, Trinovantedinium Reid, 1977 and Xandarodinium Reid, 1977. He noted that all three genera share the following characters: (1) dorsoventral compression, (2) a wall comprising an autophragm only, (3) a single plate intercalary archeopyle, and (4) processes or spines. He then listed the points of differentiation as (1) outline in dorsoventral view, (2) development of apical and antapical horns, and (3) distribution of processes or spines. Matsuoka considered Trinovantediniumdistinctive from the other two genera in its pentagonal outline and well-developed apical and (or) antapical horns, but regarded the other two genera (Xandarodinium and Sumatradinium) as being more closely comparable and possibly synonymous. In our view, many of the features cited by Matsuoka do not allow for a clear separation of Sumatradinium from Xandarodinium and Trinovantedinium; for example, some specimens of Sumatradinium have a pentagonal outline. Matsuoka (1992) did not consider the distinctive surface reticulation of Sumatradinium, a feature that clearly segregates it from the other two genera.
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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.
Sumatradinium Lentin and Williams, 1976, emend. Lentin et al., 1994. Emended diagnosis from Lentin et al. (1994, p.570). Acavate to rarely narrowly circumcavate, dorsoventrally compressed peridinialean cysts with the single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 μm in diameter. Processes or spines generally hollow, nontabulate to penitabulate or sutural, and may show a tendency to be more concentrated marginally; they may have annular thickenings or septa. The middorsal intercalary paraplate is large hexa isodeltaform, posteriorly extending almost to the equator of the cyst; this paraplate usually forms the archeopyle alone.
[Sumatradinium, Lentin and Williams, 1976, p. 77–78; Emendation: Lentin et al., 1994, p. 570.
Matsuoka (1992, p.451) considered Xandarodinium to be a possible taxonomic junior synonym of this genus.
Type species: as Xenicodinium hispidum, Drugg, 1970a (fig.12)]
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Original description: [Lentin and Williams, 1976]:
Description:
Pericyst: Ambitus rounded to ovoidal to pentagonal, widest in the pericingular region. Apex rounded, apical horn absent. Antapex rounded, flattened or with very weakly developed symmetrically located antapical lobes. Epipericyst and hypopericyst of approximately equal size.
Length: breadth ratio ca. 1. Compression dorso-ventral, usually extreme.
Endocyst: Not always observable. In some specimens appears to be appressed to pericyst throughout.
Pericoels: Absent.
Periphragm: Surface rarely laevigate, generally scabrate to granulate, reticulate or rugulate, the rugulae often developed into a hieroglyphic ornamentation. Generally nontabular, occasionally penetabular, processes of varying length are always present. They may be uniformly distributed or concentrated along the ambitus. The processes are hollow, slender, distally acuminate, oblate or bifid. Occasionally they are separated along their length by septa.
Endophragm: Where observed, very thin and laevigate.
Pericyst: Some processes appear to be penetabular but the paratabulation is obscure, although it must be peridinioid from the nature of the archeopyle. The 2a paraplate is very large, extending almost to the pericingulum, from which it is separated by a very narrow 4" paraplate. Pericingulum: May be partially delineated by penitabular processes. Planar or slightly helicoidal.
Perisulcus: Rarely determinable; when visible appears to be largely restricted to hypopericyst.
Endocyst: Paratabulation unknown, other than presumably in the vicinity of the endoarcheopyle. Large, broad hexa intercalary [archeopyle] resulting from the partial or complete detachment of the second anterior intercalary paraplate 2a. Operculum free or remaining attached along parasuture H4. Since the endophragm and periphragm are appressed in the vicinity of the archeopyle, there is no separation of the endoperculum and perioperculum so that effectively there is one archeopyle and one operculum. Transverse archeopyle index is 0.45. Transverse archeopyle ratio is 1:8. Archeopyle Formula: I/l (2a/2a?).
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Modified description:
Stover and Evitt 1978, p. 125-126:
Synopsis:
Cysts proximochorate, lenticular; outline subcircular, with or without shallow antapical concavity; autophragm variously ornamented with features of low relief and relatively short, generally nontabular processes; paratabulation indicated by archeopyle only, or by paracingulum and archeopyle; latter intercalary, Type l; archeopyle index about 0.45.
Description:
Shape: Compressed, outline subcircular; may have shallow midantapical concavity.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Surface has various features of low relief (granulate, finely reticulate, rugulate) and numerous relatively short, generally nontabular processes; occasionally processes may be concentrated near lateral margins of cyst or in poorly defined penitabular groups.
Paratabulation: Generally indicated by archeopyle only; additionally, although less frequently, indicated by paracingulum and the vague penitabular arrangement of processes.
Archeopyle: Intercalary, Type I (2a only); operculum free. Because of its large size, archeopyle may appear to be precingular, but it has the hexagonal shape characteristic of most intercalary archeopyles.
Paracingulum: Generally not indicated, or delimited partly by transverse alignment of processes.
Parasulcus: Normally not discernible.
Size: Intermediate.
Affinities:
Sumatradinium differs from other relatively simple cysts with short nontabular processes (e.g., Operculodinium, Trichodinium, Xenicodinium) in having an intercalary rather than a precingular archeopyle, and in being dorso-ventrally flattened.
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Emended description:
Lentin et al., 1994, p.570-571:
Diagnosis:
Acavate to rarely narrowly circumcavate, dorsoventrally compressed peridinialean cysts with the single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 µm in diameter. Processes or spines generally hollow, nontabulate to penitabulate or sutural, and may show a tendency to be more concentrated marginally; they may have annular thickenings or septa. The middorsal intercalary paraplate is large hexa isodeltaform, posteriorly extending almost to the equator of the cyst; this paraplate usually forms the archeopyle alone.
Description:
Shape: Cyst weakly to strongly dorsoventrally compressed, ambitus subcircular, suboval, rounded pentagonal to peridinioid. Apex rounded; antapex rounded to weakly bilobate and symmetrical or asymmetrical. Epicyst and hypocyst appear to be more or less equal in size.
Wall relationships: Usually acavate with autophragm only or with endophragm and periphragm appressed; rarely circumcavate, with periphragm and endophragm narrowly separated.
Wall features: Periphragm or autophragm bearing a complete or incomplete reticulum, with lumina generally less than 2 µm in diameter. Processes or spines generally hollow and tapering, commonly with annular thickenings (or septa) along their length; they are distally closed, acuminate to evexate to bulbous, bifid or branched. Endophragm, where observed, thin and laevigate. Processes occurring on middorsal and midventral surfaces, but commonly concentrated marginally, nontabulate to penitabulate or sutural.
Mode of excystment: Archeopyle usually involves the loss of a large hexa isodeltaform middorsal intercalary paraplate, presumably 2a, posteriorly extending almost to the equator of the cyst. The operculum is usually free but may be adnate anteriorly. Rarely, accessory archeopyle sutures develop between paraplates adjacent to 2a and a second intercalary paraplate may be dislodged. When two wall layers are observed, they appear fused on the operculum.
Paratabulation: Generally indicated by archeopyle only and assumed to be peridinialean; occasionally the alignment of processes suggests a paracingulum and possibly other parasutures. Parasulcus not identified.
Affinities:
Sumatradinium is unique among peridinialean genera with a hexa intercalary archeopyle in having processes and a complete or incomplete surface reticulation. The diagnosis and description of Sumatradinium are herein modified to restrict the genus to forms with this distinct type of ornamentation and the possession of processes or spines (the latter term is used as defined in Fensome et al. 1993, p. 261). The description is also modified to include the possibility of circumcavation and compound excystment openings and to more fully describe process variation. These modifications have resulted from study of the new species described in this paper plus reexamination of the type material of S. hispidum, the type species. Erymnodinium has the same surface ornamentation as Sumatradinium, but possesses parasutural septa and lacks processes. Barssidinium is similar to Sumatradinium in possessing processes but does not have a reticulate surface. In Barssidinium the processes tend to be concentrated marginally, whereas in Sumatradinium they tend to be more uniformly distributed. Although primary pigmentation (as observed in many protoperidinioid cysts) was not a common feature in our specimens of Sumatradinium, it is apparently an important feature of specimens from other areas (M.J. Head, pers. comm., 1992). Its absence in most offshore eastern Canadian specimens may be due to preservational or processing factors. The relationship of the two wall layers in S. soucouyantiae was described in detail by de Verteuil and Norris (1992). Matsuoka (1992) made a detailed comparison of the genera Sumatradinium, Trinovantedinium Reid, 1977 and Xandarodinium Reid, 1977. He noted that all three genera share the following characters: (1) dorsoventral compression, (2) a wall comprising an autophragm only, (3) a single plate intercalary archeopyle, and (4) processes or spines. He then listed the points of differentiation as (1) outline in dorsoventral view, (2) development of apical and antapical horns, and (3) distribution of processes or spines. Matsuoka considered Trinovantediniumdistinctive from the other two genera in its pentagonal outline and well-developed apical and (or) antapical horns, but regarded the other two genera (Xandarodinium and Sumatradinium) as being more closely comparable and possibly synonymous. In our view, many of the features cited by Matsuoka do not allow for a clear separation of Sumatradinium from Xandarodinium and Trinovantedinium; for example, some specimens of Sumatradinium have a pentagonal outline. Matsuoka (1992) did not consider the distinctive surface reticulation of Sumatradinium, a feature that clearly segregates it from the other two genera.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Sumatradinium Lentin and Williams, 1976, emend. Lentin et al., 1994. Emended diagnosis from Lentin et al. (1994, p.570). Acavate to rarely narrowly circumcavate, dorsoventrally compressed peridinialean cysts with the single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 μm in diameter. Processes or spines generally hollow, nontabulate to penitabulate or sutural, and may show a tendency to be more concentrated marginally; they may have annular thickenings or septa. The middorsal intercalary paraplate is large hexa isodeltaform, posteriorly extending almost to the equator of the cyst; this paraplate usually forms the archeopyle alone.